- Email: [email protected]
Aqueous humor dynamics in monkeys (Macaca irus and Cercopithecus ethiops)
Exp. Eye Res. (1971)
11, 195-206
Aqueous Humor Dynamics in Monkeys (Macaca irus and Cercopithecus ethiops) _A~DERS :BILL
Department of Experimental Ophthalmology, Institute of Pharmaz~!ogy, University of Up,vsala, Uyrpsala, Sweden (Received ld Septen~er 1970, Boston) - T h e ineraoeular pressure, t h e gross facility of outflow, the rate of flow of anterior c h a m b e r fluid into t h e general circula.tion via. S c h l e m m ' s canal and t h a t into uveoscleral r o u t e s were detemnined in a total of 94 veto,or a n d cbmomolgus m o n k e y s u n d e r general anesthesia. The n e t rate. of f o r m a t i o n of aqueous h u m o r , the outflow pressure a n d the recipient venous pressure were calculated. There were significant positive correlatiohs between weight a n d intraocutar pressure a n d between weight a n d arterial blood pressure. A probably significant, positive correlation was found between out,flow pressure a n d intraocalar preasure. There was a negative correlation bet~vecn uveoscleral flow a.nd flow vi~ S c h l e m m ' s canal. T h e rate of aqueous f o r m a t i o n was n o t significantly correlated to the b o d y weight, the gross facility or the intraoeular pressure. T h e results indicate t h a t uqueous h u m o r pa.~ing into t h e uveoscleral routes fIx>m the anterior c h a m b e r is modified in the u r e a , seeps ,through t h e selera and is t h e n reaorl)ed into 15~mph and blood vessels outside t h e eye. No indications were f o u n d for an extraocular regulating center that, receives inYormation a b o u t t h e conditions in t h e eye and t h a t adjusts flow rates, facility or prez~ureB. 1. I n t r o d u c t i o n
During the last few years monkeys have been used at this laboratory in studies on aqueous humor dynamics. It was found that if an ineffective dose of a drug was applied to one eye and the other eye served as a control there was little difference between the eves in all pare.meters studied. It was also fomxd, however, that there are l a r g e d i i ~ h r e n c e s b e t w e e n the. e y e s o f d i f f e r e n t a n i m a l s . E a c h o f t h e s t u d i e s m e n t i o n e d comprised too few animals to permit an analysis of the interindividual variability and the type of statistical distribution of the parameters studied. The purpose of the p r e s e n t c o m m u n i c a t i o n is t o a n a l y z e s o m e w h a t t h e v a r i a b l e s s t u d i e d : a n d d i s e n t a n g l e relationships by using a larger material. Some of the eyes included are control eyes f r o m p r e ~ i o u s s t u d i e s alre~udy re,p o r t e d , O t h e r s a r e s u c c e s s f u l c o n t r o l e y e s i n e x p e r i ments in which the "treated eye" for technical reasons was .regarded as u~uccessful; t h e r e a s o n b e i n g , e.g. t h a t t h e c a n n u l a s u s e d t o u c h e d t h e iris, wc~e t o r n o u t o f t h e anterior chamber during the experiment, or that the mechanical device connected to the anterior chamber proved lealry at the end of the experixnent, when it was r e t ~ s t e d . S t i l l o t h e r e y e s a r e f l ' o m a n u n s u c c e s s f u ! ,';~ady o f t h e e f f e c t s o f c y c l o d i a l y s i s ; i n m o s t e a s e s t h e cleft, i n t h e o p e r a t e d e y e h e a l e d , O n l y t h e c o n t r o l e y e s o f t h a t staady a r e i n c l u d e d . T h e f o l l o w i n g v ~ r i a b l e s w e r e determi:.~,~cl: l:ociy w , . i g h t , m e a n a r t e r i a l b l o o d p r e s s u r e , i n t r a o c u l a r p r e s s u r e , g r o s s f a ~ i l i t . y o f c~utfio~:~ b l ~ k t~ow o f a q u e o u s humor into the general circulation and bulk flow of aqueous "~x~ar -n~ uve~)sclerat r o u t e s . T h e r a t e o f a q u e o u s h u m o r , f o r m a t i o n w a s d e f i n e d e,s tl_*,e ~u:~ ¢,f t h e b u l k o u t f l o w t,h r o u g h t h e d i f f e r e n t r o u t e s ~ o m t h e a n t e r i o r c h a m b e r . I~_ezc, t h e t~.r~, b u l k f l o w m e a n s f l o w o f a n t e r i o r C h a m b e r f l u i d t h r o u g h p o r e s b i g e n o u g h ~',~ ~9 r e s ~ i c ~ the passage of albundn.,. 195
196
A. BILL
2. M a t e r i a l s and M e t h o d s T h e a n i m a l s u s e d were W e s t Afri.c.~:n v e r v e t s (Cercol~ithevus elhiol"~s) a n d c y n o m o l g u s m o n k e y s ( M a c a c a irus) o b t M n e d f r o m - v a r i o u s sources. All a n i m a l s w e r e a p p a r e n t l y in g o o d h e a l t h ; t h e i r age was n o t k n o ~ m b u t t h e m a j o r i t y c a n be p r e s u m e d to h a v e b e e n y o u n g a d u l t s . F o r t y - e i g h t of t.~.e v e r v e t s w e r e males, 12 w e r e f e m a l e s a n d in 3 cases t h e sex was n o t n o t e d . I n t h e c y n o m o l g u s g r o u p t h e c o r r e s p o ~ d i n g figures w e r e 9, 18 a n d 4, r e s p e c t i v e l y . I n m a n y e x p e r i m e n t s t h e a n e s t h e s i a was i n d u c e d b y i n t r a m u s c u l a r s o d i u m m e t h o h e x i t a l (Brietal, Lilly), 20 m g / k g b o d y w e i g h t . I n others, i n t r a v e n o u s s o d i u m p e n t o b a r b i t a l w a s used t o i n d u c e a n e s t h e s i a . I n all e x p e r i m e n t s a n e s t h e s i a w a s m a i n t a i n e d w i t h s o d i u m p e n t o b a ~ b i t a l g i v e n t h r o u g h a c a n n u l a t e d t a i l vein. S m a l l doses w e r e g i v e n e v e r y 1 5 - 3 0 nfin to p r e v e n t u n n e c e s s a r i l y d e e p a n e s t h e s i a . Artificial r e s p i r a t i o n was n o t u s e d in a n y of t h e e x p e r i m e n t , s. T h e a n i m a l s w e r e p l a c e d p r o n e wiT,h t h e h e a d s u p p o r t e d in s u c h a w a y t h a t t h e p u p i l s w e r e 11 c m a b o v e t h e t a b l e . A h e a t i n g p a d w a s used to keep the animals warm. M e a n a r t e r i a l blood p r e s s u r e in a c a n n u l a t e d femora.l a r t e r y was d e t e r m i n e d b y m e a n s of a p r e s s u r e t r a n s d u c e r . T h e e y e wa~ c a n u u l a t e d w i t h 3 c a n n u l a s t h a t c o n n e c t e d the a n t e r i o r c h a m b e r to a p r e s s u r e t r a n s d u c e r and. a r e s e r v o i r , t h e w e i g h t of w h i c h w a s d e t e r m i n e d c o n t i n u o u s l y , a n d to 2 p u s h - p u l l c o u p l e d syringes. T h e reservoir a m l t h e t u b i n g c o n n e c t i n g it to t h e a n t e r i o r c h a m b e r c o n t a i n e d a s o l u t i o n d e s c r i b e d b y B h r h n y (1964). This fluid w a s also the basal fluid in t h e syringes. T h e p H was 7"0. T h e gross f a c i l i t y of outflow (Bill a n d B~r,~ny, 1966) w a s d o t e r n f i n e d b y m e a s m ' i n g t h e r a t e of inflow f r o m t h e r e s e r v o i r w h e n i t was p l a c e d so as to give a n i n t r a o c u l a r pressure t h a t w a s 2 - 3 m m H g h i g h e r t h a n t h e r e s t i n g i n t r a o c u l a r pressure, a n d s u b s e q u e n t l y a t a level g i v i n g a.n i n t r a o c u l a r p r e s s u r e {.ha~ was still 7.4--9.4 m m H g higher. A f t e r t h e f a c i l i t y of outflow h a d b e e n d e t e r m i n e d the eye p r o c u r e was a d j u s t e d to it~ r e s t i n g level a n d t h e reservoirs w e r e d i s c o n n e c t e d w i t h c l a m p s . T h e n t h e a n t e r i o r chaI,.:.,., c o n t e n t s w e r e m i x e d w i t h t h o s e of t h e syringes. I n ~ o m e cases the flu.id c o n t a i n e d a l b u m i n labeled w i t h 1slI or 1~I ( p r o t e i n c o n c e n t r a t i o n a b o u t 0"1~/o), in others it c o n t a i n e d no l a b e l e d m a t e r i a l a t this stage. I n t h e l a t t e r ease a f t e r 1--1-5 h r of c o n t i n u o u s m i x i n g a t a r a t e of a b o u t 0"5 m l / m i n , a n o t h e r f a c i l i t y d e t e r m i n a t i o n was m a d e . The eye p r e s s u r e was then ad~ted to its r e s t i n g level a n d t h e t u b i n g s to t h e reservoirs w e r e c l a m p e d . The anterior c h a m b e r contents were then mixed with the radioactive albumin solution t h a t had b e e n l o a d e d i n t o t b e syringes. A f t e r "1 h r of c o n t i n u o u s nfixing of t h e a n t e r i o r c h a m b e r fluid a n d t h e r a d i o a c t i v e cont e n t s of t h e syringes, or m i x i n g e v e r y 5 rain, t h e r a d i o a c t i v e fluid in t h e a n t e r i o r c h a m b e r was r e p l a c e d b y i n a c t i v e fluid, a n d a b o u t 5 n~iu l a t e r t h e m o n k e y w a s killed a n d t h e eye a n d it~ a d n e x a w e r e dissected. I n 8 e x p e r i m e n t s in v e r v e t m o n k e y s t h e d i f f e r e n t p a r t s of t h e e y e s w e r e weighed. D u r i n g t h e h o u r w i t h r a d i o a c t i v e fluid in the a n t e r i o r c h a m b e r b l o o d s a m p l e s were t a k e n a t l e a s t e v e r y 30 rain a n d safflples were t a k e n of t h e fluid i n t h e s y r i n g e s u s i n g a m i c r o m e t e r f i t t e d t o one of t h e m . To c a l c u l a t e t h e r a t e of flow of a q u e o u s h u m o r i n t o t h e g e n e r a l c i r c u l a t i o n (see Bill 1967a) i t w a s n e c e s s a r y to _know' t h e v o l u m e of d i s t r i b u t i o n of t h e labeled a l b u m i n . I n some e x p e r i m e n t ~ t h i s v o l u m e wan d e t e r m i n e d as d e s c r i b e d p r e v i o u s l y (Bill, 1967a). I n o t h e r s it w a s assumecl to r e p r e s e n t 7-2~/6 of t h e b o d y w e i g h t . This was t h e a p p r o p r i a t e v a l u e a c c o r d i n g to a n earlier series of e x p e r i m e n t s (Bill, 1966). T h e r a t e o f u v e o s c l e r a l t t o w w a s c a l c u l a t e d f r o m t h e a m o u n t of r a d i o a c t i v e p r o t e i n r e c o v e r e d i n t h e eye arLd t h e adnexa~ (Bill, 1967a): T h i s m a y give a n o v e r e s t i m a t i o n of u v e o s c l e r a l flow, as will be d i s c u s s e d below. T h e r e c i p i e n t v e n o u s p r e s s u r e , P~, i n m m H g was calmflated, using t h e formuJ.a Pv = IOP--Fbz/(C.--0-06) (1) w h e r e I O P was t h e m e a n i n t r a o c u l a r pressure i n m m H g d a r i n g t h e h o u z w i t h r a d i o a c t i v e
,
~Ialo vervets n = 48
Female vervcts "t = 12
All vervets ~z= 63
2.51 +0.13 3.304-0.16 2-80~0.16 3.18~0-13 80.0±1.3 90.3~2,6 103.6-t-4.5 9-°.6±2.3 9.924-0.57 9.55,-4-0.41 9.91~1.11 9.70-;-0"38 0"79:t=0"10 1.12_-1:-0.06 1.08-4-0.09 1.11.-t=0.05 0.96-4-0-07 0.70=t=0-06 0.50~0.I0 0,65~0.05 1.75±0.09 1,79=t=0-07 1,57.-J=0.11 1.73=]=0.0B 0,504 J= 0.045 0-507:t=0.024 0.4'/74-0.058 0.495~0,021 0.444-.J=0,045 0.447~0.024 0.417-/-,0.058 0.435~0.021 2,064-0.15 2.22=1=0-33 1.834-0.15 o..61-:-0,382 ' , , 7.574-0-53 7.75-4-0.4.1 7.29:i:0.94 7.64__.0.69
All cynomolgi n = 31
t L .
Figures represent arit~)~,~.~ .... -- ....4;. _,~,~,,s ....... -~_:S.E.
2.40-+-0.09 80 1~1.1 9,22-4-0.59 0,764-0"12 1.09:~:0.09 1.84~0.11 0,445±0-043 0-3S5+0.043 2.47±0.41 6.69+0.50
2.87-4-0-12 81.S4=3,5 9.85±1.17 0.86±0-23 0.8I~0-14 1.674-0-22 0.470=t=0"080 0.410=t=0.080 2-534-0-76 7.30:[:0.93
*n = '.Number of animals.
Body weight (kg) Mean art. pressure (wm/-Ig) , In~.ocular p~essure (mmHg) F!o~v into blood (ttl × mhl-~) Uveoscleral flow (gl × rain -t) :Net formation of aqueou~ humor (gl ×rain -~) Grosa facility (~l × rain -1 × mmHg-x) Truo facility (gl × rain-~ × mmttg -~) Outflow I)ressu~ (mmHg) Recipient, venous pressure (mmHg)
Female c3nmmolgi n = 15
Male eynomolgi n*=9
i J
T.~ BLE I
198
A. BILL
solution in the anterior chamber. The pressure was r e a d every 10 rain. C~ was the gross facility of outflow in izl/min/rnmHg d e t e r m i n e d just before t h e anterior c h a m b e r fluid was replaced with radioactive fluid. The facility of outflow via S c h l e m m ' s canal is lower t h a n the gross facility (Bill and B~r~lny, 1966). I n anesthetized animals with a blood pressuze of a b o u t 85-95 m m t t g t h e difference is about 0.06 i z l / m i n / m m H g (Bill, 1967a, 1968). FH was the rate of flow i n / z l / m i n of anterior c h a m b e r fluid into the general circulation.
Long-term exp¢,~ime~ts In a few m o n k e y s the anterior chambers were perfused with labeled a l b u m i n for 4 hr. The only results shown were the a m o u n t s of radioactive fluid recovered in t h e different tissues.
A uto~'adiogra~hy Some experiments were performed essentially as described pre~6ously, b u t again the time of the exi)eriments was longer. B o t h anterior chambers were perfused w i t h fluid contaiuing 13~I-albumin in t h e same concentration on both sides. After the anterior c h a m b e r h a d been washed t h r o u g h with unlabeled fluid the animal ~'as killed. The whole head was i m m e r s e d in --20°0 acetone for 30 rain ~tnd t h e n further cooled .ut --40°0 for 24 hr. The cannulas were t h e n r e m o v e d a n d the head was sectioned with the eyes in situ. The sections were collected on adhesive tape according to the technique described by Ullberg (1954). They were d r i e d for 24 hr. at --16°C, p u t on film a n d exposed for 48 hr. 3. Results
~1teans and. distmbutions T a b l e I s h o w s t h a t t h e v e r v e t m o n k e y s were bigger thar, t h e c y n o m o l g u s m o n k e y s . T h e a v e r a g e w e i g h t of t h e m a l e s was h i g h e r t h a n t h a t of t h e fem,~les in b o t h species. In female eynomolgus m o n k e y s more aqueous h u m o r passed into the uveoscleral r o u t e s t h a n in v e r v e t females, a n d t h e a r t e r i a l b l o o d p r e s s u r e was lower in t h e cylmm o l g u s m o n k e y s t h a n in t h e v e r v e t m o n k e y s . O t h e r w i s e , t h e r e were n o significant differences b e t w e e n t h e species or sexes. F i g u r e 1 shows t h e d i s t r i b u t i o n of t h e flow d a t a in t h e 2 species. I n b o t h , uveoscleral
Vqrv~.t$
20•. ~- Uveosclerol -- i
F_
i
i
£ i°,o Formot on of .i~~ bl°°d oqueous hurn~ur
flow
J5 F-I-I
Lu
Inn Cynomolgi Flow into I For,nctlon of
-"1
aqueoushumou~
blood
O
!
2
0
1
2
0
1
2"
/~l/min
l~to. I. D i s t r i b u t i o n o f t h e flow d a t ~ for o y n o m o l g u s a n d v e r v e t m o n k e y s . ~ ? o r m a t i o n o f aqur~ous h u m o r wa~ d e f i n e d a8 t h e s u m o f t h e o u t f l o w v i a t h e u v e o s c l e r a l r o u t e s a n d t h a g v i a ~ho c a n a l o f S c h l e r n m i n t o
blood.
AQUEOUS
HUMOI~
DYNAMICS
IN MO~KE~/'S
199
flow a p p e a r e d skewly distributed, b u t t o t a l r a t e of f o r m a t i o n of aqueous h u m o r appeared distributed in a fairly normal fashion. Figure 2 shows t h e frequency distribution of the intraocular a n d recipient venous pressures in t h e whole material. There was no significant change in intraocular pressure during the experiments.
~
"rn-rrT-rrr'~~
,5!
"
-i5 t0
L~
0
5 IO 15 InlraOCulor Dressure (mmHg)
0
5 I0 15: Venous pressure (mmHg)
20
F~o, 2, D i s t r i b u t i o n s o f the nlean i n t r a o c u l a r pressure a n d t h e reoipienb v e n o u s pressure in 94 v e r v e t a n d e y n o m o l g u s m o n k e y s . T h e m e a n i n t r a o e u l a r pressure was c a l c u l a t e d f r o m 7 r e a d i n g s d u r i n g the h o u r with flo~: d e t e r m i n a t i o n . H a t c h e d p a r t s o f t h e bars r e p r e s e n t d a t a for c y n o m o l g u s m o n k e y s .
The facility values, averaged in Table I, were those d e t e r m i n e d shortly a f t e r t h e eyes h a d been calmula.ted. I n the eyes perfused with inactive fluid for ?L-1.5 h r before the mixing with radioactive flttid the second facility d e t e r m i n a t i o n gave higher values t h a n the first o n e - - t h e average increase was 0.232=t=0-029 t z l / m i n / m m t t g (n = 62). The increase was n o t c o r r e l a t ~ to t h e s t a r t i n g facility. Figure 3 shows skew frequency distribution of the facility d a t a . I 1t25
2O
20
15
15
if-
i-~
10 .
,
0
5 10 15 Gross focility (pI.mln-l,mmHg -t)
Fzo. 3. D i s t r i b u t i o n o f the.fac.jlity values d e t e r m i n e d early in t h e e x p e r i m e n t s . ~ratc2aed p a r t e o f the bars r e p r e s e n t d a t a f r o m eyno~fmlgus m o n k e y s .
200
A.
BILL
Figure 4 shows a plot of the amount of labeled fluid recovered in the different tissues against the total amount recovered in the orbit. In the 60-rain experiments both in the iris and in t h e cornea about the samo amounts were recovered irrespective of the total amom~ts. In the 5iliary body and the anterior selera the~e is propox-~ionMity '-
30
I
I
Ciliary
I
I
Mean
body
i ..... F
I
i
weight of prep: 239+-24mgo
20 o
e
o
I0
•
i
6'1
•
•
e
~.:" 0 30
--
• 4
• s
J
i
--
Rest of the
o
I'
I
~
"I
I
i
!.
I
..... ,
,
=
e~e
20 0
I0
% •
0 30
•
•
I e
•
,~•
•
o
o
!°
1
I
i
l'~
Choroid-retino
20 e
I0
t
__~_~ '"t
•
,:;'-.,.-.
20
0
•
40 '
,
60
I'
i--
?,
I
. I00
80 '1 "
I
'
I0
weight
-
1
'
z6o
I
Mean
Cornea
.I
140
120
[8o
I
2.00
l
o f prep: 8 o 4 ± 4 r a g
o
a
5
4
eo
0 30
o
1 "" ."t" Anterior
sclera
Mean
20 t
.re
I
I
•
...
C 50
av'=-,'W",,p ,,
elj
t----f--=
w e i g h t o f p r e p : 1 5 5 +- 1 7 r a g o
•
o •
o o
10
o
o
•
:-.. t
Posterior
-
sclera
I .
1
i
I
I
|
Mean
1 "
I
i
w e i g h t %f prep: 1 4 6 ± 7 r a g
40
eo
30
o
zo •
e
n
I0 e o m.o
0
20
•
I
:'," :
40
e
60
80
I00
120
140
F z o . ~.---co~t~i~.t~d o ~ n e x t t~age
160
180
200
AQ.3EOUS
HU~,][OR
DYx~AMICS
IN
MONKEYS
2111
F I o . 4.--co~.$inuation from pret~ous page
/
901:'
Extr
I ' "l' ~ o-ocular tissues
t
"
l
j '-
~
.'
l
-
o
80 r 701_
°
_ o
•
60
-
50
o
-~40-
o
30-
o°
°
-
o
-
e
20-
"
-¢,
•
I0-
-
J
•
•
--..: :
"''"
--
•
.'.
I
0
Ir~s
•
0
""2 0 :'t:"" 40 GO
!
I
Mean weiqh, of
80 Total
I00 amourlt
t prep:
i 17 + Img
120 140 (41~l)
i60
180
1
200
~'i(;.-1. T h e a p p a r e n t a m o u n t o f r a d i o a c t i v e a n t e r i o r c h a m b e r f l u i d p r e s e n t i n v a r i o u s t i s s u e s p l o t t e d a g a i n s t t h e t o t a l a m o u n t o f r a d ! i o a c t i v e a n t e r i o r c h a m b e r f l u i d t h a t a p p e a r e d to bc p r e s e n t i n t h e c'yc a n d i t s a d n e x a . I n s e t are t h e w e i g h t s o f ~he p r e p a r a t i o n s . T h e r e s t o f t h e e y e p r e p a r a t i o n c o n t a i n e d vitreous humor and tissue fluid lost from the ocular tissues during dissection. The oxtraoeular tissue [ w c p a r a t i o J ~ c o n t a i n e d c o n n e c t i v e t i s s u o , e y e m u s c l e s a n d £a~ f r o m t h e o r b i t . T h e e h o r o i d . r e t i n a p r e p a r a tion could not be completely freed from vitreous humor. Q, Results from experimonts with radioactive a l b u m i n in t h e a n t e r i o r c h a m b e r for 1 h r ; O , r e s u l t s f r o m e x p e r i m e n t ~ w i t h l a b e l e d albu~rtin i n t h e a n t e r i o r c h a m b e r ]'~r 4 hr.
between the a m o u n t s recovered and t,he total a m o u n t s from very low to m o d e r a t e l y I~igh totals. The 4-hr experiments s h o w t'l~t steady levels are attained[ after some time. In the choroid-retina preparat, ion and in the posterior sclera small a m o u n t s were recovered if the total amouJlts were low, but from ~bout 20 td total the a m o u n t s in the 2 tissues increased. The a m o u n t s recovered in the extraocular tissues varied greatly. The autoracliogTaph in ]?late 1 shows more closely t h e location of labeled a l b u m i n after 2 and 4 hr of anterior chamber perftLsion in a m o n k e y w i t h rapid uveoscleral flow. After 2 ttv large a m o u n t s of labeled pro~etu can be seen in almost the w h o l e choroid and sclera, a n d after 4 hr there was a large a m o u n t of protein in the episclerM tissues• W h e n this t e c h n i q u e was used very little labeled material was recovered in the ciliary In'accuses in all experiments.
Correlations There w~s a rather considerable scatter of values for m o s t variables and m o s t correlations in the different, subgroups, male vervets, female vervets, etc., are o f •doubtfifl statistical sign! .fi~nce.
202
A. B I L L
lWigure 5 shows f~he combined correlation coefficients (Snedecor, 1961, p. 178) calculated from the correlation coefficient~ for each of the 4 subgroups, male ~-ervets, female vervets, male cynomoIgi and female cynomolgi. In female cynomolgus monkeys there was a significant correlation, P < 0 . 0 1 , between the weight and the intraocular pressure. In ~he various other subgroups !1 ° :c
c
' lJ
-
]
j]
pressure
Jl Fno. ,n,o I ~ 1 U veo-sc~ era~ [L - b~ood J ] II ~
r. . . .
l
pressure
~I
I~ . ....
Ou~tlow pressure
{
1
I I
F'ormotlon of oqueou.S h u m O r
I
-
1
!
t. Recipient venous pressure
1-~o. 5. S c h e m a t i c p r e s e n t ~ t i o n o f t h e relationsb~.ps b e t w e e n the various variables s~udied. Boxes w i t h d o u b l e walls r e p r e s e n t v a r i a b l e s that. were d e t e r m i n e d i n d e p e n ( l c n t o f each or,her. ~Boxes with single walls r e p r e s e n t variables c a l c u l a t e d f r o m ~he d e t e r m i n e d ones. Figtu.es represent, eombine~[ correlation coefficients for t h e 4 groups, male a n d f e m a l e c]nlomo]gi a n d vervets. *, Correlat,ion ~v-as p r o b a b l y significant, ~ 0 - 0 5 ; * * , correlation was significant, P < 0 . 0 1 . Solid lines c o n n e c t correlated variables, b r o k e n lines c o n n e c t variables calculated from e x p e r i m e n t ~ H y d e t e r m i n e d variable~ a n d t,he variables used in t h e caleula~ior~. 3-0
i
u-
;
=
i
~ I
;
I
|
i
I
!
"'
J
,~3"G
i
2-5
2-5 o o
-~
"~
-t2-0
20 o o
N
._o 1-5
ip
i
•
~
•
%
1:2 "lllm I i
0
~-
1.0
-
•
•
13
•
ooo
~%
•~ I-5
3- ! -I
o m
t
o
o
-'110 -o
_
"~ •
•
at t
•
o
o
•
0
"- I
o
~o QQ
.
e
o
0"5
"']
4
~
°"
go
o ~ o
---I 0 "~ I
Q
~
o
!
! ~
i
_-0
-'
i
,
! t 0"5
!
~ ;
Uveo;clercl
I n t I'0 l',ow
t
I
1
1.5
I
33 2"0
'-'/~:"~
FIo. 6 . T h e r a t e o f flow via t h e c a n a l o f S c h l e m m into t h e general circulation was plot.,ted against t h e flow fihrough uveosoleral r o u t e s . 94 ]kEon~eys w e r e used, 0 , V e r v e t s ; O , eynomolgi.
~{~o~ ".H{~ .~oj oXa 'l.tl~!a otI:~ '.tq ~ ,~o$ u ! u m q l u] 1 ~,:~'[j o uo!lnlOS "a tl~,!,l~ l>OS~g.t,~d s~.'~..~a,ltU P.tl-~ .~o[.~;~+lut: lJa[ •"~|,L -uo!,~oa.,¢ Oil!. j:o ~.ldu.~,o!pe.;'o:~t~t¢ ue i>tt~ p~+~t t ;q~t,,,:,tt~ ~n~lomO:~Xo tt t!~t'~o,tt D u o ! ~,~:~ \-" "I :~,~.x:~¢![
•
.
.~
...+
, .:/i: '+ ~ ....
.
"."
.
:.:
•
, ,
;'
•
"
-
~
I
,
•
~
.
• . . . .
..
~i
"IJ~2
-
:-:, .!..
,
.~:'. ~
:
"
=
'
~
.~
"
~
'
-.~i:?.":.. +.I!}I:~...I+~iI}.5:/?:!.5~!._
~
~
~- ~
~
<
.=
•
2. +
+.;~+,
~-~l~''~:-'~'--'~\"~?~@~m'';~'~"\
; ~+,~,
'~
AQUEOUS
HUMOR
DYNAMICS
IN /~IONKEYS
203
there was a t e n d e n c y to correlation, and the combined correlation coefficient for the four groups is significant. The average weighted slope of the regression line (Snedecor, 1961, p. 394) was 0-92 m m H g / k g b o d y weight. The mean arterial blood pressure (MAP) was correlated to the b o d y weight (W) in the male vervets, P < 0 . 0 1 , M A P ----9-36 × W ÷ 59-4. There also was a tendency to a correlation in the other subgroups, and the combined correlation coefficient for t h e 4 groups is significant. There is a p r o b a b l y significant correlation between arterial b]opd~pressure a n d intxaocular pressure. An analysis of partial correlations showed, h o t ' e v e r , t h a t tiffs is due to the colTelations between weight a n d intraocular pressure, a n d weight and arterial blood pressua'e. The're is a p r o b a b l y significant negative correlation, P < 0 - 0 5 , between t h e flow into tJae general circulation a n d uveoseleral flow in both the c y n o m o l ~ a n d the vervets. The combined correlation coefficient is significant, P < 0 - 0 1 . Figure 6 shows a plot of the d a t a for the flow into the canal of Sctdemm, a n d t h a t thJ:ough the uveoscleral routes. In female c~momolgus monkeys there was a significant positive correlation between the outflow pressure and the intraocular pressure, P < 0 . 0 1 . The combined emaciation coefficient for t h e 4 groups is p r o b a b l y significant. The recipient venous pressure was calculated as the intraocular pressure minus the outflow press~ure. Since in most m o n k e y s the outflow pressure was small, the intraocular pressure was d e p e n d e n t mainly on t h e recipient venous pressure. 4. Discussion
Thc for, naeio~ of a~ueous humor The results r e p o r t e d here show t h a t the r a t e of formation of aqueous h u m o r v~rles greatly from one individual to another, a n d t h a t the main reason for the variability was not among t h e p a r a m e t e r s studied. The, draiT~age of aqueous humor
Since the original o b s e r v a t i o ~ (Bill, 1965) t h a t in perfused dead m o n k e y eyes some fluid passes f r o m t h e antcridiY-chamber t h r o u g h the ciliary mrlscle into the suprachoroid and ou~ t h r o u g h the sclera t h e r e h a v e been several in' vivo studies of this uveosc!eraI flow (Bill a n d I-Iellsing, 1965; Bill 1966, 1967a,b, 1969, 1970). I n vivo, on its w a y t h r o u g h t h e tissues, t h e anterior c h a m b e r fluid becomes m i x e d w i t h the tissue fluid in the u v e a a n d there is, of course, exchange of m a t t e r with t h e nveal b l o o d vessels. This m i g h t result in n e t resorption of t h e low molecular weight constituents of t h e anterior c h a m b e r fluid. I f such resorpt~ion were ma~ked, t h e concentration of labeled albumin in t h e tissues sholfld rise to high levels, which should give lmreasona b l y high values for t h e a p p a r e n t content of anterior c h a m b e r fluid in the tissues, t h a t is, values such as 1000/~l/g a n d more. A comparison of a p p a r e n t contents o f anterior chamber fluid in t h e various tissues a n d t h e tissue weights (Fig. 4) shows t h a t this was not the ease for a n y of the tiss,~s, w h i c h indicates t h a t there is, in fact, a n e t flew both of colloids a n d of low: molecular weight substances f r o m t h e anterior c h a m b e r t h r o u g h t h e uveoseleral routes i n t o t k e episcleral tissues. :Figure 4 indicates tha~ ~ ' 6 tia~ues b e c a m e loaded wi~h t h e radioactive albumin
204
A. BILL
from the anterior c h a m b e r in the following order: (1) anterior u r e a ; (2) choroid, anterior sclera; (3) posterior sclera; a n d (4) episcleral tissues. However, in some experiments relatively large a m o u n t s of aqueous h u m o r were recovered in the extraocular tissues in spite of a r e l a t i v e l y low t o t a l uveoscleral flow. I n these animals there was p r o b a b l y a considerable flow of aqueous h u m o r From t h e tissue spaces of the ciliary muscle via perivascular spaces into ~he extraocu]ar tissues. Evidence indicating or supporting the hypothesis of net flow of aqueous h u m o r into the ciliary muscle has been reported b y Leber (1907), Fine (1964), Wolf (1965), McMaster a n d Macri (1968). T h a t some fluid m a y leave the anterior chamber via perivaseular spaces was reported b y Leboucq (1914) and confirmed b y Fowlks, ]ffavener a n d Good (1963). The autoradiographs showed t h a t v e r y little labeled material was located in the ciliary processes. This indicates t h a t there was no or little net flow of tissue fluid from t h e ciliary mu.scle into tbe ciliary processes. The uveoscleral routes a n d the routes via Schlemm's canal are alternative p a t h w a y s fox" aqueous outflow. As could be expected there was ~ negative correlation between the 2 variables. T h e iris. The role of the iris in aqueous h u m o r ~lynamics is as y e t obscure. I t can, of course, be presumed t h a t there is either net flow of water into the iris or net outflow From. it. Zero flow is incidental. ~rhen small particles were injected into the anterior c h a m b e r t h e y could be seen in the walls of the iris capillaries within pinocytotic vesicles (Fine, 1964) b u t t h e bulk m o v e m e n t of aqueous h u m o r with this mechanism seems to be quite small b o t h in rabbits a n d monkeys. I n the former sloccies when labeled albumin is introduced into the anterior chamber, very little passes directly from t h e ocular tissues into the blood draining the vortex veins (:Bill, 1962). In the l a t t e r species when aqueous h u m o r drainage into the general circulation is stopped 1)y low intraocular pressure there is negligible m o v e m e n t of labeled albumin into the uveal blood vessels (Bill, 1967a). I t m a y be concluded t h e n t h a t the mechanism t h a t probably dominates the bloodaqueous exchange in the iris is ultrafiltration a n d diffusion through narrow pores. This will tend to give accnmulation a t absorbing p a r t s of the blood vessels of high molecular weight substances a n d particulate material introduced into the anterior chamber. Such accumulation, therefore, can give no information a b o u t the net effect of the iris vessels. The a m o u n t of labeled albumin recovered f r o m the iris in all experiments was small, a n d in the calculations of uveoscleral flow it contributed only 0 . 0 3 / z I / m i n . . a l l this m a y no doubt h a v e been due to diffusion or flow towards rcsorbing p a r t s of the capillaries. This effect is included under uveoscleral flow s i n c e it cannot be d i s t i n ~ d s h e d f r o m such flow. I n m a n , Frangois, Neetens, Leroux a n d Colette (1967) h a v e described a system of channels in t h e iris, which t h e y consider involved in uveoscleral drainage. T h e cornea. The labeled material recovered f r o m the Cornea corresponded to a bulk flow of anterior c h a m b e r fluid into the cornea of 0-02 tzl/min. I t is n o t clear to w h a t . e x t e n t this a p p a r e n t flow was due to diffusion of labeled material into t h e c o r n ~ a n d to w h a t e x t e n t it was due f~ pinoc:~bosis of anterior c h a m b e r fluid constituents ( K a y e a n d P a p p a s , 1962). This effect is also included lmder uveoscleral flow.
The rise in facility w i t h Lime t h a t was observed in m a n y experiments n m y h a v e been due~to an increase in t h e tone o f the .ciliary muscle. I f Changes in tone are pre-
AQUEOUS I~IU:~IOR DYNAMICS IN MONKEYS
205
vented b y atropine, there is no sig~lificant change in facility with the technique used herb (Bill, 1969). The m e a n values for the gross facility agree very well with previous figures (B£r~ny, 1966; Edwards, i a l l m a n and Perkins, 1967; Hoffman, 1968) a n d the frequency distribution was similar to t h a t in previous studies in monkeys (B~rhny, 1966) a n d h u m a n s (Prijot, 1961). Reciipient venous pressure and intraocular pressure A correlation in m a n between intraocular pressure a n d epis~ieral venous pressure was reported b y Weigelin and :LShlein (1952). I n the present e~pe,~iments t h e recipient venous pressure was calculated from the intraocular pressure, ~h~ r a t e of outflow via Schlemm's canal a n d t h e facility of outflow. The calculated pressure is n o t representative for the actual pressure in a n y special p a r t of the intro,- or episcleral veins; it give~ a value for the average effective recipient venous pres~3ure. I t is not ]cnown a t present, however, whether or not using the facility calculatecl from periods with elevated pressure in the determination of P~ is fully justifi~.,d. This value, therefore, m a y h a v e a systematic el~or mal~ing it somewhat too low or too high. Still, it is clear t h a t in monkeys the venous pressure is the most i m p o r t a n t of the factors t h a t influence intraocul~r pressure. The positive correlation found between i n t r a o c u l a r pressur~ a n d weight of t h e animals in this stud), helps to explain the difference betwee:a m e a n intraocular pressure in the eyes reported on here and in a series reported b y H o f f m a n (1968). H o f f m a n , working with big cynomolgus m o n k e y s (2-85-7-5 kg), ~bund intraocular pressures around 12-13 nunHg, t h a t is a b o u t 2-5 mm/=Ig higher t h a n in the cynomolgl~s m o n k e y s reported here. '['here was no significant difference between the intraocular pressures in v e r v e t m o n k e y s in the present material a n d those, in a previo~m, larger series reported b y Bhrhny and l~ohen (1963). Intraocular ]~vmeostx~sis T h e results reported here m a k e it t e m p t i n g to specr~late somewhat a b o u t the needs a n d evidence for an extraocular regulating mechanism involved in t h e m a i n t e n a n c e of ocular homeostasis. There was no correlation between the rathe of flow v i a Schlemm's canal a n d t h e facility of outflow such as one would, h a v e e:~pect~d if a low flow gave a reduct4on in facility to m a i n t a i n the outflow pressure a t a certain value. Th6re also was no correlation between r a t e of secretion a n d intraooular pres.,,ure such as'one would h~ve expected if there was a mechanism sensing pressure a.ud adjusting secretion to keep t h e pressure within a certain range. Fvxthermore, t~te secretion was so va1'iable t h a t it seems unlikely tl~at there is an accurate extex~az,1 m e c h a n i s m t h a t a d j u s t s s e c r e t i o n according to infol~nation from intraoeular receptors. I n addition, there is no obvious need for a v a r y i n g r a t e of aqueous secretion. O n e could imagine t h e n t h a t the eye h a s a v e r y high degree of a u t o n o m i c i t y , t h a t is, there !Lsno e x t r a o c u l a r m e c h a n i s m t h a t gets information a b o u t the intraocular pressure or t h e r a t e of aqueous secretion a n d t h a t adjusts secretion r a t e or outflow facility or recipient v e n o u s pressure according to a scheme. This, of course, does n o t m e a n t.hat t h e e y e is unresponsive to stimuli such a s autonomic nerve a c t i v i t y a n d h o r m o ~ s , b u t such external influences do n o t seem to be involved in a feedback r e g u i a t i 0 n i n v o l v i n g i'atraocular receptors. !Stimulation of certain areas in t h e h y p o t h a l a m u s h a s been reported to produce Changes-in i n t r a o c u l a r . ~ s u r e w i t h o u t ac,compan~dn'g changes in blood pressure
206
A. B I L L
(yon Salhnann and L S w e n s ~ n , 1955; Gloster and Gre~ves, 1957), but it remains to be determined if the area stimulated is a regulating center and, i f this is the case, whether or not it is influenced b y intraoeular receptors. The fact t h a t a rise in intraocular pressure m a y produce a- sustained discharge in the ciliary nerves (yon Sallmann, Fuortes, Maori and Grimes, 1958) is au argument suggesting t h a t the autonomicit, y hypothesis m a y be an ovex~implification. I t is interesting, however, t h a t there s6ems to be no pathologieM condition t h a t indicates clearly the involvomertt of an extraocular center regaflating the eye pl~ssttl:o or the rate of aqueous secretion according to information derived from intraocular receptors. ACKNOWLEDGMENTS Th~s work was supported by a g r a n t (B 71-14X-147-07) from the Swedish Medical Research Council a n d by a grant (EY 00475) from the National Eye Institute, U.S. Public H e a l t h Service. I wish ~ t h a n k Miss A n i t a Persson, Miss Monica Thor~n and Ing. Hans Sundberg for their valuable tectmical as,~istance. REFERENCES
Blir~ny, E. H. (1964). Invest. 029hthalmol. 3, 135. B£r~ny, E. FI. (1966). Trans. Oph¢halmol. Soy. U.K. 86, 539. B~rhny, E. H. and Rohen, J. W. (19637. Arc~. Ophthalmol. 69, 630. Bill, A. (!962). Exp. Eye 2 ~ . 1, 200. Bill, A. (19C-5). lnv,'zt. OptdhalmoL 4, 911. Bill, A. (1966). Exp. Eye Res. 5, 45. Bill, A. (1967a). [rivet. 02~hthalmol. 6, 364. Bill, A. (1967b). Exp. Eye Res. 6, 120. Bill, A. (1968). Inv~t. Ophthalmol. 7, 162. Bill, A. (1969). Exp. Eye Res. 8, 284. Bill, A. (19707. Exp. Eye Res. 10, 31. Bill, A. and B~r~ny, E. H. (1966). Arch. OphthalmoL 75, 665. Bill, A. and H611sh~g, K. (1965). InvesL O,vkthalmol. 5, 920. Edwa,-xts, 1., Hallman, V. and Perkins, E. S. (1967). Ea.'p. Eye Res. 6, 316. Pine, B. S. (19647. Invest. Ophthalmol. S, 609. Fowlks, W. L., Havener, V. and Good, J. S. (1963). Inv6s$. Ophthalraol. 2, 63. Francois, J., Neetens, A., Leroux, G. and Colette, J. M. (1967). Optdhal~mloglca 153, 215. Gloster, J. and Gre~ve~, Do P. (19577. Brit. J. OphthalmoL 41, 513. Hoffman, F. (19687. Exp. Eye Res. 7, 369. Kaye, G. I. and Pappas, G. D. (1962). J. Cell Biol. 12, 457. Leber, Th. (1903). In Graefe-Saemlsch: tlandbuvh der gesamten AugenheilkuTMe, I I Abt. II, Leipzig. Leboucq, O. (1914). Arch. Biol. 29, 1. ]~IcMaster, P. R. B. and ~[aeri, F. J. (19687. Arclt. 0tz~thalmol. 79; 297. Priiot, E. (19617. Doe. 029hthalmoL 15, 1. yon Sallman, L. and L6wenstein, O. (1955). Amer. J. Oph~hvdmol. 39, Part II, 11. yon Sallmarb L., Fuortes, hi. G. F., Mac~, ~. J. and Grimes, P. (1958). Amer. J. Opl~halmol. 45, Par~ II, 211; Snedeeor, G . W . (1961). 8tatizt~cal ~[ahods, 5th eel Iowa State University Press. Ullberg, S. (1954). A c ~ t~xllol. Suptgl. 118. ~'eig~lin, E. ~nd Lfhlein, H. (19527. Albrecht Graefes Arch. Kli,n. Exp. O:ph~halnml. 1SS, 202. Wolf, J. (1965). FoIia Mor'jphol. 13, $28.
11, 195-206
Aqueous Humor Dynamics in Monkeys (Macaca irus and Cercopithecus ethiops) _A~DERS :BILL
Department of Experimental Ophthalmology, Institute of Pharmaz~!ogy, University of Up,vsala, Uyrpsala, Sweden (Received ld Septen~er 1970, Boston) - T h e ineraoeular pressure, t h e gross facility of outflow, the rate of flow of anterior c h a m b e r fluid into t h e general circula.tion via. S c h l e m m ' s canal and t h a t into uveoscleral r o u t e s were detemnined in a total of 94 veto,or a n d cbmomolgus m o n k e y s u n d e r general anesthesia. The n e t rate. of f o r m a t i o n of aqueous h u m o r , the outflow pressure a n d the recipient venous pressure were calculated. There were significant positive correlatiohs between weight a n d intraocutar pressure a n d between weight a n d arterial blood pressure. A probably significant, positive correlation was found between out,flow pressure a n d intraocalar preasure. There was a negative correlation bet~vecn uveoscleral flow a.nd flow vi~ S c h l e m m ' s canal. T h e rate of aqueous f o r m a t i o n was n o t significantly correlated to the b o d y weight, the gross facility or the intraoeular pressure. T h e results indicate t h a t uqueous h u m o r pa.~ing into t h e uveoscleral routes fIx>m the anterior c h a m b e r is modified in the u r e a , seeps ,through t h e selera and is t h e n reaorl)ed into 15~mph and blood vessels outside t h e eye. No indications were f o u n d for an extraocular regulating center that, receives inYormation a b o u t t h e conditions in t h e eye and t h a t adjusts flow rates, facility or prez~ureB. 1. I n t r o d u c t i o n
During the last few years monkeys have been used at this laboratory in studies on aqueous humor dynamics. It was found that if an ineffective dose of a drug was applied to one eye and the other eye served as a control there was little difference between the eves in all pare.meters studied. It was also fomxd, however, that there are l a r g e d i i ~ h r e n c e s b e t w e e n the. e y e s o f d i f f e r e n t a n i m a l s . E a c h o f t h e s t u d i e s m e n t i o n e d comprised too few animals to permit an analysis of the interindividual variability and the type of statistical distribution of the parameters studied. The purpose of the p r e s e n t c o m m u n i c a t i o n is t o a n a l y z e s o m e w h a t t h e v a r i a b l e s s t u d i e d : a n d d i s e n t a n g l e relationships by using a larger material. Some of the eyes included are control eyes f r o m p r e ~ i o u s s t u d i e s alre~udy re,p o r t e d , O t h e r s a r e s u c c e s s f u l c o n t r o l e y e s i n e x p e r i ments in which the "treated eye" for technical reasons was .regarded as u~uccessful; t h e r e a s o n b e i n g , e.g. t h a t t h e c a n n u l a s u s e d t o u c h e d t h e iris, wc~e t o r n o u t o f t h e anterior chamber during the experiment, or that the mechanical device connected to the anterior chamber proved lealry at the end of the experixnent, when it was r e t ~ s t e d . S t i l l o t h e r e y e s a r e f l ' o m a n u n s u c c e s s f u ! ,';~ady o f t h e e f f e c t s o f c y c l o d i a l y s i s ; i n m o s t e a s e s t h e cleft, i n t h e o p e r a t e d e y e h e a l e d , O n l y t h e c o n t r o l e y e s o f t h a t staady a r e i n c l u d e d . T h e f o l l o w i n g v ~ r i a b l e s w e r e determi:.~,~cl: l:ociy w , . i g h t , m e a n a r t e r i a l b l o o d p r e s s u r e , i n t r a o c u l a r p r e s s u r e , g r o s s f a ~ i l i t . y o f c~utfio~:~ b l ~ k t~ow o f a q u e o u s humor into the general circulation and bulk flow of aqueous "~x~ar -n~ uve~)sclerat r o u t e s . T h e r a t e o f a q u e o u s h u m o r , f o r m a t i o n w a s d e f i n e d e,s tl_*,e ~u:~ ¢,f t h e b u l k o u t f l o w t,h r o u g h t h e d i f f e r e n t r o u t e s ~ o m t h e a n t e r i o r c h a m b e r . I~_ezc, t h e t~.r~, b u l k f l o w m e a n s f l o w o f a n t e r i o r C h a m b e r f l u i d t h r o u g h p o r e s b i g e n o u g h ~',~ ~9 r e s ~ i c ~ the passage of albundn.,. 195
196
A. BILL
2. M a t e r i a l s and M e t h o d s T h e a n i m a l s u s e d were W e s t Afri.c.~:n v e r v e t s (Cercol~ithevus elhiol"~s) a n d c y n o m o l g u s m o n k e y s ( M a c a c a irus) o b t M n e d f r o m - v a r i o u s sources. All a n i m a l s w e r e a p p a r e n t l y in g o o d h e a l t h ; t h e i r age was n o t k n o ~ m b u t t h e m a j o r i t y c a n be p r e s u m e d to h a v e b e e n y o u n g a d u l t s . F o r t y - e i g h t of t.~.e v e r v e t s w e r e males, 12 w e r e f e m a l e s a n d in 3 cases t h e sex was n o t n o t e d . I n t h e c y n o m o l g u s g r o u p t h e c o r r e s p o ~ d i n g figures w e r e 9, 18 a n d 4, r e s p e c t i v e l y . I n m a n y e x p e r i m e n t s t h e a n e s t h e s i a was i n d u c e d b y i n t r a m u s c u l a r s o d i u m m e t h o h e x i t a l (Brietal, Lilly), 20 m g / k g b o d y w e i g h t . I n others, i n t r a v e n o u s s o d i u m p e n t o b a r b i t a l w a s used t o i n d u c e a n e s t h e s i a . I n all e x p e r i m e n t s a n e s t h e s i a w a s m a i n t a i n e d w i t h s o d i u m p e n t o b a ~ b i t a l g i v e n t h r o u g h a c a n n u l a t e d t a i l vein. S m a l l doses w e r e g i v e n e v e r y 1 5 - 3 0 nfin to p r e v e n t u n n e c e s s a r i l y d e e p a n e s t h e s i a . Artificial r e s p i r a t i o n was n o t u s e d in a n y of t h e e x p e r i m e n t , s. T h e a n i m a l s w e r e p l a c e d p r o n e wiT,h t h e h e a d s u p p o r t e d in s u c h a w a y t h a t t h e p u p i l s w e r e 11 c m a b o v e t h e t a b l e . A h e a t i n g p a d w a s used to keep the animals warm. M e a n a r t e r i a l blood p r e s s u r e in a c a n n u l a t e d femora.l a r t e r y was d e t e r m i n e d b y m e a n s of a p r e s s u r e t r a n s d u c e r . T h e e y e wa~ c a n u u l a t e d w i t h 3 c a n n u l a s t h a t c o n n e c t e d the a n t e r i o r c h a m b e r to a p r e s s u r e t r a n s d u c e r and. a r e s e r v o i r , t h e w e i g h t of w h i c h w a s d e t e r m i n e d c o n t i n u o u s l y , a n d to 2 p u s h - p u l l c o u p l e d syringes. T h e reservoir a m l t h e t u b i n g c o n n e c t i n g it to t h e a n t e r i o r c h a m b e r c o n t a i n e d a s o l u t i o n d e s c r i b e d b y B h r h n y (1964). This fluid w a s also the basal fluid in t h e syringes. T h e p H was 7"0. T h e gross f a c i l i t y of outflow (Bill a n d B~r,~ny, 1966) w a s d o t e r n f i n e d b y m e a s m ' i n g t h e r a t e of inflow f r o m t h e r e s e r v o i r w h e n i t was p l a c e d so as to give a n i n t r a o c u l a r pressure t h a t w a s 2 - 3 m m H g h i g h e r t h a n t h e r e s t i n g i n t r a o c u l a r pressure, a n d s u b s e q u e n t l y a t a level g i v i n g a.n i n t r a o c u l a r p r e s s u r e {.ha~ was still 7.4--9.4 m m H g higher. A f t e r t h e f a c i l i t y of outflow h a d b e e n d e t e r m i n e d the eye p r o c u r e was a d j u s t e d to it~ r e s t i n g level a n d t h e reservoirs w e r e d i s c o n n e c t e d w i t h c l a m p s . T h e n t h e a n t e r i o r chaI,.:.,., c o n t e n t s w e r e m i x e d w i t h t h o s e of t h e syringes. I n ~ o m e cases the flu.id c o n t a i n e d a l b u m i n labeled w i t h 1slI or 1~I ( p r o t e i n c o n c e n t r a t i o n a b o u t 0"1~/o), in others it c o n t a i n e d no l a b e l e d m a t e r i a l a t this stage. I n t h e l a t t e r ease a f t e r 1--1-5 h r of c o n t i n u o u s m i x i n g a t a r a t e of a b o u t 0"5 m l / m i n , a n o t h e r f a c i l i t y d e t e r m i n a t i o n was m a d e . The eye p r e s s u r e was then ad~ted to its r e s t i n g level a n d t h e t u b i n g s to t h e reservoirs w e r e c l a m p e d . The anterior c h a m b e r contents were then mixed with the radioactive albumin solution t h a t had b e e n l o a d e d i n t o t b e syringes. A f t e r "1 h r of c o n t i n u o u s nfixing of t h e a n t e r i o r c h a m b e r fluid a n d t h e r a d i o a c t i v e cont e n t s of t h e syringes, or m i x i n g e v e r y 5 rain, t h e r a d i o a c t i v e fluid in t h e a n t e r i o r c h a m b e r was r e p l a c e d b y i n a c t i v e fluid, a n d a b o u t 5 n~iu l a t e r t h e m o n k e y w a s killed a n d t h e eye a n d it~ a d n e x a w e r e dissected. I n 8 e x p e r i m e n t s in v e r v e t m o n k e y s t h e d i f f e r e n t p a r t s of t h e e y e s w e r e weighed. D u r i n g t h e h o u r w i t h r a d i o a c t i v e fluid in the a n t e r i o r c h a m b e r b l o o d s a m p l e s were t a k e n a t l e a s t e v e r y 30 rain a n d safflples were t a k e n of t h e fluid i n t h e s y r i n g e s u s i n g a m i c r o m e t e r f i t t e d t o one of t h e m . To c a l c u l a t e t h e r a t e of flow of a q u e o u s h u m o r i n t o t h e g e n e r a l c i r c u l a t i o n (see Bill 1967a) i t w a s n e c e s s a r y to _know' t h e v o l u m e of d i s t r i b u t i o n of t h e labeled a l b u m i n . I n some e x p e r i m e n t ~ t h i s v o l u m e wan d e t e r m i n e d as d e s c r i b e d p r e v i o u s l y (Bill, 1967a). I n o t h e r s it w a s assumecl to r e p r e s e n t 7-2~/6 of t h e b o d y w e i g h t . This was t h e a p p r o p r i a t e v a l u e a c c o r d i n g to a n earlier series of e x p e r i m e n t s (Bill, 1966). T h e r a t e o f u v e o s c l e r a l t t o w w a s c a l c u l a t e d f r o m t h e a m o u n t of r a d i o a c t i v e p r o t e i n r e c o v e r e d i n t h e eye arLd t h e adnexa~ (Bill, 1967a): T h i s m a y give a n o v e r e s t i m a t i o n of u v e o s c l e r a l flow, as will be d i s c u s s e d below. T h e r e c i p i e n t v e n o u s p r e s s u r e , P~, i n m m H g was calmflated, using t h e formuJ.a Pv = IOP--Fbz/(C.--0-06) (1) w h e r e I O P was t h e m e a n i n t r a o c u l a r pressure i n m m H g d a r i n g t h e h o u z w i t h r a d i o a c t i v e
,
~Ialo vervets n = 48
Female vervcts "t = 12
All vervets ~z= 63
2.51 +0.13 3.304-0.16 2-80~0.16 3.18~0-13 80.0±1.3 90.3~2,6 103.6-t-4.5 9-°.6±2.3 9.924-0.57 9.55,-4-0.41 9.91~1.11 9.70-;-0"38 0"79:t=0"10 1.12_-1:-0.06 1.08-4-0.09 1.11.-t=0.05 0.96-4-0-07 0.70=t=0-06 0.50~0.I0 0,65~0.05 1.75±0.09 1,79=t=0-07 1,57.-J=0.11 1.73=]=0.0B 0,504 J= 0.045 0-507:t=0.024 0.4'/74-0.058 0.495~0,021 0.444-.J=0,045 0.447~0.024 0.417-/-,0.058 0.435~0.021 2,064-0.15 2.22=1=0-33 1.834-0.15 o..61-:-0,382 ' , , 7.574-0-53 7.75-4-0.4.1 7.29:i:0.94 7.64__.0.69
All cynomolgi n = 31
t L .
Figures represent arit~)~,~.~ .... -- ....4;. _,~,~,,s ....... -~_:S.E.
2.40-+-0.09 80 1~1.1 9,22-4-0.59 0,764-0"12 1.09:~:0.09 1.84~0.11 0,445±0-043 0-3S5+0.043 2.47±0.41 6.69+0.50
2.87-4-0-12 81.S4=3,5 9.85±1.17 0.86±0-23 0.8I~0-14 1.674-0-22 0.470=t=0"080 0.410=t=0.080 2-534-0-76 7.30:[:0.93
*n = '.Number of animals.
Body weight (kg) Mean art. pressure (wm/-Ig) , In~.ocular p~essure (mmHg) F!o~v into blood (ttl × mhl-~) Uveoscleral flow (gl × rain -t) :Net formation of aqueou~ humor (gl ×rain -~) Grosa facility (~l × rain -1 × mmHg-x) Truo facility (gl × rain-~ × mmttg -~) Outflow I)ressu~ (mmHg) Recipient, venous pressure (mmHg)
Female c3nmmolgi n = 15
Male eynomolgi n*=9
i J
T.~ BLE I
198
A. BILL
solution in the anterior chamber. The pressure was r e a d every 10 rain. C~ was the gross facility of outflow in izl/min/rnmHg d e t e r m i n e d just before t h e anterior c h a m b e r fluid was replaced with radioactive fluid. The facility of outflow via S c h l e m m ' s canal is lower t h a n the gross facility (Bill and B~r~lny, 1966). I n anesthetized animals with a blood pressuze of a b o u t 85-95 m m t t g t h e difference is about 0.06 i z l / m i n / m m H g (Bill, 1967a, 1968). FH was the rate of flow i n / z l / m i n of anterior c h a m b e r fluid into the general circulation.
Long-term exp¢,~ime~ts In a few m o n k e y s the anterior chambers were perfused with labeled a l b u m i n for 4 hr. The only results shown were the a m o u n t s of radioactive fluid recovered in t h e different tissues.
A uto~'adiogra~hy Some experiments were performed essentially as described pre~6ously, b u t again the time of the exi)eriments was longer. B o t h anterior chambers were perfused w i t h fluid contaiuing 13~I-albumin in t h e same concentration on both sides. After the anterior c h a m b e r h a d been washed t h r o u g h with unlabeled fluid the animal ~'as killed. The whole head was i m m e r s e d in --20°0 acetone for 30 rain ~tnd t h e n further cooled .ut --40°0 for 24 hr. The cannulas were t h e n r e m o v e d a n d the head was sectioned with the eyes in situ. The sections were collected on adhesive tape according to the technique described by Ullberg (1954). They were d r i e d for 24 hr. at --16°C, p u t on film a n d exposed for 48 hr. 3. Results
~1teans and. distmbutions T a b l e I s h o w s t h a t t h e v e r v e t m o n k e y s were bigger thar, t h e c y n o m o l g u s m o n k e y s . T h e a v e r a g e w e i g h t of t h e m a l e s was h i g h e r t h a n t h a t of t h e fem,~les in b o t h species. In female eynomolgus m o n k e y s more aqueous h u m o r passed into the uveoscleral r o u t e s t h a n in v e r v e t females, a n d t h e a r t e r i a l b l o o d p r e s s u r e was lower in t h e cylmm o l g u s m o n k e y s t h a n in t h e v e r v e t m o n k e y s . O t h e r w i s e , t h e r e were n o significant differences b e t w e e n t h e species or sexes. F i g u r e 1 shows t h e d i s t r i b u t i o n of t h e flow d a t a in t h e 2 species. I n b o t h , uveoscleral
Vqrv~.t$
20•. ~- Uveosclerol -- i
F_
i
i
£ i°,o Formot on of .i~~ bl°°d oqueous hurn~ur
flow
J5 F-I-I
Lu
Inn Cynomolgi Flow into I For,nctlon of
-"1
aqueoushumou~
blood
O
!
2
0
1
2
0
1
2"
/~l/min
l~to. I. D i s t r i b u t i o n o f t h e flow d a t ~ for o y n o m o l g u s a n d v e r v e t m o n k e y s . ~ ? o r m a t i o n o f aqur~ous h u m o r wa~ d e f i n e d a8 t h e s u m o f t h e o u t f l o w v i a t h e u v e o s c l e r a l r o u t e s a n d t h a g v i a ~ho c a n a l o f S c h l e r n m i n t o
blood.
AQUEOUS
HUMOI~
DYNAMICS
IN MO~KE~/'S
199
flow a p p e a r e d skewly distributed, b u t t o t a l r a t e of f o r m a t i o n of aqueous h u m o r appeared distributed in a fairly normal fashion. Figure 2 shows t h e frequency distribution of the intraocular a n d recipient venous pressures in t h e whole material. There was no significant change in intraocular pressure during the experiments.
~
"rn-rrT-rrr'~~
,5!
"
-i5 t0
L~
0
5 IO 15 InlraOCulor Dressure (mmHg)
0
5 I0 15: Venous pressure (mmHg)
20
F~o, 2, D i s t r i b u t i o n s o f the nlean i n t r a o c u l a r pressure a n d t h e reoipienb v e n o u s pressure in 94 v e r v e t a n d e y n o m o l g u s m o n k e y s . T h e m e a n i n t r a o e u l a r pressure was c a l c u l a t e d f r o m 7 r e a d i n g s d u r i n g the h o u r with flo~: d e t e r m i n a t i o n . H a t c h e d p a r t s o f t h e bars r e p r e s e n t d a t a for c y n o m o l g u s m o n k e y s .
The facility values, averaged in Table I, were those d e t e r m i n e d shortly a f t e r t h e eyes h a d been calmula.ted. I n the eyes perfused with inactive fluid for ?L-1.5 h r before the mixing with radioactive flttid the second facility d e t e r m i n a t i o n gave higher values t h a n the first o n e - - t h e average increase was 0.232=t=0-029 t z l / m i n / m m t t g (n = 62). The increase was n o t c o r r e l a t ~ to t h e s t a r t i n g facility. Figure 3 shows skew frequency distribution of the facility d a t a . I 1t25
2O
20
15
15
if-
i-~
10 .
,
0
5 10 15 Gross focility (pI.mln-l,mmHg -t)
Fzo. 3. D i s t r i b u t i o n o f the.fac.jlity values d e t e r m i n e d early in t h e e x p e r i m e n t s . ~ratc2aed p a r t e o f the bars r e p r e s e n t d a t a f r o m eyno~fmlgus m o n k e y s .
200
A.
BILL
Figure 4 shows a plot of the amount of labeled fluid recovered in the different tissues against the total amount recovered in the orbit. In the 60-rain experiments both in the iris and in t h e cornea about the samo amounts were recovered irrespective of the total amom~ts. In the 5iliary body and the anterior selera the~e is propox-~ionMity '-
30
I
I
Ciliary
I
I
Mean
body
i ..... F
I
i
weight of prep: 239+-24mgo
20 o
e
o
I0
•
i
6'1
•
•
e
~.:" 0 30
--
• 4
• s
J
i
--
Rest of the
o
I'
I
~
"I
I
i
!.
I
..... ,
,
=
e~e
20 0
I0
% •
0 30
•
•
I e
•
,~•
•
o
o
!°
1
I
i
l'~
Choroid-retino
20 e
I0
t
__~_~ '"t
•
,:;'-.,.-.
20
0
•
40 '
,
60
I'
i--
?,
I
. I00
80 '1 "
I
'
I0
weight
-
1
'
z6o
I
Mean
Cornea
.I
140
120
[8o
I
2.00
l
o f prep: 8 o 4 ± 4 r a g
o
a
5
4
eo
0 30
o
1 "" ."t" Anterior
sclera
Mean
20 t
.re
I
I
•
...
C 50
av'=-,'W",,p ,,
elj
t----f--=
w e i g h t o f p r e p : 1 5 5 +- 1 7 r a g o
•
o •
o o
10
o
o
•
:-.. t
Posterior
-
sclera
I .
1
i
I
I
|
Mean
1 "
I
i
w e i g h t %f prep: 1 4 6 ± 7 r a g
40
eo
30
o
zo •
e
n
I0 e o m.o
0
20
•
I
:'," :
40
e
60
80
I00
120
140
F z o . ~.---co~t~i~.t~d o ~ n e x t t~age
160
180
200
AQ.3EOUS
HU~,][OR
DYx~AMICS
IN
MONKEYS
2111
F I o . 4.--co~.$inuation from pret~ous page
/
901:'
Extr
I ' "l' ~ o-ocular tissues
t
"
l
j '-
~
.'
l
-
o
80 r 701_
°
_ o
•
60
-
50
o
-~40-
o
30-
o°
°
-
o
-
e
20-
"
-¢,
•
I0-
-
J
•
•
--..: :
"''"
--
•
.'.
I
0
Ir~s
•
0
""2 0 :'t:"" 40 GO
!
I
Mean weiqh, of
80 Total
I00 amourlt
t prep:
i 17 + Img
120 140 (41~l)
i60
180
1
200
~'i(;.-1. T h e a p p a r e n t a m o u n t o f r a d i o a c t i v e a n t e r i o r c h a m b e r f l u i d p r e s e n t i n v a r i o u s t i s s u e s p l o t t e d a g a i n s t t h e t o t a l a m o u n t o f r a d ! i o a c t i v e a n t e r i o r c h a m b e r f l u i d t h a t a p p e a r e d to bc p r e s e n t i n t h e c'yc a n d i t s a d n e x a . I n s e t are t h e w e i g h t s o f ~he p r e p a r a t i o n s . T h e r e s t o f t h e e y e p r e p a r a t i o n c o n t a i n e d vitreous humor and tissue fluid lost from the ocular tissues during dissection. The oxtraoeular tissue [ w c p a r a t i o J ~ c o n t a i n e d c o n n e c t i v e t i s s u o , e y e m u s c l e s a n d £a~ f r o m t h e o r b i t . T h e e h o r o i d . r e t i n a p r e p a r a tion could not be completely freed from vitreous humor. Q, Results from experimonts with radioactive a l b u m i n in t h e a n t e r i o r c h a m b e r for 1 h r ; O , r e s u l t s f r o m e x p e r i m e n t ~ w i t h l a b e l e d albu~rtin i n t h e a n t e r i o r c h a m b e r ]'~r 4 hr.
between the a m o u n t s recovered and t,he total a m o u n t s from very low to m o d e r a t e l y I~igh totals. The 4-hr experiments s h o w t'l~t steady levels are attained[ after some time. In the choroid-retina preparat, ion and in the posterior sclera small a m o u n t s were recovered if the total amouJlts were low, but from ~bout 20 td total the a m o u n t s in the 2 tissues increased. The a m o u n t s recovered in the extraocular tissues varied greatly. The autoracliogTaph in ]?late 1 shows more closely t h e location of labeled a l b u m i n after 2 and 4 hr of anterior chamber perftLsion in a m o n k e y w i t h rapid uveoscleral flow. After 2 ttv large a m o u n t s of labeled pro~etu can be seen in almost the w h o l e choroid and sclera, a n d after 4 hr there was a large a m o u n t of protein in the episclerM tissues• W h e n this t e c h n i q u e was used very little labeled material was recovered in the ciliary In'accuses in all experiments.
Correlations There w~s a rather considerable scatter of values for m o s t variables and m o s t correlations in the different, subgroups, male vervets, female vervets, etc., are o f •doubtfifl statistical sign! .fi~nce.
202
A. B I L L
lWigure 5 shows f~he combined correlation coefficients (Snedecor, 1961, p. 178) calculated from the correlation coefficient~ for each of the 4 subgroups, male ~-ervets, female vervets, male cynomoIgi and female cynomolgi. In female cynomolgus monkeys there was a significant correlation, P < 0 . 0 1 , between the weight and the intraocular pressure. In ~he various other subgroups !1 ° :c
c
' lJ
-
]
j]
pressure
Jl Fno. ,n,o I ~ 1 U veo-sc~ era~ [L - b~ood J ] II ~
r. . . .
l
pressure
~I
I~ . ....
Ou~tlow pressure
{
1
I I
F'ormotlon of oqueou.S h u m O r
I
-
1
!
t. Recipient venous pressure
1-~o. 5. S c h e m a t i c p r e s e n t ~ t i o n o f t h e relationsb~.ps b e t w e e n the various variables s~udied. Boxes w i t h d o u b l e walls r e p r e s e n t v a r i a b l e s that. were d e t e r m i n e d i n d e p e n ( l c n t o f each or,her. ~Boxes with single walls r e p r e s e n t variables c a l c u l a t e d f r o m ~he d e t e r m i n e d ones. Figtu.es represent, eombine~[ correlation coefficients for t h e 4 groups, male a n d f e m a l e c]nlomo]gi a n d vervets. *, Correlat,ion ~v-as p r o b a b l y significant, ~ 0 - 0 5 ; * * , correlation was significant, P < 0 . 0 1 . Solid lines c o n n e c t correlated variables, b r o k e n lines c o n n e c t variables calculated from e x p e r i m e n t ~ H y d e t e r m i n e d variable~ a n d t,he variables used in t h e caleula~ior~. 3-0
i
u-
;
=
i
~ I
;
I
|
i
I
!
"'
J
,~3"G
i
2-5
2-5 o o
-~
"~
-t2-0
20 o o
N
._o 1-5
ip
i
•
~
•
%
1:2 "lllm I i
0
~-
1.0
-
•
•
13
•
ooo
~%
•~ I-5
3- ! -I
o m
t
o
o
-'110 -o
_
"~ •
•
at t
•
o
o
•
0
"- I
o
~o QQ
.
e
o
0"5
"']
4
~
°"
go
o ~ o
---I 0 "~ I
Q
~
o
!
! ~
i
_-0
-'
i
,
! t 0"5
!
~ ;
Uveo;clercl
I n t I'0 l',ow
t
I
1
1.5
I
33 2"0
'-'/~:"~
FIo. 6 . T h e r a t e o f flow via t h e c a n a l o f S c h l e m m into t h e general circulation was plot.,ted against t h e flow fihrough uveosoleral r o u t e s . 94 ]kEon~eys w e r e used, 0 , V e r v e t s ; O , eynomolgi.
~{~o~ ".H{~ .~oj oXa 'l.tl~!a otI:~ '.tq ~ ,~o$ u ! u m q l u] 1 ~,:~'[j o uo!lnlOS "a tl~,!,l~ l>OS~g.t,~d s~.'~..~a,ltU P.tl-~ .~o[.~;~+lut: lJa[ •"~|,L -uo!,~oa.,¢ Oil!. j:o ~.ldu.~,o!pe.;'o:~t~t¢ ue i>tt~ p~+~t t ;q~t,,,:,tt~ ~n~lomO:~Xo tt t!~t'~o,tt D u o ! ~,~:~ \-" "I :~,~.x:~¢![
•
.
.~
...+
, .:/i: '+ ~ ....
.
"."
.
:.:
•
, ,
;'
•
"
-
~
I
,
•
~
.
• . . . .
..
~i
"IJ~2
-
:-:, .!..
,
.~:'. ~
:
"
=
'
~
.~
"
~
'
-.~i:?.":.. +.I!}I:~...I+~iI}.5:/?:!.5~!._
~
~
~- ~
~
<
.=
•
2. +
+.;~+,
~-~l~''~:-'~'--'~\"~?~@~m'';~'~"\
; ~+,~,
'~
AQUEOUS
HUMOR
DYNAMICS
IN /~IONKEYS
203
there was a t e n d e n c y to correlation, and the combined correlation coefficient for the four groups is significant. The average weighted slope of the regression line (Snedecor, 1961, p. 394) was 0-92 m m H g / k g b o d y weight. The mean arterial blood pressure (MAP) was correlated to the b o d y weight (W) in the male vervets, P < 0 . 0 1 , M A P ----9-36 × W ÷ 59-4. There also was a tendency to a correlation in the other subgroups, and the combined correlation coefficient for t h e 4 groups is significant. There is a p r o b a b l y significant correlation between arterial b]opd~pressure a n d intxaocular pressure. An analysis of partial correlations showed, h o t ' e v e r , t h a t tiffs is due to the colTelations between weight a n d intraocular pressure, a n d weight and arterial blood pressua'e. The're is a p r o b a b l y significant negative correlation, P < 0 - 0 5 , between t h e flow into tJae general circulation a n d uveoseleral flow in both the c y n o m o l ~ a n d the vervets. The combined correlation coefficient is significant, P < 0 - 0 1 . Figure 6 shows a plot of the d a t a for the flow into the canal of Sctdemm, a n d t h a t thJ:ough the uveoscleral routes. In female c~momolgus monkeys there was a significant positive correlation between the outflow pressure and the intraocular pressure, P < 0 . 0 1 . The combined emaciation coefficient for t h e 4 groups is p r o b a b l y significant. The recipient venous pressure was calculated as the intraocular pressure minus the outflow press~ure. Since in most m o n k e y s the outflow pressure was small, the intraocular pressure was d e p e n d e n t mainly on t h e recipient venous pressure. 4. Discussion
Thc for, naeio~ of a~ueous humor The results r e p o r t e d here show t h a t the r a t e of formation of aqueous h u m o r v~rles greatly from one individual to another, a n d t h a t the main reason for the variability was not among t h e p a r a m e t e r s studied. The, draiT~age of aqueous humor
Since the original o b s e r v a t i o ~ (Bill, 1965) t h a t in perfused dead m o n k e y eyes some fluid passes f r o m t h e antcridiY-chamber t h r o u g h the ciliary mrlscle into the suprachoroid and ou~ t h r o u g h the sclera t h e r e h a v e been several in' vivo studies of this uveosc!eraI flow (Bill a n d I-Iellsing, 1965; Bill 1966, 1967a,b, 1969, 1970). I n vivo, on its w a y t h r o u g h t h e tissues, t h e anterior c h a m b e r fluid becomes m i x e d w i t h the tissue fluid in the u v e a a n d there is, of course, exchange of m a t t e r with t h e nveal b l o o d vessels. This m i g h t result in n e t resorption of t h e low molecular weight constituents of t h e anterior c h a m b e r fluid. I f such resorpt~ion were ma~ked, t h e concentration of labeled albumin in t h e tissues sholfld rise to high levels, which should give lmreasona b l y high values for t h e a p p a r e n t content of anterior c h a m b e r fluid in the tissues, t h a t is, values such as 1000/~l/g a n d more. A comparison of a p p a r e n t contents o f anterior chamber fluid in t h e various tissues a n d t h e tissue weights (Fig. 4) shows t h a t this was not the ease for a n y of the tiss,~s, w h i c h indicates t h a t there is, in fact, a n e t flew both of colloids a n d of low: molecular weight substances f r o m t h e anterior c h a m b e r t h r o u g h t h e uveoseleral routes i n t o t k e episcleral tissues. :Figure 4 indicates tha~ ~ ' 6 tia~ues b e c a m e loaded wi~h t h e radioactive albumin
204
A. BILL
from the anterior c h a m b e r in the following order: (1) anterior u r e a ; (2) choroid, anterior sclera; (3) posterior sclera; a n d (4) episcleral tissues. However, in some experiments relatively large a m o u n t s of aqueous h u m o r were recovered in the extraocular tissues in spite of a r e l a t i v e l y low t o t a l uveoscleral flow. I n these animals there was p r o b a b l y a considerable flow of aqueous h u m o r From t h e tissue spaces of the ciliary muscle via perivascular spaces into ~he extraocu]ar tissues. Evidence indicating or supporting the hypothesis of net flow of aqueous h u m o r into the ciliary muscle has been reported b y Leber (1907), Fine (1964), Wolf (1965), McMaster a n d Macri (1968). T h a t some fluid m a y leave the anterior chamber via perivaseular spaces was reported b y Leboucq (1914) and confirmed b y Fowlks, ]ffavener a n d Good (1963). The autoradiographs showed t h a t v e r y little labeled material was located in the ciliary processes. This indicates t h a t there was no or little net flow of tissue fluid from t h e ciliary mu.scle into tbe ciliary processes. The uveoscleral routes a n d the routes via Schlemm's canal are alternative p a t h w a y s fox" aqueous outflow. As could be expected there was ~ negative correlation between the 2 variables. T h e iris. The role of the iris in aqueous h u m o r ~lynamics is as y e t obscure. I t can, of course, be presumed t h a t there is either net flow of water into the iris or net outflow From. it. Zero flow is incidental. ~rhen small particles were injected into the anterior c h a m b e r t h e y could be seen in the walls of the iris capillaries within pinocytotic vesicles (Fine, 1964) b u t t h e bulk m o v e m e n t of aqueous h u m o r with this mechanism seems to be quite small b o t h in rabbits a n d monkeys. I n the former sloccies when labeled albumin is introduced into the anterior chamber, very little passes directly from t h e ocular tissues into the blood draining the vortex veins (:Bill, 1962). In the l a t t e r species when aqueous h u m o r drainage into the general circulation is stopped 1)y low intraocular pressure there is negligible m o v e m e n t of labeled albumin into the uveal blood vessels (Bill, 1967a). I t m a y be concluded t h e n t h a t the mechanism t h a t probably dominates the bloodaqueous exchange in the iris is ultrafiltration a n d diffusion through narrow pores. This will tend to give accnmulation a t absorbing p a r t s of the blood vessels of high molecular weight substances a n d particulate material introduced into the anterior chamber. Such accumulation, therefore, can give no information a b o u t the net effect of the iris vessels. The a m o u n t of labeled albumin recovered f r o m the iris in all experiments was small, a n d in the calculations of uveoscleral flow it contributed only 0 . 0 3 / z I / m i n . . a l l this m a y no doubt h a v e been due to diffusion or flow towards rcsorbing p a r t s of the capillaries. This effect is included under uveoscleral flow s i n c e it cannot be d i s t i n ~ d s h e d f r o m such flow. I n m a n , Frangois, Neetens, Leroux a n d Colette (1967) h a v e described a system of channels in t h e iris, which t h e y consider involved in uveoscleral drainage. T h e cornea. The labeled material recovered f r o m the Cornea corresponded to a bulk flow of anterior c h a m b e r fluid into the cornea of 0-02 tzl/min. I t is n o t clear to w h a t . e x t e n t this a p p a r e n t flow was due to diffusion of labeled material into t h e c o r n ~ a n d to w h a t e x t e n t it was due f~ pinoc:~bosis of anterior c h a m b e r fluid constituents ( K a y e a n d P a p p a s , 1962). This effect is also included lmder uveoscleral flow.
The rise in facility w i t h Lime t h a t was observed in m a n y experiments n m y h a v e been due~to an increase in t h e tone o f the .ciliary muscle. I f Changes in tone are pre-
AQUEOUS I~IU:~IOR DYNAMICS IN MONKEYS
205
vented b y atropine, there is no sig~lificant change in facility with the technique used herb (Bill, 1969). The m e a n values for the gross facility agree very well with previous figures (B£r~ny, 1966; Edwards, i a l l m a n and Perkins, 1967; Hoffman, 1968) a n d the frequency distribution was similar to t h a t in previous studies in monkeys (B~rhny, 1966) a n d h u m a n s (Prijot, 1961). Reciipient venous pressure and intraocular pressure A correlation in m a n between intraocular pressure a n d epis~ieral venous pressure was reported b y Weigelin and :LShlein (1952). I n the present e~pe,~iments t h e recipient venous pressure was calculated from the intraocular pressure, ~h~ r a t e of outflow via Schlemm's canal a n d t h e facility of outflow. The calculated pressure is n o t representative for the actual pressure in a n y special p a r t of the intro,- or episcleral veins; it give~ a value for the average effective recipient venous pres~3ure. I t is not ]cnown a t present, however, whether or not using the facility calculatecl from periods with elevated pressure in the determination of P~ is fully justifi~.,d. This value, therefore, m a y h a v e a systematic el~or mal~ing it somewhat too low or too high. Still, it is clear t h a t in monkeys the venous pressure is the most i m p o r t a n t of the factors t h a t influence intraocul~r pressure. The positive correlation found between i n t r a o c u l a r pressur~ a n d weight of t h e animals in this stud), helps to explain the difference betwee:a m e a n intraocular pressure in the eyes reported on here and in a series reported b y H o f f m a n (1968). H o f f m a n , working with big cynomolgus m o n k e y s (2-85-7-5 kg), ~bund intraocular pressures around 12-13 nunHg, t h a t is a b o u t 2-5 mm/=Ig higher t h a n in the cynomolgl~s m o n k e y s reported here. '['here was no significant difference between the intraocular pressures in v e r v e t m o n k e y s in the present material a n d those, in a previo~m, larger series reported b y Bhrhny and l~ohen (1963). Intraocular ]~vmeostx~sis T h e results reported here m a k e it t e m p t i n g to specr~late somewhat a b o u t the needs a n d evidence for an extraocular regulating mechanism involved in t h e m a i n t e n a n c e of ocular homeostasis. There was no correlation between the rathe of flow v i a Schlemm's canal a n d t h e facility of outflow such as one would, h a v e e:~pect~d if a low flow gave a reduct4on in facility to m a i n t a i n the outflow pressure a t a certain value. Th6re also was no correlation between r a t e of secretion a n d intraooular pres.,,ure such as'one would h~ve expected if there was a mechanism sensing pressure a.ud adjusting secretion to keep t h e pressure within a certain range. Fvxthermore, t~te secretion was so va1'iable t h a t it seems unlikely tl~at there is an accurate extex~az,1 m e c h a n i s m t h a t a d j u s t s s e c r e t i o n according to infol~nation from intraoeular receptors. I n addition, there is no obvious need for a v a r y i n g r a t e of aqueous secretion. O n e could imagine t h e n t h a t the eye h a s a v e r y high degree of a u t o n o m i c i t y , t h a t is, there !Lsno e x t r a o c u l a r m e c h a n i s m t h a t gets information a b o u t the intraocular pressure or t h e r a t e of aqueous secretion a n d t h a t adjusts secretion r a t e or outflow facility or recipient v e n o u s pressure according to a scheme. This, of course, does n o t m e a n t.hat t h e e y e is unresponsive to stimuli such a s autonomic nerve a c t i v i t y a n d h o r m o ~ s , b u t such external influences do n o t seem to be involved in a feedback r e g u i a t i 0 n i n v o l v i n g i'atraocular receptors. !Stimulation of certain areas in t h e h y p o t h a l a m u s h a s been reported to produce Changes-in i n t r a o c u l a r . ~ s u r e w i t h o u t ac,compan~dn'g changes in blood pressure
206
A. B I L L
(yon Salhnann and L S w e n s ~ n , 1955; Gloster and Gre~ves, 1957), but it remains to be determined if the area stimulated is a regulating center and, i f this is the case, whether or not it is influenced b y intraoeular receptors. The fact t h a t a rise in intraocular pressure m a y produce a- sustained discharge in the ciliary nerves (yon Sallmann, Fuortes, Maori and Grimes, 1958) is au argument suggesting t h a t the autonomicit, y hypothesis m a y be an ovex~implification. I t is interesting, however, t h a t there s6ems to be no pathologieM condition t h a t indicates clearly the involvomertt of an extraocular center regaflating the eye pl~ssttl:o or the rate of aqueous secretion according to information derived from intraocular receptors. ACKNOWLEDGMENTS Th~s work was supported by a g r a n t (B 71-14X-147-07) from the Swedish Medical Research Council a n d by a grant (EY 00475) from the National Eye Institute, U.S. Public H e a l t h Service. I wish ~ t h a n k Miss A n i t a Persson, Miss Monica Thor~n and Ing. Hans Sundberg for their valuable tectmical as,~istance. REFERENCES
Blir~ny, E. H. (1964). Invest. 029hthalmol. 3, 135. B£r~ny, E. FI. (1966). Trans. Oph¢halmol. Soy. U.K. 86, 539. B~rhny, E. H. and Rohen, J. W. (19637. Arc~. Ophthalmol. 69, 630. Bill, A. (!962). Exp. Eye 2 ~ . 1, 200. Bill, A. (19C-5). lnv,'zt. OptdhalmoL 4, 911. Bill, A. (1966). Exp. Eye Res. 5, 45. Bill, A. (1967a). [rivet. 02~hthalmol. 6, 364. Bill, A. (1967b). Exp. Eye Res. 6, 120. Bill, A. (1968). Inv~t. Ophthalmol. 7, 162. Bill, A. (1969). Exp. Eye Res. 8, 284. Bill, A. (19707. Exp. Eye Res. 10, 31. Bill, A. and B~r~ny, E. H. (1966). Arch. OphthalmoL 75, 665. Bill, A. and H611sh~g, K. (1965). InvesL O,vkthalmol. 5, 920. Edwa,-xts, 1., Hallman, V. and Perkins, E. S. (1967). Ea.'p. Eye Res. 6, 316. Pine, B. S. (19647. Invest. Ophthalmol. S, 609. Fowlks, W. L., Havener, V. and Good, J. S. (1963). Inv6s$. Ophthalraol. 2, 63. Francois, J., Neetens, A., Leroux, G. and Colette, J. M. (1967). Optdhal~mloglca 153, 215. Gloster, J. and Gre~ve~, Do P. (19577. Brit. J. OphthalmoL 41, 513. Hoffman, F. (19687. Exp. Eye Res. 7, 369. Kaye, G. I. and Pappas, G. D. (1962). J. Cell Biol. 12, 457. Leber, Th. (1903). In Graefe-Saemlsch: tlandbuvh der gesamten AugenheilkuTMe, I I Abt. II, Leipzig. Leboucq, O. (1914). Arch. Biol. 29, 1. ]~IcMaster, P. R. B. and ~[aeri, F. J. (19687. Arclt. 0tz~thalmol. 79; 297. Priiot, E. (19617. Doe. 029hthalmoL 15, 1. yon Sallman, L. and L6wenstein, O. (1955). Amer. J. Oph~hvdmol. 39, Part II, 11. yon Sallmarb L., Fuortes, hi. G. F., Mac~, ~. J. and Grimes, P. (1958). Amer. J. Opl~halmol. 45, Par~ II, 211; Snedeeor, G . W . (1961). 8tatizt~cal ~[ahods, 5th eel Iowa State University Press. Ullberg, S. (1954). A c ~ t~xllol. Suptgl. 118. ~'eig~lin, E. ~nd Lfhlein, H. (19527. Albrecht Graefes Arch. Kli,n. Exp. O:ph~halnml. 1SS, 202. Wolf, J. (1965). FoIia Mor'jphol. 13, $28.