Lack of Effect of an IUD on In-Vivo Uterine Contractility in the Rat

Lack of Effect of an IUD on In-Vivo Uterine Contractility in the Rat M. A. ZAMBRANA, MD,* and GILBERT S. GREENWALD, PHD

of the antifertility effect of the IUD is still unknown. It is generally agreed that there are considerable species differences in the action of the IUD.5,8 One of the suggested mechanisms for several species, including man, is that the IUD modifies uterine activity which, consequently, interferes with egg implantation. 6 , 9,12 However, to date, the results on the effect ofIUD's on myometrial activity are contradictory.3,4,1o,1l,16 The present study was therefore designed to study in vivo the effect of a silk suture on motility of the rat uterus. THE MECHANISM

MATERIAL AND METHODS

Twenty-eight female Holtzman rats (175-280 g) were used. In each of 19 rats, a 4-0 silk suture was inserted through the antimesometrial surface of the middle third of one horn, as previously described. 9 These animals were divided into two groups: 1. Eight females were caged with fertile males 5 days after the operation. The day that spermatozoa were recovered in the vaginal smear was designated as Day 1 of pregnancy. These animals were killed on Day 5 postcoitum and ova were Hushed from the cornua with a 22 gauge needle attached to a 5-ml syringe. Day 5 was selected because the eggs enter the uterus early in the morning of this day, and implantation is initiated in the late afternoon. Portions of uterine horns adjacent to the silk suture and of a corresponding area from the opposite horn were removed for histologic study. 2. Eleven rats were smeared daily for three cycles or more and were then placed with fertile males on the evening of proestrus. Day 1 of preg.

From the Department of Obstetrics and Gynecology, University of Kansas Medical Center, Kansas City. Kan. Supported by grants from NIH (HD-00596), US Public Health Service, and The Ford Foundation. *Ford Foundation Fellow in Reproductive Biology.

993

994

ZAMBRANA

&

GREENWALD

FERTILITY

&

STERILITY

nancy was designated by a sperm-positive vaginal smear on the following morning. A second laparotomy was performed 12-15 days postcoitum, and the number of embryos was counted in the treated and the contralateral uterine horns. This group was examined again at delivery. The young were removed from their mothers on the day of birth. The females were then remated in order to study and compare uterine contractility on Day 5 of pregnancy in treated and untreated horns. A control series of nine mated normal rats was used to record uterine contractility in both horns on Day 5 of pregnancy. After light ether anesthesia, pentobarbital sodium* was injected IP (2530 mg/kg body weight). Light ether anesthesia was continued until the end of the experiment. A tracheostomy was performed, and a polyethylene catheter was inserted. The uterus was exposed by a midventral incision and the bladder and rectum were emptied. A small incision through the peritoneum at the vesicouterine junction exposed the vaginal wall, when the bladder was retracted posteriorly. The vagina was opened and the cervix exposed. Both cervical orifices were widened and cannulated with PE 50 polyethylene catheters, filled with normal saline. The tips of the catheters were inserted into the uterus, 2-3 cm from the cervix. The catheters were fixed to the cervix with a ligature and the other end of each catheter was extended through the vagina or abdominal wall. Each catheter was connected to a Stathamt transducer (sensitivity 0-50 mm Hg) coupled to a Sanborn strain gauge amplifier (Model 67-500). Before recording, 0.02 ml of saline was introduced into each uterine horn via the catheter. The paper speed was 3 em/min, and direct calibration was used. RESULTS

Of 8 animals killed on Day 5 of pregnancy, only one sutured horn contained ova (Table 1). Histologically, there were polymorphonuclear leu cocytes in the uterine epithelium as well as in the stroma of the treated horns. In contrast, the untreated horns were normal. These results agree with previous findings. 9 It is interesting that an egg was recovered in the sutured horn with the least inflammatory reaction. In the series of 11 animals that were laparotomized between Days 12 and 15 of pregnancy (Table 1), 10 females had no embryos in the sutured horn, while an average of 6.3 embryos were found in the control side. Fewer . eggs were recovered at Day 5 than the number of embryonic swellings *Napental, The S. E. Massengill Co., Bristol, Tenn. tStatham Laboratories, Inc., Hato Rey, Puerto Rico; Sanborn Division, 175 Wyman St, WaItham, Mass.

VOL.

20, No.6, 1969

IUD AND UTERINE CONTRACTILITY

995

TABLE 1. Effect of an IUD on Egg Transport and Embryonic Development in the Rat Day uterus flushed or examined

1Vo. of animals

---_._------ - - - - -

5

12-15

Mean No. of eggs or embryos (± SE)

----------Sutured side

o 1

o 5

Unsutured side

4.6 ± .69 6 6.3 ± .54 6

counted at Days 12 and 15 (Table 1), but the difference was not statistically significant. In one animal the inserted thread did not enter into the uterine lumen, and this female had 5 embryos in the sutured horn, with 6 embryos in the control side. All 11 animals delivered normal young and were remated to study uterine contractility on Day 5 of the second pregnancy. Uterine Contractility on Day 5 of Pregnancy in Control Animals

A total of 29 recordings from both horns of the control animals and from the control horns of the treated rats were evaluated. Although a uniform pattern of contractility was not found, all recordings obtained on Day 5 of pregnancy (day of implantation) were characterized by irregular contractions. This pattern· of contractility was not observed in recordings of the uterus of the nongravid rat. According to the degree of irregularity, intensity, and frequency of the contractions, we have classified two types of contractility. Type A corresponds to irregular contractions of high frequency (30-50/10 min) and low intensity (4-17 cm H:P). Occasionally, the irregularity of the contractions makes a quantitative evaluation practically impossible (Fig 1). Type B corresponds to more coordinated contractions of less frequency (16-26/10 min) and greater intensity (15-35 cm H 2 0). These contractions are also characterized by a wide base and two or more peaks (Fig 1). Often, small peaks are superimposed on the contraction or relaxation phases of a contraction cycle, similar to those described by Posse 15 as "overlappings" in recordings of the nonpregnant human uterus. Uterine Contractility on Day 5 of Pregnancy with Intrauterine Suture

The patterns of contractility from the horns with the silk suture are comparable to those described in the controls as Types A and B. Moreover, . simultaneous recordings of uterine horns with and without an IUD in the same rat are similar as shown in Fig 2 and 3. In both the treated and untreated horns, spontaneous changes were observed in the pattern of

E

u

o .~J

40

o

N

::I:

E

SM~BORN ("f.:,c,,-,·J•• :,; !~·~'''~~P';'''''''.:

0.}

L

l':~;:

..... :.: ••• : I~ t,~~ ••. :. ::j •• :. f:'rPIE

.......... 1"1. •••••••••••• , •... .: .. '
r : .: . .

... ' ••.

.:: .:.:.' •• :

B.:.: ..;:' :"f . : •..•.;.:. . . .: •.• .:. .::. :.' .

!'S.:. •.. :.••••••

";'~i' '~i ~ •.~

••••

,~ ~!l

::

.::.: .•• i' •• ';;.:: f

.: •••••• ~

...• :;~~::: .~•••• ••.••. :.:. ::::" ••• : : .• "I,li!!: !utili 1m, •• : •.•• '.'f1l: .•. :. .::. : •.. :. : ••••

'N'~

•••••

ilii 'iii ••• i ii: -1\. 'il: ••. ,:" • ,;I,.:" . ••• :~ ••• ••• y "':'.':::: jH~H •• il!l1Hl mLj~ 'u't:. ') .:.: .,,' .. ; • • • ..., .i .. .. " Ji. ,t•• •'t. 7 :1":'~. ii' •••• : ,ii; !f ::: •• i••• ' )

:j\

jI :'.'1\ ••••••••

:' •••••• V.· ...• LIV '''''i" •• ,'\V .:1,'

.i..... ..... . ii" •• :V.'.' y.': .... -r. 'i:' •• :: :.. :•••• ;" .... :.....: :.

••• ;

'.'A'I.r i.' :.!. ii ••

ti,;Jr' •.•. ~.. •••. .

'.'.~II."

iiii mil

,iii ::tI' P: P'; :'11 i: .~

Ii;;

:: ..... "i. o :: .• :•. ," . '. :.: .': •• :••. : .• to .j:i .;;: .•• ::., ~ • ~~; i,:. jm m, m: ~:il; !;;tiW; m: ;J.;:;t:m ~:i; ;; •. m. ;!.: Wi ;;~. ,.:. :-:, ,m ;;: ~m m: 1!:: :.:: ,:~i ;i:; .u. ,;:' ::;; i i. ;lll :m ;!;I :'1:1 L'" :::: .0· ':.': .......•. t.: ••1.2£ 'lJ22 'Y Hi: 1". ~••i i:E lift !i,! ::i' "•• '.l~lJr F.:! m:~il. i? 'i •• 'i~ :.g.. i:~. :". :ii~ :1:. ':it UUJIP H .'E G.U nrr USllli :WIii:Hif\i U~ Ildl u

c

........ ::,

I

I

I

I

~

I

I

.~

MINUTES

Fig 1. Type A and B contractions in control uteri. In this and the following figures, all records were obtained on Day 5 of pregnancy.

40 o

....

N

~

~ ~" ... "

u , ". . . .

o ....

:.:~~

.. ,. ,.,.

• 40

m,

;;

,<> .,.

.

. . ",. _. ,-

-.~

-: ....

::~-r.-

" , : . ':. ~Ifh-~ Ii; ~~ ~f

",

"~',~: ,. ~:,

j...

.~.,

I,

,,,

,:: ::" it...., T",.

j'

.

iill'r

• ,• . _. •=-i • "' -;:-;- .:t..: ._± .:-=-'

, .. '!..... ' . • ;-;.

. "

1'"

..•

-

~"Iffi r~rffi ' : tl~Hffi'F.t !j1n~r~

~,'~£~j:i.;':~" ~ ·:'·'.~,~t,I~,f~:~.: :"'," ;~~I:~I~ .

" ' ; !IH~jIV\\Jih tth:

,... 'EB.

'

d.

Tt'

~:ti;:.gg~I' fit: ·c:twiliI "i' g

I.II.'IIIIIIIIIIIII!II li:II'II"I'!"

'~::." ~~":"

111111;llllill'I'IIIIII'III'IIIII'I'II'I!:1 ".,,1 .. 111,1,11,':,

oN

:I:

E u

o

~"$_r:-;;trljilffijlr~

~

~..",~~,rt" ,~:rr~_ltIffiU!l't '-H

..

..

,

.,

~.,

~h@wk::b-El±tj-;H!::

, ••.••.•.

...........

".,

MINUTES Fig 2. Simultaneous recording of Type A in both sutured and control horns.

•.

,f-

I:~;~ ,~i "i iiiH;~iiii"i i' ..•. .. 40::: :::'ii .!ri i!!:tC iiii " ' : ! i ON I.• ' •. : :,: :::: '!!. ::.: ••••..••.• i iii ••.• I~ •••• , i.·i

:l:

i::n;. ",'1 .•• !. J 'i" .i •••••• '•• i,,'

~ ~I~}'~f\~ o

l

••

'i.>. 1\

••••••.• '.::.' .•••••. :. "•• ~<

'

..•.

ij'i .: :j:': iii. :::lHL IG\ ii" .' •• :.i :ni }i' 1m ~; ~i: : :: :••• ::: :::: :... .

.

.ii'

:i ••

i:i' i'" ii' .

IX i.·i ••...

i"'~

... : ..

:,,::! i I::;

•••• '.'::: •••• :: :••. i·; ..f:' 'ii; :; ••••• :.: i:i ::ii ii i" .

.i.

\n...~i'i'·'

I .. "

I

i.;. •i

ii·i · · · · i :

.i::'V i:::: .••.•••• i< :.: '\ 'i":: ••• il"V. :ii. : : " ' i : '\

11hZ, W?.,v~Ti·t~ :~R~ . . m:~~~!i~ . . j ~~i.J i' l

ii ii·.,,0 •••• ; ••••• iii:.ii; .i.: .••• •••• ......::

'8 n

:

:i.: iii • .... , ,•••

r.~ ·1, ,~:~ l~i .:il .i.: ~~:': .• :.• :......:. :• :": :.

....

~~

sill':';:!:.::'

d!Li::,.\;;, it!, iii: iii: ;:: .: •• :: i::i iiiii ::i i; ••• i.: •",i. i•• i Jill: I:' f: ~ii IIIIIIIII~ il III III! iilllill ill! 1IIIIIIi 'iillill IIIII!II lilllilli;: :::iflillj;i'i in.. I1I illl iii' .ii. iii :;; iill iff' ;:i ii: 'Eli FiI1'''; 'i'; ',:.i :'i:i.i .ii. ;i.i;: ffii :i'i .1

'1

A'~

40

~!ji i~i i:i~

:11,

j:ft; ~ f ;j;' ~#: iii.~:: :~; i'ii~ 'ri T ~~~L:: ••• ::: ; ::i i:!! '::? if: .~ii f:~ ~i.ilit F~:,,: :;" ij}! ,ftf,: ';;1 iii: iii: iii: ':lj tiEl ii'. C :ii: :" :i iii. i~: ::. ::-;:'" .i-, ';: :;E .::' " ... : .::. I::. :::.:: :: :ii. ~:.: '::: i:' .i:: :i:i~ ":. ;:l:!ifll1 i" :::1 :::~ i[,"~1: l:§ii±z1'i:i 'i" !!H~tj ;,,: iT, :'ii ii •••••• :•• ~: i ii~i 11]

[ii; :

:i:.::. I::: :,:; ~'i :iii }: f~:l iii: ;; i~: ii~ ~t

::ci: i iii ii'

n!~

iii: ••••

~ ~.~ ;~:' ';~ .;~. ';" ~m ': •.•• :" .;·.I~: .::...: I~\ -;:: ••.. ~.';fi ;n. ~: ~'!~ ~ m. m':ll~ mi~J: ~;~ ;;ilm, ~ii ~~. ~"i i:l~ ]; : ;i~:;:: ::: ~i. iIT: ~~; ~~ ;:...... ~.• :.z· ·W :..' E u

.:l::;' 19\ :::i:. ~ii Ie iii':::/ '\'L:':: i :\:':.::[11 '1\j ',: iii! j~; .'iii~ fj~ ;':j1:1 'F#~:'~: :':! :~)F'inj i.fEij': iii; i#; OfF,!mlV iii ~ii' :~tWt~!i~i ii:: ::: i\ iii; iiii':\! ii ::: T ii .:i~ti 'i'iX i i i 1:' lI\i::; ~/ !T iV iii ~i~ ii" iii: ii't: r2ct~ J if :;: l\,i~ :,i :~i iiii i!!' :iii :',: :ii: ;:'i:1" if: :ii' it;i i1/ g i;' :if 'it #i: j\ i.;.:~: iii :,,: ..Xif ii: j'IL iii i!!iJ ii :ii: i::: ':i' :ii ':lfibJ ::i: E:! frE 'i:. ':: iii ~i;. t~, :" iii:: ~;~: ii:i iii: i'i if:: :i::i\..:: :ii, ;tli ',; 'Li :i'i:i': 'W 'Jf': :!ii ::i~

o :~ :m .~: ~ll ~:~n;: m::

i.

.•:.:: .: . :2~:;: :..:. ·:·l ~i!~!~: ~·nm ~;I; t~~ ~::~I; :~;. ;:;i il : ~:: ~;.: ';'; ':.; .w ·mr:mTI.: 0 :i.' i':' ':: ':i:: '::; :mm: .':. T' :m :m ill~~ !:i:

I

I

I

I

Fig 3. Simultaneous recording of Type B in both sutured and control horns.

MINUTES

pffjr, f~ nhE~j ~i~ 'iL';";

I;,,,

i:'i; 0~ ; :- ·T ,,"~ ~ffi '~~f:;:~': ii~ fr~Jm 2i' i::' :~; ::=: :~.'ffi: :::E ::: :iii ;;!: ~ 1m[i"ffi1 l

;;: ii;' 'lflci:Sl :::i :.::: ;~! ~i; ~~'i ;EAf;; iii ::i' "if!:::: '~~i!H' •• :. ~ :iii i;ii 'ii 'i' i;:: i'i' '~i "ii '.i if': " -;r,r 51: :~. 'iii:", ;:~;i~; :~ii "ii ;:i1 W-. 'ii i~r~ l=t~. E"'.i< 'i~' i} ii 'ii: i:' i' h i.~ 5;:;U:i';:i: i:i :;:;3#, iiB ;:;tl$ifJ. ,~; lP E ';I' :'i Y ii::: :; i •• iiii.ii /WJ iii: :i:; ::~E;::-:::!.1:tlRfrit;; '-~ ~i': ;'r"'j! [ill;:;; i'i:

o

u

o

.;;. ;'.' •••• 'ii"'i i:: ::i: i'i

in:

','r::

~ m ~~;~~;'/~'::'S. 1,:. :.;; ~m:~~i~~:;~ 1~Jmi!~·: '11·' ,;. '·~I;· if~ ~::~ ~~~-?~~~~

:::: :;;:

:~~i ::~~ ::~~~Uj ~~HJH;~~ ~H-£1h~ ;:!i :i+:jj;! HB

!il!tiii,lii!!I,'I.·I!.'I·,.I.· Ii! I:', .

·,.1

dl

"

:~:I':r't/-j~:: I'~

!fRi:

JTITInnniUiiH

,IIII ':"I·'i·IY!. ' , '! . ~!

I'I!

1,1"

I.,':

; I ,: i :', ';"

'.

40

o

N

~

"·I·r,·~rr . +m:~;i' : :.

E CJ

o Fig 4. Spontaneous changes of pattern of contractility from Type B to Type A.

MINUTES

,<'

. .,' ,'!

i

40

o

'"

:t:

E u

0'

~1'I il'I !1

;1

I' I"

m::T

t ~ii~

:;~; ~i~:

+: ~.

j"

'W--:!::" ,

E o

±JJl:lff1:illfi

iii

c-'

fifilltt4!m

o MINUTES Fig 5. Contractions temporarily inhibited in both control and sutured horns and simultaneous resumption of uterine activity.

VOL.

20, No.6, 1969

IUD AND UTERINE CONTRACTILITY

1001

contractility (Fig 4). In one animal with mucous obstruction of the respiratory tract, the uterine contractions were temporarily inhibited in both sutured and control horns. The contractions reappeared in both cornua when the mucus was aspirated (Fig 5). DISCUSSION

Since the studies by Doyle and Margolis,6 it has been confirmed that a properly placed silk suture prevents implantation in the rat, but implantation takes place in the contralateral horn. The mechanism of action of this foreign body is still unknown. However, there is agreement that eggs enter the uterus normally on Day 5 of pregnancy6 and then undergo premature expulsion. 9 It has also been suggested that the sutured cornu produces a deleterious substance which prevents implantation. 1,2 The expulsion of ova per vaginam before the time of implantation has been interpreted in terms of alterations in uterine activity.6, 7 Previously, the most plausible explanation was that myometrial activity was increased by inflammation acting via increased neural stimulation of the uterus or by a myogenic response. 9 The present experiment confirms the development of an inflammatory reaction to the IUD.9,14 However, the results of recording uterine activity in vivo suggest that in a rat of proven fertility, a uterine silk suture prevents implantation without greatly modifying the pattern of contractility. These results differ from those described by Marcus et al,l1 who studied the rat uterus in vitro and found that the presence of an IUD in one uterine horn was associated with a significant increase in muscle activity over that of the control horn. The studies performed by Behrman and Burchfield3 and Johnson et al 10 in the human showed that the presence of an IUD does not cause significant modifications in uterine activity, a conclusion in agreement with our own. The different results obtained by other authors 4 , 11, 16 can probably be ascribed to the different methods and species used in their investigations. It is particularly interesting that Parr 13 obtained normal pregnancies in both uterine horns of rats after electrically stimulating one horn on Day 5 of pregnancy. According to his results, uterine hypercontractility does not affect implantation in the rat. Having confirmed that fertilized eggs are rapidly expelled from the threaded horn on Day 5 of pregnancy,6, 9 and with no evidence that uterine activity is responsible for the loss of ova, it is necessary to seek another cause for their premature expulsion. We agree with Rozin et a[16 that the uterus normally has a potential cavity and that the IUD in situ can shape the uterus into a hollow organ. Under these conditions, blastocysts lacking

1002

ZAMBRANA & GREENWALD

FERTILITY & STERILITY

physical contact with the endometrium may be rapidly expelled from the uterus. Another possibility is that an increase in luminal fluid, formed as a consequence of the inflammatory reaction, flushes the fertilized eggs towards the vagina. The fertilized egg transported into a uterus which contains an IUD may also undergo degeneration by substances produced as the result of inflammatory changes. This is currently under investigation.

SUMMARY Uterine contractility was studied in vivo on Day 5 of pregnancy (day of implantation), in a control series of rats and in a group with a silk suture inserted into the lumen of one uterine horn. Similar patterns of contractility were observed in the horns with the silk suture and in control cornu. It is therefore concluded that premature expulsion of eggs on Day 5 of pregnancy from a uterine horn containing an IUD is not related to altered uterine activity. Depaltment of Obstetl'ics and Gynecology University of Kansas Medical Center 39th and Rainbow Blvd Kansas City, Kan 66101

REFERENCES 1. BATTA, S. K., and CHAUDHURY, R. R.

The anti-implantation property of intraluminal fluid in rats with an intrauterine silk thread suture. 1 Reprod Feltil 16: 145,1968. 2. BATTA, S. K., and CHAUDHURY, R. R. Antifertility effect of an intrauteIine silk thread suture in rats with a connection between the two uterine horns. 1 Reprod

Fertil16:371, 1968.

3. BEHRMAN, S. J., and BURCHFIELD, W. The intrauterine contraceptive device and myometrial activity. Amer 1 Obstet Gynec 100:194,1968. 4. BENGTSSON, L. P., and MOAWAD, A. H. The effect of the Lippes loop on human myometrial activity. Amer J Obstet Gynec 98:957, 1967. 5. CORFMAN, P. A., and SEGAL, S. J. Biologic effects of intrauterine devices. Amer 1 Obstet Gynec 100:448, 1968. 6. DOYLE, L. L., and MARGOLIS, A. J. Intrauterine foreign body: Effect on pregnancy in the rat. Science 139:833, 1963. 7. DOYLE, L. L., and MARGOLIS, A. J. Intrauterine foreign body. 1. Effect on reproductive processes in the rat. Fertil Steril15:597, 1964. 8. ECKSTEIN, P. Intrauterine contraceptive devices: The scientific background. Proc Roy Soc Med 60:392, 1967. 9. GREENWALD, G. S. Interruption of pregnancy in the rat by a uterine suture. 1 Reprod Fertil 9:9, 1965. 10. JOHNSON, W. L., EK, T. W., and BREWER, L. L. Motility of the human uterus before and after insertion of an intrauterine device. Obstet Gynee 28:526, 1966. II. MARCUS, S. L., MARCUS, C. C., and WILSON, K. H. Effect of an intrauterine contraceptive device on uterine motility in the rat. Obstet Gynee 27:238, 1966.

VOL. 20, No.6, 1969

IUD AND UTERINE CONTRACTILITY

1003

12. MARSTON, J. H., and KELLY, W. A. The effects and mode of action of intrauterine devices. Vet Rec 79:644, 1966. 13. PARR, E. "Studies on Mechanism of Action of Intra-uterine Foreign Bodies in Rodents." In Proc Second Int Cont on Intrauterine Contraception. Excerpta Med Foundation, New York, 1964, p. 247. 14. PARR, E. L., SCHAEDLER, R. W., and HIRSCH, J. C. The relationship of polymorphonuclear leukocytes to infertility in uteri containing foreign bodies. I Exp Med 126:523, 1967. 15. POSSE, N. The motility pattern of the non-pregnant uterus. Acta Obstet Cynec Scand 37 (Suppl.) :2, 1958. 16. RozIN, S., SCHWARTZ, A., and SCHENKER, J. C. Studies of ijte mode of action of intrauterine contraceptive device. Obstet Cynec 30:855, 1967.