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Distribution of intravenously injected [86Rb]Cl in different tissues of the rabbit eye
Exp. Eye Res. (1977) 25, 195-197
Distribution of Intravenously Injected [86Rb]C1in Different Tissues of the Rabbit Eye J&i
OBENBERGER
AKD ARXO~
BABI(T&
The penetration of intravenously injected [s6Rb]C1 into intraocular fluids and individual eye tissues was studied in the rabbit. The radioactivity of samples of whole blood and plasma, anterior and posterior aqueous, central and peripheral cornea, iris and lens. was measured at five different intervals after intravenous injection of the radioisotope. Thts dynamics of [s6Rb] penetration are compared with previous results on [24!Sa]. Key lords: [H6Rb], aqueous, cornea, iris, lens.
1. Introduction The localizat’ion in ocular tissuesof intravenously injected radioactive cations enables their tlistribution pattern to be investigated under normal and pathological condit,ions. Isotopic methods also represent a means of revealing consensualreactions when the physiological st)at’eof untreated eye is influenced by local injuries or topically applirtl drugs to t,he contralateral eyes (Obenberger and Babickf. 1973a). Thus 45C!aha,sbeen used in several studies dealing with experimental calcification. alloxan treatment of the cornea, endotoxin keratitis and alkali burlIs (Obenberger and BabickS;, 197Oa,b ; 1972, 1973). iVlore recently the distribution pattern of intravenously injected [24Na]C1in different tissuesof the rabbit eye has been used to compare the effects of burns caused by sodium hydroxide and hydrochloric acid (ObenI)erger and Bal)ick$, 1975a, b). Rubidium resemblespotassium in many respects and in experiments using radioactive isotopes s6Rbhas the advantage over cLK of a much longer half-life (18.66 days as compared with 12.4 hr). This paper describesthe dynamics of transfer of the intravenousIS injected s6Rbfrom blood into aqueous, cornea, iris and lensof the rabbit eve. ‘I’he purpose of t)he study was to establish t,he most suitable interval between ;htt injoct,ion of s6Rh(‘1and sacrifice of experimental animals to be usedin future investigatiom of functional alterations taking place after experimental injuries of the rabbit eye. 2. Materials and Methods Twelve Chinchilla rabbits were intravenously injected with saline containing 200$i of a6RhCl/l ml, according to their weights, receiving a doseof 0.5 ml/l kg. Bnimalswere sacrificed after 15, 30, 60, 120 and 240 nliu., respectively. Four eyes of two rabbits represented one group. One ml of blood was withdrawn from the ear vein by a heparinized tuberculin syringe arid thereafter the animals were killed by au overdose of Thiopental Spofa and the eyes were enucleated. Blood, conjunctiva, orbital tissues, and extraocula,r muscles were removed from the eyes. Pre-weighed gelatin capsules (Parke, Davies and Co., Hounslow, London) filled with
G
195
3. Results Table I summarizes the radioactivity of’ *%b (mean fs.D.) of saiiiples at (li fkrmt intervals after intravenous injection of t,his isotope. The radioactivity of plasma decreased more rapidly than of the corresponding samples of the whole blood. During the period between the first sample (15 min) and the last (240 min), the radioa&ivity of blood and plasma decreased by 40(!{, autl 7X”& respectively. the
Sa,mples
and intervals
15 min
13lood Plasma Posterior aqueous Anterior aqueous (‘orneal ccntrc Corneal periphery Iris Lens
The table shows standard deviation
average values of the mean.
of radioactivities
(ct min-’
mg’)
of four
s~~~plcs toget~hcr
wibh
the
The ratios of radioactivities bet’ween samples aqueous and plasma obtained fro11I the same animals were calculated from individual measurements. By 15 miu the radioactivity of the posterior aqueousapproached that in the plasma and there were no significant differences between the anterior and posterior aqueous. During the whole experiment a steady increase of tissue radioactivitlv of cornea1 tissue was observed. The arbitrarily chosen central and peripheral regions of the cornea did not differ significantly proving the aqueous to be the main source?of @Rb for the whole cornea. The ratios of tissue radioactivities of both part,s of t,he tlissected cornea and anterior aqueous showed a continuous uptake of 86Kb. Of all samplesunder investigation, iris exhibited the most remarkable uptake of radioactivity, reaching a peak at the 30-min interval and well in excessof radioactivity measuredin plasma and blood at corresponding time intervals. As with the cornea, the ratio of t,issueradioactivities between lens am1 posterior aqueousreflected *6Rb accumulation inside the lens.
[86Rb]C’l
IN
EYE:
TISSUES
1%
4. Discussion In our previous experiments 2C7a has been intravenouslv injected (Ohenberger and Bahickf, 1975a,b). The blood clearance of 24Na was sloiver than that of s6Rb. If t)he radioactivities of blood samples at 15-min int,erval area taken as loo”& than thca radioactivities of samples at 240 min int,ervals of 24Na and *“Rb are 80.5”;, and 60” 0‘ respectively. Cl) t,o 30 min the radioactivity of s6Rbboth in anterior and posterior portions of thch aclueouswas hi,qher than the radi0activit.v of 24?Ga whereas after 60 min the rwww was trufl.
Thr~rubidium content of the cornea showeda steady increase for the whole pet&l. \vherchasthe level of sodium in the cornea followed the radioact’ivit,y of aqueous. .1s with l)otassium, rubidium accumulation is probably cellular. Maurieta ant1 Rilr~ (1970) gave stromal K as 21 mEq/kg water as compared T&h ,4.9 in aqueous. thcl corresponding values of Na being 165 and 144. Uptake of the intravenously itl,jectP(I rul)itlium clependsin somedegree on the vitality of the cornea1cells. Kecc~nt~lywe have found a marked decreaseof rubidiuul uljtake in corneas hurnetl with nitric acid. On the basisof the present data no difierences in the uptake of’~odiunl and rul)idium \vith respect to the cent’ral and peripheral parts of the cornea wt’r(’ ol)scrvc~l. whilst, in a similar study using 45(“aupt,ake in t hc central areit, QW highf~r than in the periphery (Obenberger and Babickj, 1967). Aulong all eyr! tissues the highest level of 86Rb accumulation was in thcx iris its rarly as 30 min. This could be explained by a very intensive uptake of 86Rt) in iritliat smooth nluscle cells, probahlv aided by the extensive vascularization of t’his tisslle. The transport of rubidium”into the lens has been the object of extensive invest.&tions ill vitro. The results of our present study. which show a st!eadily increasing a,(‘cumulation of int,ravenously injected *SRb by the normal IPW. suggestthat this intrktvenously injectetl rubidium method may he suitable for cluantitative evaluation ot changc~tlcatSiontransport in cataract,s of living animals. Intervals of :S1 hr WPIII tea 1~1tttc, tllost sat,isfactor,y for this purpose.
Wr wish to thank Mrs Niroslava Folkovii, Mrs VBclava RoMenovA ami Mr ChrutlG Chromecfor their capableassistance. REFERENCES Xaurice, D. Academic Obenberger, of %a Obenberger,
31.. Riley. BZ. V. (1970). In Riochrw~intry of thr E’ys (Ed. (+raymore, C. N.). P. 10. Press, London, New York. J. and Babirkg. 9. (1970a). Experimental cornea1 ralcifieatio:~. :1 study of transport into the aqueous and cornea. Ophthnl. Res. 1, 187-91”. J. and Babicki, A. (1970b). Penetration of radioactive calcium into the aqueous and corneaof normaland alloxan treated rabbits. Am. J. Ophthnlnaol. 70, 1003S5. Obenberger. J. and Babickj. A. (1973a). Alkali burns of the rahbit cornea. (‘orneal uptake 01’ ‘Y-glucose injected into the anterior chamber. Ophfhal. &es. 5, 1 -9. Obenberger, J. and Babick$, A. (1973b). Experimental endotoxine beratitis. Study oflY’a penetration in riuo into the aqueous humour and cornea (In Czech). Cesk. Ophthnlmol. 29, 34749. Obenherger, J. and Babick;, A. (1975a). Distribution of intravenously injected ‘“NaCl in different tissues of the rabbit exe. Ez~. Eye Res. 20, 189-93. Obenbeger, J. and Babicky, A. (197513). Dist’ribution of ““NaC’l in tissues of alkali- and acid-hurrwl rabbit eyes. Ex~. Eye Res. 20, 19%2063.
Distribution of Intravenously Injected [86Rb]C1in Different Tissues of the Rabbit Eye J&i
OBENBERGER
AKD ARXO~
BABI(T&
The penetration of intravenously injected [s6Rb]C1 into intraocular fluids and individual eye tissues was studied in the rabbit. The radioactivity of samples of whole blood and plasma, anterior and posterior aqueous, central and peripheral cornea, iris and lens. was measured at five different intervals after intravenous injection of the radioisotope. Thts dynamics of [s6Rb] penetration are compared with previous results on [24!Sa]. Key lords: [H6Rb], aqueous, cornea, iris, lens.
1. Introduction The localizat’ion in ocular tissuesof intravenously injected radioactive cations enables their tlistribution pattern to be investigated under normal and pathological condit,ions. Isotopic methods also represent a means of revealing consensualreactions when the physiological st)at’eof untreated eye is influenced by local injuries or topically applirtl drugs to t,he contralateral eyes (Obenberger and Babickf. 1973a). Thus 45C!aha,sbeen used in several studies dealing with experimental calcification. alloxan treatment of the cornea, endotoxin keratitis and alkali burlIs (Obenberger and BabickS;, 197Oa,b ; 1972, 1973). iVlore recently the distribution pattern of intravenously injected [24Na]C1in different tissuesof the rabbit eye has been used to compare the effects of burns caused by sodium hydroxide and hydrochloric acid (ObenI)erger and Bal)ick$, 1975a, b). Rubidium resemblespotassium in many respects and in experiments using radioactive isotopes s6Rbhas the advantage over cLK of a much longer half-life (18.66 days as compared with 12.4 hr). This paper describesthe dynamics of transfer of the intravenousIS injected s6Rbfrom blood into aqueous, cornea, iris and lensof the rabbit eve. ‘I’he purpose of t)he study was to establish t,he most suitable interval between ;htt injoct,ion of s6Rh(‘1and sacrifice of experimental animals to be usedin future investigatiom of functional alterations taking place after experimental injuries of the rabbit eye. 2. Materials and Methods Twelve Chinchilla rabbits were intravenously injected with saline containing 200$i of a6RhCl/l ml, according to their weights, receiving a doseof 0.5 ml/l kg. Bnimalswere sacrificed after 15, 30, 60, 120 and 240 nliu., respectively. Four eyes of two rabbits represented one group. One ml of blood was withdrawn from the ear vein by a heparinized tuberculin syringe arid thereafter the animals were killed by au overdose of Thiopental Spofa and the eyes were enucleated. Blood, conjunctiva, orbital tissues, and extraocula,r muscles were removed from the eyes. Pre-weighed gelatin capsules (Parke, Davies and Co., Hounslow, London) filled with
G
195
3. Results Table I summarizes the radioactivity of’ *%b (mean fs.D.) of saiiiples at (li fkrmt intervals after intravenous injection of t,his isotope. The radioactivity of plasma decreased more rapidly than of the corresponding samples of the whole blood. During the period between the first sample (15 min) and the last (240 min), the radioa&ivity of blood and plasma decreased by 40(!{, autl 7X”& respectively. the
Sa,mples
and intervals
15 min
13lood Plasma Posterior aqueous Anterior aqueous (‘orneal ccntrc Corneal periphery Iris Lens
The table shows standard deviation
average values of the mean.
of radioactivities
(ct min-’
mg’)
of four
s~~~plcs toget~hcr
wibh
the
The ratios of radioactivities bet’ween samples aqueous and plasma obtained fro11I the same animals were calculated from individual measurements. By 15 miu the radioactivity of the posterior aqueousapproached that in the plasma and there were no significant differences between the anterior and posterior aqueous. During the whole experiment a steady increase of tissue radioactivitlv of cornea1 tissue was observed. The arbitrarily chosen central and peripheral regions of the cornea did not differ significantly proving the aqueous to be the main source?of @Rb for the whole cornea. The ratios of tissue radioactivities of both part,s of t,he tlissected cornea and anterior aqueous showed a continuous uptake of 86Kb. Of all samplesunder investigation, iris exhibited the most remarkable uptake of radioactivity, reaching a peak at the 30-min interval and well in excessof radioactivity measuredin plasma and blood at corresponding time intervals. As with the cornea, the ratio of t,issueradioactivities between lens am1 posterior aqueousreflected *6Rb accumulation inside the lens.
[86Rb]C’l
IN
EYE:
TISSUES
1%
4. Discussion In our previous experiments 2C7a has been intravenouslv injected (Ohenberger and Bahickf, 1975a,b). The blood clearance of 24Na was sloiver than that of s6Rb. If t)he radioactivities of blood samples at 15-min int,erval area taken as loo”& than thca radioactivities of samples at 240 min int,ervals of 24Na and *“Rb are 80.5”;, and 60” 0‘ respectively. Cl) t,o 30 min the radioactivity of s6Rbboth in anterior and posterior portions of thch aclueouswas hi,qher than the radi0activit.v of 24?Ga whereas after 60 min the rwww was trufl.
Thr~rubidium content of the cornea showeda steady increase for the whole pet&l. \vherchasthe level of sodium in the cornea followed the radioact’ivit,y of aqueous. .1s with l)otassium, rubidium accumulation is probably cellular. Maurieta ant1 Rilr~ (1970) gave stromal K as 21 mEq/kg water as compared T&h ,4.9 in aqueous. thcl corresponding values of Na being 165 and 144. Uptake of the intravenously itl,jectP(I rul)itlium clependsin somedegree on the vitality of the cornea1cells. Kecc~nt~lywe have found a marked decreaseof rubidiuul uljtake in corneas hurnetl with nitric acid. On the basisof the present data no difierences in the uptake of’~odiunl and rul)idium \vith respect to the cent’ral and peripheral parts of the cornea wt’r(’ ol)scrvc~l. whilst, in a similar study using 45(“aupt,ake in t hc central areit, QW highf~r than in the periphery (Obenberger and Babickj, 1967). Aulong all eyr! tissues the highest level of 86Rb accumulation was in thcx iris its rarly as 30 min. This could be explained by a very intensive uptake of 86Rt) in iritliat smooth nluscle cells, probahlv aided by the extensive vascularization of t’his tisslle. The transport of rubidium”into the lens has been the object of extensive invest.&tions ill vitro. The results of our present study. which show a st!eadily increasing a,(‘cumulation of int,ravenously injected *SRb by the normal IPW. suggestthat this intrktvenously injectetl rubidium method may he suitable for cluantitative evaluation ot changc~tlcatSiontransport in cataract,s of living animals. Intervals of :S1 hr WPIII tea 1~1tttc, tllost sat,isfactor,y for this purpose.
Wr wish to thank Mrs Niroslava Folkovii, Mrs VBclava RoMenovA ami Mr ChrutlG Chromecfor their capableassistance. REFERENCES Xaurice, D. Academic Obenberger, of %a Obenberger,
31.. Riley. BZ. V. (1970). In Riochrw~intry of thr E’ys (Ed. (+raymore, C. N.). P. 10. Press, London, New York. J. and Babirkg. 9. (1970a). Experimental cornea1 ralcifieatio:~. :1 study of transport into the aqueous and cornea. Ophthnl. Res. 1, 187-91”. J. and Babicki, A. (1970b). Penetration of radioactive calcium into the aqueous and corneaof normaland alloxan treated rabbits. Am. J. Ophthnlnaol. 70, 1003S5. Obenberger. J. and Babickj. A. (1973a). Alkali burns of the rahbit cornea. (‘orneal uptake 01’ ‘Y-glucose injected into the anterior chamber. Ophfhal. &es. 5, 1 -9. Obenberger, J. and Babick$, A. (1973b). Experimental endotoxine beratitis. Study oflY’a penetration in riuo into the aqueous humour and cornea (In Czech). Cesk. Ophthnlmol. 29, 34749. Obenherger, J. and Babick;, A. (1975a). Distribution of intravenously injected ‘“NaCl in different tissues of the rabbit exe. Ez~. Eye Res. 20, 189-93. Obenbeger, J. and Babicky, A. (197513). Dist’ribution of ““NaC’l in tissues of alkali- and acid-hurrwl rabbit eyes. Ex~. Eye Res. 20, 19%2063.