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Urine gamma-glutamyl transferase in rat kidney toxicology: Nephropathy by repeated injections of mercuric chloride. Effects of sodium selenite
Toxicology, 12 (1979} 299- 305 © Elsevier/North-Holland Scientific Publishers Ltd.
URINE GAMMA-GLUTAMYL TRANSFERASE IN RAT KIDNEY TOXICOLOGY: NEPHROPATHY BY REPEATED INJECTIONS OF MERCURIC CHLORIDE. EFFECTS OF SODIUM SELENITE
S. SENER, J.P. BRAUN, A.G. RICO, P. BENARD and V. BURGAT-SACAZEa Laboratoire de Biochimie and aLaboratoire de Pharmacie-Toxicologie, Ecole Nationale V~t~rinaire, 31076 Toulouse Cedex (France)
(Received November 9th, 1978) (Revision received March 7th, 1979) (Accepted March 12th, 1979)
SUMMARY Groups of 5 male and 5 female Cobs CD rats weighing 2 5 0 - 3 5 0 g were injected intraperitoneally, daily for 15 days, with 5 pmol HgC12/kg, 5 pmol Na2SeO3/kg, or (5 ~mol HgCl: + 5 pmol Na2SeO3)/kg in a 10 ml/kg vol. of saline. Control animals were injected with saline only. Injection of saline or sodium selenite produced neither modification of diuresis, nor of urine elimination of sodium, potassium, chloride, phosphates, urea, creatinine and gamma-glutamyl transferase (GGT). Injection of mercuric chloride induced a massive increase of urine GGT, diuresis and phosphaturia and a decrease of kaliuria and natriuria. Those effects reflect a kidney tubular lesion which seems to be more severe in males than in females. Injection of mixed sodium selenite and mercuric chloride or separate injection of both compounds had similar effects. In both sexes, urine GGT elimination was delayed and about 2 times lower than with HgC12 alone. In females, the other urine parameters were almost normal whereas in males, diuresis and phosphaturia were slightly increased and kaliuria decreased. The observation of urine GGT elimination attests, in vivo, that sodium selenite decreases tubular toxicity of mercuric chloride and resulting kidney function disturbances.
INTRODUCTION In the rat, selenium decreases both morbidity and mortality induced by Abbreviation: GGT, gamma-glutamyl transferase.
299
mineral or organic mercuric c o m p o u n d s [3,4,8,15,23]. The precise mechanism of this antagonism and its effects on the different organs is not y e t well known: only Parizek [17] demonstrated, by histology, the absence of kidney lesions 26 h after a single injection of mercuric chloride and sodium selenite. This last aspect is studied here; kidney lesions are studied by use of the measurement of enzymuria which is as sensitive as histology [13,18,21,22] b u t that do n o t require sacrificing the animals. Gamma-glutamyl transferase (GGT; EC 2.3.2.2) has been used because, in the rat, it is kidney-specific, easily measurable in the urine, and intensively increased in acute mercuric nephropathy [ 1 ]. MATERIALS AND METHODS The experiment was performed in male Cobs CD (Charles River) rats weighing 250--350 g. Before any treatment the animals were accustomed to metabolic cages for 5 days. Then, on the 4 following days, the 24-h urines were collected and analysed in the aim of determining individual urine references; then, groups of 5 males and 5 females were given the following treatments for 15 days. Control group: daily intraperitoneal (i.p.) injection of 10 ml/kg of saline, Hg group: daffy i.p. injection of 5 g m o l HgC12/kg in the same volume of saline, Se group: daily i.p. injection of 5 pmol Na2SeO3/kg in the same volume of saline. (Hg + Se) groups: daily i.p. injection of (5 p m o l Na2SeO3 + 5 p m o l HgC12)/kg in the same volume of saline, or 2 daily i.p. separate injections on both sides of the a b d o m e n of 5 p m o l HgC12/kg and 5 ~mol Na2SeO3/kg, both in half a volume of saline to have an equal injected volume of saline. All 24-h urines were collected at room temperature and their volume was measured; then the urines were centrifuged for 5 mn at 3000 g and the following parameters were measured as previously described [1]: sodium, potassium, chloride, inorganic phosphate, urea and creatinine by continuous flow colorimetry; GGT activity was measured by use of a kinetic commercial procedure (Boehringer No. 125938) at 30°C. On the 15th day, the animals were killed; GGT activity was measured in the blood and in the 3000 g supernatants of kidney homogenates (1/10; m/m) in ice-cold saline. RESULTS First, it has been observed that the daily injection of saline or of sodium selenite produced no modification of the urine parameters in males as well as in females. Moreover, it has been verified that up to a concentration of 2 mmol/1, sodium selenite induced no inhibition of rat urine GGT. Repeated injections of mercuric chloride produced in both sexes an important increase of urine GGT (Fig. 1); this increase t o o k place earlier
300
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T Fig. 1. Variations of daily urine elimination of GGT. Results are percent of the mean (T) of the 4 days before daily i.p injections of 5 u m o l HgCl:/kg () of (5 u m o l HgCl: + 5 ~ m o l Na:SeO~)/kg ( - - - - - - ) to groups of 5 male ( , ) o f 5 female (e) rats. T-values(m • o): males Hg: 11.93 +- 1.55 U / 2 4 h, Hg + Se: 9.82 -+ 4.06 U / 2 4 h; females Hg: 3.43 +_ 0.58 U / 2 4 h, Hg + Se: 3.85 ± 0.53 U / 2 4 h.
and was proportionately more intense in females whose increase of enzymuria lasted longer, values came back to those of the controls on the 9th day; in males, on the contrary, the increase of enzymuria was shorter and on the 4th day, urine GGT was significantly below its reference value; then it was slightly increased on days 10 and 11. In the same time, functional urine parameters were strongly disturbed; diuresis (Fig. 2) was very much increased although it showed important daily variations. This increase of urine volume was parallel to a decrease of daily excretion of potassium (Fig. 3) and of sodium whereas phosphaturia (Fig. 4) was increased; other urine parameters were irregularly modified. No significant differences could be observed in animals given the mixture of Na:SeO: + HgC12 and those given 2 separate injections; this could result from the mixing of both compounds within the peritoneum. The results are those of the mixture. In both sexes, urine GGT elimination was about 2 times lower than in animals given HgCl: alone; moreover enzymuria t o o k place later and lasted a longer time in females, whereas in males it did not show a long period below reference values as it was observed with HgCI: alone. Similarly diuresis (Fig. 3) exhibited only a little increase on day 3 in
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Fig. 2. V a r i a t i o n s o f diuresis. E x p e r i m e n t a l p r o c e d u r e a n d s y m b o l s are t h e same as in Fig. 1. T-values ( m -+ o): m a l e s Hg: 17.4 -+ 4.4 m l / 2 4 h, Hg + Se: 18.4 -+ 4.4 m l / 2 4 h ; f e m a l e s Hg: 10.3 + 3.7 m l / 2 4 h, Hg + Se: 16.5 ± 4.8 m l / 2 4 h.
543
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T Fig. 3. V a r i a t i o n s o f Kaliuria. E x p e r i m e n t a l p r o c e d u r e a n d s y m b o l s are t h e s a m e as in Fig. 1. T-values ( m ± ~): males Hg: 5.17 ± 0.56 m E q / 2 4 h, Hg + Se: 4 . 4 0 ± 0.58 m E q / 24 h; females Hg: 3 . 1 2 ± 1.18 m E q / 2 4 h, Hg + Se: 3.69 ± 0.54 m E q / 2 4 h.
302
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Fig. 4. Variations of phosphaturia. E x p e r i m e n t a l p r o c e d u r e and symbols are t h e same as in Fig. 1. T-values (m -+ a): males Hg: 2.46 ± 0.68 rag/24 h, Hg + Se: 2.72 -+ 0.63 rag/24 h; females Hg: 0.96 -+ 0,31 rag/24 h, Hg + Se: 2.68 ~ 0.94 m g / 2 4 h.
males and was maximal on day 4, b u t it was a b o u t 2 times lower than with HgC12 alone. In females, the other urine parameters were not significantly modified whereas in males, one could observe a slight increase of phosphaturia (Fig. 4) from day 7 and a more important decrease of kaliuria all along the treatment (Fig. 3). At the m o m e n t of sacrificing the animals, blood GGT did n o t show any difference between groups. Kidney GGT was very similar in controls, in (Hg + Se) group and in Se group; on the contrary, it was slightly decreased {-10%; P ~< 0.20) in rats given HgC12 alone. DISCUSSION
In the rat, simultaneous administration of selenium and mercury changes the distribution of Hg in the b o d y : Hg retention is increased [1,7,11,23] and so are its concentrations in blood, liver, heart, brain or testicle; on the contrary Hg concentration in kidney is decreased between 0.5 and 0.1 [3,5,6,7,11,14,23]. The antagonism between Hg and Se could be attributed to stable proteic complexes between both elements [2,16] ; it is maximal for an equimolecular ratio of Se and Hg [7,11] : this antagonism decreases the HgC12-induced synthesis of metallothionein in the kidney [ 1 9 ] . Repeated administration of 0.5 ~mol HgC12/kg induced in males and females an important kidney tubular lesion shown by the massive increase of urine GGT originating from the brush borders of the proximal tubule cells [9,10], which are the toxic target of mercuric chloride [ 2 4 ] . The lower sensitivity of females [12] to the toxic effects of HgC12 is confirmed, even with repeated dosages. In females, dairy urine GGT excretion reference values are a b o u t 3 times lower than in males and HgC12 induced increases of urine GGT that seem proportionately larger than in males. This increase of enzymuria lasts a longer time and is n o t strongly decreased below refer-
303
ences values as in males. This decrease can be i n t e r p r e t e d as a lack o f r e g e n e r a t i o n o f k i d n e y t u b u l e cells or as an escape o f t h e i r e n z y m a t i c c o n t e n t [20] a n d is p r o b a b l y n o t a c o n s e q u e n c e of a decrease o f t o x i c i t y . I n t r a p e r i t o n e a l i n j e c t i o n o f m e r c u r i c chloride a n d s o d i u m selenite i n d u c e s the s a m e e f f e c t s w h e n b o t h m o l e c u l e s are injected s e p a r a t e l y or m i x e d as it had a l r e a d y b e e n s h o w n f o r s u b c u t a n e o u s injections with t h e s a m e doses [ 1 1 ] . In b o t h sexes, s o d i u m selenite decreases k i d n e y t o x i c i t y o f HgC12 as t h e increase o f e n z y m u r i a is smaller, lasts a longer t i m e a n d is n o t s t r o n g l y d e c r e a s e d b e l o w r e f e r e n c e values: this s h o w s smaller and less intense lesions o f t u b u l a r cells. S i m u l t a n e o u s l y , k i d n e y f u n c t i o n is n o t d i s t u r b e d in f e m a l e s a n d a l m o s t n o t in males: in males, diuresis is increased f r o m d a y 3 to d a y 6, a f t e r t h e m a x i m u m o f e n z y m u r i a ; similarly, kaliuria is l o w e r e d for all the time. V a r i a t i o n s in kaliuria w e r e less t h a n in e n z y m u r i a a n d like diuresis indicated a functional tubular disturbance. CONCLUSION T h e u r i n a r y e x c r e t i o n o f G G T as a m e a s u r e of renal d a m a g e caused b y HgC12 was d e c r e a s e d b y t h e s i m u l t a n e o u s a d m i n i s t r a t i o n o f e q u i m o l a r doses o f selenite w h e n b o t h c o m p o u n d s w e r e given i.p. f o r several days. ACKNOWLEDGEMENTS T h e a u t h o r s are i n d e b t e d t o Marie-B~atrice O u h m e d i and Claudine A f i r e f o r able t e c h n i c a l assistance a n d to R o b e r t G r e g o r y f o r t h e reviewing o f t h e English m a n u s c r i p t . REFERENCES 1 J.P. Braun, A.G. Rico, P. Benard, V. Burgat-Sacaze, B. Eghbali and J.C. Godfrain, Toxicology, 11 (1978) 73. 2 R.F. Burk, K.A. Foster, P.M. Greenfield and K.W. Kiker, Proc. Soc. Exp. Biol. Med., 145 (1974) 782. 3 R.F. Burk, H.E. Jordan and K.W. Kiker, Toxicol. Appl. Pharmacol., 40 (1977) 71. 4 L.W. Chang, A.W. Dudley, M.A. Dudley, H.E. Ganther and M.I. Sunde, in L. Roizin, H. Shiraki and Grzevic (Eds.), Neurotoxicology, Raven Press, New York, 1977, p. 275. 5 R.W. Chen, V.L. Lacy and P.D. Whager, Res. Commun. Chem. Pathol. Pharmacol., 12 (1975) 297. 6 R.W. Chen, P.D. Whager and S.C. Fang, Pharmacol. Res. Commun., 6 (1974) 571. 7 S.C. Fang, Chem.-Biol. Interact., 17 (1977) 25. 8 9 10
11 12 13 14
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H.E. Ganther, C. Goudie, M.L. Sunde, M.J. Kopecky, P. Wagner, S.H. Oh and W.G. Hoekstra, Science, 175 (1972) 1122. G.G. Gleener and J.E. Folk, Nature, 192 (1961) 338. H. Heinle, A. Wendel and U. Schmidi, FEBS Lett., 77 (1977) 220.
L. Magos, M. Webb, Arch. Toxieol., 36 (1976) 63. L. Magos, M. Webb and W.H. Butler, Br. J. Exp. Pathol., 55 (1974) 589. H. Mattenheimer, Med. Clin. North Am., 55 (1971) 1493.
A.C. Moffitt and J.J. Clary, Res. Commun. Chem. Pathol. Pharmaeol., 7, (1974) 593.
15 16 17 18 19 20 21 22 23 24
G. Ohi, S. Nishigaki, H. Seki, Y. Tamura, T. Maki, H. Kuono, S. Ochai, H. Yamada, Y. Shimamura, I. Mizoguchi and M. Yagyu, Environ Res., 12 (1976) 49. J. Parizek, in G.F. Nordberg (Ed.), Effects and Dose-Response Relationships of Toxic Metals. Elsevier, Amsterdam, 1976, p. 498. J. Parizek, J. Kalouskova, A. Babicky, J. Benes and L. Pavlik, in W.G. Hoekstra, J.W. Suttie, H.E. Ganther and W. Mertz (Eds.), Trace Elements Metabolism in Animals. University Park Press, Baltimore 1974, p. 119. R.J. Pierce, R.G. Price and J.S.L. Fowler, Biochem. Soc. Trans., 5 (1977) 238. J.K. Piotrowski, E.M. Bern and A. Werner, Biochem. Pharmacol., 26 (1977) 2191. F. Planas-Bohne, Arch. Toxicol., 37 {1977) 319. W.P. Raab, Clin. Chem., 18 (1972) 5. W.P. Raab, in U.C. Dubach (Ed.), Enzymes in Urine and Kidney, Hans Huber Publishers, Berne, 1968, p. 17. B.R. StiUings, H. Lagally, P. Baversfeld and J. Soares, Toxicol. Appl. Pharmacol., 30 (1974) 243. W.E. Stroo and J.B. Hook, Toxicol. Appl. Pharmacol., 39 (1977) 423.
305
URINE GAMMA-GLUTAMYL TRANSFERASE IN RAT KIDNEY TOXICOLOGY: NEPHROPATHY BY REPEATED INJECTIONS OF MERCURIC CHLORIDE. EFFECTS OF SODIUM SELENITE
S. SENER, J.P. BRAUN, A.G. RICO, P. BENARD and V. BURGAT-SACAZEa Laboratoire de Biochimie and aLaboratoire de Pharmacie-Toxicologie, Ecole Nationale V~t~rinaire, 31076 Toulouse Cedex (France)
(Received November 9th, 1978) (Revision received March 7th, 1979) (Accepted March 12th, 1979)
SUMMARY Groups of 5 male and 5 female Cobs CD rats weighing 2 5 0 - 3 5 0 g were injected intraperitoneally, daily for 15 days, with 5 pmol HgC12/kg, 5 pmol Na2SeO3/kg, or (5 ~mol HgCl: + 5 pmol Na2SeO3)/kg in a 10 ml/kg vol. of saline. Control animals were injected with saline only. Injection of saline or sodium selenite produced neither modification of diuresis, nor of urine elimination of sodium, potassium, chloride, phosphates, urea, creatinine and gamma-glutamyl transferase (GGT). Injection of mercuric chloride induced a massive increase of urine GGT, diuresis and phosphaturia and a decrease of kaliuria and natriuria. Those effects reflect a kidney tubular lesion which seems to be more severe in males than in females. Injection of mixed sodium selenite and mercuric chloride or separate injection of both compounds had similar effects. In both sexes, urine GGT elimination was delayed and about 2 times lower than with HgC12 alone. In females, the other urine parameters were almost normal whereas in males, diuresis and phosphaturia were slightly increased and kaliuria decreased. The observation of urine GGT elimination attests, in vivo, that sodium selenite decreases tubular toxicity of mercuric chloride and resulting kidney function disturbances.
INTRODUCTION In the rat, selenium decreases both morbidity and mortality induced by Abbreviation: GGT, gamma-glutamyl transferase.
299
mineral or organic mercuric c o m p o u n d s [3,4,8,15,23]. The precise mechanism of this antagonism and its effects on the different organs is not y e t well known: only Parizek [17] demonstrated, by histology, the absence of kidney lesions 26 h after a single injection of mercuric chloride and sodium selenite. This last aspect is studied here; kidney lesions are studied by use of the measurement of enzymuria which is as sensitive as histology [13,18,21,22] b u t that do n o t require sacrificing the animals. Gamma-glutamyl transferase (GGT; EC 2.3.2.2) has been used because, in the rat, it is kidney-specific, easily measurable in the urine, and intensively increased in acute mercuric nephropathy [ 1 ]. MATERIALS AND METHODS The experiment was performed in male Cobs CD (Charles River) rats weighing 250--350 g. Before any treatment the animals were accustomed to metabolic cages for 5 days. Then, on the 4 following days, the 24-h urines were collected and analysed in the aim of determining individual urine references; then, groups of 5 males and 5 females were given the following treatments for 15 days. Control group: daily intraperitoneal (i.p.) injection of 10 ml/kg of saline, Hg group: daffy i.p. injection of 5 g m o l HgC12/kg in the same volume of saline, Se group: daily i.p. injection of 5 pmol Na2SeO3/kg in the same volume of saline. (Hg + Se) groups: daily i.p. injection of (5 p m o l Na2SeO3 + 5 p m o l HgC12)/kg in the same volume of saline, or 2 daily i.p. separate injections on both sides of the a b d o m e n of 5 p m o l HgC12/kg and 5 ~mol Na2SeO3/kg, both in half a volume of saline to have an equal injected volume of saline. All 24-h urines were collected at room temperature and their volume was measured; then the urines were centrifuged for 5 mn at 3000 g and the following parameters were measured as previously described [1]: sodium, potassium, chloride, inorganic phosphate, urea and creatinine by continuous flow colorimetry; GGT activity was measured by use of a kinetic commercial procedure (Boehringer No. 125938) at 30°C. On the 15th day, the animals were killed; GGT activity was measured in the blood and in the 3000 g supernatants of kidney homogenates (1/10; m/m) in ice-cold saline. RESULTS First, it has been observed that the daily injection of saline or of sodium selenite produced no modification of the urine parameters in males as well as in females. Moreover, it has been verified that up to a concentration of 2 mmol/1, sodium selenite induced no inhibition of rat urine GGT. Repeated injections of mercuric chloride produced in both sexes an important increase of urine GGT (Fig. 1); this increase t o o k place earlier
300
800
500
I-
t
\
~"\V/,°"t ,,,41
lOG
DAYS
T Fig. 1. Variations of daily urine elimination of GGT. Results are percent of the mean (T) of the 4 days before daily i.p injections of 5 u m o l HgCl:/kg () of (5 u m o l HgCl: + 5 ~ m o l Na:SeO~)/kg ( - - - - - - ) to groups of 5 male ( , ) o f 5 female (e) rats. T-values(m • o): males Hg: 11.93 +- 1.55 U / 2 4 h, Hg + Se: 9.82 -+ 4.06 U / 2 4 h; females Hg: 3.43 +_ 0.58 U / 2 4 h, Hg + Se: 3.85 ± 0.53 U / 2 4 h.
and was proportionately more intense in females whose increase of enzymuria lasted longer, values came back to those of the controls on the 9th day; in males, on the contrary, the increase of enzymuria was shorter and on the 4th day, urine GGT was significantly below its reference value; then it was slightly increased on days 10 and 11. In the same time, functional urine parameters were strongly disturbed; diuresis (Fig. 2) was very much increased although it showed important daily variations. This increase of urine volume was parallel to a decrease of daily excretion of potassium (Fig. 3) and of sodium whereas phosphaturia (Fig. 4) was increased; other urine parameters were irregularly modified. No significant differences could be observed in animals given the mixture of Na:SeO: + HgC12 and those given 2 separate injections; this could result from the mixing of both compounds within the peritoneum. The results are those of the mixture. In both sexes, urine GGT elimination was about 2 times lower than in animals given HgCl: alone; moreover enzymuria t o o k place later and lasted a longer time in females, whereas in males it did not show a long period below reference values as it was observed with HgCI: alone. Similarly diuresis (Fig. 3) exhibited only a little increase on day 3 in
301
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Fig. 2. V a r i a t i o n s o f diuresis. E x p e r i m e n t a l p r o c e d u r e a n d s y m b o l s are t h e same as in Fig. 1. T-values ( m -+ o): m a l e s Hg: 17.4 -+ 4.4 m l / 2 4 h, Hg + Se: 18.4 -+ 4.4 m l / 2 4 h ; f e m a l e s Hg: 10.3 + 3.7 m l / 2 4 h, Hg + Se: 16.5 ± 4.8 m l / 2 4 h.
543
,.,.
DAYS
V
T Fig. 3. V a r i a t i o n s o f Kaliuria. E x p e r i m e n t a l p r o c e d u r e a n d s y m b o l s are t h e s a m e as in Fig. 1. T-values ( m ± ~): males Hg: 5.17 ± 0.56 m E q / 2 4 h, Hg + Se: 4 . 4 0 ± 0.58 m E q / 24 h; females Hg: 3 . 1 2 ± 1.18 m E q / 2 4 h, Hg + Se: 3.69 ± 0.54 m E q / 2 4 h.
302
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Fig. 4. Variations of phosphaturia. E x p e r i m e n t a l p r o c e d u r e and symbols are t h e same as in Fig. 1. T-values (m -+ a): males Hg: 2.46 ± 0.68 rag/24 h, Hg + Se: 2.72 -+ 0.63 rag/24 h; females Hg: 0.96 -+ 0,31 rag/24 h, Hg + Se: 2.68 ~ 0.94 m g / 2 4 h.
males and was maximal on day 4, b u t it was a b o u t 2 times lower than with HgC12 alone. In females, the other urine parameters were not significantly modified whereas in males, one could observe a slight increase of phosphaturia (Fig. 4) from day 7 and a more important decrease of kaliuria all along the treatment (Fig. 3). At the m o m e n t of sacrificing the animals, blood GGT did n o t show any difference between groups. Kidney GGT was very similar in controls, in (Hg + Se) group and in Se group; on the contrary, it was slightly decreased {-10%; P ~< 0.20) in rats given HgC12 alone. DISCUSSION
In the rat, simultaneous administration of selenium and mercury changes the distribution of Hg in the b o d y : Hg retention is increased [1,7,11,23] and so are its concentrations in blood, liver, heart, brain or testicle; on the contrary Hg concentration in kidney is decreased between 0.5 and 0.1 [3,5,6,7,11,14,23]. The antagonism between Hg and Se could be attributed to stable proteic complexes between both elements [2,16] ; it is maximal for an equimolecular ratio of Se and Hg [7,11] : this antagonism decreases the HgC12-induced synthesis of metallothionein in the kidney [ 1 9 ] . Repeated administration of 0.5 ~mol HgC12/kg induced in males and females an important kidney tubular lesion shown by the massive increase of urine GGT originating from the brush borders of the proximal tubule cells [9,10], which are the toxic target of mercuric chloride [ 2 4 ] . The lower sensitivity of females [12] to the toxic effects of HgC12 is confirmed, even with repeated dosages. In females, dairy urine GGT excretion reference values are a b o u t 3 times lower than in males and HgC12 induced increases of urine GGT that seem proportionately larger than in males. This increase of enzymuria lasts a longer time and is n o t strongly decreased below refer-
303
ences values as in males. This decrease can be i n t e r p r e t e d as a lack o f r e g e n e r a t i o n o f k i d n e y t u b u l e cells or as an escape o f t h e i r e n z y m a t i c c o n t e n t [20] a n d is p r o b a b l y n o t a c o n s e q u e n c e of a decrease o f t o x i c i t y . I n t r a p e r i t o n e a l i n j e c t i o n o f m e r c u r i c chloride a n d s o d i u m selenite i n d u c e s the s a m e e f f e c t s w h e n b o t h m o l e c u l e s are injected s e p a r a t e l y or m i x e d as it had a l r e a d y b e e n s h o w n f o r s u b c u t a n e o u s injections with t h e s a m e doses [ 1 1 ] . In b o t h sexes, s o d i u m selenite decreases k i d n e y t o x i c i t y o f HgC12 as t h e increase o f e n z y m u r i a is smaller, lasts a longer t i m e a n d is n o t s t r o n g l y d e c r e a s e d b e l o w r e f e r e n c e values: this s h o w s smaller and less intense lesions o f t u b u l a r cells. S i m u l t a n e o u s l y , k i d n e y f u n c t i o n is n o t d i s t u r b e d in f e m a l e s a n d a l m o s t n o t in males: in males, diuresis is increased f r o m d a y 3 to d a y 6, a f t e r t h e m a x i m u m o f e n z y m u r i a ; similarly, kaliuria is l o w e r e d for all the time. V a r i a t i o n s in kaliuria w e r e less t h a n in e n z y m u r i a a n d like diuresis indicated a functional tubular disturbance. CONCLUSION T h e u r i n a r y e x c r e t i o n o f G G T as a m e a s u r e of renal d a m a g e caused b y HgC12 was d e c r e a s e d b y t h e s i m u l t a n e o u s a d m i n i s t r a t i o n o f e q u i m o l a r doses o f selenite w h e n b o t h c o m p o u n d s w e r e given i.p. f o r several days. ACKNOWLEDGEMENTS T h e a u t h o r s are i n d e b t e d t o Marie-B~atrice O u h m e d i and Claudine A f i r e f o r able t e c h n i c a l assistance a n d to R o b e r t G r e g o r y f o r t h e reviewing o f t h e English m a n u s c r i p t . REFERENCES 1 J.P. Braun, A.G. Rico, P. Benard, V. Burgat-Sacaze, B. Eghbali and J.C. Godfrain, Toxicology, 11 (1978) 73. 2 R.F. Burk, K.A. Foster, P.M. Greenfield and K.W. Kiker, Proc. Soc. Exp. Biol. Med., 145 (1974) 782. 3 R.F. Burk, H.E. Jordan and K.W. Kiker, Toxicol. Appl. Pharmacol., 40 (1977) 71. 4 L.W. Chang, A.W. Dudley, M.A. Dudley, H.E. Ganther and M.I. Sunde, in L. Roizin, H. Shiraki and Grzevic (Eds.), Neurotoxicology, Raven Press, New York, 1977, p. 275. 5 R.W. Chen, V.L. Lacy and P.D. Whager, Res. Commun. Chem. Pathol. Pharmacol., 12 (1975) 297. 6 R.W. Chen, P.D. Whager and S.C. Fang, Pharmacol. Res. Commun., 6 (1974) 571. 7 S.C. Fang, Chem.-Biol. Interact., 17 (1977) 25. 8 9 10
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