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To assess the effects of sodium valproate on rat sperm morphology, sperm count, motility, and histopathological changes in testis.
Male Wistar rats (12 week old) were treated with sodium valpraote and sacrificed at the end of 2nd, 4th, 5th, 7th, 10th and 15th week after the last exposure to sodium valproate. Epididymal sperm count, sperm motility, sperm morphology, and histopathology of testes were analyzed.
Sperm count and sperm motility were decreased significantly by sodium valproate. The percentage of abnormal sperms increased in a dose-dependent manner. A histopathological study revealed that sodium valproate had caused sloughing of epithelial cells in testes.
Sodium valproate causes reversible change in sperm motility, sperm count, morphology, and cytoarchitecture of testes.
Epilepsy is a curable disease, which necessitates continuous treatment with optimal dose of antiepileptic drugs. Sodium valproate is one of the drugs of choice in primary generalized tonic-clonic seizures, absence seizures, and myoclonic seizures. It is also the drug of choice in epileptic syndromes such as the Lennox-Gastaut syndrome because of its wide therapeutic spectrum, and it may be useful in infantile spasms.[3,4] Oral administration for 60 days in rats significantly decreased testicular weight, sperm cell concentration, live sperms, and percentage of progressively motile spermatozoa and increased percentage of morphologically abnormal spermatozoa. It has been reported that in epileptic children receiving valproic acid, the latter produces a significant change in sister chromatid exchange. It is also reported that it lacks mutagenic potential within the therapeutic dose range when administered chronically to adult male patients with epilepsy.
There is a report of dose-dependent effect of chronic valproate treatment on testicular morphology in rats. Nishimura et al suggest that sperm motility and histopathological evaluation of testes are sensitive methods for assessing toxicity of valproate on male reproductive organs. However, there is a paucity of reports on the effects of valproate on reproductive toxicity with regard to its time, duration, and reversibility. Hence, a study was planned to assess the effects of sodium valproate on sperm morphology, sperm count, motility, and histopathological changes in epididymis and testis.
Twelve week old male Wistar rats (150-200g) bred locally in the central animal house were selected for the study. They were housed in propylene cages and were provided bedding with paddy husk. Temperature was maintained at 25 ± 1°C with a humidity of 45 ±1%. Animals had free access to sterile food (animal chow) and water ad libitum. Animal care and handling was done as per the guidelines set by the Indian National Academy New Delhi, India. The study was started after getting clearance from the institutional animal ethics committee. The registration number of animal facility is 94/1999/CPCSEA.
A total of 144 rats were segregated to 24 groups of 6 animals each. Six groups each were treated with 0.1 ml of distilled water, gum acacia control, sodium valproate 200 mg, and sodium valproate 400 mg for 60 days (N=6/group/dose/sample time). Rats were sacrificed by terminal anesthesia (pentobarbital sodium, 45 mg/kg) at the end of 2nd, 4th, 5th, 7th, 10th, and 15th week after the last exposure to sodium valproate. The sacrifice time points represent the sampling of spermatozoa in the epididymis and testis, spermatids, primary spermatocytes, secondary spermatocytes, spermatogonia, and stem cells (10th and 15th week), respectively.[10‐12]
The powdered form of sodium valproate was obtained from Knoll Pharmaceuticals Ltd, Mumbai. The median lethal dose of sodium valproate in rodents varies between 1100 and 3900 mg/kg body weight. The dose and route of administration were selected based on earlier reports.[8,14] The powdered form of sodium valproate was weighed using an electronic weighing balance and was dissolved in water and administered orally.
The epididymal sperm suspension is prepared in 1 ml of phosphate buffered saline (PBS) at pH 7.2. The sperm count was determined in a hemocytometer. An aliquot from the suspension (1 ml) was diluted 1:40 with PBS. A sample of the diluted suspension is charged into a counting chamber (Neubauer's chamber). The total sperm count in eight squares (Except the central erythrocyte area) of 1 mm2 each was determined and multiplied by 5 × 104 to get the total count. Sperm motility was also counted in same eight squares and percentage of motile sperms was recorded.
A fine suspension was made and stained with 0.2 ml of 1% aqueous eosin. About one drop of stained suspension was placed on the clean slide. It was dried, cleaned, and mounted in Di-N-Butyle Phthalate in Xylene (DPX). Slides were looked for sperm-shape abnormality, 1000 sperms/animal being scored. Sperms were classified into normal and abnormal sperms. The abnormal sperms were classified under head abnormalities and tail abnormalities. The head abnormalities were classified as amorphous, hook less, banana shaped, double headed, and bent. The tail abnormalities were classified as coiled/folded and double tailed.
The testes/epididymis were removed and fixed in Bouin's fluid for 24 h. After excessive washing in 70% alcohol, the tissue was processed for paraffin embedding and 5 μ thick paraffin sections were stained with hematoxylin and eosin. The sections were analyzed for the presence or absence of vacuoles, gaps, and abnormal cells.
The diameters of 20 transversely cut tubules were measured using ocular micrometer calibrated with the stage micrometer (Erna Opticals, Japan). In each tubule, two measurements were made one perpendicular to the other and their average is taken. The epithelial height was measured in ten tubules for each animal. In each tubule, the SEH was measured from the basement membrane to the surface of the epithelium at two different regions and the mean was taken.
Six animals were used in each group and mean ± SD (standard deviation) was calculated. Results were analyzed by one-way Analysis of Variance (ANOVA). Values of P< 0.05 were considered statistically significant.
Both 200 mg/kg and 400 mg/kg of sodium valproate significantly decreased sperm count, starting from the 2nd week sampling time and continued through the 4th, 5th, and 7th week. The lowest sperm count was observed during the 7th week and the sperm count returned to control levels by 15th week. Complete recovery was observed by 15th week and the recovery was almost the same in both the doses [Figure 1].
Sperm motility was significantly decreased significantly at 2nd, 4th, 5th, and 7th week with both doses of the drug. By the 10th week, there was complete recovery and the sperm motility values reached the control values. For the rats treated with 200 mg/kg sperm motility was least during the 7th week sampling time and for 400 mg/kg, sperm motility was least at 5th week sampling time. Recovery period to normal values of sperm motility was same in both 200 mg/kg and 400 mg/kg treated rats and reached complete recovery by the 10th week sampling time [Figure 2].
The percentage of abnormal sperms increased significantly in a time-dependent manner at 4th, 5th, and 7th week sampling time in rats treated with both the doses. The maximum sperm abnormality was observed at the 5th week with the higher dose [Figure 3] and during the 7th week sampling time in rats treated with 200 mg/kg.
Sloughing of epithelial cells in testes was observed in the rats treated with lower as well as with higher dose of the drug. The sloughed cells were found in the lumen of the seminiferous tubules. The presence of vacuoles was seen at both the doses. However, the maximum number of vacuoles appeared at 5th and 7th week with the higher dose. Atrophy of the tubules was rarely seen and multinucleated cells were absent [Figures [Figures44 and and55].
Sodium valproate did not alter the weight of the testes significantly. However, the diameter of the seminiferous tubule was significantly decreased in the rats treated with the higher dose in 4th, 5th, and 7th week samples. However, the tubular diameter was significantly increased in rats treated with the higher dose at 2nd week sampling time. Complete recovery of the tubular diameter was seen only at the 15th week [Figure 6].
The epithelial height of the tubules was significantly reduced at all sampling weeks except for the 15th week, regardless of the dose. Maximum reduction of the epithelial height was observed at 5th week in both doses of the drug. Recovery period for both the doses was long and normal height was attained only by the 15th week [Figure 7].
Sperm count is one of the most sensitive tests for spermatogenesis, since it gives the cumulative result of all stages in sperm production, and it is highly correlated with fertility. Our results show that sodium valproate is cytotoxic to the sperm since it decreases the sperm count significantly in a linear manner from 2nd to 7th week sampling time, regardless of the dose. The duration of spermatogenic cycle in rats is 52 to 60 days and our findings point out that the germ cells affected are approximately the spermatids, spermatocytes, and spermatogonia. The count was reduced even at the end of the 10th week. This in all probability signifies its effect on the stem cells. The decline in sperm count was highest at the 7th week, which possibly indicates that the spermatogonia are more vulnerable to the toxic effects of sodium valproate.
Since the very earliest (spermatogonial) phase is when nearly all cell multiplication occurs, chemicals which interfere with this phase will probably have a disproportionately greater effect on sperm output than chemicals acting during the spermatid phase. It was not mutagenic to the sperms at 7th week. This can be demonstrated by the reduced number of abnormal sperms observed by the end of that week.
A study conducted to determine the gonadotoxic effect of sodium valproate found that serum testosterone levels were not significantly changed, but there was a highly significant increase in FSH and LH concentrations at the high dose. However, an earlier study by Soliman et al had reported a decrease in plasma testosterone, FSH and LH and an increase in prolactin levels on treatment with sodium valproate. The decrease in the sperm count in the present study may be due to the decreased levels of intratesticular testosterone at the 2nd to 7th week sampling time, as testosterone level is directly linked to spermatogenesis. It is also possible that the Sertoli cells might have been affected and the other possibility might be due its effect on the epididymal function. According to Ameen et al recovery of sperm count was complete at the low dose level (270 mg/kg), but was incomplete at the high dose level (540 mg/kg), 8 weeks after discontinuing valproate. In contrast, in the present study regardless of the dose, there was a reduction in the sperm count 7 weeks after discontinuing the drug. However, reversal of the harmful effects on the sperms was observed by the end of the 15th week, which indicates that the stem cells were not affected severely.
Studies have examined rat sperm motility as a reproductive end-point[19‐22] and sperm motility assessments are an integral part of some reproductive toxicity test guidelines.[19,20,23‐25] Sodium valproate decreased the percentage of sperm motility in a time-dependent manner. Similar results were observed by earlier workers.[11,26] The sperm motility largely depends on the microtubular apparatus of the sperm tail. In the current study it was also observed that a considerable number of abnormal sperms were with a defect in their tail. Valproate is known to compromise mitochondrial function. Mitochondria are needed for the energy production of the cells and motility of the sperm requires normal mitochondrial function and therefore mitochondrial effects of the valproate might be a cause of reduced sperm motility.
According to Russel and Russel, male germ cells are very ideal and easy for the study of the genotoxicity of drugs since they exist in different phases of cell development and differentiation. Genotoxic effects of the drug would result in morphologically abnormal sperms and therefore the counting and classification of the types of abnormal sperm can determine the presence and extent of genotoxicity. Sodium valproate treatments resulted in more than double the percentage of abnormal sperms and hence it could be considered as mutagen. Currently it is widely accepted that the induction of sperm abnormality mainly takes place through point mutation.[31,32] Therefore, it is possible that change in the sperm structure might have been due to point mutation.
The question as to why the higher dose of sodium valproate increased the tubular diameter is a little difficult to address. The most likely reason would be the extensive sloughing that was seen at 2nd week sampling time. According to Nakai et al, the sloughed cells can block the efferent ductules and hence increase the diameter of the tubules.
This study concludes that sodium valproate has a reversible mutagenic effect on the germ cells and somatic cells. Findings from this study point out the gonadotoxic and cytotoxic potential of this drug.
Source of Support: Nil
Conflict of Interest: None declared