Evaluation of teratogenic potential of sodium sulfite in rats.

The teratogenicity of sodium sulfite was examined in Wistar rats. The pregnant rats were fed diets containing 5, 2.5, 1.25, 0.63 or 0.32% of sodium sulfite heptahydrate(Na2SO3.7H2O) ad libitum from day 8 to 20 of pregnancy. Maternal toxicity, as evidenced by decreased body weight gain and decreased food consumption was observed at the 5% group, but no clinical signs of toxicity were observed. A significant reduction in the fetal body weight of both sexes was observed in all dose groups except 2.5% group. No significant differences in the numbers of live fetuses and intrauterine death (dead fetuses and resorptions) or sex ratios of fetuses were found between the sodium sulfite-treated and control groups. Fetal external, skeletal and internal malformations were not observed at any dose level. However, several types of skeletal and internal variations as well as delayed ossifications were observed in some groups treated with sodium sulfite, but the incidences were not significantly different from controls. Also, some fetuses with dilatation of the renal pelvis and the lateral ventricle were found in all groups except 1.25% group, but there was no dose-response. The live birth index and survival rate of offspring within 4 weeks and their body weight gain at 3 weeks after birth were not affected by sodium sulfite-treatment. In conclusion, sodium sulfite (0, 0.32, 0.63, 1.25, 2.5 or 5.0% as Na2SO3.7H2O) administered in the diet to Wistar rats during days 8-20 of pregnancy produced related signs of fetal toxicity but no evidence of teratogenicity.