Susceptible period for the teratogenicity of di- n-butyltin dichloride in rats

Pregnant rats were given di- n-butyltin dichloride (DBT) by gastric intubation at a dose of 20 mg/kg on days 7–9, 10–12 or 13–15 of pregnancy or at a dose of 20 or 40 mg/kg on day 6,7,8 or 9 of pregnancy. While treatment with DBT on days 7–9 was significantly and high teratogenic, no evidence of teratogenicity was detected when DBT was given on days 10–12 or 13–15. Treatment on day 7 or 8 with both doses of DBT, but neither on day 6 or 9, resulted in an increased incidence of fetuses with malformations. The highest incidence of malformed fetuses occurred after treatment on day 8. The incidence of malformed fetuses was proportional to the dose of DBT. Anomaly of tail, anal atresia, club foot, omphalocele, deformity of the vertebral column, defect of the ribs and anophthalmia or microphthalmia were predominantly observed. It could be concluded that, following maternal exposure to DBT in rats, developing offspring are not susceptible to teratogenic effects of DBT on day 6 and that day 7 is the earliest susceptible period, day 8 is the highest susceptible period and day 9 is no longer a susceptible period for teratogenesis of DBT.