Early pregnancy failure induced by dibutyltin dichloride in mice.

In this study, we examined the adverse effects of dibutyltin on initiation and maintenance of pregnancy after maternal administration during early pregnancy in mice. Following successful mating, female ICR mice were given dibutyltin dichloride (DBTCl) at 0, 7.6, 15.2, or 30.4 mg/kg bw/day by gastric intubation on days 0-3 or days 4-7 of pregnancy. Female mice were sacrificed on day 18 of pregnancy, and the pregnancy outcome was determined. After administration of DBTCl on days 0-3, the rate of nonpregnant females and the incidence of preimplantation embryonic loss were significantly increased at 30.4 mg/kg bw/day. The incidences of postimplantation embryonic loss in females given DBTCl on days 0-3 at 15.2 mg/kg and higher and on days 4-7 at 7.6 mg/kg bw/day and higher were increased. No increase in the incidence of fetuses with external malformations was observed after the administration of DBTCl on days 0-3 or days 4-7. A decline in the serum progesterone levels was detected in mice given DBTCl at 30.4 mg/kg bw/day on days 0-3 or days 4-7 of pregnancy. The data show that DBTCl adversely affects the initiation and maintenance of pregnancy when administered during early pregnancy in mice and suggest that the decline in serum progesterone levels is responsible for pregnancy failure.

A two-generation reproductive toxicity study of diethyl phthalate (DEP) in rats.

A two-generation reproductive toxicity study was performed to evaluate the effects of diethyl phthalate on parental reproductive performance, including features of the endocrine system and development and growth of offspring at dietary dose levels of 0, 600, 3000 and 15000 ppm. In F0 and F1 parents, no treatment-related adverse effects were observed in clinical findings, body weights, food consumption, reproductive parameters, and gross or histopathological findings in any treated group. Increased liver weights and enhanced activities of metabolic enzymes were observed in F0 males at 15000 ppm. F0 males also exhibited an increase in the content of CYP3A2, a cytochrome P450 isozyme, at 15000 ppm, and a decrease in the levels of serum testosterone at 3000 and 15000 ppm, suggesting sex steroid metabolism might be changed. However, these were not considered adverse effects because the degree of change was too slight to affect the reproductive capability to produce progeny. Body weight gains before weaning were inhibited in F1 and F2 pups and vaginal opening was slightly delayed in F1 females at 15000 ppm. No changes were observed in the reproductive performance. Therefore, the no-observed-adverse-effect level (NOAEL) from this study is considered to be 15000 ppm for parental animals, and 3000 ppm for development and growth of the pups.