Abstract
Rats on day 21 of pregnancy received a subcutaneous injection of Paraquat (2, 7 or 25 mg/kg). The inner diameter of the ductus arteriosus (DA) of their fetuses was measured using the whole-body freezing method 1, 3, 6 and 24 hours after injection. The 7 mg/kg dose group showed a significant constriction of the DA 3 hours after paraquat treatment. The 25 mg/kg dose group showed a significant constriction 3 and 6 hours after treatment. The constrictive effect was dose-dependent, that is, the magnitude of constriction observed 3 hours after paraquat injection was greater in the 25mg/kg dose group than in the 7 mg/kg dose group. The 2 mg/kg dose group showed no significant change in the inner diameter of the DA at any point of measurement (1, 3, 6 and 24 hours after injection), compared to the saline treated controls. These results indicate that paraquat induces constriction of the fetal rat DA in a dose-dependent manner when administered in late stages of gestation, and that this effect of paraquat is not seen at a dose level of 2 mg/kg.
