EFFECT OF MATERNAL PARAQUAT ADMINISTRATION ON THE FETAL DUCTUS-ARTERIOSUS IN THE RAT

The ductus arteriosus (DA) in the fetal rat was calibrated using a who le-body freezing method, 3 hr after maternal treatment with paraquat a t a dose of 25 mg/kg of body weight on days 19-21 of gestation. On day s 20 and 21, the DA was significantly constricted. The DA was also sig nificantly constricted on day 19 2/3 but not on day 19 1/2. It is conc luded that paraquat has a constrictive effect on the DA and that the o nset of this effect occurs in the first half of day 19 of gestation.