Evaluation of an in utero through lactational exposure protocol for detection of estrogenic effects of ethinyl estradiol on the offspring of rats: preliminary trial

As a preliminary trial of an in utero through lactational exposure protocol, ethinyl estradiol, 0, 0.5, 5, or 50 micro g/kg/day, was administered by gavage to pregnant Crj: CD (SD) IGS BR rats from gestational day (GD) 7 to day 18 after delivery to evaluate the efficacy of this protocol and to estimate optimal endpoints. The dams showed no abnormalities. Cleft phallus was observed in female offspring at 50 micro g/kg. Other than a retardation of body weight gain in both sexes at 50 micro g/kg/day, no other abnormal findings were detected. The fact that cleft phallus was the only change induced suggests that the protocol is applicable to the detection of effects of estrogenic chemicals given to pregnant rats on offspring development and that the morphology of the female external genitalia may be a useful endpoint.