Effects of in utero and lactational exposure to flutamide in SD rats: comparison of the effects of administration periods.

Pregnant CD(SD) IGS rats were given flutamide (FLUT) orally at doses of 0.4, 2, or 10 mg/kg/day from gestational day 6 to postnatal day (PND) 20, and the effects of FLUT exposure on male offspring were examined 10 weeks after birth, and compared to the effects in offspring treated after weaning and in offspring untreated after weaning. Although the body weight of the dams treated with FLUT remained normal, two dams in the 10 mg/kg/day group were killed because of abnormal parturition periods and loss of all the pups. The number of stillborns and dead newborns at birth was significantly higher in the 10 mg/kg/day group than in the control groups. No abnormalities in the reproductive parameters of the other dams treated with FLUT were detected. The body weights of the male offspring in each group remained normal from birth until the end of the study. The ano-genital distance was significantly shortened in 2 and 10 mg/kg/day groups. Changes in the organ weights and gross findings were detected in the 2 and/or 10 mg/kg/day groups with or without the continuous administration of FLUT after weaning; these changes were more appreciable in groups treated with FLUT after weaning than in groups untreated after weaning. The prolongation of preputial separation was observed in the 0.4 and 2 mg/kg/day groups treated with FLUT after weaning, but this change was not detected in the same dose groups untreated after weaning. The testosterone levels were higher in the 10 mg/kg/day group treated with FLUT after weaning. The present data demonstrated that the endocrine-mediated effects on rats were more appreciable in offspring treated with FLUT after weaning than in offspring untreated after weaning.