Neonatal imprinting of sex differences in the hepatic metabolism of a chlorinated cyclodiene by rat liver microsomes.

The effects of neonatal gonadectomy and the neonatal administration of steroid hormones on the development of sex differences in hepatic drug metabolism in the adult rat have been investigated. Castration of male rats at birth prevented the development of sex differences in metabolism in adult life. The effects of neonatal castration of male rats on the development of sex differences in adult life were reversed by treatment of the neonate with testosterone but not by estradiol or dihydrotestosterone treatment. Treatment of neonatal female rats with testosterone had no effect on the development of a feminine pattern of metabolism unless the ovaries were removed before puberty, suggesting that the effects of neonatal imprinting by testosterone can be repressed by the actions of the ovaries in adulthood.