Neonatal imprinting of enzyme levels in rat adrenals

The metabolism of [4 ¹⁴C]4 androstene 3,17 dione was studied in adrenals from adult male and female rats gonadectomized at birth, at 14 and 43 days of age. A control group consisted of adult male and female rats sham operated at birth. Another group consisted of adult male and female rats castrated at birth and treated with a single dose of testosterone propionate 24 hr after the operation. The 5α reductase activity was found to be higher in female than in male sham operated rats (P < 0.02); postpubertal castration led to an increased enzyme activity in both male and female rats. Neonatal testectomy led to higher 5α reductase activity than testectomy at 14 days of age (P< 0.05) and treatment with testosterone propionate at birth tended to lower the 5α reductase activity. These results indicate that during the neonatal period testicular androgens irreversibly 'imprint' or 'programme' the adrenal 5α reductase activity to a lower, masculine level. The 11β hydroxylase system was also subject to androgenic inhibition in 2 ways: by irreversible 'imprinting' or 'programming' neonatally and by reversible suppression in adult life. The neonatal masculinization process effectuated by testicular androgens and previously shown to affect hypothalamic functions and liver enzyme levels also affects the activities of steroid metabolizing enzymes in adrenal tissue with possible effects on the adrenal secretion of steroid hormones (17 references).