Neonatal steroid exposure increases in vitro aromatization ability of peripubertal hamster ovaries

Neonatal female hamsters were exposed to doses of testosterone propionate or estradiol benzoate that would lead to behavioral masculinization and defeminization at adulthood. At Days 20, 30, or 40 of life, ovaries were removed and incubated in Kreb's Ringer bicarbonate for 4 h with or without the addition of 1 X 10(-9) M testosterone as a substrate. Incubation medium was assayed by radioimmunoassay (RIA) for the accumulation of estradiol. Ovaries from steroid-exposed animals aromatized testosterone to estradiol at a greatly increased rate compared to ovaries from oil-injected control animals. Serum from treated animals contained androgen, which could act as substrate for aromatization in vivo. Neonatally estrogenized females exhibited elevated circulating estradiol levels. Increased aromatizing ability could be due to early antral follicle formation as a result of elevated luteinizing hormone (LH) and/or follicle-stimulating hormone (FSH). Implications of increased aromatization ability of ovaries in the process of behavioral sexual differentiation are discussed.