Conversion of androgen to estrogen by the rat fetal and neonatal female gonad: effects of dcAMP and FSH.

Female gonads of fetal (on days 14.5, 16.5, 18.5 and 20.5 postcoitum) and neonatal rats (on days 4.5 and 8.5 postpartum) were cultured in Medium 199 in the presence of [3H]testosterone and the conversion into [3H]estrone and [3H]estradiol was estimated. Formation of both estrogens was found in all fetal and neonatal ovaries explanted in control medium. Dibutyryl cAMP (1 mM) had a clear-cut stimulatory effect as early as 16.5 days postcoitum, but had little or no effect at 8.5 days postpartum. In contrast, ovine or rat FSH (0.3 or 1 microgram/ml, respectively) increased the aromatase activity only from 20.5 days postcoitum. The effects of FSH and dibutyryl cAMP were more obvious after preculture for 48 h in control medium. These results indicate that: a biochemical sex differentiation, revealed by the difference in aromatase activity levels between ovaries and testes or other tissues occurs in female gonads as early as 14.5 days postcoitum; aromatase activity in the ovaries increases markedly after birth; functional FSH receptors are absent before 20.5 days postcoitum in the ovaries.