Studies on the regulation of the onset of steroid hormone biosynthesis in fetal rabbit gonads.

TLDR: It is established that from the onset of estrogen synthesis the fetal ovary possesses all of the enzymes necessary to form estrogens from pregnenolone, including sufficient 3β-hydroxysteroid dehydrogenase-Δ4,5-isomerase activity.

Abstract: Two aspects of the differentiation of the fetal rabbit gonad have been studied. First, the ability of the fetal ovary to synthesize 17β-estradiol from [7-3H]pregnenolone was measured. By day 18 of gestation, the fetal ovary was capable of synthesizing 17β-estradiol from radioactive pregnenolone (5 mol 2 h-1 mg protein-1), thus establishing that from the onset of estrogen synthesis the fetal ovary possesses all of the enzymes necessary to form estrogens from pregnenolone, including sufficient 3β-hydroxysteroid dehydrogenase-Δ4,5-isomerase activity. Second, a method was developed to estimate the rate of cholesterol side chain cleavage activity by measuring the total amount of six steroids [progesterone, pregnenolone, dehydroepiandrosterone, androstenedione, Δ5-androstenediol (5-androstene-3β,17β-diol), and testosterone] produced in 2-h incubations of fetal rabbit gonads. Cholesterol side chain cleavage activity in fetal testes was linear with time up to 2 h and with increasing concentrations of hCG up to a ...