Metabolism of 4-14C-Progesterone by Human Fetal Testis and Ovaries

Abstract

Homogenates of testes and ovaries, obtained from human fetuses at 9–11, 12–15 and 19 weeks of gestational age, were incubated with 4-¹⁴C-progesterone. The media of the individual incubations were combined into groups according to sex and age, and analyzed for conversion products of progesterone by the reverse isotope dilution technique. Testes tissue converted progesterone to testosterone, 17α-hydroxyprogesterone (a major metabolite) and 16α-hydroxyprogesterone. Testosterone synthesis by the older (12–15 weeks) tissue was at least 7-fold that of the younger testes tissue. In contrast, ovarian tissue exhibited little metabolic activity toward progesterone except for the oldest (19 weeks) age group. Here, progesterone was extensively reduced to 20α-hydroxy-4-pregnene- 3-one. During the second quarter of human gestation, the fetal testis shows extensive proliferation of the Leydig cells, presumably with concomitant androgen synthesis and secretion. At this time, the fetal ovary is still hormonally quiescent. The marked difference found in the levels of progesterone metabolism are in accord with these morphological and biological observations. (Endocrinology74: 833, 1964)