Androgen Biosynthesis in Human Ovarian Follicles: Cellular Source, Gonadotropic Control, and Adenosine 3′,5′ Monophosphate Mediation*

Abstract

Thecal and granulosa cells isolated from human ovarian follicles were incubated separately for various time intervals (0, 0.5, 1, and 2 h) in the presence or absence of hCG or highly purified FSH. At the end of the incubation period, absolute ethanol was added to the culture tubes and androgen and cAMP production were determined by RIA and protein-binding assay, respectively. In the absence of gonadotropin, human thecal cells produced androgen and cAMP in vitro. While FSH (0.01-10 μg/ml) failed to exert any significant effect on this androgen and cAMP production during a 2-h incubation, synthesis of androgen (2- to 5-fold) and the nucleotide (5- to 50-fold) was markedly increased by hCG (1 IU/ml). These responses of the theca to the gonadotropin were dose dependent, and as little as 0.1 IU hCG/ml medium was effective in enhancing androgen production by 2- to 3-fold. A temporal relationship between the hCG-stimulated androgen and cAMP synthesis seems to exist, with significant increases in the production of the steroid being preceded by that of the nucleotide by at least 1 h. Addition of dibutyryl cAMP (1 to the incubation medium markedly (2- to 20-fold) stimulated thecal androgen production. Chromatographical separation of testosterone and 17β-hydroxy-5α-androstan-3-one in the samples indicated that the androgen measured consisted mainly of testosterone and that 17β-hydroxy-5α-androstan-3-one was present in much smaller amounts. Granulosa cells isolated from the same ovarian follicles produced little or no androgen under the same experimental conditions as those used for the thecal preparations. FSH, hCG, and dibutyryl cAMP were not effective in stimulating androgen production by human granulosa cells. cAMP production by these cells was stimulated by FSH but not by hCG. The inability of granulosa cells to respond to hCG in cAMP production could possibly be due to the immaturity of the follicles examined. It is concluded that the theca is the cellular source of follicular androgen and that LH (hCG), possibly via cAMP, regulates androgen production by the human ovaries. These findings are consistent with the concept that in ovarian follicles, the theca provides the aromatizable substrate needed for 17β-estradiol synthesis in the granulosa cells.