Site of Action of Androgens on Follicle-Stimulating Hormone-Induced Aromatase Activity in Cultured Rat Granulosa Cells*

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Abstract
Experiments on cultured granulosa cells isolated from ovaries of immature rats designed to locate the site of action of androgens on FSH-induced aromatase activity are described. Treatment of cells during a 36 h induction period with (Bu)2cAMP, 8-Br-cAMP, FSH, prostaglandin E2, or cholera toxin resulted in induction of aromatase activity measured as 17.beta.-estradiol accumulation during a 6 h test period with testosterone (5 .times. 10-7 M) added to medium as substrate. Presence of testosterone (5 .times. 10-7 M) during the induction period enhanced the effects of FSH, cholera toxin and prostaglandin E2 on aromatase activity, but not those of the cAMP analogs. The effects of culturing and steroids on responsiveness of granulosa cells to FSH (measured as FSH-stimulated cAMP production during a 1 h test period) were examined. Culturing in medium alone for 36 h resulted in a decrease in the ability of FSH to stimulate cAMP production when compared to that of freshly isolated cells. After culture with testosterone (5 .times. 10-7 M), dihydrotestosterone (DHT) (5 .times. 10-7 M), or 17.beta.-estradiol (5 .times. 10-7 M), responsiveness was at least partially restored. After treatment with progesterone (5 .times. 10-7 M), FSH stimulation of cAMP production was not significantly different from that of cells cultured in medium alone. Hydroxyflutamide (5 .times. 10-5 M), an antiandrogen known to block androgen-receptor interaction, abolished the effect of DHT and depressed the effect of testosterone on responsiveness of granulosa cells to FSH. Cells treated for 36 h with testosterone (5 .times. 10-7 M) bound significantly more [125I]iodo-FSH than cells cultured in medium alone. Although DHT (5 .times. 10-7 M) slightly increased FSH binding, the effect was not statistically significant. Apparently, androgens regulate granulosa cell aromatase activity not only as substrates, but also by acting at a site before cAMP production (possibly at the level of the FSH receptor) in the control of FSH-induced enzyme activity.

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