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

Abstract

This paper describes 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. Treatment of cells during a 36-h induction period with (Bu)2cAMP, 8- BrcAMP , 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 X 10(-7) M) added to medium as substrate. Presence of testosterone (5 X 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. The data showed that 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 X 10(-7) M), dihydrotestosterone (DHT) (5 X 10(-7) M), or 17 beta-estradiol (5 X 10(-7) M), responsiveness was at least partially restored. After treatment with progesterone (5 X 10(-7) M), FSH stimulation of cAMP production was not significantly different from that of cells cultured in medium alone. Hydroxyflutamide (5 X 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 X 10(-7) M) bound significantly more [125I]iodo-FSH than cells cultured in medium alone. Although DHT (5 X 10(-7) M) slightly increased FSH binding, the effect was not statistically significant. These results suggested that 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.

In human granulosa cells from small antral follicles, androgen receptor mRNA and androgen levels in follicular fluid correlate with FSH receptor mRNA

“…Previous studies have shown that androgens enhance granulosa cells expression of FSHR in vitro resulting in an increased aromatase expression and an augmented conversion of androgen to estrogen (rat: De Zwart, 1981, 1982;Daniel and Armstrong, 1984;primate: Harlow et al, 1986). However, in rhesus monkeys treated with large doses of exogenous androgens, testosterone was without effect on granulosa cell expression of aromatase and circulating levels of estradiol became reduced (Weil et al, 1999).…”

Catalytic differences between porcine blastocyst and placental aromatase isozymes

“…The production of 19-norandrostenedione in porcine and equine follicular fluid suggests that this compound is involved in the regulation of follicular function [15]. 19-Norandrostenedione, like testosterone, can act in synergy with dibutyryl cAMP to inhibit the germinal vesicle breakdown in porcine oocytes [18]. Similar to androgens, 19-norandrogens can regulate the activity of the 3b-hydroxysteroid dehydrogenase (HSD)/isomerase and affect progesterone synthesis by granulosa cells [19].…”

Steroid Receptors in the Uterus and Ovary

“…Whereas ER-mediated E2 actions are believed to enhance the amount and effectiveness of FSH-stimulated intracellular cAMP without obvious changes in FSH-receptor levels, evidence suggests that androgens may act at a site prior to adenylyl cyclase. For example, neither T nor DHT synergize with (Bu) 2 -cAMP to induce aromatase activity in rat granulosa cells 719 whereas E2 does. 442,720 Instead, ARmediated androgen actions may largely act by increasing the level of FSH receptor in granulosa cells of preantral follicles.…”