Aminoglutethimide Augments Follicle-Stimulating Hormone-Induced Aromatase Activity in Cultured Porcine Granulosa Cells

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Abstract
The role of endogenous progestin synthesis in the modulation of FSH-induced aromatase activity was examined. Granulosa cells isolated from nonatretic medium-sized (3-5 mm) follicles of prepubertal pigs were cultured for an initial 48-h period, during which time aromatase activity was induced by FSH in the absence or presence of aminoglutethimide (AG). After induction, the cell monolayers were washed before being cultured for a further 6-h period in the presence of the substrate testosterone (0.5 .mu.m). The aromatase activity was assessed by measuring the accumulation of estradiol during the test period. Basal aromatase activity was negligible and was unaffected by the presence of AG (0.1-100 .mu.M) during the induction period. But when cells were cultured with FSH and AG (0.1-1000 .mu.M) during the induction period, there was a dose-dependent, biphasic increase in the FSH-induced estradiol synthesis during the test period. Maximal enhancement was obtained with 10 .mu.M AG (3.5-fold). Thereafter the aromatase activity declined and, at 1000 .mu.m AG, was significantly (P < 0.05) inhibited. At the same time, the FSH-stimulated progestrin production during the induction period was inhibited in a dose-related fashion by AG. This AG-enhanced aromatase activity was dose and time dependent but was independent of the FSH concentration used. The apparent median effective dose of AG was 2.4 .mu.M and a minimal time of 24 h or less was needed to potentiate the induction of aromatase activity by FSH. If AG was, however, added to the cell cultures during the test period, the FSH-induced aromatase activity was inhibited, showing that AG is an inhibitor of FSH-induced aromatase activity. This action of AG during the test period could be alleviated by the addition of testosterone during the induction period. The viability of the granulosa cells and the total cellular protein were not significantly (P > 0.05) altered by AG. These results show that the induction of aromatase activity by FSH could be enhanced by AG, which probably acts by inhibiting progestrin production during the induction period, leading us to conclude that endogenous progestrins might play an important role in modulating the induction of aromatase activity by FSH.