Control of rat granulosa cell mitosis by phorbol ester-, cyclic AMP-, and estradiol-17 beta-dependent pathways

The present studies examined the effect of 8-bromo-cAMP (8-Br-cAMP), phorbol ester (TPA), and estradiol-17 beta (E2) on the capacity of rat granulosa cells (GC) to undergo mitosis. In the first series of experiments, GC were either maintained within immature rat ovaries in perifusion culture or isolated and placed in tissue culture. GC were cultured for 24 h with 1) control medium, 2) 8-Br-cAMP, 3) TPA, or 4) 8-Br-cAMP plus TPA in the presence of 3H-thymidine (3H-T). In perifusion culture, 8-Br-cAMP stimulated both 3H-T incorporation (p < 0.05) and E2 secretion (p < 0.05) while TPA increased 3H-T (p < 0.05) without altering E2 secretion (p > 0.05). Simultaneous exposure to 8-Br-cAMP and TPA enhanced 3H-T incorporation and suppressed E2 as compared to 8-Br-cAMP treatment alone (p < 0.05). In tissue culture, 8-Br-cAMP did not increase 3H-T incorporation or cell number. TPA increased both 3H-T incorporation (p < 0.05) and cell number (p < 0.05), while 8-Br-cAMP suppressed both of these TPA-induced responses. In the presence of testosterone, 1) TPA's mitogenic action was also observed, 2) basal E2 secretion ranged between 30 and 35 pg/ml, 3) neither 8-Br-cAMP nor TPA stimulated E2 secretion over basal levels, and 4) Rp-cAMP, a cAMP antagonist, blocked TPA-induced cell proliferation. E2 at 250 pg/ml also blocked TPA's mitogenic action. In a second series of experiments, GC were collected from eCG-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)