Modulation of cAMP-mediated differentiation in ovarian granulosa cells by epidermal growth factor and platelet-derived growth factor.

The modulating actions of peptide growth factors on ovarian follicular maturation were studied in granulosa cells during CAMP-dependent differentiation induced by follicle-stimulating hormone (FSH). During a 48-h culture of granulosa cells from hypophysectomized diethylstilbestrol-treated immature rats, FSH induced a 100-fold rise in cAMP and progesterone accumulation and a Ibfold increase in luteinizing hormone (LH) receptors. Epidermal growth factor (EGF) reduced each of these parameters in a concentration-dependent manner and inhibited FSH action by 80% between 24 and 48 h of culture. The inhibitory effect of EGF on cAMP formation was due to both reduction of FSHstimulated adenylate cyclase activity at 24 and 48 h of culture and increased catabolism of CAMP. The impairment of FSH-stimulated progesterone production was caused by increased steroid metabolism rather than decreased synthesis, since formation of 20a-dihydroprogesterone was increased by EGF treatment. In contrast, platelet-derived growth factor (PDGF) enhanced the actions of FSH upon cAMP and progestin production and LH receptor formation by about 2-fold between 12 and 48 h of culture. PDGF also maintained FSHsensitive adenylate cyclase activity during culture and reduced phosphodiesterase activity. The growth factors were not mitogenic and had little effect in the absence of FSH. No effects of growth factors on receptor binding of FSH were observed during the first 4 h or after 48 h of culture. In addition to their effects on cAMP production, both growth factors also modified CAMP-dependent pathways involved in granulosa cell differentiation. Thus, EGF prevented the stimulatory actions of 8-bromo-CAMP and choleragen on LH receptor formation, while PDGF amplified this response. Both EGF and PDGF enhanced progesterone and 20adihydroprogesterone levels induced by 8-bromo-CAMP and choleragen. These results indicate that modulation of both FSH-induced cAMP production and cAMP action contributes to the synergistic or inhibitory effects of PDGF and EGF on LH receptor expression and steroidogenesis in the ovarian granulosa cell.