Effects of human chorionic gonadotropin, prostaglandin F_2α and protein kinase C activators on the cyclic AMP and inositol phosphate second messenger systems in cultured human granulosa-luteal cells

The effects of human chorionic gonadotropin (hCG) and prostaglandin F_2α (PGF_2α) on the adenylate cyclase-cAMP and inositol phospholipid-phospholipase C-inositol trisphosphate and diacylglycerol transmembrane signalling systems were evaluated in cultured human granulosa-luteal cells. Granulosa-luteal cells obtained from patients undergoing in vitro fertilization were cultured for 72 h prior to addition of hormones. During the last 24 h of culture granulosa-luteal cells were incubated with [³H]inositol. Neither hCG nor gonadotropin-releasing hormone (GnRH) stimulated the nositol pholipid-phospholipase C signalling system. PGF_2α stimulated increases in inositol mono-, bis-, and trisphosphate accumulation in 30 min incubations. NaF (20 mM) mimicked the stimulatory effect of PGF_2α on inositol phosphate accumulation suggesting the involvement of a guanine nucleotide regulatory protein in the activation of phospholipase C. In contrast, hCG but not PGF_2α or NaF stimulated cAMP accumulation in 30 min incubations. Simultaneous treatment with hCG and PGF_2α did not alter the stimulatory effect of PGF_2α on inositol phosphate accumulation but reduced (37%) the stimulatory effect of hCG on cAMP accumulation. The protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA) inhibited the stimulatory effects of hCG (76%) and PGF_2α (62%) on cAMP and inositol phosphate accumulation, respectively. Thus, cultures of human granulosa-luteal cells possess multiple transmembrane signalling systems which may be modulated by the activation of protein kinase C.