Regulation of prostaglandin e, progesterone, and cyclic adenosine monophosphate production in ovarian granulosa cells by luteinizing hormone and gonadotropin-releasing hormone agonist: Comparative studies

The early direct effects of GnRH on the ovary were investigated using cultured granulosa cells from preovulatory rat follicles, and compared to the known stimulatory effects of LH. Stimulation of ovarian functions by a GnRH agonist include a rapid receptor-mediated phosphatidylinositol turnover (~5 min). On the other hand, LH action on granulosa cells is initiated by increased cAMP production (~10-15 min), consisting of an indomethacin-resistant and indomethacin-sensitive pools (40% and 60%, respectively). The GnRH agonist [D-Ala⁶] des-Gly¹⁰ N-ethylamide (GnRHa) at concentrations of 10^-12- 10^-8 M had no effect on basal or LH-stimulated cAMP production during a 4-h incubation test. Both LH and GnRHa increase progesterone formation (30 and 120 min, respectively) with ED₅₀ values of 2.5 ng/ml and 10^-9 M, respectively and the stimulatory effect is not blocked by indomethacin. LH and GnRHa increase also prostaglandin E (PGE) formation (180 and 120 min, respectively) and the ED₅₀ values were 0.1 µg/ml and 10^-9 M, respectively. No inhibitory effect of GnRHa on LH actions was observed during 4 h of incubation. It is concluded that: 1) GnRH mimicks LH stimulation of ovarian PGE and progesterone production; 2) cAMP does not play a role in mediating the direct stimulatory effects of GnRH agonists on ovarian PGE and progesterone production; 3) PGE is not involved in mediating GnRH and LH stimulation of progesterone formation. 4) LHinduced cAMP production consists of indomethacin-sensitive and indomethacin-resistant pools.