PROSTAGLANDINS ALTER THE ABUNDANCE OF MESSENGER-RIBONUCLEIC-ACID FOR STEROIDOGENIC ENZYMES IN CULTURED PORCINE GRANULOSA-CELLS

The effects of prostaglandin F2alpha (PGF2alpha) and prostaglandin E2 (PGE2) on the accumulation of progesterone and mRNA for the steroidogenic enzymes 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and cytochrome P450 side-chain cleavage (P450scc) were determined in luteinized granulosa cells. These cells were aspirated from 3-5-mm follicles of prepubertal pigs and cultured 48 h with 10% serum and then 48 h under serum-free conditions. Cells were then incubated with medium (control), ovine LH (20 ng/ml), (bu)2cAMP (0.5 mM) and doses of PGF2alpha (0.08-2.0 mug/ml) or PGE2 (0.1-1.0 mug/ml), or combinations of PGF2alpha (0.1-1.0 mug/ml) or PGE2 (0-1-1.0 mug/ml) with and without 20 ng/ml LH. Cultures were terminated after 12 h of incubation. and the abundance of mRNA for 3beta-HSD and P450scc was determined by hybridization with specific cDNA probes. Parallel cultures were terminated at 24 h for analysis of progesterone in the medium by RIA. The results demonstrated that LH and (bu)2cAMP elevated progesterone by 3- to 6-fold and the accumulation of mRNA for 3beta-HSD by 1.5 to 3.5 or 4-fold and for P450scc by 2-4-fold. PGF2alpha reduced the basal level of progesterone accumulation, as well as the steady-state concentrations of mRNA for both 3beta-HSD and P450scc. PGF2alpha interfered with LH and (bu)2cAMP induction of 3beta-HSD and P45Qscc message, and this interference was dependent on the PGF2alpha dose employed. PGE2 alone increased the accumulation of progesterone, as well as the message for 3beta-HSD and P450scc. PGE2 overcame the abrogation by PGF2alpha of LH-induced synthesis of progesterone and transcription of 3beta-HSD and P450scc. It is concluded that PGF2alpha regulates ovarian cell function, at least in part, by reducing the transcription of the rate-limiting steroidogemic enzyme P450scc and the progesterone synthetic enzyme 3beta-HSD. PGE2 induces transcription of both enzymes and can overcome the luteolytic effects of PGF2alpha, which are visited on the genome in this cell system.