Prostaglandins Alter the Abundance of Messenger Ribonucleic Acid for Steroidogenic Enzymes in Cultured Porcine Granulosa Cells1

The effects of prostaglandin F2α (PGF2α) and prostaglandin E2 (PGE2) on the accumulation of progesterone and mRNA for the steroidogenic enzymes 3β-hydroxysteroid dehydrogenase (3β-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 PGF2α (0.08−2.0 μg/ml) or PGE2 (0.1−1.0 μg/ml), or combinations of PGF2α (0.1−1.0 μg/ml) or PGE2 (0.1−1.0 μg/ml) with and without 20 ng/ml LH. Cultures were terminated after 12 h of incubation, and the abundance of mRNA for 3β-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 3β-HSD by 1.5 to 3.5 or 4-fold and for P450scc by 2–4-fold. PGF2α reduced the basal level of progesterone accumulation, as well as the steady-state concentrations of mRNA for both 3β-HSD and P450scc. PGF2α interfered with LH and (bu)2cAMP induction of 3β-HSD and P450scc message, and this interference was dependent on the PGF2α dose employed. PGE2 alone increased the accumulation of progesterone, as well as the message for 3β-HSD and P450scc. PGE2 overcame the abrogation by PGF2α of LH-induced synthesis of progesterone and transcription of 3β-HSD and P450scc. It is concluded that PGF2α regulates ovarian cell function, at least in part, by reducing the transcription of the rate-limiting steroidogenic enzyme P450scc and the progesterone synthetic enzyme 3β-HSD. PGE2 induces transcription of both enzymes and can overcome the luteolytic effects of PGF2α, which are visited on the genome in this cell system.