REGULATION OF MESSENGER-RNA EXPRESSION OF 3-BETA-HYDROXY-5-ENE STEROID DEHYDROGENASE IN PORCINE GRANULOSA-CELLS IN CULTURE - A ROLE FOR THE PROTEIN-KINASE-C PATHWAY

We studied the effect of the tumor-promoting phor-bol ester phorbol 12-myristate 13-acetate (PMA), which activates protein kinase-C, on porcine granulosa cells in culture. PMA as well as cholera toxin, forskolin, and hCG increased cAMP accumulation. PMA further augmented the elevation in cAMP accumulation induced by cholera toxin, forskolin, and hCG. In the same cell culture model, hCG induced a time-dependent increase in the 3β-hydroxy-5-ene steroid dehydrogenase (3βHSD) mRNA levels with a maximal 3-fold stimulation obtained at 8-16 h of incubation with 1 III hCG/ml. PMA inhibited the increase in 3βHSD mRNA levels induced by hCG in a dose-dependent manner. The phorbol ester also inhibited the increase in 3βHSD mRNA levels stimulated by LH as well as cholera toxin and forskolin and the cAMP analogs (Bu)2cAMP and 8-bromo-cAMP. Activation of protein kinase-C by mezerein similarly inhibited hCG stimulation of 3βHSD mRNA levels. The present data indicate that activation of the protein kinase-C pathway induces generation of cAMP, but causes a near-complete inhibition of the stimulatory effects of hCG, LH, forskolin, cholera toxin, and cAMP analogs bn 3βHSD mRNA levels in porcine granulosa cells in culture. © 1990 by The Endocrine Society.