3-BETA-HYDROXY-5-ENE STEROID DEHYDROGENASE GENE-EXPRESSION REGULATIONIN PORCINE GRANULOSA-CELLS - DIFFERENTIAL EFFECT OF FSH AND LH ON GENE-TRANSCRIPTION

The objective of this study was to investigate the effect of the tumor -promoting phorbol ester phorbol 12-myristate 13-acetate (PMA) on FSH- and LH-induced 3 beta-HSD-gene expression in cultured porcine granulo sa cells. FSH and LH induced a dose dependent increase in the accumula tion of 3 beta-HSD mRNA, measured by Northern blot. A 1.6- to 1.8-fold increase (p < 0.01) was observed with 10 ng/mL of FSH or LH. Maximal levels of 2.5- to 2.9-fold increases, relative to control, were reache d at 30 and 100 ng/mL of the gonadotropins. When granulosa cells were treated with PMA (100 nM) just before the addition of FSH, the 3 beta- HSD rnRNA levels induced by 10 or 30 ng/mL of FSH were inhibited or pa rtially inhibited, respectively. PMA did not inhibit elevated levels o f 3 beta-HSD mRNA induced by FSH at concentrations of 100, 300, and 10 00 ng/mL. Alternatively, PMA added just before LH, inhibited LH-stimul ated 3 beta-HSD mRNA levels at all doses of LH tested (10, 30, 100, 30 0, and 1000 ng/mL). The protein kinase A-stimulators, dibutyryl-cAMP ( cAMP) (0.5 mM) and forskolin (10 nM), also elevated the 3 beta-HSD-gen e transcription, 3.5- and 4.0-fold respectively. PMA prevented the sti mulation of the 3 beta-HSD-gene transcription when it was added just b efore cAMP or forskolin. We concluded that stimulation of PKC by PMA a ppears to have inhibited the gonadotropin-induced increase in 3 beta-H SD mRNA levels by preventing cAMP-activated 3 beta-HSD-gene transcript ion. The data also suggest that the effect of PMA appears to be more s pecific for regulation of LH-stimulated intracellular signals than tho se of FSH. This effect may indicate a site of differential regulation of FSH and LH on the stimulation of 3 beta-HSD-gene transcription.