3-BETA-HYDROXY-5-ENE STEROID DEHYDROGENASE GENE-EXPRESSION REGULATIONIN PORCINE GRANULOSA-CELLS .1. FSH-MEDIATED AND LH-MEDIATED TRANSCRIPTIONAL ACTIVATION

In this report we examined the effect of FSH and LH, on the steady sta te levels of 3 beta-5-hydroxy-5-ene steroid dehydrogenase (3 beta-HSD) mRNA and on the 3 beta-HSD-gene transcriptional activation in porcine cultured granulosa cells. Exposure of granulosa cells to 100 ng/ml FS H or LH for 8 h, elevated to 3.0 and 2.5-fold respectively the levels of SB-HSD mRNA measured by Northern blot analyses. The withdrawal of F SH and LH induced a rapid decay of the 3 beta-HSD levels, reaching the control values after 2 h. Re-addition of FSH and LH after 4 h withdra wal elevated the levels of 3 beta-HSD mRNA to 4.8 and 5.3-fold respect ively. Addition of actinomycin D, to granulosa cells previously treate d with FSH or LH, induced a rapid decay in the levels of 3 beta-HSD mR NA, reaching the control values after 2 h, with an estimated half life 1.3 and 1.2 h respectively. FSH and LH stimulated the 3 beta-HSD-gene transcription, measured by nuclear run-on assays, by 1.7 and 19-fold respectively. Addition of cholera toxin (10 ng/ml) or forskolin (10 nM ) stimulated the 3 beta-HSD-gene transcription by 2.15 and 2.4-fold re spectively. We conclude that gonadotropins positively regulate 3 beta- HSD transcriptional activation and appear to have no effect on the 3 b eta-HSD mRNA stability.