PARENT SESSION
Gene Regulation & Function

PROGESTINS AND GLUCOCORTICOIDS REGULATES TRANSCRIPTION OF THE CYTOCHROME-P450scc (P450scc) GENE IN STABLE GRANULOSA CELLS.

Chedrese, Jorge¹, Furlan, Micheal¹, Smida, Andrea¹, Agostini, Maria¹, Urban, Randall², ^{1 2}

ABSTRACT- We have previously reported that the synthetic progestin levonorgestrel (LNG) stimulates progesterone (P4) synthesis in the stable porcine granulosa cells, JC-410. We have now investigated the effects of P₄, LNG, the P₄-receptor antagonist RU486, and the glucocorticoids, hydrocortisone (HC) and dexametasone (DX), on transcription of P450scc gene. Transcription of the P450scc gene was investigated by transient expression of the luciferase gene linked to 2320-bp of the P450scc gene promoter and nuclear run-on assay, in cultures of the JC-410 cells. In transient expression assays, low concentrations of P₄ and LNG, 3 and 10 M, increased transcription in a dose response fashion up to 2.5-fold, while higher concentrations, 100 M, inhibited transcription to 0.2-fold. RU486, HC and DX, 3 to 100 M, increased transcription in a dose-response fashion, up to 2.5, 2.8, and 3.1-fold respectively. No inhibition of transcription was observed with RU486, HC and DX at these concentrations. RU486 combined with P₄ and LNG at 3 and 10 mM, did not affect stimulation of transcription. However, RU486 blocked the inhibitory effect of P₄ and LNG at 100 ng/ml. The nuclear run-on assays showed a similar pattern of stimulation and inhibition observed in the transient expression assays. The results correspond with our previous observation in which LNG and P₄ induced an increase followed by a decrease, in the levels P450scc mRNA and that RU486 act like a P₄ agonist. The glucocorticoids, that stimulate progesterone synthesis, also activate transcription of the P450scc gene. The JC-410 cells do not express the P₄-receptor. Therefore, we conclude that progestins may regulate transcription of the P450scc gene via the glucocorticoid receptor in the granulosa cells. Supported by MRC/Saskatchewan Health, NSERC and CNTC grants to P. J. Chedrese.

KEY WORDS: granulosa cells, progestins, glucocorticoids, steroidogenesis