GLUCOCORTICOID AND CYCLIC ADENOSINE 3'5'-MONOPHOSPHATE-MEDIATED INDUCTION OF CHOLESTEROL SIDE-CHAIN CLEAVAGE CYTOCHROME-P450 (P450SCC) IN MA-10 TUMOR LEYDIG-CELLS - INCREASES IN MESSENGER-RNA ARE CYCLOHEXIMIDE SENSITIVE

The regulation of cholesterol side-chain cleavage enzyme (P4508cc) was investigated in MA-10 tumor Leydig cells. We recently demonstrated that the constitutive and cAMP-stimulated expression of P450scc in normal mouse Leydig cells is negatively regulated by glucocorticoids. We now report that glucocorticoids have the opposite effect in MA-10 cells causing a 1.7-fold increase in the rate of P4508CC synthesis and a 2.1-fold increase in the amount of P450scc mRNA. Treatment of MA-10 cells with 10 μM 8-bromo-cAMP (8-Br-cAMP) (cAMP) resulted in a 1.7-fold increase in P450scc synthesis and a 3-fold increase in P450scc mRNA. Combined treatment with dexamethasone and cAMP resulted in additive increases in synthesis (2.8-fold) and mRNA (5.3-fold). Increases in de novo synthesis and mRNA levels were reflected by modest increases in the amount of immunoreactive P4508CC enzyme protein. Dexamethasone-me-diated stimulation in synthesis and accumulation of P4508CCmRNA were blocked by the antiglucocorticoid RU-486. Cycloheximide blocked both cAMP-and dexamethasone-induced increases but had no effect on constitutive levels of P4508CC mRNA. Treatment of MA-10 cells with 10 μM 8-Br-cAMP had no effect on cell morphology and stimulated progresterone accumulation to a minor degree. Treatment of MA-10 cells with 1 mM 8-Br-cAMP resulted in cell rounding and loss of cells from culture dishesThe results of this study demonstrate that: 1) dexamethasone increases P4508CCde novo synthesis and mRNA levels in MA-10 tumor Leydig cells, opposite to the effect in normal Leydig cells; 2) dexamethasone-and cAMP-stimulated increases occur via distinct mechanisms; 3) and synthesis of protein factor(s) is required to mediate the action of both dexamethasone and cAMP. © 1990 by The Endocrine Society.