Evidence for the presence of cholesterol side chain cleavage cytochrome P-450 and adrenodoxin in fresh granulosa cells. Effects of follicle-stimulating hormone and cyclic AMP on cholesterol side chain cleavage cytochrome P-450 synthesis and activity.

Abstract

The synthesis of cholesterol side chain cleavage cytochrome P-450 (cytochrome P-450scc) and adrenodoxin was studied both in freshly harvested bovine granulosa cells and in granulosa cells maintained in primary monolayer culture. In addition, the action of follicle-stimulating hormone (FSH) and cyclic AMP analogs to stimulate the synthesis of cytochrome P-450scc was investigated in cultured cells. Precursor forms of cytochrome P-450scc and adrenodoxin were immunoisolated from a cell-free translation system directed by RNA prepared from freshly obtained granulosa cells that were not luteinized. Furthermore, the presence of cytochrome P-450scc in lysates of granulosa cells freshly obtained from very small follicles (containing less than 0.1 ml of follicular fluid) and in mitochondria of freshly obtained granulosa cells was demonstrated by using an immunoblotting technique. Continuous treatment of cultured granulosa cells with FSH or with cyclic AMP analogs (dibutyryl cyclic AMP or 8-bromo cyclic AMP) for 72 h increased incorporation of [35S]methionine into immunoprecipitable cytochrome P-450scc. Moreover, FSH, dibutyryl cyclic AMP, and 8-bromo cyclic AMP stimulated pregnenolone production by cultured granulosa cells (2.3-, 4.0-, and 7.5-fold increase over control, respectively), indicative of an increase in cholesterol side chain cleavage activity. The results of this study demonstrate for the first time the presence of two components of the cholesterol side chain cleavage system in freshly obtained granulosa cells, and provide direct evidence for the trophic effect of FSH and its presumed mediator, cyclic AMP, on the synthesis of cytochrome P-450scc in granulosa cells.