Regulation of steroidogenic genes by insulin-like growth factor-1 and follicle-stimulating hormone: differential responses of cytochrome P450 side-chain cleavage, steroidogenic acute regulatory protein, and 3{beta}-hydroxysteroid dehydrogenase/isomerase i

The present study sought to characterize the concerted ac-tion of FSH and insulin-like growth factor-1 (IGF-1) on func-tional differentiation of prepubertal rat ovarian granulosa cells in culture. To this end, we examined the regulation of three key genes encoding pivotal proteins required for progesterone bio-synthesis, namely, side-chain cleavage cytochrome P450 (P450scc), steroidogenic acute regulatory (StAR) protein, and 3b-hydroxysteroid dehydrogenase/isomerase (3b-HSD). Time-de-pendent expression profiles showed that P450scc, StAR, and 3b-HSD gene products accumulate in chronic, acute, and consti-tutive patterns, respectively. Each of these genes responded to FSH and/or IGF-1 in a characteristic manner: A synergistic ac-tion of IGF-1 was indispensable for FSH induction of P450scc mRNA and protein; IGF-1 did not affect FSH-mediated upregu