The actions of insulin and somatomedin C (insulin-like growth factor I) on cholesterol side-chain cleavage activity and the synthesis of cytochrome P-450(scc) and adrenodoxin were investigated in primary cultures of swine ovarian (granulosa) cells. Nanomolar concentrations of pure human somatomedin C stimulated biosynthesis of progesterone and 20α-hydroxypregn-4-en-3-one. Moreover, in the presence of exogenous sterol substrate for cholesterol side-chain cleavage, somatomedin C significantly enhanced pregnenolone biosynthesis in a time- and dose-dependent manner. This augmentation of functional cholesterol side-chain cleavage activity was accompanied by a dose-dependent (2-16-fold) increase in [35S]methionine incorporation into specific immunoprecipitable cytochrome P-450(scc) and adrenodoxin. Micromolar concentrations of insulin (but not proinsulin or desoctapeptide) also induced synthesis of cholesterol side-chain cleavage constitutents by 4-7-fold. These results demonstrate that an insulin-like growth factor, somatomedin C, exerts discrete differentiating effects on ovarian cells characterized by increased synthesis of immunospecific cytochrome P-450(scc) and adrenodoxin. Thus, we infer that somatomedin C may serve a critical role in the differentiation of steroidogenic cells in the mammalian ovary.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|State||Published - 1986|
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