title: The insulin-like growth factor, somatomedin C, induces the synthesis of cholesterol side-chain cleavage cytochrome P-450 and adrenodoxin in ovarian cells.
abstract: The actions of insulin and somatomedin C (insulin-like growth factor I) on cholesterol side-chain cleavage activity and the synthesis of cytochrome P-450scc and adrenodoxin were investigated in primary cultures of swine ovarian (granulosa) cells. Nanomolar concentrations of pure human somatomedin C stimulated biosynthesis of progesterone and 20 alpha-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-450scc and adrenodoxin. Micromolar concentrations of insulin (but not proinsulin or desoctapeptide) also induced synthesis of cholesterol side-chain cleavage constituents 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-450scc and adrenodoxin. Thus, we infer that somatomedin C may serve a critical role in the differentiation of steroidogenic cells in the mammalian ovary.
mesh_terms: D000325:Adrenodoxin / Q000096:biosynthesis*; D000818:Animals; D002478:Cells, Cultured; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000096:biosynthesis*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007527:Isoenzymes / Q000096:biosynthesis*; D010053:Ovary / Q000187:drug effects* / Q000201:enzymology; D010088:Oxidoreductases / Q000096:biosynthesis*; D011284:Pregnenolone / Q000096:biosynthesis; D011372:Progestins / Q000096:biosynthesis; D013002:Somatomedins / Q000494:pharmacology*; D013552:Swine; D013997:Time Factors
chemical_list: D007527:Isoenzymes; D011372:Progestins; D013002:Somatomedins; D000325:Adrenodoxin; D007334:Insulin-Like Growth Factor I; D011284:Pregnenolone; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D002786:Cholesterol Side-Chain Cleavage Enzyme