Differentiation Of Steroidogenic Cells Research Articles

The insulin-like growth factor, somatomedin C, induces the synthesis of cholesterol side-chain cleavage cytochrome P-450 and adrenodoxin in ovarian cells.

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.

Peripheral androgen concentrations and testicular morphology in embryonic and young male Japanese quail.

Abstract Plasma samples and gonads from male Japanese quail embryos were examined to determine the association of serum androgen concentrations and differentiation of steroidogenic cells. Embryos were sampled at 1- and 2-day intervals and seven posthatch samples were taken between 1 and 24 days of age. Plasma samples were analyzed by radioimmunoassay specific for testosterone. Gonadal samples were examined by electron microscopy. Plasma androgen was elevated on the eighth day of the 17-day incubation, declined, and rose again between 13 days of incubation through 3 days posthatch. Circulating androgen subsequently remained low until after 18 days of age. Interstitial cells in the embryonic quail testes retained a fibroblast-like appearance through hatching. Between 2 and 3 weeks posthatch interstitial cells differentiated into presumptive Leydig cells, as characterized by smooth endoplasmic reticulum and lipid droplets. Differentiation at that time appeared to be coincident with the increasing testosterone concentrations.