Effect of insulin on porcine granulosa cells: implications of a possible receptor mediated action.
The mechanism of direct action of insulin on porcine granulosa cells cultured in vitro was investigated. Specific receptors for insulin with two classes of binding sites were present. No significant difference in receptor characteristics was observed between granulosa cells obtained from small (1-2 mm), medium (3-5 mm) or large (6-11 mm) follicles. Insulin (25 mIU/ml) augmented both basal and hCG-stimulated progesterone secretion. Insulin was also essential for hCG-stimulated morphological luteinization of cultured porcine granulosa cells obtained from small follicles. Furthermore, 2 h pre-incubation with insulin (100 mIU/ml) increased glucose incorporation by cultured porcine granulosa cells as determined by pulsing with D-[14C](U)-glucose. The same dose of insulin also stimulated the glucose-6-phosphate independent form of glycogen synthase. These results suggest that porcine granulosa cells possess insulin receptors and that insulin, mediated by its specific receptors, enhances glucose metabolism by stimulating glycogen synthase. Thus, insulin may play a pivotal role in morphological and functional differentiation of porcine granulosa cells.
D000818:Animals; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D005947:Glucose / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D011374:Progesterone / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism*; D013552:Swine
D006063:Chorionic Gonadotropin; D007328:Insulin; D011374:Progesterone; D006006:Glycogen Synthase; D011972:Receptor, Insulin; D005947:Glucose