SYNCHRONOUS GENERATION OF OVARIAN HCG BINDING-SITES AND LH-SENSITIVE ADENYLATE-CYCLASE IN IMMATURE RATS FOLLOWING TREATMENT WITH PREGNANT MARE SERUM GONADOTROPIN

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 3  (3) , 163-176
Abstract
A concomitant increase in the activity of LH[luteinizing hormone]-sensitive adenylate cyclase and in the number of LH-hCG [human chorionic gonadotropin] binding sites was induced in ovaries of immature rats upon administration of pregnant mare serum gonadotropin (PMSG), a hormone preparation known to have predominantly follicle stimulating (FSH-like) activity. When an optimal dose of PMSG (15 IU/rat) was administered to 25 day old rats, specific activity of LH-dependent adenylate cyclase and the number of binding sites for LH/hCG per mg protein remained unchanged during the first 24 h, but 48 h after injection a 2- to 4-fold increase in both parameters was observed. By contrast, there was no change in basal adenylate cyclase activity or in the response of the enzyme to the stimulatory action of guanosine-5''-(.beta..gamma.-imino) triphosphate (Gpp (NH)p), GTP, or NaF. Specific activity of succinate cytochrome c reductase, glucose-6-phosphatase and 5''-nucleotidase were found to be unaffected by the hormonal pretreatment, although total protein determined in these homogenates increased 3-fold in the course of this treatment. It is inferred that during follicular maturation, FSH enhances the responsiveness of ovarian adenylate cyclase to LH by stimulating the insertion of LH/hCG-receptors into the cell membrane.