Steroidogenic Properties of Gonadotrophins

Abstract

The effect in vitro of the interstitial cell stimulating hormone (ICSH or LH), of pregnant mare serum gonadotrophin (PMSG) and of lactogenic hormone (LTH), on the synthesis of progesterone in slices of ovaries taken from pseudopregnant rats was investigated. It was found that ovine ICSH stimulated the synthesis of progesterone at a level of 0.01 μg/g of tissue; PMSG had no effect at a level of 0.1 μg/g of tissue, and a stimulating effect at higher levels; LTH had no steroidogenic effect. In addition, the effects of two follicle-stimulating hormone (FSH) preparations, one largely free of ICSH and the other containing minute quantities of ICSH, were studied in hypophysectomized rats and on the stimulation of progesterone synthesis in the ovaries of pseudopregnant rat. At concentration of less than 25 μg, ovine FSH had no effect on uterine growth and on interstitial tissue repair in the hypophysectomized female rat, and also had no effect on the synthesis of progesterone at concentrations of less than 50 μg/g of tissue. The ICSH contaminant in FSH was determined by comparing the steroidogenic properties of FSH with those of ICSH. Furthermore, studies with combinations of FSH and ICSH demonstrated that quantities of ICSH which in themselves are unable to stimulate steroidogenesis, are effective when combined with FSH.