Effects of Luteinizing Hormone Receptor-Binding Inhibitor on the in Vitro Steroidogenesis by Rat Ovary and Testis*

Abstract

An inhibitor for LH receptor site binding (LHRBI) was tested for its effect on in vitro LH-stimulated progesterone biosynthesis by an ovarian slice preparation from pseudopregnant rats and for its effect on testosterone biosynthesis by a testicular mince preparation. LH-RBI was extracted from pseudopregnant rat ovaries stored at -20 C for 10 weeks or longer after excision. There was a >100% increase of progesterone production in the 2-h incubated control compared to the unincubated control. LH (1.7 μg/ml) further stimulated progesterone production (>100% over the incubated control). LH-RBI preparation in quantities of 10–100 mg tissue equivalent significantly inhibited the LH- and hCG-stimulated progesterone biosynthesis but did not affect basal progesterone biosynthesis. In contrast to the effect on ovarian progesterone biosynthesis, a similar preparation of LH-RBI, alone or in conjunction with LH, significantly stimulated testosterone biosynthesis in the testicular mince preparation. Extracts prepared f...