EFFECT OF THE ALPHA SUBUNIT OF EQUINE LH ON THE FSH INDUCED CAMP PRODUCTION IN RAT SEMINIFEROUS TUBULE CELLS

Abstract

Previous observations from our laboratory have shown that equine LH can suppress the FSH induced cyclic AMP production in rat seminiferous tubule cells in vitro. The present investigation was carried out to determine the effect of various subunits in this system. The ratios (w/w) of subunits to equine FSH tested was 1:3, 3:1 and 30:1 with a standard dose of 0.3 μg of the FSH. It was noted that equine LH-β was not effective up to a 10 microgram concentration in inhibiting the cyclic AMP production induced by equine FSH. Under these conditions, equine LH-α suppressed the FSH activity in a dose dependent manner. However, alpha subunits derived from several other species of LH were without any effect on FSH action. Histidine modified derivatives of equine LH and its alpha subunit, both of which lack biological activity in the rat Leydig cell assay for LH, were found to be inactive as inhibitors of the equine FSH response. Thus, these results show that the suppressive effect of equine LH on FSH action in the rat seminiferous tubule is a function of the equine LH alpha subunit.