Human recombinant inhibin A suppresses plasma follicle-stimulating hormone to intact levels but has no effect on luteinizing hormone in castrated rams

Abstract

This study tested the hypothesis that inhibin is a major negative feedback regulator of FSH secretion but has minimal effects on LH secretion in rams. In experiment 1, castrated rams (wethers) were given either vehicle or human recombinant inhibin A (hr-inhibin) as three s.c. or three i.v. 50-μg injections 6 h apart or as one 50-μg i.v. injection followed by 100-μg infusion over 12 h. Human recombinant inhibin suppressed plasma FSH while the vehicle had no effect. The greatest suppression in plasma FSH was achieved following i.v. administration of hr-inhibin given either by repeated injection or by infusion. In experiment 2, wethers were given vehicle or a 50-μg i.v. injection followed by 80..