Inhibin Interaction with LHRH Receptors at the Pituitary Level

In order to investigate whether inhibin could modulate the action of luteinizing hormone releasing hormone (LHRH), the in vitro effect of inhibin on LHRH binding to the pituitaries from intact adult male rats was studied. The inhibin preparations suppressed the binding of labeled LHRH to pituitary receptors in a dose-related manner. In vivo administration of inhibin decreased the pituitary LHRH receptor concentration, with an apparent increase in the affinity of these receptors. A dose-related decrease was observed in serum follicle stimulating hormone (FSH) levels in the same group whereas the serum luteinizing hormone (LH) levels remained unaltered. There may be a direct action of inhibin at the pituitary level to suppress FSH levels specifically.