Stimulation of ovarian cyclic guanosine 3',5'-monophosphate levels by the subunits of human chorionic gonadotropin

Injection of human chorionic gonadotropin (HCG) into the tail vein of superovulated rats resulted in a significant (P<0.01) increase in peripheral plasma progesterone without a concomitant increase in ovarian cyclic GMP (cGMP) levels. However, when equimolar quantities of α and β subunits of HCG were injected, a significant increase in plasma progesterone was accompanied by a concomitant and significant (P<0.01) increase in ovarian cGMP levels. The observation that these subunits increase ovarian cGMP levels without increasing cAMP suggests the possibility of cGMP involvement in steroidogenesis induced by subunits.