The effect of long-acting ACTH on plasma corticosteroids, testosterone, and LH levels in the male pig.

Intramuscular injection of long-acting ACTH (10 micrograms/kg body weight) into male pigs, fitted with permanently indwelling jugular catheters, resulted in a significant rise of plasma corticosteroid concentrations for a period of between 0.5 and 20 hours after injection. Plasma testosterone levels were significantly increased between 60 and 120 min after ACTH administration. Between 6 and 12 hours after ACTH application, however, they were significantly depressed, evidencing a two phase effect of ACTH on testosterone levels. Plasma LH concentrations showed a slight but progressive decrease which was significant between 2.5 and 12 hours p.i. From these results it has been concluded that long-acting ACTH stimulates testosterone release. Because LH levels were depressed, they cannot have been responsible for the increase in plasma testosterone. The increase of plasma testosterone concentrations was not accompanied by a change of plasma prolactin levels.