Inhibition of testicular luteinizing hormone receptor level by treatment with a potent luteinizing hormone-releasing hormone agonist or human chorionic gonadotropin

Treatment of adult male rats with a potent luteinizing hormone-releasing hormone agonist, [D-Leu 6, Des-Gly-NH 2 10] LHRH ethylamide or human chorionic gonadotropin for one week caused a marked decline in luteinizing hormone receptors in testicular tissue. Testicular weight was also significantly decreased by these treatments while plasma testosterone levels were decreased by treatment with the LHRH agonist and increased after hCG. A single injection of the LHRH agonist or hCG also induced a long-lasting loss of testis LH binding sites with receptor levels returning to control values at 8 days. These findings indicate than an elevation of endogenous LH, whether induced by single or repeated injection of a potent LHRH agonist, is capable of down regulating testicular LH receptors with a resultant long-term effect of reduced testicular size and decreased plasma testosterone concentration.