Unusual anti-reproductive properties of the analog [d-Leu6,des-Gly-NH2(10)]-luteinizing hormone-releasing hormone ethylamide in male rats.

Nanogram quantities of a luteinizing hormone-releasing hormone (LHRH) agonist, [D-Leu6,des-Gly-NH2(10)]-LHRH ethylamide, were injected into immature male rats twice daily for 40 days. Treatment with the analog significantly increased serum luteinizing hormone and follicle-stimulating hormone levels, but suppressed accessory sex organ weights. Plasma and testicular concentrations of testosterone were also significantly decreased. The agonist did not alter body, pituitary, or testis weights. Spermatogenesis and the morphology or density of the Leydig cells also appeared not to be affected. A possible direct effect of the analog on the testes is discussed.