Potent inhibitory activity of [D-Leu6, Des-Gly-NH2(10)]LHRH ethylamide on LH/hCG and PRL testicular receptor levels in the rat.

Injection of male rats with 40-200 ng of [D-Leu6, des-Gly-NH2(10)]LHRH ethylamide for 7 days caused a maximal 80% reduction of testicular LH/hCG receptor level with one injection per day being as efficient as 3 daily injections. A similar inhibitory effect was observed on testicular PRL receptors. Testis and seminal vesicle weight as well as plasma testosterone levels were also significantly reduced by this treatment. These data indicate that a LHRH agonist, when given at a relatively low dose, is capable of reducing testicular LH/hCG and PRL receptor levels as well as testicular function, the effect being probably mediated by increased endogenous gonadotropin secretion.