Development of a Method to Test Anti-LH-RH Activity in Rats

Abstract
A method for testing anti-LH-RH activity wasdevised. The substance to be investigated was infused for 2 h i.e. in ovariectomized, estrogen- and progesterone-pretreated rats, followed by an acute injection of synthetic LH-RH into the jugular vein. The serum LH concentration was investigated be-fore and 20 min after the injection of LH-RH. Among all the peptides investigated, des-His-2-LH-RH was the only one that did not modify the response to LH-RH. The infusion with (pyro)Glu-His-Trp-NH2, Leu-3-LH-RH, and des-Trp-3-des-Gly-10-LH-RH only partially inhibited the response to LH-RH, whereas comparatively lower doses of des-His-2-des-Gly-10-LH-RH-ethylamide significantly blocked the LH release after the administration of LH-RH.