Serum gonadotropin concentrations and ovarian response in ewes treated with analogs to LH-RH/FSH-RH.

Abstract

Serum gonadotropin concentrations and ovarian response in ewes treated with analogs to luteinizing hormone-releasing hormone/follicle s timulating hormone-releasing hormone (LH-RH/FSH-RH) are reported. In Ex periment 1, 32 ewes received either .5, 5, 50 or 500 mcg of des Gly10-LH-RH ethylamide or LH-RH/FSH-RH. Peak LH concentration was signi ficantly higher (p less than .01) in ewes treated with .5 mcg analog than in ewes treated with .5 mcg LH-RH/FSH-RH and there was a greater number (p less than .05) of ovulations in the ewes treated with analog than in ewes treated with LH-RH/FSH-RH. In Experiment 2, 10 ewes were treated either with 500 mcg anlog or saline. All were artificially inse minated 12 hours postinjection. A greater number of ovulations (p less than .05) occurred in ewes treated with the analog than in those treated with saline, but none of the ewes conceived. In Experiment 3, 70 ewes r eceived either the analogs D-ALa6 des Gly10-FH-RH ethylamide, D-leu6 des Gly10-LH-RH-ethylamide or LH-RH/FSH-RH. An increase (p less than .05) in total LH, mean peak LH and duration of the LH release in ewes treated with either .5, 5, 50 mcg D-Ala6 and D-Leu6 analog was seen as compared to ewes which received corresponding doses of LH-RH/FSH-RH. The analogs were 9, 4 and 3 times more potent in total LH releasing ability when compared to LH-RH/FSH-RH at the .5, 4 and 50 mcg doses, respectively. These data indicate that the maximal pituitary response was obtained with 50 mcg of the D-Ala6 or D-Leu6 analog but that 500 mcg of LH-RH/FSH-RH was required before maximal LH release was attained.