U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
1984
Abstract
The luteinizing hormone (LH), folliclestimulating hormone (FSH) and testosterone response of bull calves implanted with estradiol-17β to continuous and pulsatile infusion of luteinizing hormone releasing hormone (LHRH) has been examined. Estradiol-17β reduced serum LH and FSH concentrations and suppressed testosterone secretion and testicular growth when compared with sham-implanted bulls. Putsatile iv infusion of LHRH [500 ng every 2 h (6 μg/d)] for a 4-wk period to estradiol-17β- implanted bulls resulted in elevated mean serum LH and testosterone concentrations that were characterized by discrete secretory episodes. Mean serum FSH was also increased by LHRH pulse infusion, but LHRH-coup!ed secretory episodes were not apparent . Continuous infusion of LHRH (6 μg/d) did not increase the low serum gonadotropin levels observed in estradiol- 17β-implanted calves. Testicular growth was normal in LHRH pulse-infused calves, but was markedly curtailed in continuously infused calves. These results suggest that estradiol-17β inhibits testicular development by blocking gonadotropin release at the level of the hypothalamus because pulsatile administration of LHRH can override the inhibitory effect by increasing LH and FSH secretion.
Comments
Published in Journal of Animal Science (1984) 58:4 943-948