U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska

 

Document Type

Article

Date of this Version

1984

Comments

Published in Journal of Animal Science (1984) 58:4 943-948

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.

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