HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Schanbacher, B. D. Search for Related Content PubMed PubMed Citation Articles by Schanbacher, B. D.

Pituitary-Testicular Responses of Estradiol-17β-Implanted Bull Calves to Continuous versus Pulsatile Infusion of Luteinizing Hormone Releasing Hormone¹

US Department of Agriculture^2,3,, Clay Center, NE 68933

Abstract

The luteinizing hormone (LH), folliclestimulating hormone (FSH) and testosterone response of bull calves implanted with estradiol-17/β to continuous and pulsatile infusion of luteinizing hormone releasing hormone (LHRH) has been examined. Estradiol-17/β reduced serum LH and FSH concentrations and suppressed testosterone secretion and testicular growth when compared with sham-implanted bulls. Pulsatile 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-coupled 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-17/β 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.

¹ The author acknowledges the technical assistance of Kathy Sorenson, Cindy Rainbolt and Debbie Brown and the cooperation of the Univ. of Nebraska and the Nebraska Agr. Exp. Sta. Acknowledgement is also extended to Dr. D. J. Bolt, USDA, ARS, Beltsville, MD, for LH antiserum (DJB 3-12/11); Dr. K. W. Cheng, Univ. of Manitoba (Winnipeg), for FSH antiserum, Dr. P. N. Rao, Southwest Foundation for Research and Education, San Antonio, TX, for testosterone antiserum (X-181) and the Endocrine Study Section, National Institutes of Health, Bethesda, MD, for the bovine reference standards (NIH-LH-B10 and NIH-FSH-B1).

² Roman L. Hruska U.S. Meat Animal ResearchCenter, ARS.

³ Mention of trade names or companies does not constitute an implied warranty or endorsement by the author or USDA.