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

This Article Full Text Full Text (PDF) All Versions of this Article: 74/1/58    most recent biolreprod.105.043760v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by At-Taras, E.E. Articles by Roser, J.F. Search for Related Content PubMed PubMed Citation Articles by At-Taras, E.E. Articles by Roser, J.F. Agricola Articles by At-Taras, E.E. Articles by Roser, J.F.

Reducing Estrogen Synthesis Does Not Affect Gonadotropin Secretion in the Developing Boar¹

Department of Animal Science, ³ Department of Population Health & Reproduction,⁴ School of Veterinary Medicine, University of California, Davis, California 95616

ABSTRACT

Boars have high concentrations of plasma and testicular estrogens, but how this hormone is involved in feedback regulation of the gonadotropins and local regulation of testicular hormone production is unclear. The present study examined the effects of reducing endogenous estrogens by aromatase inhibition on concentrations of plasma LH and FSH and on testicular and plasma concentrations of testosterone (T) and immunoreactive inhibin (INH). Thirty-six littermate pairs of boars were used. One boar from each pair was assigned to the control group (vehicle); the other boar to the treatment group (aromatase enzyme inhibitor, Letrozole, 0.1 mg/kg body weight [BW]). Weekly oral treatment started at 1 wk of age and continued until castration at 2, 3, 4, 5, 6, 7, or 8 mo. Plasma concentrations of gonadotropins, INH, T, estradiol (E₂), and estrogen conjugates (ECs) were determined. Testicular tissue was collected at castration for determination of INH and T and for confirmation of reduced aromatase activity. The acute effects of aromatase inhibition on gonadotropins were monitored in two adult boars treated once with Letrozole (0.1 mg/kg BW). Treatment with the aromatase inhibitor reduced testicular aromatase activity by 90% and decreased E₂ and ECs without changing acute, long-term, or postcastration LH and FSH. Plasma T, testicular T, and circulating INH concentrations did not change. Testicular INH was elevated in treated boars compared with controls. In conclusion, estrogen does not appear to play a regulatory role on gonadotropin secretion in the developing boar. This is in direct contrast to findings in males of several other species.

estradiol, follicle-stimulating hormone, inhibin, luteinizing hormone, testosterone

¹ Supported by National Research Initiative Competitive grant 2002-35203-12606 from the USDA Cooperative State Research, Education, and Extension.

² Correspondence: Janet F. Roser, Department of Animal Science, University of California, One Shields Ave., Davis, CA 95616. FAX: 530 752 0175; jfroser{at}ucdavis.edu

¹⁰⁶ DOI: 10.1095/biolreprod.105.043760

This article has been cited by other articles:

				C. A Pearl, E. At-Taras, T. Berger, and J. F Roser Reduced endogenous estrogen delays epididymal development but has no effect on efferent duct morphology in boars Reproduction, October 1, 2007; 134(4): 593 - 604. [Abstract] [Full Text] [PDF]

				A. Wagner, N. Messe, M. Bergmann, O. Lekhkota, and R. Claus Effects of Estradiol Infusion in GnRH Immunized Boars on Spermatogenesis J Androl, November 1, 2006; 27(6): 880 - 889. [Abstract] [Full Text] [PDF]

				E. E. At-Taras, T. Berger, M. J. McCarthy, A. J. Conley, B. J. Nitta-Oda, and J. F. Roser Reducing Estrogen Synthesis in Developing Boars Increases Testis Size and Total Sperm Production J Androl, July 1, 2006; 27(4): 552 - 559. [Abstract] [Full Text] [PDF]