Comparison of the ability of the three endogenous GnRHs to stimulate release of follicle-stimulating hormone and luteinizing hormone in chickens

Proudman, John A.; Scanes, Colin G.; Johannsen, Sara A.; Berghman, Luc R.; Camp, Mary J.

doi:10.1016/j.domaniend.2005.10.002

« Previous Next »Domestic Animal Endocrinology
Volume 31, Issue 2 , Pages 141-153, August 2006

Comparison of the ability of the three endogenous GnRHs to stimulate release of follicle-stimulating hormone and luteinizing hormone in chickens

John A. Proudman
- Biotechnology and Germplasm Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA
- Corresponding author. Tel.: +1 301 504 8094; fax: +1 301 504 5123.
Colin G. Scanes
- Department of Animal Science, Iowa State University, Ames, IA 50011, USA
- Present address: Office of Research/Department of Poultry Science, Mississippi State University, Mississippi, MS 39762, USA.
Sara A. Johannsen
- Department of Animal Science, Iowa State University, Ames, IA 50011, USA
Luc R. Berghman
- Departments of Poultry Science and Veterinary Pathobiology, Texas A&M University, College Station, TX 77843, USA
Mary J. Camp
- Biometrical Consulting Service, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA

Received 11 August 2005; received in revised form 3 October 2005; accepted 5 October 2005. published online 21 November 2005.

Abstract

It is well established that GnRH can stimulate the release of LH and FSH in mammals. Two GnRHs have been found in the chicken hypothalamus, cGnRH-I and -II. There is controversy as to whether either peptide can stimulate release of FSH in birds. The present studies compared the ability of cGnRH-I and -II to stimulate the release of FSH and LH in chickens. Lamprey (l) GnRH-III may be a specific-releasing factor for FSH, as it selectively stimulates FSH release in rodents and cattle, and has been detected in the hypothalamus of rodents, sparrows and chickens. Therefore, the ability of lGnRH-III to stimulate LH and FSH release was also examined. In our first experiment, the effects of cGnRH-I and -II were studied using 17-week prepubertal females. Intravenous injection of cGnRH-II at 1 and 10μg/kg BW significantly increased LH secretion more than did cGnRH-I. Neither peptide significantly increased plasma FSH levels. In our second study, we administered cGnRH-I, -II or lGnRH-III to mature males maintained on a short photoperiod. cGnRH-II was again more potent than cGnRH-I in stimulating LH release, while lGnRH-III produced a modest LH rise. No GnRH peptide provided specific or potent stimulus to FSH secretion, although the high dose of cGnRH-II modestly enhanced FSH levels in the adult male (P<0.05). Our results are not consistent with the view that lGnRH-III is a specific FSH-releasing hormone across multiple classes of vertebrates. We conclude that the mechanism by which independent release of FSH occurs in chickens remains unresolved.