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Reproduction (2004) 127 35-43
DOI: 10.1530/rep.1.00022
Copyright © 2004 Society for Reproduction and Fertility
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RESEARCH

Evidence that lamprey GnRH-III does not release FSH selectively in cattle

M Amstalden1,2,3, D A Zieba1,2,3, M R Garcia1,2,3, R L Stanko1,4, T H Welsh, Jr2, W H Hansel5 and G L Williams1,2,3

1 Animal Reproduction Laboratory, Texas A&M University Agricultural Research Station, Beeville, Texas 78102, USA, 2 Department of Animal Science and 3 Center for Animal Biotechnology and Genomics, Texas A&M University, College Station, Texas 77843, USA, 4 Department of Animal and Wildlife Sciences, Texas A&M University-Kingsville, Kingsville, Texas 78363 USA and 5 Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana 70808, USA

Correspondence should be addressed to G L Williams; Email: glw{at}fnbnet.net

Experiments were performed to test the hypothesis that lamprey GnRH-III (lGnRH-III) selectively releases FSH. Primary cultures of bovine adenohypophyseal cells were treated with mammalian GnRH (mGnRH) and lGnRH-III (10-9, 10-8, 10-7 and 10-6 M) or control media in Experiment 1. All doses of mGnRH and the two highest doses of lGnRH-III stimulated (P < 0.001) a non-selective release of LH and FSH. In Experiments 2–4, Latin Square designs were utilized in vivo to examine whether physiological and hormonal milieu regulate putative selective effects of lGnRH-III. In Experiments 2 and 3, ovariectomized cows with basal levels of estradiol only (Experiment 2) or in combination with luteal phase levels of progester-one (Experiment 3) were injected with mGnRH and lGnRH-III (0.055, 0.11, 0.165 and 1.1 µg/kg body weight (BW) and saline. All doses of mGnRH released (P < 0.001) LH and FSH, but only the highest dose of lGnRH-III stimulated (P < 0.001) a non-selective release of both LH and FSH (Experiment 3). For Experiments 4A and 4B, intact, mid-luteal phase cows were injected with mGnRH and lGnRH-III (1.1 µg/kg BW; Experiment 4A), lGnRH-III (1.1 and 4.4 µg/kg BW; Experiment 4B) and saline. As before, mGnRH released (P < 0.001) both LH and FSH at all doses. In contrast, lGnRH-III at the highest dose released (P < 0.001) LH but not FSH. These findings suggest that lGnRH-III may act as a weak competitor for the mGnRH receptor and do not support the hypothesis that it selectively releases FSH in cattle.




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A. Bowen, S. Khan, L. Berghman, J. D. Kirby, R .P. Wettemann, and J. A. Vizcarra
Immunization of pigs against chicken gonadotropin-releasing hormone-II and lamprey gonadotropin-releasing hormone-III: Effects on gonadotropin secretion and testicular function
J Anim Sci, November 1, 2006; 84(11): 2990 - 2999.
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