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

Abstract

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 microg/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 microg/kg BW; Experiment 4A), lGnRH-III (1.1 and 4.4 microg/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.

• Authors: M Amstalden, D A Zieba, M R Garcia, R L Stanko, T H Welsh Jr, W H Hansel, G L Williams
• Journal: Reproduction (Cambridge, England) (Reproduction) Vol. 127 Issue 1 Pg. 35-43 (Jan 2004) ISSN: 1470-1626 [Print] England
• PMID: 15056768 (Publication Type: Journal Article)

Chemical References

• Oligopeptides
• gonadotropin-releasing hormone-III
• Gonadotropin-Releasing Hormone
• Progesterone
• Estradiol
• Follicle Stimulating Hormone
• Pyrrolidonecarboxylic Acid

Topics

• Animals
• Cattle (physiology)
• Cells, Cultured
• Estradiol (pharmacology)
• Estrus (physiology)
• Female
• Follicle Stimulating Hormone (metabolism)
• Gonadotropin-Releasing Hormone (pharmacology)
• Oligopeptides (pharmacology)
• Ovariectomy
• Pituitary Gland, Anterior (drug effects, metabolism)
• Progesterone (pharmacology)
• Pyrrolidonecarboxylic Acid (analogs & derivatives)
• Stimulation, Chemical