Relative effect of gonadotropin-releasing hormone (GnRH)-I and GnRH-II on gonadotropin release.

Abstract

Two forms of GnRH (GnRH-I and GnRH-II) are expressed in the hypothalamus of humans and rhesus monkeys, but their relative abilities to stimulate LH and FSH release are unknown. Therefore, young (8-12 yr) and old (21-23 yr) female rhesus monkeys were treated i.v. with bolus injections of either GnRH-I or GnRH-II (dose range, 0.01-10 microg/kg body weight); serial blood samples were remotely collected through a vascular catheter for up to 2 h after injection. Overall, plasma LH concentrations were similarly elevated after treatment with GnRH-I and GnRH-II, and the responses were slightly greater in the younger animals. Although plasma FSH concentrations were unaffected by a single exposure to GnRH-I or GnRH-II, they showed a similar significant increase after repeated exposures (every 2 h for 24 h). In a subsequent experiment, antide, a GnRH-I receptor antagonist, was administered (100 microg/kg body weight) together with a single injection of GnRH-I or GnRH-II (1 microg/kg body weight). As expected, GnRH-I-induced LH release was significantly attenuated by this combined treatment; moreover, GnRH-II-induced LH release was completely blocked. Taken together, these data show that GnRH-II can potently stimulate gonadotropin release in vivo and that this action is likely mediated through the GnRH-I receptor.

• Authors: Valerie S Densmore, Henryk F Urbanski
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 88 Issue 5 Pg. 2126-34 (May 2003) ISSN: 0021-972X [Print] United States
• PMID: 12727965 (Publication Type: Comparative Study, Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Oligopeptides
• Receptors, LHRH
• Gonadotropin-Releasing Hormone
• Luteinizing Hormone
• Follicle Stimulating Hormone
• LHRH, His(5)-Trp(7)-Tyr(8)-
• iturelix

Topics

• Aging
• Animals
• Female
• Follicle Stimulating Hormone (metabolism)
• Gonadotropin-Releasing Hormone (analogs & derivatives, pharmacology)
• Humans
• Kinetics
• Luteinizing Hormone (metabolism)
• Macaca mulatta
• Oligopeptides (pharmacology)
• Receptors, LHRH (antagonists & inhibitors, physiology)
• Signal Transduction (drug effects)