Relative effect of gonadotropin-releasing hormone (GnRH)-I and GnRH-II on gonadotropin release.
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.
Densmore
Valerie S
VS
Division of Neuroscience, Oregon National Primate Research Center, Beaverton, Oregon 97006, USA.
Urbanski
Henryk F
HF
D000375:Aging; D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism*; D008253:Macaca mulatta; D009842:Oligopeptides / Q000494:pharmacology; D011966:Receptors, LHRH / Q000037:antagonists & inhibitors / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects
D009842:Oligopeptides; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-; C057022:iturelix