Response to gonadotrophin-releasing hormone by the intact male dog: serum testosterone, luteinizing hormone and follicle-stimulating hormone.
In Expt 1, gonadotropin-releasing hormone (GnRH) (Cystorelin, CEVA) was administered intramuscularly to two intact male dogs; one dog received one injection of 50 micrograms GnRH and one dog received four daily injections of 50 micrograms GnRH. Both dogs exhibited a significant and immediate rise in luteinizing hormone (LH) following GnRH administration, with a peak observed at 15 min following injection. Testosterone was increased over baseline concentrations for 5 and 7 days, respectively, after the injection. In Expt 2, eight intact male dogs were injected intramuscularly with 0.7 microgram GnRH (Factrel, Fort Dodge) kg-1. Baseline testosterone concentrations were established by daily sampling for 14 days before treatment. All dogs exhibited an LH peak 15 min and a testosterone peak 60 min after the GnRH injection. Testosterone concentrations had returned to baseline concentrations by 4 h after the injection. Testosterone tended to fall below baseline concentrations for several days following the injection of GnRH. No peak was noted for follicle-stimulating hormone. In Expt 3, five additional dogs were injected with 0.7 microgram GnRH (Factrel, Fort Dodge) kg-1. Testosterone concentrations rose in all dogs 1 h after the injection and returned to baseline concentrations by 24 h after injection. In the male dog, GnRH stimulated an LH peak 15 min and a testosterone peak 1 h after injection. Further investigations are needed to elucidate the different effects on testosterone concentration observed with two different GnRH preparations.
Purswell
B J
BJ
Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg 24061.
Wilcke
J R
JR
D000818:Animals; D004285:Dogs; D004341:Drug Evaluation; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006065:Gonadotropins, Pituitary / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects; D013739:Testosterone / Q000097:blood*; D013997:Time Factors
D006065:Gonadotropins, Pituitary; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone