Lamprey GnRH-III stimulates FSH secretion in barrows.
Although studies have indicated that follicle-stimulating hormone (FSH) and luteinizing hormone (LH) release can be dissociated in the pig, the underlying mechanisms are still to be answered. Since it was demonstrated that lamprey gonadotropin-releasing hormone (l-GnRH-III) has preferential FSH-releasing potency in several mammalian species, we have investigated the gonadotropin-releasing activity of l-GnRH-III in barrows. Each of nine barrows (body weight: 85-90 kg; age: 207 days) received 2 ml saline (S-barrow), followed by 150 microg l-GnRH-III (1.6-1.7 microg/kg body weight) dissolved in 2 ml saline intramuscularly 7 days later. Three pre-treatment and 13 post-treatment blood samples were taken at intervals of 30 min to 8 h to assess basal and treatment-associated concentrations of FSH and LH, respectively, by radioimmunoassay. Animals were defined as having responded to treatment if, 2 h post-treatment, plasma FSH and/or LH levels were >3 SD of the respective basal concentrations. There was no treatment-associated FSH response after saline treatment, but a clear FSH response in all l-GnRH-III-injected barrows. On average, the maximum FSH level (205% of the basal concentration) was observed at 1 h post-treatment. Mean FSH values were elevated until 10 h post-treatment. There was no LH response either to saline or to l-GnRH-III. In conclusion, this study demonstrates a selective FSH-releasing activity of 150 microg l-GnRH-III in barrows. Further studies are needed to investigate whether this effect is ubiquitous in the pig and what the physiological relevance is.
Kauffold
J
J
Large Animal Clinic for Theriogenology and Ambulatory Services, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany. kauffold@rz.uni-leipzig.de
Schneider
F
F
Zaremba
W
W
Brüssow
K-P
KP
D000818:Animals; D019540:Area Under Curve; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007273:Injections, Intramuscular / Q000662:veterinary; D007700:Kinetics; D007798:Lampreys; D007986:Luteinizing Hormone / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009842:Oligopeptides / Q000008:administration & dosage / Q000494:pharmacology*; D011761:Pyrrolidonecarboxylic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D011863:Radioimmunoassay / Q000379:methods / Q000662:veterinary; D013552:Swine / Q000502:physiology*
D009842:Oligopeptides; C448022:gonadotropin-releasing hormone-III; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D011761:Pyrrolidonecarboxylic Acid