title: Effects of growth hormone secretagogues on the release of adenohypophyseal hormones in young and old healthy dogs.
abstract: The effects of three growth hormone secretagogues (GHSs), ghrelin, growth hormone-releasing peptide-6 (GHRP-6), and growth hormone-releasing hormone (GHRH), on the release of adenohypophyseal hormones, growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinising hormone (LH), prolactin (PRL) and on cortisol were investigated in young and old healthy Beagle dogs. Ghrelin proved to be the most potent GHS in young dogs, whereas in old dogs GHRH administration was associated with the highest plasma GH concentrations. The mean plasma GH response after administration of ghrelin was significantly lower in the old dogs compared with the young dogs. The mean plasma GH concentration after GHRH and GHRP-6 administration was lower in the old dogs compared with the young dogs, but this difference did not reach statistical significance. In both age groups, the GHSs were specific for GH release as they did not cause significant elevations in the plasma concentrations of ACTH, cortisol, TSH, LH, and PRL. It is concluded that in young dogs, ghrelin is a more powerful stimulator of GH release than either GHRH or GHRP-6. Ageing is associated with a decrease in GH-releasing capacity of ghrelin, whereas this decline is considerably lower for GHRH or GHRP-6.
authors.affiliation: Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, Merelbeke, Belgium. Sofie.Bhatti@UGent.be
authors.forename: Sofie F M
authors.initials: SF
authors.lastname: Bhatti
authors.forename: Luc
authors.initials: L
authors.lastname: Duchateau
authors.forename: Luc M L
authors.initials: LM
authors.lastname: Van Ham
authors.forename: Sarne P
authors.initials: SP
authors.lastname: De Vliegher
authors.forename: Jan A
authors.initials: JA
authors.lastname: Mol
authors.forename: Ad
authors.initials: A
authors.lastname: Rijnberk
authors.forename: Hans S
authors.initials: HS
authors.lastname: Kooistra
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D018592:Cross-Over Studies; D004285:Dogs / Q000502:physiology*; D005260:Female; D054439:Ghrelin; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism; D008297:Male; D009842:Oligopeptides / Q000494:pharmacology*; D036361:Peptide Hormones / Q000494:pharmacology*; D010908:Pituitary Hormones, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000097:blood / Q000378:metabolism; D011897:Random Allocation; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism
chemical_list: D054439:Ghrelin; D009842:Oligopeptides; D036361:Peptide Hormones; D010908:Pituitary Hormones, Anterior; C041048:growth hormone releasing hexapeptide; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D007986:Luteinizing Hormone; D013972:Thyrotropin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D006854:Hydrocortisone