Effects of growth hormone-releasing peptides in healthy dogs and in dogs with pituitary-dependent hyperadrenocorticism.
The aim of this study is to investigate the effects of ghrelin and GH-releasing peptide-6 (GHRP-6) on the release of growth hormone (GH), adrenocorticotrophic hormone (ACTH), and cortisol in dogs with pituitary-dependent hyperadrenocorticism (PDH) and in healthy dogs of comparable age. In eight healthy dogs, the responses to ghrelin and GHRP-6 were compared to those of GH-releasing hormone (GHRH) and NaCl 0.9% (control). In seven dogs with PDH, the effects of ghrelin and GHRP-6 were compared with their effects in healthy dogs. In the healthy dogs, GHRH, GHRP-6, and ghrelin caused a significant rise in plasma GH concentrations. GHRH administration elicited significantly higher plasma GH concentrations than administration of ghrelin and GHRP-6. In the dogs with PDH, the GHRP-6-induced release of GH was significantly lower than in healthy dogs. Administration of ghrelin elicited a GH release that did not differ significantly between dogs with PDH and healthy dogs. Ghrelin and GHRP-6 did not cause a significant rise in plasma ACTH and cortisol concentrations in either the healthy dogs or the dogs with PDH. It is concluded that in comparison with GHRH, GHRP-6 and ghrelin have a low GH-releasing potency in healthy dogs. In dogs with PDH, the GH release in response to GHRP-6 is impaired. Neither GHRP-6 nor ghrelin activates the pituitary-adrenocortical axis in healthy elderly dogs and dogs with PDH.
Bhatti
S F M
SF
Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium. sofie.bhatti@rug.ac.be
De Vliegher
S P
SP
Van Ham
L
L
Kooistra
H S
HS
D000308:Adrenocortical Hyperfunction / Q000378:metabolism / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D004283:Dog Diseases / Q000378:metabolism*; D004285:Dogs / Q000378:metabolism*; D005260:Female; D054439:Ghrelin; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D009842:Oligopeptides / Q000494:pharmacology*; D036361:Peptide Hormones / Q000494:pharmacology*
D054439:Ghrelin; D009842:Oligopeptides; D036361:Peptide Hormones; C041048:growth hormone releasing hexapeptide; D000324:Adrenocorticotropic Hormone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D006854:Hydrocortisone