title: Growth hormone (GH)-releasing activity of chicken GH-releasing hormone (GHRH) in chickens.
abstract: Two peptides with sequence similarities to growth hormone releasing hormone (GHRH) have been identified by analysis of the chicken genome. One of these peptides, chicken (c) GHRH-LP (like peptide) was previously found to poorly bind to chicken pituitary membranes or to cloned and expressed chicken GHRH receptors and had little, if any, growth hormone (GH)-releasing activity in vivo or in vitro. In contrast, a second more recently discovered peptide, cGHRH, does bind to cloned and expressed cGHRH receptors and increases cAMP activity in transfected cells. The possibility that this peptide may have in vivo GH-releasing activity was therefore assessed. The intravenous (i.v.) administration of cGHRH to immature chickens, at doses of 3-100 μg/kg, significantly increased circulating GH concentrations within 10 min of injection and the plasma GH levels remained elevated for at least 30 min after the injection of maximally effective doses. The plasma GH responses to cGHRH were comparable with those induced by human (h) or porcine (p) GHRH preparations and to that induced by thyrotropin releasing hormone (TRH). In marked contrast, the i.v. injection of cGHRH-LP had no significant effect on circulating GH concentrations in immature chicks. GH release was also increased from slaughterhouse chicken pituitary glands perifused for 5 min with cGHRH at doses of 0.1 μg/ml or 1.0 μg/ml, comparable with GH responses to hGHRH1-44. In contrast, the perifusion of chicken pituitary glands with cGHRH-LP had no significant effect on GH release. In summary, these results demonstrate that cGHRH has GH-releasing activity in chickens and support the possibility that it is the endogenous ligand of the cGHRH receptor.
authors: Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada. Electronic address: steve.harvey@ualberta.ca.
authors: S
authors: S
authors: Harvey
authors: Department of Chemistry, University of Virginia, Charlottesville, VA 22908, USA.
authors: C
authors: C
authors: Gineste
authors: Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
authors: B D
authors: BD
authors: Gaylinn
mesh_terms: D000818:Animals; D002645:Chickens / Q000378:metabolism*; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D006801:Humans; D010446:Peptide Fragments / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism; D018013:Receptors, Neuropeptide / Q000378:metabolism*; D018017:Receptors, Pituitary Hormone-Regulating Hormone / Q000378:metabolism*; D013552:Swine; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D018013:Receptors, Neuropeptide; D018017:Receptors, Pituitary Hormone-Regulating Hormone; D013973:Thyrotropin-Releasing Hormone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; C048250:somatotropin releasing hormone receptor
keywords: Chicken; Growth hormone; Growth hormone releasing hormone like peptide; Growth hormone-releasing hormone; Thyrotrophin-releasing hormone