title: Bombesin-like peptides stimulate growth hormone secretion mediated by the gastrin-releasing peptide receptor in cattle.
abstract: This study was designed to determine the effects of bombesin-like peptides (BLPs) on the secretion of growth hormone (GH) and to characterize the receptor subtypes mediating these effects in cattle. Four experiments were conducted: (1) six steers were randomly assigned to receive intravenous (IV) bolus injections of 0, 0.2, 1.0, 12.5 and 50.0 μg/kg neuromedin C (NMC); (2) seven pre-weaned calves were IV injected with 1.0 μg/kg NMC; (3) six steers were IV injected with 2.5μg/kg bovine gastrin-releasing peptide (GRP), 1.0 μg/kg NMC combined with 20.0 μg/kg [d-Lys(3)]-GHRP-6 (an antagonist for the GH secretagogue receptor type 1a [GHS-R1a]), 1.0 μg/kg NMC combined with 20.0 μg/kg N-acetyl-GRP(20-26)-OCH(2)CH(3) (N-GRP-EE, an antagonist for the GRP receptor), 20.0 μg/kg N-GRP-EE alone, 1.0 μg/kg neuromedin B (NMB); and (4) four rats were IV injected 1.0 μg/kg NMC. A serial blood sample was collected before and after injection. Plasma GH levels dose-dependently increased at 5 min after NMC injection and the minimal effective dose was 1.0 μg/kg. Plasma GH level was elevated by GRP, but not by NMB. The NMC-induced elevation of GH was completely blocked by N-GRP-EE. The administration of NMC elevated GH level in pre-weaned calves but not in rats. Ghrelin level was unaffected by any treatments; and [d-Lys(3)]-GHRP-6 did not block the NMC-induced elevation of GH. The results indicate BLP-induced elevation of GH levels is mediated by the GRP receptor but not through a ghrelin/GHS-R1a pathway in cattle.
authors.affiliation: Department of Life Science and Agriculture, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan. zhaohongqiong@sina.com
authors.forename: Hongqiong
authors.initials: H
authors.lastname: Zhao
authors.forename: Seinosuke
authors.initials: S
authors.lastname: Matsuda
authors.forename: Sint
authors.initials: S
authors.lastname: Thanthan
authors.forename: Swe
authors.initials: S
authors.lastname: Yannaing
authors.forename: Hideto
authors.initials: H
authors.lastname: Kuwayama
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001839:Bombesin / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D019886:Gastrin-Releasing Peptide / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D054439:Ghrelin / Q000097:blood / Q000378:metabolism; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D018004:Receptors, Bombesin / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D054439:Ghrelin; D010446:Peptide Fragments; D018004:Receptors, Bombesin; D019886:Gastrin-Releasing Peptide; C040794:neuromedin C; D013006:Growth Hormone; D001839:Bombesin