title: Identification of tilapia ghrelin and its effects on growth hormone and prolactin release in the tilapia, Oreochromis mossambicus.
abstract: We have identified ghrelin and cDNA encoding precursor protein from the stomach of a euryhaline tilapia, Oreochromis mossambicus. The sequence of 20-amino acid tilapia ghrelin is GSSFLSPSQKPQNKVKSSRI. The third serine residue was modified by n-decanoic acid. The carboxyl-terminal end of the peptide possessed an amide structure. RT-PCR analysis revealed high levels of gene expression in the stomach and low levels in the brain, kidney and gill. Tilapia ghrelin stimulated growth hormone (GH) and prolactin (PRL) release from the organ-cultured tilapia pituitary at a dose of 10 nM. Thus, a novel regulatory mechanism of GH secretion by gastric ghrelin seems to be conserved in the tilapia. Stimulation of PRL release by homologous ghrelin has been reported in human, bullfrog and eel, and suggests the presence of growth hormone secretagogue receptor not only on somatotrophs but also on PRL cells of the tilapia pituitary.
authors.affiliation: Department of Biochemistry, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Osaka 565-8565, Suita, Japan. kaiya@ri.ncvc.go.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaiya
authors.forename: Masayasu
authors.initials: M
authors.lastname: Kojima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoda
authors.forename: Larry G
authors.initials: LG
authors.lastname: Riley
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hirano
authors.forename: E Gordon
authors.initials: EG
authors.lastname: Grau
authors.forename: Kenji
authors.initials: K
authors.lastname: Kangawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020869:Gene Expression Profiling; D054439:Ghrelin; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009928:Organ Specificity; D036361:Peptide Hormones / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010902:Pituitary Gland / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017385:Sequence Homology; D013270:Stomach / Q000737:chemistry; D017210:Tilapia / Q000378:metabolism*
chemical_list: D054439:Ghrelin; D036361:Peptide Hormones; D012333:RNA, Messenger; D011388:Prolactin; D013006:Growth Hormone