Kaiya Hiroyuki, Kojima Masayasu, Hosoda Hiroshi, Riley Larry G, Hirano Tetsuya, Grau E Gordon, Kangawa Kenji
Department of Biochemistry, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Osaka 565-8565, Suita, Japan.
Comp Biochem Physiol B Biochem Mol Biol. 2003 Jul;135(3):421-9. doi: 10.1016/s1096-4959(03)00109-x.
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.
我们已从广盐性罗非鱼（莫桑比克罗非鱼）的胃中鉴定出胃饥饿素及编码前体蛋白的cDNA。20个氨基酸的罗非鱼胃饥饿素序列为GSSFLSPSQKPQNKVKSSRI。第三个丝氨酸残基被正癸酸修饰。该肽的羧基末端具有酰胺结构。逆转录聚合酶链反应（RT-PCR）分析显示，该基因在胃中高表达，而在脑、肾和鳃中低表达。罗非鱼胃饥饿素以10 nM的剂量刺激器官培养的罗非鱼垂体释放生长激素（GH）和催乳素（PRL）。因此，胃饥饿素对GH分泌的一种新型调节机制似乎在罗非鱼中是保守的。在人类、牛蛙和鳗鱼中已报道同源胃饥饿素对PRL释放有刺激作用，这表明罗非鱼垂体中不仅生长激素促分泌素受体存在于生长激素细胞上，也存在于PRL细胞上。
