A novel growth hormone secretagogue, ghrelin: Identification and biological activity in fish

Abstract

We isolated two 21-amino acid forms of ghrelin from the stomach of the Japanese eel, Anguilla japonica. cDNA and mass spectrometric analyses revealed the following sequences: eel ghrelin-21, GSS(O-n-octanoyl)FLSPSQRPQGKDKKPPRV-amide and eel ghrelin-21-C10, GSS(O-n-decanoyl)FLSPSQRPQGKDKKPPRV-amide. Eel ghrelin mRNA was observed only in the stomach by Northern blot analysis. Low levels of gene expression were observed in anterior- and middle-intestines by RT-PCR analysis. Plasma GH levels increased following intravenous injection of eel ghrelin into rats. The effect was more potent than that of rat ghrelin. Eel ghrelin potently stimulated GH secretion in cultured tilapia pituitary. These results indicate that a novel regulatory mechanism of GH secretion by ghrelin is conserved from fish to human. © 2002, The Japanese Society of Fisheries Science. All rights reserved.