A peptide resembling COOH-terminal tetrapeptide amide of gastrin from a new gastrointestinal endocrine cell type

Abstract

THE gastrointestinal hormones gastrin and cholecystokinin (CCK) share identical COOH-terminal sequences. In both hormones the COOH-terminal tetrapeptide amide constitutes the biologically active region, and the rest of the two molecules determines their potency and selectivity for different target cells. Their similarity in structure and activity may reflect a common phylogenetical origin¹. The COOH-terminal tetrapeptide amide is highly immunogenic in each hormone and many gastrin antisera are specific for this sequence and also bind CCK. In order to study the hormones by immunocytochemistry and radioimmunoanalysis, antisera specific for several distinct sequences must be used. Previously, we have used such antisera to characterise antral gastrin cells and intestinal cholecystokinin cells by immunocytochemistry². We now report the identification of three distinct types of gastrointestinal cells which show COOH-terminal gastrin (or CCK) immunoreactivity. One type corresponds to gastrin-producing G cells, another to CCK-producing I cells and a third type to TG cells which react only with antisera against the COOH-terminal tetrapeptide.