COEXISTENCE AND CORELEASE OF GASTRIN-34 N-TERMINAL WITH GASTRIN-17 IMMUNOREACTIVITY IN RAT STOMACH

Little gastrin (G-17) and big gastrin (G-34) are the principal active forms of gastrin. In this study, the distribution of gastrin forms in rat gastrointestinal tissues and forms of gastrin released from the perfused rat stomach were examined. G-34 N-terminal immunoreactivity (IR-G-34-N) was detected in extracts of the rat stomach and proximal duodenum; the highest concentration was found in the antral mucosa extract. The concentration of IR-G-34-N was lower than that of G-17-like immunoreactivity (IR-G-17). Gel filtration showed that IR-G-34-N in the antral mucosa extract consisted primarily of a G-34 N-terminal pentadecapeptide [G-34(1-15)], and the concentration of G-34 was approximately one tenth the concentration of G-17. Methacholine and gastrin-releasing peptide (GRP) caused an IR-G-34-N release from the isolated perfused rat stomach. During these stimulations, IR-G-17 was also released. Integrated release of IR-G-34-N was lower than that of IR-G-17. Gel filtration ofthe perfusate from the rat stomach revealed the presence of G-34(1-15) as the primary component. The present results demonstrate that post-trans1ational processing of the gastrin precursor in the rat antrum produces G-34, which is further converted in the tissue to G-17, and that the G-34 N-terminal fragment formed during the G-34 conversion is stored and released concurrently with G-l7. © 1990, Biomedical Research Press. All rights reserved.