Contribution of the antrum and duodenum to circulating forms of gastrin in the dog

Gastrin release was stimulated in four anaesthetized dogs with meat extract and acetylcholine. The different forms of gastrin were analyzed in antral and duodenal mucosa and in blood from antral, duodenal and peripheral veins by use of radioimmunoassay with a region-specific antibody, Sephadex gel filtration, and SDS-gel electrophoresis. The duodenum contributed less than 4% of antral gastrin to circulating gastrin. The molecular forms of antral and duodenal gastrins were similar. On the basis of the electrophoretic results and the properties of the antibody, gastrin in the antral and duodenal veins consisted of a minor fraction of G 17 and a predominant fraction of C-terminal fragments of smaller molecular size. This fraction was even more marked in the peripheral venous circulation. In the peripheral blood, however, not only smaller forms of gastrin were present but also an increasing ratio of big gastrin immunoreactivity. Thus, there is active postsecretory processing of gastrin in the circulation of the anaesthetized dog.