Corelease of amidated and glycine-extended antral gastrins after a meal

Glycine-extended gastrin, the immediate precursor of bioactive (i.e., carboxyamidated) gastrin, was recently identified in antral tissue and in peripheral blood. Studies on pituitary cell lines have shown that although only bioactive peptides are released along the regulated pathway, i.e., stored at high concentrations in secretory granules and released upon appropriate stimulation, the release of precursors is constitutive, i.e., secreted continuously without secretagogue stimulation. To determine whether the secretion of glycine-extended gastrin from the antral G-cell is regulated, meal-induced release was examined. In anesthetized pigs (n = 8) the antral veins were catheterized and blood was collected continuously before and after intragastric instillation of meat extract. Surgical biopsies of antral mucosa were obtained from six animals. Glycine-extended and amidated gastrins were measured and characterized by radioimmunoanalysis and chromatography. The results demonstrate that glycine-extended gastrin is released in a regulated manner from antral G-cells and furthermore the component pattern is identical in mucosa and blood.