Role of calcium in the stimulus-secretion coupling of antral gastrin release.

The role of calcium in the stimulus-secretion coupling of antral gastrin release was examined in isolated sheets of canine antral mucosa. Mucosa was obtained from 137 dogs and mounted in Ussing chambers to separate the luminal from nutrient surfaces. The influence of verapamil, LaCl3, A23187, and EGTA on the release of gastrin by luminal calcium and ethyl alcohol was examined and the release of immunoreactive gastrin (IG) was measured in luminal perfusates. Release of IG by luminal calcium was dose-related, unsaturable, and impaired by verapamil and by LaCl3. Release of IG by alcohol was prevented by leaching the mucosa of calcium and restored by repletion of the calcium. IG release induced by alcohol was prevented by topical, but not by nutrient, application of LaCl3. Molecular sieve and affinity chromatography of the endogenous IG released in the absence of luminal calcium, and of the exogenous gastrin added, indicated that antral gastrin was released as heptadecapeptide gastrin, and that which was released in the presence of CaCl2 degraded rapidly into a C-terminal fragment. The data indicate that calcium may participate in the stimulus-secretion coupling of canine antral gastrin release in vitro.