Calcium and stimulus-secretion coupling in gastric fundic mucosa. Effect of inhibition of calcium transport by verapamil on gastric acid secretion in the isolated guinea pig fundic mucosa and in healthy subjects.

The effect on gastric acid secretion of blocking transmembrane Ca2+ influx into the parietal cells has been studied in the isolated guinea pig fundic mucosa and in healthy volunteers. Verapamil inhibited in a dose-related manner histamine-stimulated acid secretion in the guinea pig mucosa, whereas stimulation with theophylline and dibutyryl cyclic-AMP was unaffected. The effect of verapamil (Isoptin, 2.0 mg/h) on acid secretion stimulated by increasing doses (50, 200, 500 ng/kg-h) of 15-leucine synthetic human gastric I was studied in seven healthy volunteers, alone and in combination with infusion of calcium gluconate (1.0 meq Ca2+/kg-h). Verapamil inhibited the acid response to the lowest dose of gastrin, resulting in a significant increase of D50 of 15-leucine synthetic human gastrin I. This effect was partly reversed by calcium infusion. It is concluded that one of the mechanisms by which extracellular calcium concentration influences acid secretion is by transmembrane influx of Ca2+ during stimulation.