Calcium and Stimulus-Secretion Coupling in Gastric Fundic Mucosa

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Abstract
The effect on gastric acid secretion of blocking transmembrane Ca2+ influx into the parietal cells was 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 cAMP was unaffected. The effect of verapamil (Isoptin, 2.0 mg/h) on acid secretion stimulated by increasing doses (50, 200 and 500 ng/kg .cntdot. h) of 15-leucine synthetic human gastrin I was studied in 7 healthy volunteers, alone and in combination with infusion of calcium gluconate (1.0 meq Ca2+/kg .cntdot. h). Verapamil inhibited the acid response to the lowest dose of gastrin, resulting in a significant increase of D50 [median dose] of 15-leucine synthetic human gastrin I. This effect was partly reversed by Ca infusion. One of the mechanisms by which extracellular Ca concentration influences acid secretion is by transmembrane influx of Ca2+ during stimulation.

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