Calcium and Stimulus-Secretion Coupling in Gastric Fundic Mucosa

Abstract

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, and 500 ng/kg-h) of 15-leucine synthetic human gastrin 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.

Key words:

• Acid secretion
• calcium
• gastrin