Evaluation of the gastric Na: H exchange mechanism using histamine and Diamox

¹ Department of Medicine, Division of Gastroenterology, University of Alabama Medical Center, Birmingham, Alabama

This study tested a theory of gastric secretion comprising: a) the secretion of Cl, as NaCl and KCl in water, from which b) an exchange of Na⁺ for H⁺ occurs. Thirty-one studies were made in eight unanesthetized dogs equipped with esophagostomy and gastric cannula. A 3-hr intravenous infusion of 1 mg histamine base/hour as the control experiment was modified in two ways—by the intravenous injection of 1 g of Diamox (D) either immediately before (D-H) or half-way through (H-D) the histamine infusion. Diamox (either D-H or H-D) reduced gastric [H⁺] by 50 mEq/liter and increased [Na⁺] by 44–50 mEqliter, and H:Na exchange fell from 95% to 70% with osmolality and [Cl^–] relatively unaffected; but K⁺ secretion was markedly inhibited. Pepsin secretion was essentially unchanged. The output of Na (VNa) increased by 100% despite a 63% decrease in volume of gastric juice. The reciprocal Na:H changes without change in [Cl^–] or osmolality, and the twofold increase in VNa support the concept of a Na:H exchange in the regulation of gastric [H⁺].