Effects of Hypercapnia on Histamine Stimulated Gastric Acid Secretion

Abstract

Summary The separate and interacting effects of hypercapnia and hypoxia on histaminestimulated gastric acid secretion were studied in unanesthetized dogs equipped with Heidenhain stomach pouches. Hypercapnia, induced by inspiring 7.5 per cent of CO 2 in air for 40 minutes was uniformly associated with a significant decrease in the rate of acid secretion. Changes in the accompanying O 2 tension over a wide range of 67 to 138 mm. Hg did not seem to influence histamine-stimulated secretion, nor modify secretory responses associated with high, normal, or low CO 2 tensions. Evidence was obtained that suggests that changes in blood plasma pH during hypercapnia may have played a role in modifying secretion. These responses of histaminestimulated secretion to changes in CO 2 are essentially contrary to those described for vagal stimulated secretion in dogs and posttest meal secretion in man. These findings are interpreted to indicate that the effects that hypercapnia, or for that matter hypoxia, can be demonstrated to exert on gastric acid secretion are dependent upon the nature of the secretory studies carried out, particularly in reference to the preparation and the type of background secretory activity used.