Ionic flux across canine duodenum. Movement of bicarbonate.

Effect of isosmotic biocarbonate-rich solutions on the Brunner's gland area were studied by means of proximal duodenal explants in eight anesthetized dogs. Volume gain occurred with all instillates and varied indirectly with the concentration of the bicarbonate in the instilled solutions. Net bicarbonate gain occurred with instillate of 40 mEq./1.; net insorption occurred with instillates of higher bicarbonate concentration, the rate of which was dependent on the instillate concentration. Insorption of chloride occurred with the lower bicarbonate solutions and enterosorption occurred at higher concentrations. The modification of intraluminal bicarbonate by the proximal duodenal mucosa is important in the regulation of intraduodenal pH and abnormal function of this mechanism may play a role in the pathogenesis of duodenal ulceration because of incomplete hydrochloric acid neutralization.