Sodium space and acid secretion in frog gastric mucosa

Abstract

Inulin, arabinose, mannitol, choline, and sodium, but not radioiodinated serum albumin (RISA), penetrate a space of about 320 ml/kg in gastric mucosa of Rana pipiens. Sixty-three to seventy-eight per cent of the space not penetrated by RISA is reached by the others from the serosal side. Sodium is quickly eluted from the mucosa by sodium-free solutions, only 2 mEq/kg remaining after 1 hr. When sodium is replaced by choline or mannitol the mucosa can still secrete acid. In sodium-free solutions containing mannitol at 200 mm the tissue loses potassium and its ability to secrete, but when [K] of bathing solution is increased tissue potassium rises and secretion is possible. Optimal external [K] is 36 mm. Sodium is not essential for acid secretion; it passes through the highly permeable basal membrane of the oxyntic cells into an intracellular space where its major function is osmotic. Potassium is the more important ion for acid secretion.