Effect of luminal pH and nutrient bicarbonate concentration on restitution after gastric surface cell injury

Frog fundic mucosas whose surface layers were severely injured by exposure to 1 M NaCl for 10 minutes in an Ussing chamber uniformly recovered both physiologically and anatomically within 4 to 6 hours. The purpose of the present study was to examine the effects of luminal H+ and nutrient HCO-3 concentrations on this process of reconstitution. With 18 mM HCO-3, return of the transmucosal potential difference, tissue electrical resistance, and short-circuit current toward normal and anatomic recovery occurred at luminal pH of 7.4, 5.0, and 4.0 but not at 3.0. An inhibitor of pepsin did not favorably affect the outcome of luminal pH 3.0, but a nutrient HCO-3 concentration of 47.8 mM completely prevented the adverse effects of luminal pH 3.0. Reconstitution of epithelial integrity did not occur in the absence of HCO-3 at luminal pH 4.0. Thus, low luminal pH inhibits and high nutrient HCO-3 concentration supports the epithelial restitution after mucosal damage caused by hyperosmolar NaCl.