Summary

HCO3- secretion, which is believed to neutralize acid within the mucus gel, is the most studied duodenal defense mechanism. In general, HCO3- secretion rate and mucosal injury susceptibility correlate closely. Recent studies suggest that luminal acid can lower intracellular pH (pHi) of duodenal epithelial cells and that HCO3- secretion is unchanged during acid stress. Furthermore, peptic ulcers are rare in cystic fibrosis (CF), although, with impaired HCO3- secretion, increased ulcer prevalence is predicted, giving rise to the ‘CF Paradox’. We thus tested the hypothesis that duodenal epithelial cell protection occurs as the result of pHi regulation rather than by neutralization o