Gastric bicarbonate appearance with ethanol ingestion. Mechanism and significance.

Increasing quantities of HCO3- appeared in the stomach and in gastric pouches of conscious dogs with gastric infusion of increasing concentrations of ethanol. HCO3- appearance was closely correlated with gains of K+ and of glucose to the contents and with reductions in transmucosal potential differences, each of which is associated with increased mucosal permeability. We concluded that increased diffusion of HCO3- through a more permeable mucosa accounted for the appearance of HCO3- with the lower concentrations of ethanol we used (5-20%) and that bulk movement of the interstitial fluid into the contents added to HCO3- entry with the most damaging, desquamating, concentration (40%). With the gastric contents at 100 mM HCl, an unstirred layer of mucus gel over the mucosa would need to be of greater depth than previous estimates to produce mucosal surface neutrality at the rates of HCO3- appearance we observed. However, faster rates of HCO3- production combined with an unstirred layer could provide significant protection to the gastric mucosa.