Salivary carbonic anhydrase protects gastroesophageal mucosa from acid injury

Saliva contains several factors that protect the alimentary canal mucosa against acidity. We measured the secretory carbonic anhydrase (CA VI) levels in the saliva of patients with gastrointestinal disorders using a time-resolved immunofluorometric assay. The mean enzyme concentrations were found to be lower in patients with verified esophagitis, gastric ulcer, or duodenal ulcer than in control patients with nonacid peptic diseases. The biochemical data from the enzyme activity assays and western blots of the human gastric mucosa and gastric juice samples indicated that the swallowed CA VI probably retains its activity in the harsh environment of the gastric lumen. In the upper alimentary canal, CA VI may neutralize the acid by catalyzing the formation of carbon dioxide and water. The present findings suggest that drugs supplemented with CA VI may prove beneficial in treating acid-peptic diseases.