The defensive factors that prevent the human duodenal mucosa from acidic and peptic damage have not been fully evaluated. To determine whether duodenal mucosal
bicarbonate production was altered in patients with inactive
duodenal ulcer, we measured basal and
acid-stimulated
bicarbonate output from the duodenal bulb and the distal duodenum in healthy subjects and patients with inactive
duodenal ulcer. As compared with 16 normal subjects, the 12 patients had significantly less mean (+/- SE) basal proximal duodenal mucosal
bicarbonate secretion (185 +/- 13 vs. 107 +/- 18 mumol per centimeter per hour; P less than 0.001). Moreover, in response to a physiologic amount of
hydrochloric acid (2 mmol per five minutes) instilled directly into the duodenal bulb, peak proximal duodenal
bicarbonate output in the patients was 41 percent of the normal response (263 +/- 65 vs. 642 +/- 77 mumol per centimeter per hour; P less than 0.01). There was little overlap between groups. In contrast,
bicarbonate outputs in the distal duodenum were similar in the two groups. We conclude that most patients with
duodenal ulcer disease have decreased proximal duodenal mucosal
bicarbonate production at rest, in response to
hydrochloric acid, and in relation to peak gastric acid secretion. Impaired proximal duodenal mucosal
bicarbonate secretion may be an important factor in the development and natural history of
duodenal ulcer.