Gastroduodenal mucosal surface and luminal pH in gastric ulcer.

Gastroduodenal mucosal surface pH was measured in situ by electrode in endoscopically normal and gastric ulcer patients. With the exception of the antrum, mucosal surface pH in the ulcer group (GU) resembled that of the endoscopically normal group. In contrast, the antral mucosal surface pH of the GU group of 7.06 +/- 0.11 (22) was significantly (P less than 0.001) higher than that of 5.46 +/- 0.36 (34) for the endoscopically normal group. This difference was also evident when comparison was restricted to subjects in both groups having a fundal luminal fluid pH of less than 3. When the fundal luminal pH was below pH 3, antral mucosal surface pH was 4.79 +/- 0.41 (24) in endoscopically normal subjects and significantly less (P less than 0.001) than the value of 6.98 +/- 0.18 (12) for gastric ulcer patients. Mucosal surface alkalinity of the GU antrum may be a response to damage but seems inappropriate in view of the likelihood of acid dependent inhibition of gastric acid secretion.