Gastric acid secretion and lesion formation in rats under water-immersion stress.

In attempts to investigate the roles of acid in the pathogenesis of stress-induced gastric lesions, gastric acid secretion was studied in pylorus-ligated and lumen-perfused rats under restraint alone (R) or restraint with additional water immersion (WI). Gastric mucosal blood flow (GMBF) was measured with the aminopyrine clearance method in acute fistula rats. Acid secretion in pylorus-ligated rats significantly decreased under R or WI of either 3.5 or 7 hr stress. In the lumen-perfused or acute-fistula rats, exposure of rats to stress for 7 hr produced a similar decrease; however, in the WI group, there was a significant increase of acid secretion for 3-4 hr during stress, but not exceeding the prestress level. Only in the WI group did GMBF exhibit similar increases to those of acid secretory activity, and these increases were significantly inhibited by intraperitoneal administration of atropine (1 mg/kg) or cimetidine (60 mg/kg). Gastric lesions developed in both groups at 3.5 hr and became extensively severe at 7 hr only in the WI group. Cimetidine failed to influence the formation of lesions at 3.5 hr but significantly inhibited the later outgrowth of lesions at 7 hr, while atropine or pylorus ligation all but completely prevented lesions induced by either 3.5- or 7-hr WI stress. These results indicate that exposure of rats to stress (R or WI) generally decreased acid secretory activity, but there was a rise in acid secretion toward normal levels during WI stress, which may play an important role in the aggravating process of stress-induced gastric lesions.