Role of luminal acidity in the pathogenesis of stress-induced gastroduodenal disease.

Infusion of progressively more acidic fluids into the stomachs of rats stressed by immobilization had disparate effects on gastric erosive disease despite their producing a stepwise fall in venous pH. At the highest concentration infused, disease was exacerbated. However, at lower concentrations, disease was ameliorated. The acidity of the infusate altered the incidence but not the magnitude of the duodenal disease that accompanies stress. When bicarbonate was given parenterally, systemic pH was normalized but gastric disease still developed. Thus the level of mucosal pH does not reliably predict whether or not gastric disease will develop. When a series of progressively more basic fluids was infused into the stomachs of stressed rats, gastric disease was lessened in only those rats infused with the highest concentration of bicarbonate. Increasing the pH of the infusate in a stepwise fashion produced a stepwise diminution of duodenal disease incidence with no effect on duodenal disease severity. When the stressed rat's mucosa was stimulated to secret acid by the parenteral injection of secretagogues, gastric disease severity was the same as in control animals given saline. Although secretagogue infusion did not affect the incidence of stress-induced duodenal disease, it significantly exacerbated the magnitude of the elicited disease. These experiments suggest that luminal acid plays a negligible role in the onset of stress-induced gastric disease but may be important in determining the severity of the gastric disease once it has begun. Conversely the amount of luminal acid correlates with the incidence of stress-induced duodenal disease but does not seem to play a role in determining the severity of the duodenal disease after it has begun.