Spectrum of injury produced in the duodenum by perfusion with luminal acid in the rat.

The dose and time dependence of duodenal mucosal injury by luminal acid perfusion was studied. Saline, 0.01, 0.05, 0.15, and 0.3N HCl, were perfused through the proximal duodena of rats for 5, 15, or 30 minutes and then harvested for histological examination. In a second set of studies, after a 30-minute perfusion, duodena were harvested either immediately or 2, 4, 8, or 24 hours after the perfusion to study the recovery from injury. Acid disappearance (acid delivered minus acid recovered) was measured in all groups. Duodena were examined grossly, then fixed, stained, and scored histologically. Whereas no gross mucosal injury was noted, there was graded histological injury proportional to acid concentration. Injury occurred early in the perfusion and changed little with increased perfusion durations. The initial injury lead to an acid disappearance rate that was proportional to acid concentration and, therefore, the degree of injury. After the initial injury occurred, the rate of acid neutralization was unchanged by increased duration of acid perfusion. This acid neutralization protected against further injury despite the continued presence of acid. Recovery from injury was complete with physiological (0.01 and 0.05N HCl) but not pharmacological (0.15 and 0.3N HCl) concentrations of acid. It is concluded that acid-induced duodenal injury occurs within 5 minutes of exposure, is proportional to the acid concentration, and results in acid neutralization that protects against extension of the injury with continued acid exposure.