Adaptation of the gastric mucosa to repeated administration of aspirin in the rat

The effects of single and repeated doses of aspirin on the gastric mucosa of the rat were compared to determine whether the mucosal response alters after repeated aspirin. Aspirin (120 mg/kg) was administered by esophageal intubation either as a single dose or daily for 3, 14, 28 and 56 days. Mucosal damage was present in all treated rats but, on histologic quantitation, there was a highly significant reduction in the numbers of acute erosions in the groups receiving repeated daily aspirin. This apparent adaptation did not persist when aspirin administration was interrupted for 3 days. Repeated aspirin administration was not associated with any reduction in aspirin absorption or excretion, nor was there any significant change in hydrochloric acid or pepsin secretion. The investigation has shown an adaptation to repeated aspirin in the rat which appears to result from an alteration in the gastric mucosa. The precise mechanism of the adaptation remains uncertain.Supported by the National Health and Medical Research Council and the Alfred Hospital.Presented, in part, to the Gastroenterological Society of Australia, May 1971.