Change in formation of gastric lesions by aspirin during aging in rats

Formation of gastric lesions induced by orally administered aspirin (100 mg/kg) was examined in 4 to 86 week-old Sprague-Dawley male rats. Gastric mucosal prostaglandin I2 level and gastric secretion in basal state were also examined in these rats. Gastric mucosal PGI2 level was measured by bioassay and gastric secretion was collected by the pyloric ligation method for 4 h. Gastric lesions reached the maximum value in 7 week-old, and lowest in 60 week-old. Acid output also reached the maximum value in 7 week-old. As for PGI2 level, it showed the maximum value in 20 week-old, and moderately decreased thereafter. In 86 week-old, PGI2 level was further lowered to about 35% of 20 week-old rats. A linear positive correlation was noted between formation of aspirin-induced gastric lesion and acid secretion. From these results, it was concluded that formation of gastric lesions by aspirin was closely related to acidity of the gastric secretion. It was also suggested that in aged rats, aspirin-induced gastric lesions may at least partly be associated with the reduced PGI2 level.