Pathogenic Mechanisms Involved in Mepirizole-Induced Duodenal Damage in the Rat

Abstract

Mepirizole (60 and 200 mg/kg) administered s.c. induced damage in the surface epithelial cells of the rat proximal duodenum as early as 2 hr after the treatment. 16, 16-Dimethyl prostaglandin E₂ (dmPGE₂, 30 μg/kg) administered s.c. significantly protected the duodenal mucosa against mepirizole-induced damage for up to 6 hr. Gastric acid secretion in acute fistula preparations was significantly reduced 1 hr after administration of mepirizole (60 and 200 mg/kg). The secretion reverted to the control level 2 hr later. In the 60 mg/kg-treated group, however, there was a significant increase in the acid output for up to 6 hr. Duodenal HCO₃^-secretion stimulated with 10 mM HCl was significantly inhibited with mepirizole (60 and 200 mg/kg). Mepirizole (60 and 200 mg/kg) significantly increased the amount of acid in the duodenum for 2 to 6 hr after the treatment. dmPGE² (30 μg/kg) significantly inhibited gastric acid secretion, stimulated duodenal HCO₃^-secretion, and reduced the increased amount of acid in the duodenum in response to mepirizole. Endogenous prostaglandin E₂ and 6-keto prostaglandin F_1α in the duodenal mucosa were significantly reduced by mepirizole (200 mg/kg) 1 to 2 hr later. Mepirizole-induced duodenal damage appears to be caused by the increased amount of acid in the duodenum.