ANTIOXIDANT EQUIPMENT OF JEJUNAL EPITHELIAL CELLS: RESPONSE TO ACUTE AND CHRONIC METABOLIC ACIDOSIS

We investigated whether acute and chronic acidosis affect the antioxidant enzymatic equipment of rat jejunum, including g-GT, involved in glutathione homeostasis. Lipid peroxidation level and expressions of (Na+, K+)-ATPase and GLUT2 were also tested, as well as the possibile influence of acidosis on ROS action. Isolated apical membranes, everted sac preparations and homogenates from acidotic rats were used. g-GT activity is inhibited after incubation of isolated membranes at acidic pH; using the whole intestinal tract this inhibition disappears, while superoxide dismutase and glutathione reductase activities are enhanced,indicating that acidosis elicited an antioxidant defense. Also in metabolic acidosis g-GT activity is unaffected, but antioxidant activities keep constant: thus we can hypothesize thatafter 7 days of chronic acidosis the compensatory response is accomplished.(Na+, K+)-ATPase expression increases whilst GLUT2 level decreases in acidotic animals, suggesting a specific regulation of function. Lipid peroxidation level is unaffected by acidosis. H2O2 inhibits g-GT activity only in isolated membranes; in the whole isolated tissue it enhances catalase and superoxide dismutase activities and reduces GLUT2 expression. The pattern of responses to various oxidant agents is unaffected by acidosis. Although jejunum seems quite resistant to acidosis, results suggest specific responses to this condition and may direct further research on antioxidant supplementation.