Differences in the reducing power along the rat GI tract: Lower antioxidant capacity of the colon

The ability of the gastrointestinal (GI) tract, as well as other tissues, t o cope with reactive oxygen species (ROS) efflux in pathological events is determined partly by epithelial antioxidant levels. These levels are compri zed of tissue antioxidant enzymes and low molecular weight antioxidants (LM WA). While glutathione levels and the activity of enzymatic antioxidants al ong the GI tract have been studied, the contribution of the overall LMWA to the total antioxidant capacity has not yet been determined. In this study the overall antioxidant activity in the mucosa/submucosa and muscularis/serosa of various sections along the small intestine and colon o f the rat was evaluated by determining the reducing power, which reflects t he total antioxidant activity derived from LMWA, using cyclic voltammetry. The activity of the antioxidant enzymes superoxide dismutase (SOD) and cata lase was also measured. The reducing power (total antioxidant activity) was higher in the mucosa/submucosa of the small intestine as compared to the m ucosa/submucosa of the colon. Similarly, catalase and SOD activity in the m ucosa/submucosa of the small intestine was significantly higher than in the mucosa/submucosa of the colon. Differences were also observed in the reduc ing power and SOD activity in the muscularis/serosa of the rat small intest ine as compared to the colon. The low antioxidant capacity in the colon may facilitate reactive oxygen sp ecies (ROS)-mediated injury and lead to inflammatory diseases such as ulcer ative colitis, specifically in the colon.