Phagocytic and intestinal endothelial and epithelial barrier function during the early stage of small intestinal ischemia and reperfusion injury

The effects of intestinal ischemia and reperfusion (I/R) on small intestina l mucosal endothelial and epithelial barrier integrity and phagocytic funct ion were assessed in rats subjected to 20- or 40-min mesenteric ischemia an d a 3-h reperfusion. The results showed that human serum albumin (I-125-HSA ) flux through the endothelial layer to the interstitial space increased as did I-125-HSA clearance from blood to the gut lumen and I-131-HSA flux fro m the gut lumen to the interstitial space in rats with I/R, E.coli adhering to microvilli, invading and passing into the microvessels, were noted on t he small intestinal mucosa in animals subjected to 40-min ischemia and a 3- h reperfusion. Phagocytic function increased, especially in the small intes tinal wall, lungs, liver, and spleen in the groups with I/R, correlating wi th the length of ischemia. The results imply that both endothelial and epit helial barrier integrity is impaired in the early phase after I/R and that the epithelial barrier more effectively restricts macromolecular leakage co mpared with the endothelial barrier. I/R impairs the intestinal barrier not only by causing tissue hypoxia but also by activating the phagocytic syste m and aggravating barrier damage, which finally may result in bacterial tra nslocation and remote organ dysfunction.