Jejunal mucosal injury and restitution: role of hydrolytic products of food digestion.

The effects of hydrolytic products of carbohydrate, protein, and lipid digestion on jejunal mucosal injury and restitution were assessed in anesthetized rats. Mucosal epithelial integrity was continuously monitored by measuring the blood-to-lumen clearance of 51Cr-labeled EDTA. Perfusion of the lumen with hydrolyzed casein (3%) or glucose (150 mM) did not affect 51Cr-EDTA clearance compared with saline controls. By contrast, perfusion with emulsified lipids (20 mM sodium taurocholate and 10-40 mM oleic acid) increased 51Cr-EDTA clearance in a dose-dependent manner. The lipid-induced increase in 51Cr-EDTA clearance returned toward control levels when the lipid infusion was terminated and saline perfusion resumed. Histological evaluation of jejunal mucosa indicated that the epithelial lining of the villous tips was damaged during lipid infusion and that restitution of the lining occurred within 50 min after resumption of saline perfusion. In vitro studies indicated that neither glucose nor hydrolyzed casein affected the integrity of rat intestinal epithelial cell (IEC-18) monolayers in culture. Oleic acid emulsified in rat hepatic bile produced a dose-dependent disruption of the epithelial monolayer. Biochemical determination of lipid peroxidation products in vivo and in vitro yielded negative results, indicating that the lipid-induced epithelial cell injury was not due to lipid peroxidation. Because the concentrations of the various nutrients used in the present study are similar to those measured in postprandial chyme, the findings of the present study suggest that the intestinal epithelium is injured and restitutes during the normal course of digestion and absorption of a meal.