The main concern of this work was to examine the relation between altered antioxidant status on the one hand and increase in L-tryptophan absorption in the small intestine in order to bring further information regarding to possible role of vitamin A and zinc to maintaining of intestinal epithelial barrier integrity, on the other hand. In control, only some ideal tight junctions at the tip of the villi were permeable to ZnC1(2), whereas in A-hypovitaminosis permeability increased significantly. Studies demonstrate that an increased L-tryptophan accumulation in the intestinal mucous may result from a free radical damage to the mucous surface with formation of "leaky" junctions in the ilea. The results suggest that the zinc plays a crucial role in stabilizing biomembranes.