Ultrastructure and biochemistry of ischemic damages of small intestinal epithelial cells

Ischemia (one hour) and following reperfusion (up to one hour) of the small intestine induce biochemical changes which are indices for the formation and action of oxygen free radicals and which occur predominantly during the reperfusion period. But the villi and the epithelial cells show different patterns of damage, occurring both at the end of the ischemic period and during the reperfusion period. Although the quantitative morphological changes are increased during the reperfusion in comparison with the ischemic phase the quality of the pattern of structural damage is the same in both periods of the experiment. This pattern of the damage includes: 1. the neighbourhood of groups of villi with total ischemic-lytic dissolution of the villi, of villi with damage of the epithelial cells at the tip and at the lateral area and of normal villi; 2. the different degree of structural damage of neighbouring epithelial cells within one villus whose cells are either of regular structural or damaged at subcellular organelles including the plasma membrane or of those being necrotically destroyed and on the way of release into the luminal space; 3. a differentiation of the structural changes of the microvilli and other organelles within single and neighbouring epithelial cells. The biochemical findings on purine nucleotide metabolism and on the formation of oxygen free radicals as "mean values" of a homogenate from a large group of cells cannot reflect the morphological-ultrastructural changes of single villi or even single epithelial cells. The possible reasons for the mosaicism of the morphological changes during ischemia and reperfusion are discussed.