Oxidative stress and cardiac microvascular structure in ischemia and reperfusion: the protective effect of antioxidant vitamins.

Reperfusion of the ischemic myocardium results in structural changes in the capillary bed, which may contribute to decreased microcirculatory flow ("no reflow"). This study was designed to correlate the endothelial cell shape changes with both oxidative stress and lipid peroxidation and to evaluate the beneficial potential of Trolox (a hydrophilic analogue of alpha-tocopherol) and ascorbic acid. Isolated buffer-perfused rat hearts were made ischemic for 45 min and then reperfused with 100 microM Trolox and/or 100 microM ascorbic acid. Morphological changes were quantified by measuring capillary cross-sectional areas. Increased myocardial content of oxidized glutathione and its release into the coronary effluent were used as indices of oxidative stress. Myocardial MDA, an end product of lipid peroxidation, was also measured. Luminal membrane blebs and capillary "constriction" in the ischemic groups occurred when there was no change in either glutathione status or MDA concentrations. Reperfusion altered the redox state of the heart sufficiently to induce lipid peroxidation. It also induced endothelial cell swelling and a reduction in luminal area. Ascorbic acid was a more effective antioxidant than Trolox as it significantly reduced both oxidative stress and ultrastructural injury. The combined antioxidant treatment returned both the stress ratio and the capillary measurements to control values. We conclude that endothelial cell swelling correlates with the degree of oxidative stress and that antioxidant vitamins reduce membrane damage by preventing lipid peroxidation.