Is lipid peroxidation responsible for the damage caused by postischemic reperfusion?

Peroxidation of membrane phospholipid polyunsaturated fatty acids is considered a major mechanism of the damage occurring during post-ischemic reperfusion. The evidences in support for this mechanism of damage are based on tissue malondialdehyde (MDA) quantitation by the thiobarbituric acid test (TBA-test). In an attempt to verify this topic we have subjected isolated and Langendorff perfused rabbit hearts to a period of 60 min of severe ischemia plus 30 min of reperfusion. At appropriate time points MDA was determined in the tissue by means of TBA-test and directly by reversed phase, high pressure, liquid chromatography (HPLC). We have found no correlation between the 2 compared assays. During reperfusion, there was the formation of non-lipid related, MDA like, TBA-reactive substance which leads to overestimation of the extent of lipid peroxidation. On the contrary, by direct HPLC quantitation, there was a decrease of tissue MDA during ischemia and during the early phases of reperfusion. Our results demonstrate that TBA-test is not a reliable index of lipid peroxidation in organ systems and that MDA accumulation does not precede the evidence of the functional alterations occurring on reperfusion of the previously ischemic myocardium. These results are of relevance in the understanding of the exact mechanism of reperfusion damage as, in the same experimental model, oxy radicals have been shown to be generated and antioxidants are protective.