Reactive oxygen species and other oxidants are involved in the mechanism of postischemic contractile dysfunction, known as myocardial stunning. The present study investigated the oxidative modification of cardiac proteins in isolated Langendorff-perfused rabbit hearts subjected to 15 min normothermic ischemia followed by 10 min reperfusion. Reperfusion under these conditions resulted in only 61.8±2.7 % recovery of developed pressure relative to preischemic values and this mechanical dysfunction was accompanied by oxidative damage to cardiac proteins. The total sulfhydryl
group content was significantly reduced in both ventricle homogenates and mitochondria isolated from stunned hearts. Fluorescence measurements revealed enhanced formation of bityrosines and conjugates of lipid peroxidation-end products with proteins in cardiac homogenates, whereas these parameters were unchanged in the mitochondrial fraction. Reperfusion did not alter protein surface hydrophobicity, as detected by a fluorescent probe 1-anilino-8-naphthalenesulfonate. Our results indicate
that oxidation of proteins in mitochondria and possibly in other intracellular
structures occurs during cardiac reperfusion and might contribute to ischemia-reperfusion injury.
In the myocardium, the sarcoplasmic reticulum (SR) plays an essential role in the regulation of cytosolic free Ca2 + ion concentration and, hence, in the contraction-relaxation cycle. The aim of this review is to summarize the role of the SR, particularly the main SR Ca2+ transport proteins, Ca2+-ATPase pump and Ca2+ release channel (ryanodine receptor), in contractile impairment during ischaemia and reperfusion. As suggested by most studies, SR dysfunction may contribute to contractile failure during ischaemia. However, SR function is largely restored during reperfusion and minor changes are unlikely to explain the severe postischaemic contractile dysfunction.