Histochemical studies of myocardial injury caused by hydrogen peroxide after reperfusion using the cerium method

Free radicals have been implicated in myocardial reperfusion injury. Hydrogen peroxide (H2O2) is a precursor of highly reactive oxygen intermediates. In this study, we investigated myocardial injury caused by endogenous H2O2 during the early reperfusion period following brief ischemia with electron microscopy and the cerium method. This method involves formation of an electron-dense precipitate when H2O2 reacts with cerium chloride (CeCl3). We used isolated, functioning hearts prepared according to the working heart model, which were reperfused with a solution containing 0.5mM CeCl3 for 5 min after 10 min of ischemia. Some hearts were treated with 3-amino-1,2,4,-triazole (ATZ) to inhibit catalase; others were treated with ATZ and Superoxide dismutase (SOD), which dismutates the Superoxide anion to hydrogen peroxide. In the control group (no drugs given) and the ATZ-treated group, the CeCl3-H2O2-dependent reaction products during the reperfusion period appeared in 12% and 28%, respectively, of the microvascular spaces. Treatment with SOD did not produce a decrease in electron-dense precipitates or a decrease in myocardial injury during ischemiareperfusion. Moreover, in the ATZ group, moderately injured myocytes were seen (swelling of mitocondria, intermyofibrillar edema). Our results indicate that in myocytes, catalase plays an important role in the defense against H2O2 and that the increase in H2O2 is a cause of reperfusion injury. However, SOD does not protect against H2O2 in the absence of catalase. © The Clinical Electron Microscopy Society of Japan 1998.