Ultrastructural effects of exogenous hydrogen peroxide on the myocardium

Abstract

It has been suggested that hydrogen peroxide (H2O2) is indirectly associated with postischemic-reperfusion injury of the heart. Previously, we reported that the heart was not damaged when perfused with exogenously generated superoxide anions. However, H2O2, a dismutation product of superoxide anion severely affected the heart structure and function. In this study, we evaluated the ultrastructural changes of the cel1 membranes in isolated rat hearts and cultured myocytes follow-ing treatment with exogenous H2O2.In the isolated hearts, 300 μM of H2O2, a concentration which was based on our earlier study was perfused for 5 minutes. For the last 2 minutes, 100 mg (2200 U/mg) of horseradish peroxidase was perfused to see the permeability of the cell membranes. In the isolated cultured myocytes, 300 μM of H2O2 was added to the medium for 30 minutes. Both the hearts and the isolated myocytes were fixed with 2.5% buffered glutaraldehyde, postfixed with 1% osmium tetroxide and were processed for electron microscopy.