Ultrastructural effects of lipid peroxidation on the cardiac sarcolemma of the isolated rat heart

Abstract

Previously we reported that hydrogen peroxide (H2O2) is primarily cytotoxic to the cardiac cell membranes presumably through lipid peroxidation (LP). However, the effect of LP on the altered cell membrane permeability remains unknown. In this study, we evaluated the ultrastructural effects of LP on the sarcolemma of the isolated rat heart using H2O2and N,N’-diphenyl-p-phenylene diamine (DPPD), an antilipid peroxidative agent.The hearts were perfused with 300 μM H2O2for 15 minutes. In the other experiment the hearts were perfused with 2.5 μM DPPD for 20 minutes prior to perfusion with H2O2for 15 minutes. Coronary effluent was collected at the end of the equilibration period and during H2O2treatment for malondialdehyde (MDA) determination. Two minutes prior to the termination of the experiment, horseradish peroxidase (HRP: 220 U/mg × 55 mg) was perfused to assess the enhanced permeability of the cell membranes. The tissue slices were incubated in Graham-Karnovsky medium for one hour followed by postfixation with buffered 1% OsO4.