Rat liver and heart microsomes catalyze the transfer of single electrons from NADPH to adriamycin forming semiquinone radicals which, in turn, activate molecular oxygen. This process stimulated lipid peroxidation 5- to 7-fold as measured by malonaldehyde formation. Adriamycinaugmented lipid peroxidation was linear with time to 60 min, optimal at 1.0 mg of microsomal protein/ml and pH 7.5, and was proportional to the adriamycin concentration up to 100 μM. An NADPH-generating system was superior to NADPH, and an oxygen atmosphere tripled the rate of peroxidation as compared to air. Nitrogen abolished adriamycin-stimulated peroxidation. Superoxide dismutase, reduced glutathione, α-tocopherol, EDTA, dioxopiperazinylpropane (ICRF-187), and dimethylurea were effective inhibitors of lipid peroxidation. This suggests that Superoxide anion and possibly hydroxyl radical may be formed by the oxidation of the adriamycin semiquinone radical and thus stimulate the peroxidation of microsomal unsaturated fatty acids. Although adriamycin failed to stimulate lipid peroxidation in heart microsomes from control animals, peroxidation was dramatically increased when adriamycin was added to cardiac microsomes from α-tocopherol-deficient rats. Lipid peroxidation in α-tocopheroldeficient liver microsomes was four times greater than in control microsomes with the NADPH-generating system, and adriamycin did not further increase that high rate of peroxidation; however, when NADPH was used as the source of electrons in place of the NADPH-generating system, adriamycin stimulated peroxidation more than 2-fold. These results suggest that microsomal lipid peroxidation may play a role in the cytotoxicity and cardiotoxicity of adriamycin.
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