Formation of Keto and Hydroxy Compounds of Linoleic Acid in Submitochondrial Particles of Bovine Heart

To observe lipid peroxidation of additive-free submitochondrial particles, we incubated submitochondrial particles in the absence of exogenous irons and t-butyl hydroperoxide. After the incubation, the phospholipids were hydrolyzed by phopholipase A2, and the fatty acid constituents were analyzed by high-performance liquid chromatography, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry. Contrary to a commonly accepted theory, lipid peroxidation in the submitochondrial particles did not need the addition of NADH. In the phospholipid constituent fatty acids of the oxidized submitochondrial particles, derivatives of hydroperoxides of linoleic acid such as keto, hydroxy, trihydroxy, and hydroxyepoxy compounds were generated. Lipid peroxidation in the submitochondrial particles was not inhibited by the addition of catalase, superoxide dismutase, hydroxyl radical scavengers, or ethylenediaminetetraacetic acid, but was inhibited by the addition of KCN, antimycin-A, NADH, ubiquinol, deferoxamine mesylate, ascorbic acid, and α-tocopherol. The cardiolipin–cytochrome c lipid peroxidation system could mimic the lipid peroxidation of the submitochondrial particles, in terms of linoleic acid products and the inhibitory patterns of radical scavengers and electron transfer chain inhibitors. Thus, lipid peroxidation in the submitochondrial particles seems to be due to phospholipid–hemoprotein lipid peroxidation systems such as the cardiolipin–cytochrome c system.