Non-enzymatic peroxidation of lipids isolated from rat liver microsomes, mitochondria and nuclei

Studies were carried out to determine the level of lipoperoxidation ascorbate-Fe2+ dependent on polar and neutral lipids isolated from rat liver microsomes, mitochondria and nuclei subjected to an incubation at 37 degrees C for 140 min. Three experimental approaches were used: recording of low-level chemiluminescence, determination of fatty acid composition and measurement of radioactivity of lipidic species of each kind of membrane during the peroxidation process. Membrane light emission decreased in the order microsomes > mitochondria > nuclei using 1.5 mg of protein of each preparation. The peroxidizability index was profoundly affected in polar lipids whereas that of neutral lipids was not. The most sensitive fatty acids for peroxidation were arachidonic acid, C20:4 n6 and docosahexanoic acid, C22:6 n3. Experiments carried out with membranes labelled in vivo indicate a selective release of radioactivity from polar rather than from neutral lipids during the peroxidation process.