NONENZYMATIC PEROXIDATION OF LIPIDS ISOLATED FROM RAT-LIVER MICROSOMES, MITOCHONDRIA AND NUCLEI

Studies were carried out to determine the level of lipoperoxidation as corbate-Fe2+ dependent on polar and neutral Lipids isolated from rat l iver microsomes, mitochondria and nuclei subjected to an incubation at 37 degrees C for 140 min. Three experimental approaches were used: re cording of low-level chemiluminescence, determination of fatty acid co mposition and measurement of radioactivity of lipidic species of each kind of membrane during the peroxidation process. Membrane light emiss ion decreased in the order microsomes > mitochondria > nuclei using 1. 5 mg of protein of each preparation. The peroxidizability index was pr ofoundly affected in polar lipids whereas that of neutral lipids was n ot. The most sensitive fatty acids for peroxidation were arachidonic a cid, C20:4 n6 and docosahexanoic acid, C22:6 n3. Experiments carried o ut with membranes labelled in vivo indicate a selective release of rad ioactivity from polar rather than from neutral lipids during the perox idation process.