Non-enzymatic lipid peroxidation of rat liver nuclei and chromatin fractions

In the study reported here, the non-enzymatic (ascorbate-Fe2+) lipid peroxidation of rat liver nuclei and chromatin fractions was assayed. Chromatin obtained by sonication of nuclei suspended in 0.25 M sucrose was fractionated by differential sedimentation according to the following scheme: 3000, 12 000 and 27 500g for 10 min each. The lowest density chromatin fraction was obtained by precipitation with cold ethanol of the supernatant obtained from the last centrifugation. Light emission = chemiluminescence, measured as cpm/mg protein, decreased in the order heavy > low density chromatin fractions during the peroxidation process. Analysis of fatty acids by gas chromatography showed that heavy density chromatin fractions are enriched with C20:4 n6 arachidonic acid, when compared with low density chromatin fractions. The amount of arachidonic acid C20:4 n6 was higher in repressed chromatin fractions as compared to the amount in the transcriptionally active chromatin which correlates with the level of lipid peroxidation. (C) 1998 Elsevier Science Ltd. All rights reserved.