Age-associated oxidative damage in microsomal and plasma membrane lipids of rat hepatocytes

Phosphatidylcholine hydroperoxide (PC-OOH) and phosphatidylethanolamine hydroperoxide (PE-OOH) concentrations were determined in microsomes and plasma membranes prepared from 2- and 17-month-old male Sprague-Dawley rat hepatocytes, to verify the dissimilarity of age dependency of lipid peroxidation in organelle membranes. The hydroperoxides were directly measured by chemiluminescence detection-high-performance liquid chromatography (CL-HPLC), and 1-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl) phosphatidylcholine (PLPC-OOH) and 1-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl) phosphatidylethanolamine (PLPE-OOH) were enzymatically synthesized and utilized as standards for the calibration. Baseline concentrations of hydroperoxides (PC-OOH + PE-OOH) of the 17-month-old rats were 46 pmol per mg protein in microsomes (2.7 times higher than the 2-month-old rats) and 306 pmol per mg protein in plasma membranes (9.9 times higher than the 2-month-old rats). Both microsomal and plasma membrane lipids were severely peroxidized and converted to phospholipid hydroperoxides by NADPH-dependent lipid peroxidation in vitro, but the age-dependency was only observed in the plasma membranes. These results demonstrate that substantial oxidative damage to membrane phospholipids occurs with ageing both in microsomes and plasma membranes, but is more prevalent in plasma membranes in rat hepatocytes. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.