The effects of pH on the oxidation of low-density lipoprotein by copper and metmyoglobin are different.

The amplification of low-density lipoprotein (LDL) peroxidation in vitro by copper and myoglobin are well-studied biochemical approaches for investigating the oxidative modification of LDL and its role in the pathogenesis of atherosclerosis. Since the acidity of the environment is increased in inflammatory sites, the aim of this study was to investigate the effects of acidic pH on the oxidisability of LDL mediated by the haem protein myoglobin in comparison with that of copper-mediated LDL oxidation. The results show that acidic pH enhances myoglobin-mediated LDL oxidation as measured by conjugated dienes, lipid hydroperoxides and electrophoretic mobility, whilst a retardation is observed with copper as pro-oxidant; the mechanism probably relates to the effects of pH on the decomposition and formation of lipid hydroperoxides and the relative influences of copper ions and of myoglobin under these conditions.