Relationship between the action of reactive oxygen and nitrogen species on bilayer membranes and antioxidants

Membrane lipid peroxidation (LPO) induced by hydroxyl ((OH)-O-.) and ascorbyl ((.)Asc) radicals and by peroxynitrite (ONOO-) was investigated in asolectin (ASO), egg phosphatidylcholine (PC) and PC/phosphatidic acid mixtures (PC:PA) liposomes and rat liver microsomes (MC). Enthalpy variation (DeltaH) of PC:PA at different molar ratios were obtained by differential scanning calorimetry. It was also evaluated the LPO inhibition by quercetin, melatonin and Vitamin B-6. The oxidant effect power follows the order (OH)-O-. approximate to .Asc > ONOO- on PC and MC; whilst on ASO liposomes, it follows (.)Asc > (OH)-O-. approximate to ONOO-. Increasing amounts of PA in PC liposomes resulted in lower levels of LPO. The DeltaH values indicate a more ordered membrane arrangement as a function of PA amount. The results were discussed in order to provide a complete view involving the influence of membranes, oxidants and antioxidants intrinsic behavior on the LPO dynamics. (C) 2004 Elsevier Ireland Ltd. All rights reserved.