SUPEROXIDE ANION-INDUCED PEROXIDATION OF HUMAN LOW-DENSITY LIPOPROTEINS (LDL) - INFLUENCE OF THE PH

This study aimed to quantitatively analyse the initiation of low densi ty lipoprotein (LDL) peroxidation by O2.BAR/HO2. free radicals produce d by gamma radiolysis. The consequences of the action of increasing ir radiation doses on aqueous LDL solutions have simultaneously been eval uated by considering several parameters: decrease of endogenous vitami n E and formation of lipid peroxidation products evidenced by the appe arance of thiobarbituric acid-reactive substances (TBARS) and conjugat ed dienes. Initial irradiation yields of vitamin E decrease and TBARS formation have been determined at pH 7 and pH 5.7 as a function of LDL concentration (from 0.75 to 9 g.l-1). The comparison of these yields with that of 02.BAR radicals produced by water radiolysis allowed us t o propose some reaction mechanisms for LDL peroxidation initiated by O 2.BAR/HO2. free radicals.