PEROXIDATION OF LOW-DENSITY LIPOPROTEINS BY SEVERAL OXYGEN FREE-RADICALS GENERATED BY GAMMA-RADIOLYSIS

In vitro studies of lipid peroxidation of human low density lipoproteins (LDL 1,5 g.l-1) in aqueous solutions buffered at pH 7 have been investigated using steady state radiolysis to produce selectively oxygen-centred free radicals OH. or O2.. The effects of increasing doses (up to 800 Gy, dose rate = 3,4.10(-2) Gy.s-1) have been followed by measuring : 1) the formation of malondialdehyde (MDA), 2) the disappearance of vitamin E, and 3) the evolution of the electrophoretic mobility on agarose gel. In each case studied, vitamin E was consumed in a dose-dependent manner before the onset of lipid peroxidation, in agreement with the antioxidant properties of this vitamin. In the absence of oxygen, OH. radicals produced only very limited peroxidation (G(MDA) congruent-to 10(-8) mol.J-1), whereas in the presence of oxygen the initial G value of MDA was enhanced by a factor of 10 (G(MDA) congruent-to 10(-7) mol.J-1). Superoxide anions induced, as expected, little lipid peroxidation (G(MDA) congruent-to 10(-8) mol.J-1). The electrophoretic mobility increased with the degree of lipid peroxidation measured by the formation of MDA.