INVERSE DEUTERIUM KINETIC ISOTOPE EFFECT FOR PEROXIDATION IN HUMAN LOW-DENSITY-LIPOPROTEIN (LDL) - A SIMPLE TEST FOR TOCOPHEROL-MEDIATED PEROXIDATION OF LDL LIPIDS

alpha-Tocopherol (alpha-TOH) can act as a pro- or antioxidant for isol ated ubiquinol-10-free human low density lipoprotein (LDL). We demonst rate that alpha-TOH is a more potent prooxidant than other forms of vi tamin E for LDL peroxidation initiated by mild fluxes of aqueous perox yl radicals and low concentrations of Cu2+. A simple deuterium exchang e test shows that alpha-TOH switches from pro- to anti-oxidant at Cu2:LDL ratios > 2.5. The results suggest that this test may be useful to distinguish 'inhibited' peroxidation of emulsion lipids propagated vi a the lipid peroxyl radical from that mediated via the antioxidant rad ical.