engleski

Slow autoxidation of LDL spares alpha-tocopher

Slow oxidation of LDL is characterized by tocopherol-mediated peroxidation (TMP). Here we show that in very slow TMP alpha-tocopherol is not used to a detectable level. Buffered LDL (with presence of EDTA) undergoes slow autoxidation at physiological temperature. In a closed system, after a lag period of about one day, oxygen is consumed and peroxides formed. The process is followed by reduction of the peroxides and simultaneous appearance of free radicals that are trapped predominantly on the apoproteins. In the above process no change of alpha-tocopherol level has been detected. Under our experimental conditions oxidation is probaly initiated by very few (chelated) transition-metal ions in only few LDL particles. In the initial phase (lag phase) tocopherol is protected or the tocopheroxyl radical regenerated by ubiquinol-10 and/or some other lipid-soluble antioxidant, in a way that is not well understood. In the propagation phase tocopherol reversibly flips between the oxidized and reduced forms, serves as a chain-transfer reagent and keeps the oxidation process active. After dissolved oxygen is consumed , tocopherol participates in the samne manner in the formation of the lipid-centered free radicals. The L. radicals react with the protein moiety (radical fixation to protein) and terminats the process.

LDL oxidation; lipoproteins; tocopherol

doi: 10.1016/S0021-9150(97)89094-6