ALPHA-TOCOPHEROL CONSUMPTION DURING LOW-DENSITY-LIPOPROTEIN OXIDATION

1. The kinetics of the depletion of α-tocopherol in human low-density lipoprotein (LDL) were measured during macrophage-mediated and cell-free oxidation. The formation of oxidatively modified, high-uptake species of LDL in these systems was not detectable until all of the endogenous α-tocopherol had been consumed. 2. Supplementation of the α-tocopherol content of LDL by loading in vivo extended the duration of the lag period during which no detectable oxidative modification occurred. 3. The addition of a flavonoid (morin) prevented both α-tocopherol consumption and oxidative modification of LDL. 4. The α-tocopherol contents of LDLs from a range of individual donors could not be used to predict their relative resistance to oxidation, indicating that other endogenous antioxidants may also be present, and quantitatively significant, in human LDL.