Human LDL, HDL and lipoprotein deficient plasma isolated from 15 normal subjects was exposed to oxygen free radicals generated by gamma rays and the formation of peroxides and changes in levels of LDL α-tocopherol were measured. LDL exhibited an initial resistance against oxidation stress when compared to HDL. The results obtained for different individuals showed that there was no correlation between the initial levels of vitamin E in LDL or plasma and the amount of peroxide formed after exposure of the LDL to a standard quantity of oxygen radicals. Kinetic experiments with original LDL and LDL containing incorporated a-tocopherol demonstrated that the vitamin performed its antioxidant role by conferring some early protection to the lipids, being consumed in the process, but it was clear that additional factors are also instrumental in determining the total antioxidant potential of the human LDL.
- LDL peroxide
- Vitamin E