Inhibition of microsomal lipid peroxidation by alpha-tocopherol and alpha-tocopherol acetate.
1. The antioxidant effects of alpha-tocopherol and alpha-tocopherol acetate were assayed for the (a) oxygen uptake, (b) chemiluminescence and (c) malondialdehyde formation, of tert-butyl hydroperoxide-supplemented rat liver microsomes. 2. Oxygen uptake was inhibited 60% by both alpha-tocopherol and alpha-tocopherol acetate with the half-maximal effect at 5 nmol tocopherol/mg protein. Chemiluminescence and malondialdehyde formation were equally inhibited 35% by both tocopherols with half-maximal effects at 2 nmol tocopherol/mg protein. 3. The rate of O2 uptake by tocopherol-supplemented microsomes was dependent on O2 concentration. A 60% inhibition by 5 nmol tocopherol/mg protein at 0.2 mM O2 is decreased to 5% inhibition at 0.6 mM O2. 4. The inhibition of O2 uptake, chemiluminescence and malondialdehyde formation indicate that both alpha-tocopherol and alpha-tocopherol acetate have similar effects as free radical traps in the hydrophobic domain of biomembranes. The different inhibition observed at different O2 concentrations indicate competition between vitamin E and O2 by unoxygenated lipid radicals.
Gonzalez Flecha
B S
BS
Institute of Biochemistry and Biophysics, School of Pharmacy and Biochemistry, University of Buenos Aires, Argentina.
Repetto
M
M
Evelson
P
P
Boveris
A
A
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D066298:In Vitro Techniques; D015227:Lipid Peroxidation / Q000187:drug effects*; D008163:Luminescent Measurements; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013858:Thiobarbiturates / Q000378:metabolism; D024505:Tocopherols; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000494:pharmacology*; D024502:alpha-Tocopherol / Q000031:analogs & derivatives*
D000975:Antioxidants; D011506:Proteins; D013858:Thiobarbiturates; D014810:Vitamin E; D008315:Malondialdehyde; D006861:Hydrogen Peroxide; D024502:alpha-Tocopherol; D024505:Tocopherols