Thioredoxin reductase reduces lipid hydroperoxides and spares alpha-tocopherol. 
We investigated whether and how rat liver thioredoxin reductase spares alpha-tocopherol in biomembranes.  Purified hydroperoxides of beta-linoleoyl-gamma-palmitoylphosphatidylcholine were decreased 35% by treatment with thioredoxin reductase and 54% by thioredoxin reductase plus E. coli thioredoxin.  Thioredoxin reductase also halved the amount of hydroperoxides that had been formed during photoperoxidation of liposomes composed of beta-linoleoyl-gamma-palmitoylphosphatidylcholine, and of emulsions of both cholesterol and cholesteryl linolenate.  In erythrocyte ghosts, thioredoxin reductase spared alpha-tocopherol from oxidation by both soybean lipoxygenase and ferricyanide.  Thioredoxin reductase also decreased F(2)-isoprostanes in ghosts oxidized by ferricyanide, suggesting that its ability to spare alpha-tocopherol relates to reduction of lipid hydroperoxides.