The modulating influence of vitamin E in biological membrane unsaturated phospholipid metabolism

A tissue culture system in which the composition of the medium, with respect to vitamin E, linoleic acid, and cholesterol, can be manipulated at will, was used to study the effect of vitamin E on the fatty acid profiles of fibroblast membrane phospholipids. The effect was studied of alpha-tocopherol, and of butylated hydroxytoluene, on the uptake of isotopically labeled linoleic acid and cholesterol, and of the effect of these antioxidants on the metabolic interconversion of linoleic acid with other unsaturated fatty acids. Butylated hydroxytoluene was without effect on any of the parameters measured, alpha-tocopherol caused a large enhancement in the content and radioactivity of the arachidonyl residues of phosphatidyl choline, phosphatidyl serine, and phosphatidyl ethanolamine, generally at the expense of linoleic acid in the same phospholipids. There was no effect of alpha-tocopherol on the unsaturated fatty acids of the neutral lipids, suggesting that there was no general effect on the chain elongation and desaturation of linoleic acid. The results are thought to demonstrate a specific effect of alpha-tocopherol upon the architecture of membrane phospholipids by controlling the profiles of their unsaturated fatty acid components. The uptake of radioactive cholesterol, and the content of cholesterol and cholesterylesters in cultured cells was also significantly increased by the presence of alpha-tocopherol in the medium.