Characterization of cellular uptake and distribution of vitamin E.

We previously reported that tocotrienols acted as more potent inhibitors against selenium deficiency-induced cell death than the corresponding tocopherol isoforms (J. Biol. Chem. 2003;278:39428-39434). In the present study, we first compared the differences in the cellular uptake between alpha-tocopherol (alpha-Toc) and alpha-tocotrienol (alpha-Toc-3). The initial rate of cellular uptake of alpha-Toc-3 was 70-fold higher than that of alpha-Toc. Subcellular fractionation analysis of alpha-Toc-3 and alpha-Toc-fortified cells showed similar cellular distribution of these antioxidants, which was directly proportional to the lipid distribution. The cells containing similar amounts of alpha-Toc-3 and alpha-Toc showed similar resistance against the oxidative stress caused by peroxides. These results suggest that the apparent higher cytoprotective effect of alpha-Toc-3 than alpha-Toc is primarily ascribed to its higher cellular uptake.