The uptake of (R,R,R)alpha-tocopherol by human endothelial cells in culture

Endothelial cells from human umbilical cord vein in culture incorporate physiological and pharmacological amounts of (R,R,R)alpha-tocopherol in a time-dependent and dose-dependent manner. Incorporated tocopherol was found to associate predominantly with membrane fractions of the cell. When expressed on the basis of organelle protein, the highest amount of tocopherol was found in plasma membrane, and decreasing amounts in mitochondria, endoplasmic reticulum and cytosol. With the relatively wide range of tocopherol concentrations used in these studies (23.2-92.8 microM), there was no apparent toxicity on the cells as judged by unaltered cell numbers and cell viability. When the cells were enriched with tocopherol and cell tocopherol levels were monitored in tocopherol-free medium, there was a rapid phase of tocopherol disappearance, which was followed by a slower phase. The half-time for the disappearance of incorporated tocopherol was found to be approximately 65 +/- 8.6 hr (mean +/- SD, n = 3). The results of this study clearly show that human endothelial cells in culture are a feasible model for the study of vitamin E uptake. The cell culture model could potentially be used to study other fat-soluble vitamins and essential nutrients.