The uptake and depletion of alpha- and gamma-tocopherol separately (A) and together (B) by RAW264.7 Macrophages. Confluent RAW264.7 macrophages were incubated with either 5.6 μM alpha-tocopherol or 4.9 μM gamma-tocopherol (A) or with both tocopherols (4.6 μM alpha- plus 5.2 μM gamma-tocopherol) together (B) and the uptake of tocopherols measured during 6 hours of incubation. After 6 hours, the medium with tocopherols was removed and replaced with medium not containing tocopherols and depletion of tocopherols followed for 4 hours. Tocopherols in the medium and cells were immediately determined by HPLC with an electrochemical detector as described in the Methods section. Values are the means ± SD of three wells. Each experiment was performed twice with excellent reproducibility.