Enhancement of the transfer of alpha-tocopherol between liposomes and mitochondria by rat-liver protein(s).

alpha-Tocopherol transfer from liposomes to mitochondria was enhanced by a cytosolic protein in rat liver. This protein was separated from the exchange protein specific for phosphatidylcholine. The stimulation was specific for alpha-tocopherol and the "affinity" order of tocopherols for the cytosolic protein was found to be as follows: alpha-tocopherol greater than gamma-tocopherol much greater than alpha-tocopheryl acetate, alpha-tocopherol quinone. The transfer-stimulating protein may act as a carrier, since an intermediate (alpha-tocopherol)-protein complex could be detected when liposomes containing alpha-tocopherol were incubated with the cytosol. This transfer-stimulating activity was present not only in liver, but also in heart, spleen and lung.