Membrane-to-membrane transfer of tocopherol in red blood cells

The direct cell-to-cell transfer of tocopherol between red blood cells (RBCs) was examined. Two kinds of RBCs were provided; 1) Tocopherol-deficient ones showing complete dialuric acid-hemolysis and 2) tocopherol-supplemented ones showing no dialuric acid-hemolysis. The two kinds of RBCs were mixed and incubated with gentle swirling in a buffer solution. If no tocopherol transfer occurred between the two kinds of RBCs in the cell suspensions, hemolysis should not change during incubation because hemolysis is limited only in the -deficient cells in the suspensions. However, it was actually observed that when RBCs with adequate amounts of tocopherol were incubated with tocopherol-deficient RBCs, dialuric acid-induced hemolysis decreased during a 3-h incubation period. Contrarily, when an inadequate amount of tocopherol constituting a limiting level for inhibition of hemolysis, existed in RBCs which were mixed with -deficient ones, hemolysis increased after incubation. This indicates that tocopherol is transferred from the tocopherol-rich RBCs to the -deficient RBCs. The transfer was greater as the hematocrit of cell suspensions increased. Gum arabic contained in the suspensions inhibited the transfer, while bromelain (a protease which lowers the electric charge on the cell surface) increased it. These findings indicate that the transfer of tocopherol is related to the frequency of collision between cells.