Specific binding sites for D-alpha-tocopherol on human erythrocytes.

Since vitamin E deficiency is associated with increased susceptibility of erythrocytes to hemolysis, we investigated the presence of tocopherol binding sites in human red blood cells. Erythrocytes were found to have specific binding sites for D-alpha-[3H]tocopherol with properties of receptors. Kinetic studies of binding demonstrated two binding sites: one with high affinity (equilibrium association constant Ka = 2.6 x 10(7) M-1), low capacity (7600 sites/cell) and the second with low affinity (Ka = 1.24 x 10(6) M-1), high capacity (150 000 sites/cell). These sites are at least partly protein in nature.