1. The formation of Heinz bodies, after exposure of erythrocytes to hydrogen peroxide vapour, was significantly greater in cells from patients with plasma tocopherol levels of 11·6 μmol/l (5 mg/1) or less than in those from subjects with plasma tocopherol levels greater than 11·6 μmol/l.
2. Six patients with low plasma tocopherol levels received intramuscular or oral tocopherol for 3–14 days. In four cases, the abnormally great production of Heinz bodies by hydrogen peroxide was much reduced after tocopherol therapy.
3. The addition of tocopherol to suspensions of erythrocytes from such patients markedly reduced the Heinz body formation by hydrogen peroxide in two out of six cases.
4. In one case of erythrocyte glutathione peroxidase deficiency, where the plasma tocopherol concentration was normal, exposure of the erythrocytes to hydrogen peroxide resulted in abnormally great Heinz body formation. On repeating the experiment after the patient had received daily tocopherol injections for 5 days, the production of Heinz bodies by hydrogen peroxide was then no greater than in erythrocytes from normal subjects.
5. The effect of phenylhydrazine in producing Heinz bodies in erythrocytes in vitro was significantly reduced by the addition of tocopherol to the erythrocyte suspension; tocopherol had no significant effect on Heinz body formation by other oxidant drugs tested.