Abstract
The formation of methemoglobin (metHb) from oxyhemoglobin (oxyHb) in the erythrocyte by O2-was studied under the O2--generating system of photoactivated riboflavin with oxygen by using a catalase inhibitor, 3-amino-1, 2, 4-triazole (AT). In the AT-treated erythrocytes in vitro which have little catalase activity, the rate of metHb formation was increased remarkably compared with that of untreated normal erythrocyte. Furthermore, catalase added to 60 unit/ml to the suspending medium contained AT-treated erythrocytes caused a strong inhibition of formation of metHb, suggesting that H2O2 is generating in the external medium of erythrocytes by the reaction of photoactivated riboflavin or spontaneous dismutation of O2-. Addition of superoxide dismutase (5μg/ml) caused an acceleration but not inhibition of the metHb formation. Hemolysis was scarcely observed in the time course of this experiment. These results may be interpreted that H2O2 generated in the outside of cells moves across the membrane and results in oxidative attack to oxyHb in the erythrocyte without the hemolytic effect. Another possible participation of O2- may be suggested to exert its enhanced oxidation of oxyHb, namely that O2- generated in the outside of cells may pass through the membrane directly.
