Exposure of erythrocytes to methylene blue shows the active role of catalase in removing hydrogen peroxide.

Methylene blue (MB) is a powerful reducing agent that is widely used in clinical practice as well as for metabolic studies of the erythrocyte. We have investigated the role of catalase as a specific enzyme for the removal of hydrogen peroxide by measuring the in vitro effects of MB on human red cells. In the presence of MB, catalase underwent inactivation even with the co-existence of active generation of NADPH, leaving the glutathione concentration unaffected. The data obtained in the present investigation show, using a different tool (MB), that catalase is the active enzyme in H2O2 detoxification and that its integrity is largely dependent on an adequate generation of NADPH.