NADH- and NADPH-dependent reduction of methemoglobin in the nucleated erythrocytes from hen and bullfrog

Abstract NADH- and NADPH-dependent reduction of methemoglobin in the cytosolic and membrane fractions of the nucleated erythrocytes from hen, and adult bullfrog and tadpole was studied. Results obtained are as follows. 1. 1. The NADH-methemoglobin reductase activity was found only in the membrane fraction of the nucleated erythrocytes tested, while the NADPH-methemoglobin reductase activity was found exclusively in the cytosolic fraction of the erythrocytes except the tadpole cells which did not have the NADPH-dependent enzyme activity. 2. 2. It was suggested on the basis of the rates of the methemoglobin reduction measured in the nitrite-treated erythrocytes that NADH-methemoglobin reductase associated with membrane plays a major role in catalyzing the reduction of methemoglobin in the nucleated erythrocytes.