Acceleration of Methaemoglobin Reduction by Riboflavin in Human Erythrocytes

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Abstract
The effect of riboflavin on nitrite treated erythrocytes from normal subjects and patients with hereditary methemoglobinemia due to the deficiency of NADH-cytochrome b5 reductase was studied in the presence of glucose, 2-deoxy-D-glucose or lactate. When glucose or 2-deoxy-D-glucose was used as a substrate for these erythrocytes, the rate of methemoglobin reduction in these cells was accelerated more than 2-fold in the presence of riboflavin. The acceleration was dependent on the concentration of riboflavin and was suppressed by the addition of atebrin. The stimulative effect of riboflavin was not observed when lactate was used in place of glucose or 2-deoxy-D-glucose. The acceleration of methemoglobin reduction by riboflavin was considered to be due to the activation of NADPH-flavin reductase in erythrocytes by the reagent. The availability of riboflavin for patients with methemoglobinemia due to the deficiency of NADH-cytochrome b5 reductase and for those with toxic methemoglobinemia is discussed in relation to methemoglobin reducing systems in erythrocytes.