[Steady-state dependence of the methemoglobin reduction rate on its concentration in intact human erythrocytes]

The rate of methemoglobin reduction by the methemoglobin reductase system of intact human erythrocytes was measured as a rate of pyruvate formation in a quasi-steady state. Various methemoglobin concentrations (up to 100%) were generated by sodium nitrite additions. The steady state methemoglobin levels were maintained by infusion of a nitrite solution at a rate of 2.8 mmol/h/l cells. The rate of pyruvate formation was proportional to the steady state methemoglobin concentration in the range from the physiological value to 100%, the maximal value being as high as 500 mumol/h/l cells. It was found that the rate of CO2 output by the erythrocytes markedly increased in the presence of 8 mM sodium nitrite, reaching up to about 40% of the possible maximal value.