Comparative aspects of methemoglobin formation and reduction in opossum (Didelphis virginiana) and human erythrocytes.

Glucose-depleted, nitrite-treated opossum erythrocytes effectively reduce methemoglobin in an environment of physiological saline and added glucose does not accelerate the rate of reduction. In autologous plasma or 25 mM phosphate-buffered saline pH 7.4, added glucose significantly accelerates methemoglobin reduction in glucose-depleted, nitrite-treated opossum erythrocytes. Human red cells require added glucose to carry out reduction of methemoglobin and increased phosphate concentration or autologous plasma does not alter the rate of this process. Within the opossum red cell in vitro, autooxidation of hemoglobin proceeds at a much slower rate than that observed in human erythrocytes.