On the Mechanism of the Oxidation of Human and Rat Hemoglobin by Propylene Glycol Dinitrate
NAVY TOXICOLOGY UNIT BETHESDA MD
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The kinetics and stoichiometry of the oxidation of human and rat oxyhemoglobin O2Hb by propylene glycol dinitrate PGDN have been investigated in vitro in both hemolysate and in intact red blood cell preparations. In hemolysate fractions from both these species, the rate constant for oxidation is nearly constant between pH 7.0 and 9.0, but it increases dramatically at lower pH values. The reaction is molecular and approximately first-order in both PGDN and in O2Hb. The rate of oxidation is related complexly to the O2 concentration. No oxidation occurs at zero O2 concentration or at very high O2 concentrations. Maximal rates are observed at O2 concentrations where the hemoglobin is only partially saturated with O2. The stoichiometry appears to be 1.5 hemes oxidized per ester bond broken. In whole cells, the reaction is still molecular, is approximately first-order in both reactants, and has a stoichiometry of 1.9 to 2.3 moles heme oxidized per mole of reacted ester.