Hemoglobin Concentration Overestimates Oxygen Carrying Capacity of Blood in Phenylhydrazine-Induced Hemolytic Anemia in Dogs 1

Acute hemolytic anemia in patients with red blood cells deficient in enzymes such as G-6-PD is characterized by excessive oxidation of hemoglobin (Hb) to a variety of soluble heme pigments and to precipitates, attached to the inner surface of the red cell membrane, known as Heinz bodies (1). These pigments and precipitates do not carry oxygen. The cyanmethemoglobin method. widely used to determine blood Hb concentration, detects not only Hb but methemoglobin and other non-oxygen carrying heme pigments as well; sulfhemoglobin is not detected by this method (2). The present study tested the hypothesis that non-oxygen carrying pigments might constitute a significant fraction of “hemoglobin,” as measured by the cyanmethemoglobin method, during the course of acute hemolytic anemia induced in dogs by phenlyhydrazine, a potent oxidizing agent. Measured blood oxygen carrying capacity (C _maxO2) was less than the C _maxO2 expected from Hb in anemic dogs. The data thus confirm the hypothesis. Additional studies indicate that Heinz bodies constituted a major fraction of the non-O₂ carrying “hemoglobin”.

Materials and Methods. Eight adult mongrel dogs of both sexes weighing from 10 to 21 kg were injected intravenously twice with phenylhydrazine hydrochloride (Fisher Scientific Co.), 20 mg/kg body weight, as a 38-44 mg/ml solution in 0.9 mEq/liter NaCl. Dogs 1 through 6 were injected on Days 0 and 2 and dogs 7 and 8 on Days 0 and 3 (Table I). Two other dogs, C₁ and C₂ in Table I, were injected with saline alone on Days 0 and 2. Venous blood was drawn before the first injection and then daily, if possible, for determination of Hb and C _maxO2. The C _maxO2 of Hb in aqueous solution was studied 7 days after the first of 2 injections in 6 additional dogs.