The role of methemoglobin in oxidative degradation of hemoglobin

Heinz body anemia and methemoglobinemia in ponies given red maple (acer rubrum L.) leaves

Ponies given dried red maple (Acer rubrum L.) leaves at a dose of 3.0 gm/kg body weight became ill and died one to five days after administration of the leaves. Two clinical patterns of disease were seen. Ponies given dried leaves collected after September 15 died by 18 hours, while ponies given dried leaves collected before September 15 became ill with a hemolytic syndrome and died by three to five days. Freshly harvested leaves administered immediately after collection did not produce disease in ponies, but when dried, they became toxic and remained so for at least 30 days. Overnight freezing did not alter the toxicity of the leaves. Leaves were toxic when administered at doses of 1.5 gm/kg of body weight. The clinical signs of ponies with the hemolytic syndrome included polypnea, tachycardia, icterus, cyanosis, scleral petechiation, and brownish discoloration of the urine and blood. Blood changes of ponies with the hemolytic syndrome included anemia, hemoglobinemia, Heinz bodies, depletion of erythrocyte reduced glutathione, increased erythrocyte fragility, and increased serum levels of aspartate amino transferase, sorbitol dehydrogenase, plasma protein, and bilirubin. Lesions of ponies that died from the hemolytic syndrome included icterus, centrilobular hepatic degeneration, hemoglobinemic nephrosis, and erythrophagocytosis by splenic, adrenal, and hepatic phagocytes. Only brownish discoloration of the blood and mild centrilobular hepatic degeneration were observed in the four ponies that died peracutely.

Relationship between the pentose phosphate shunt and methemoglobin reductase activity in human erythrocytes: Effect of aging on methemoglobin reductase activity

The increase in methemoglobin reductase activity in human erythrocytes upon incubation with inosine, phosphate, pyruvate occurs only in the presence of methylene blue. No difference in activity of the methemoglobin reductases was observed between enzyme extracts of fresh cells and aged cells.

The demonstration of ferrihemochrome intermediates in heinz body formation following the reduction of oxyhemoglobin A by acetylphenylhydrazone

Interaction of acetylphenylhydrazine with oxyhemoglobin A in a hemolysate or in intact red cells resulted in the formation of ferrihemochromes as shown by a characteristic optical spectrum. The same optical spectrum was observed in a suspension of red cell ghosts containing numerous Heinz bodies. Electron paramagnetic resonance of actylphenylhydrazine-incubated red cells disclosed the presence of previously identified reversible ferrihemochromes, which can be reduced to functional hemoglobin, and irreversible ferrihemochromes, which cannot be reduced to functional hemoglobin. (Ferrihemochromes are defined as low spin forms of ferric hemoglobin having heme ligands endogenous to the protein structure). In contrast, only irreversible ferrihemochromes could be observed in ghosts containing Heinz bodies. In addition both optical and magnetic features of sulfhemoglobin were observed in an acetylphenylhydrazine-treated red cell hemolysate. Similar optical features are produced by the interaction of aromatic nitrogen-containg reductants with purified oxyhemoglobin in the presence of (NH4)2S. This reaction is not effected by the presence of catalase, suggesting that H2O2 is not an intermediate of the reaction. It is concluded that the mechanism of action of acetylphenylhydrazine with oxyhemoglobin is two-fold, ultimate reduction to high spin ferric hemoglobin followed by ferrihemochrome formation. Thus it appears that the pathway of denaturation of hemolytic anemias and thalassemia or induced by chemical reagents, entails a common route involving the formation of ferric hemoglobin by a reductive mechanism, followed by reversible ferrihemochromes, irreversible ferrihemochromes, and ultimately, precipitation.