The potentiometric method was applied to the study of the influence of cyanide and of hydroxyl ion on methemoglobin. Both of these ions appear to combine with the iron of the methemoglobin molecule and reduce its oxidant activity. From the magnitude of the effect produced by cyanide and by variation in pH on the oxidation-reduction potential of the methemoglobin-hemoglobin system, it is conclud...

OBJECTIVE The aim of this work was to establish reference values for methemoglobin levels in 6 to 10-year-old children. METHODS Methemoglobin concentrations were studied in clinically healthy children. The method for methemoglobin measurement used, neither uses highly toxic chemical compounds nor expensive enzymatic methods, thus it is feasible in the laboratory routine. RESULTS The results...

BACKGROUND Private water systems are more likely to have nitrate levels above the maximum contaminant level (MCL). Pregnant women are considered vulnerable to the effects of exposure to high levels of nitrates in drinking water due to their altered physiological states. The level of methemoglobin in the blood is the biomarker often used in research for assessing exposure to nitrates. The object...

Hemoglobin has functions besides carrying oxygen to the tissues, and regulates vascular tone and inflammation via a redox couple with methemoglobin. Hemoglobin has iron in the reduced valance Fe(II) and methemoglobin has iron in the oxidized valance Fe (III), with a free energy capable of producing water from oxygen. In generating methemoglobin the couple functions as a nitrite reductase. The d...

Nitrite intoxication occurs frequently in ruminants and equines. The most common treatment of this disorder is administration of 1% methylene blue, although the use of some antioxidant agents e.g. vitamins and complementary treatment may also be useful. The aim of this study was to evaluate the in vitro antioxidative effects of some vitamins on methemoglobinemia induced by sodium nitrite. For t...

reductase activity (MHR), measured by the Hegesh assay, decreases as normal red cells age. This probably accounts for the slighlty increased concentration of methemoglobin in older red cells. Exaggeration of normal MHR age lability was demonstrated in several individuals with various molecular abnormalities of NADH-diaphorase and was associated with more striking accumulation of methemoglobin i...

Methemoglobin is not present in spectroscopically detectable amounts’ in freshly drawn blood of normal animals of the following and, presumably, other mammalian species: human, dog, cat, rabbit, rat, mouse, horse, monkey (Macacus rhesus), cattle, swine. Furthermore, methemoglobin is not demonstrable in incubated sterile blood from normal animals of these species for many hours after removal fro...

When cyanide poisoning is treated with a methemoglobin-forming agent, oxidative metabolism is protected at the expense of the oxygen capacity of the blood. The affinity of methemoglobin for CN- is high enough to compete with cytochrome oxidase, which protects the latter from becoming blocked, but all hemoglobin used for this purpose is lost for the transport of oxygen. Therefore, the fractions ...

The final step in the erythrocyte methemoglobin reduction pathway, the transfer of an electron from cytochrome b5 to methemoglobin, has been studied using magnetic circular dichroism spectroscopy. Spectral analysis allowed us to determine accurately the concentration of each redox species in mixtures of the two heme-proteins and to follow simultaneously the kinetics of the appearance or disappe...

Although nitrite has been extensively used as an agent for the formation of methemoglobin, the quantitative relations of the reaction appear to be uncertain; three widely different values have been reported for the amount of methemoglobin formed to nitrite utilized. The first statement of a quantitative relationship was made by Barcroft and Miiller (1) in 1911. In a preliminary report containin...