Cyanmethemoglobin

Total plasma protein concentration was determined by the buiret method (16) after correction of plasma hemoglobin which was determined by the cyanmethemoglobin method (15). Plasma osmolality was measured by a Wescor model 5100 vapor pressure osmometer. 

Reacts with Flgb in erythrocytes, producing cyanmethemoglobin, and cyanide ions. Primarily excreted in urine. Half-life less than 10 min. 

Total hemoglobin was measured as cyanmethemoglobin (22). Trace concentration of hemoglobin, such as that in the extracellular fluid of suspension A, was measured using a modified benzidine method (23). 

Preparation of Hemolysate. Washed red cells were lysed in distilled water (20% HCT) for 15 min. The stroma was extracted in carbon tetrachloride, and the aqueous layer containing the hemolysate was recovered. This solution was diluted appropriately with PBS to a specified hemoglobin concentration, and labeled fibrinogen was added. The final solution was adjusted to isotonicity and pH 7.35. Hemoglobin concentrations were determined by the cyanmethemoglobin method (18). 

The cyanide antidote kit contains amyl nitrite, sodium nitrite, and sodium thiosulfate. The nitrites convert hemoglobin to methemoglobin, which has a higher affinity for the cyanide ion (forming cyanmethemoglobin) than cjTochrome oxidase. Subsequent treatment with sodium thiosulfate results in the formation of methemoglobin and thiocyanate ions. 

O) Aibiiinisiering sodium nitrite causes cyanmethemoglobin to form, releasing cytochrome oxidase horn the cyanide. 

The basic aim of rapid detoxification of cyanide is prevention or reversal of inhibition of cytochrome oxidase by cyanide. This is usually facilitated by providing a large pool of ferric iron in the form of methemoglobin to complex cyanide. Cyanide preferentially competes with the Fe + of methemoglobin as compared with that of cytochrome oxidase and eventually binds with the former to form cyanmethemoglobin. Thereby, the activity of inhibited cytochrome oxidase is restored (Baskin et al., 1992). The various methemoglobin inducers used as cyanide antidotes are discussed. 

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