Diazotization reaction of nitric oxide trapped by hemoglobin

The present study addresses to determine whether hemoglobin within red blood cells can be utilized as a spin-trap agent for nitric oxide. We demonstrate the diazotization method coupled with a gel filtration chromatography, which is simply due to the separation of nitrosylhemoglobin from nitrite, nitrate or other low molecular nitroso-compounds in biological systems and to the liberation of nitric oxide from nitrosyl heme-complexes in the acidic condition. The amount of nitric oxide can be estimated by the difference of absorbances at 542 nm between diazo-compounds formed by Griess reagent and hemichrome by phosphoric acid. Our results indicate that hemoglobin in red cells as a spin-trap agent would be useful for monitoring nitric oxide in the circulation under the several disease states.