The kinetic differences between sodium nitrite, amyl nitrite and nitroglycerin oxidation of hemoglobin

Abstract

The effect of sodium nitrite, amyl nitrite and nitroglycerin (glyceryl trinitrate) on the hemoglobin of adult erythrocytes was examined in vitro. Both amyl nitrite and nitroglycerin reacted immediately with oxyhemoglobin to effect oxidation into methemoglobin while sodium nitrite required an inductionary period (lag phase) prior to the reaction. Kinetic studies of the biniolecular rate law for each of the preceeding reaction's reactionary periods (log phases) allowed rate constant calculations to be made. The values are 1.14 x 10JM niin I, 7.45 x IOJbl lmin I , and 3.50 x 10IM ' m i n 1 for sodium nitrite, amyl nitrite and nitroglycerin, respectic ely. A comparison of the amyl nitrite and nitroglycerin rate constants reveals that aniyl nitrite is approximately 2000-fold more toxic to oxyhemoglobin than nitroglycerin. These oxidant's effect on in !/itro hemoglobin solutions are comparable since both reactions approximate to rectangular hyperbolae. Sodium nitrite reacts about 300-fold faster with oxyhemoglobin than does nitroglycerin. However, the sodium nitrite reaction proceeds in a sigmoidal fashion which makes a strict comparison between these compounds relative toxicities less clear cut.