Is N2O3 the main nitrosating intermediate in aerated nitric oxide (NO) solutions in vivo?: If so, where, when, and which one?

The widespread opinion that N2O3 as a product of NO oxidation is the only nitros(yl)ating agent under aerobic conditions is based on experiments in homogeneous buffered water solutions. In vivo NO is oxidized in heterogeneous media and this opinion is not correct. The equilibrium in the system being dependent on temperature and Delta G((sol)) for NO, NO2, isomers of both N2O3, and N2O4. For polar solvents including water, DeltaG((sol)) for N2O3 is high enough, and a stationary concentration of N2O3 in the mixture with other oxides is sufficient to guarantee the hydrolysis of N2O3 to nitrite. In heterogeneous media, the mixture contains solvates NO2(sol), N2O3(sol), and N2O4(sol) at stationary nonequilibrium concentrations. As far as DeltaG((sol)) is decreased in heterogeneous mixtures with low polar solvents and/or at increased temperatures, the equilibrium in such a system shifts to NO2. Although NO2 is a reactive free radical, it almost does not react with water. In contrast, the reaction with most functional protein groups efficiently proceeds by a radical type with the formation of nitrite and new radicals (X) further stabilized in various forms. Therefore, the ratio of the nitrosylated and nitrated products yields depends on actual concentrations of all NOx. (C) 2002 Wiley Periodicals, Inc.