At neutral pH, S-nitrosoglutathione was formed by the reaction of reduced glutathione and sodium nitrite. The degradation of S-nitrosoglutathione, presumably by transnitrosation/denitrosation, was catalyzed by L-cysteine, or CoA-SH. Additionally, from the crude extract of rat brain, one protein with a large molecular mass was nitrosolated with nitrite, and was split into duplet peptides noted in Western blot. Furthermore, the incubation of nitrite with IgG may generate the intermediates of active nitrogen/oxygen species and lead to significant production of gas bubbles.