Evidence for peroxynitrite formation during S-nitrosoglutathione photolysis in air saturated solutions.

Flash photolysis of S-nitrosoglutathione (GSNO) in aerated solutions at pH 10 gave rise to an absorption with a maximum around 310-320 nm. This peak is spectrally similar to that displayed by ONOO-. The decay kinetics of this absorption was compared to that of authentic ONOO-, generated independently. An excellent correlation was obtained. Further proof of ONOO- generation was provided by HPLC studies showing the production of 3-nitrotyrosine on irradiation of GSNO in the presence of tyrosine at pH 7.4. In addition, the nitration yield was increased approximately 5-fold in the presence of bicarbonate and totally eliminated with DMPO, indicating the requirement of a radical intermediate for peroxynitrite production during S-nitrosothiol photolysis.