Detection of superoxide radicals and peroxynitrite by 1-hydroxy-4-phosphonooxy-2,2,6,6-tetramethylpiperidine: Quantification of extracellular superoxide radicals formation

The reactions of the new sterically hindered hydroxylamine 1-hydroxy-4-phosphonooxy-2,2,6,6-tetramethylpiperidine (PP-H) with superoxide radical and peroxynitrite have been studied. These reactions produce the nitroxide 4-phosphonooxy-2,2,6,6-tetramethyl-piperidinyloxy. The rate constant for reaction of superoxide with PP-H is determined as (8.4+/-0.6) . 10(2) M-1 s(-1). It was found that PP-H provides almost the same spin trapping efficacy as 1-hydroxy-3-carboxy-pyrrolidine (CP-H). The background oxidation of PP-H in blood is much less than for CP-H. The extremely slow PP-H penetration into the cells makes possible the study of extracellular formation of superoxide radical. The acute treatment of blood with nitroglycerin is shown to induce an extracellular superoxide radical formation. PP-H is more sensitive for detection of reactive oxygen species as compared with CP-H. PP-H is an effective scavenger of superoxide radical and of peroxynitrite, and can be used to quantify the extracellular formation of these reactive oxygen species. (C) 1998 Academic Press.