Characterization of MPO-dependent initiation of lipid peroxidation of endogenous plasma lipids.

Fresh human plasma (50%, vol/vol) was incubated with isolated human MPO (30 nM) at 37°C in HBSS supplemented with DTPA (100 μM, pH 7.0) and an H₂O₂-generating system composed of G/GO for 12 hours (Complete System). Under this condition, a continuous flux of H₂O₂ is formed at 10 μM/h. The contents of 9-H(P)ODE and 9-H(P)ETE formed within endogenous plasma lipids were then determined by LC/ESI/MS/MS as described in “Materials and methods.” Additions or deletions to the Complete System were as indicated. Final concentrations of additions to the Complete System were 1 mM NaN₃, 300 nM catalase, 300 nM heat-inactivated catalase, 200 nM SOD, 100 μM methionine, and 100 μM ascorbate. Data represent the mean ± SD of 3 independent experiments.