Formation of myeloperoxidase compound II during aerobic stimulation of rat neutrophils

We have made simultaneous spectrophotometric and O2 measurements on suspensions of rat neutrophils during activation of the respiratory burst. Under aerobic conditions an absorption increase attributable to myeloperoxidase compound II was observed in parallel with the rapid phase of O2 uptake. Identification of this compound was confirmed by analysis of a spectrum obtained with purified myeloperoxidase and H2O2. Whereas a second addition of stimulus did not increase O2 uptake any further, a second phase of myeloperoxidase release and compound II formation was observed. These results suggest that in vivo myeloperoxidase reacts with H2O2 generated via the respiratory burst to form compound II under conditions in which the chlorination reaction would be the expected major pathway.