Oxidative burst in human neutrophils is triggered by hemin.

(A) Human PMNs were incubated for 1 hour at 37°C with hemin (0.1-20 μM) or 100 nM PMA in the presence of 0.05% NBT. After that, cells were stained with safranin, and formazan deposits were quantified under a light microscope. At least 5 random fields were analyzed per data point. Data shown are from a typical experiment, representative of 3 identical studies. *P < .01. (B) Intracellular production of superoxide was evaluated through the reduction of cytochromec. Neutrophils were incubated with distinct amounts of heme in the presence or absence of DPI. PMA (100 nM) was used as a positive control for superoxide production. Incubations were carried out at 37°C for 30 minutes. Data shown are from a typical experiment, representative of 3 identical studies performed in triplicate. *P < .01.