Figure 2. Flow cytometric analysis of the oxidative burst in 10,000 leukocytes of a single donor using different stimuli in the presence of nitrous oxide (N²O). They axis represents the hydrogen peroxide (H (²) O²) generation (rhodamine-123 fluorescence) in arbitrary units. The x axis indicates the side scatter of leukocytes as a marker of cellular granularity: neutrophils (pmn), monocytes (mo), lymphocytes (ly). (A) Unstimulated leukocytes. Neutrophils in B and C were stimulated with N-formyl-methionyl-leucyl-phenylalanine (FMLP)(100 nm), the latter in the presence of N²O (70%). Therefore, B serves as a control for C. The response to FMLP was heterogeneous; only a subset of neutrophils showed a generation of oxidative product (60%). The percentage of nonresponsive cells, as given on the right of each dot plot, was higher in the presence of N²O (80%) compared with the control percentage (40%). The reaction of neutrophils after PMA stimulation was homogeneous (D). In conclusion, the fluorescence of reacting neutrophils was not lowered, but the percentage of reacting neutrophils decreased in the presence of N²O. This correlated to an overall reduction of the mean fluorescence value as given on top of each dot plot.