Figure 3.

Inhibition of superoxide ion generation by 2-APT in human platelets adhering to fibrinogen. Intracellular superoxide ion generation was tested by DHE-dependent single cell fluorescence imaging of platelets dispensed over fibrinogen-coated glass. DMSO (0.1% v/v) or 2-APT (0.5 μM) were added at the 5 min time point, for which representative time courses are shown in panels A and B respectively. Following treatment with different concentrations of 2-APT (10 nM to 10 μM), the superoxide generation in fibrinogen-adhering platelets was measured and expressed as % of the response in the absence of the inhibitor. The results from three independent experiments were plotted using a variable slope sigmoidal dose–response algorithm, resulting in an IC₅₀ value of 227 nM (C). Non-selective NOX inhibitors apocynin (0.5 mM) and DPI (100 μM) were tested alone or in addition to 2-APT (0.5 μM), and mean (± SEM) single cell fluorescence counts at time point 10 min are shown in panel D. **P < 0.01; one-way anova with Bonferroni post test; n = 6.