A, flow cytometric analysis of the preconditioning-induced changes in the inner mitochondrial membrane potential in BEAS-2B cells. The BEAS-2B cells were exposed to H2O2, and stained with the potentiometric dyes JC-1. Bivariate plots of red (FL2) versus green (FL1) fluorescence were used as an estimate of mitochondrial membrane potential (ΔΨm). B, percent of cells with ΔΨm disruption vs. exposure time. Cells were treated with 200, 500 μM, and 1 mM of H2O2 for 10, 30, 60, and 120 min. Untreated controls and H2O2-treated cells were then stained with JC-1 and analyzed by flow cytometry as described in Methods. n = 10, 000 cells/analysis. *, **, significantly different from controls at p < 0.05 and p < 0.01, respectively (Mann-Whitney U-test).