Flow cytometric analysis of JLP 119 and EW-36 treated with different concentrations of H₂O₂ . (A) Flow cytometer data. Cells (5 × 10⁵/mL) were incubated in growth medium for 24 hours after the addition of the indicated concentrations of H₂O₂ (0, 25, 50, 75, or 100 μmol/L). FACS analysis of fixed cells was performed as described in the Materials and Methods. Rows 1 and 3, cytograms showing forward and side light scatter (FSC and SSC, respectively) for 10,000 cellular events. Rows 2 and 4, histograms of FITC-labeled DNA for the cells shown in the cytograms. Rows 1 and 2, results for JPL-119. Rows 3 and 4, results for EW-36. Cells with a high FITC-labeling intensity represent apoptotic cells. The data shown are from a representative study that was repeated three times. (B) Proportion of JLP 119 (▴) and EW-36 (▵) cells that are undergoing apoptosis at each concentration of H₂O₂ . The percentage of apoptosis equals the high FITC-labeled population divided by the total cell population. Each point is derived from 10,000 cellular events and represents the mean ± SEM of triplicate cultures.