and tBHP increased sub-G
cell populations in different Bβ2 clones as indicated by cell cycle histograms. Exponential growing cells were cultured with different concentrations of H2O2 or tBHP for 48 h. The trypsinized cells were analyzed by flow cytometry following staining with propidium iodide. The percentage distribution of cell cycle phases for H2O2 (A, top) or tBHP (B, bottom) was determined by Cell Quest software. The results represented averages of three independent experiments and the results were average values in three individual experiments as mean ± standard errors of three independent experiments.