Growth inhibition (A) and apoptosis (B) induced by As₂O₃ in NB4, su-DHL-4, and HL-60 cells, and basal GSH levels (C). Cells were treated with different concentrations of As₂O₃ for 3 days. Cell growth and apoptotic cell number were determined with fluorescence staining as described in Materials and Methods. Values are the mean of three independent experiments.