Intracellular AA (iAA) protects HL60 and U266 cells depleted from GSH and treated with As₂O₃. As₂O₃ toxicity in HL60 (A) and U266 (D) cells with (□) or without (▪) GSH. Cell viability (B,E) and colony formation (C,F) of HL60 and U266 cells depleted of GSH, loaded with vitamin C, and treated with 1 μMAs₂O₃. Cell viability was determined 48 hours after treatment. (A-F) Data are expressed as the mean ± SD of 3 independent experiments.