Effects of As₂O₃ and DHA on intracellular accumulation of ROS in HL-60 cells. Cells were treated with 1 μM As₂O₃,25 μM DHA, or the combination of both substances for 12 hours. For comparison, cells were treated with 25 μM OA ± 1 μM As₂O₃ or left untreated (control). Intracellular ROS were measured by flow cytometry using an oxidation-sensitive fluorescent probe, DCFH-DA, which is oxidized to DCF in the presence of ROS. For improved illustration, a guidance line (dotted line) has been drawn through histograms to be compared.