Arsenic induces ROS production. (A) ROS detection by flow cytometry using dihydrorhodamine 123 as a probe. Pretreatment with NAC significantly blunts ROS production after arsenic treatment. (B) ROS detection by luminol chemiluminescence. Cotreatment with NAC significantly blunts arsenic-induced ROS. Experiments were repeated twice with similar results. The y-axis represents arbitrary units of signal intensity, and the x-axis represents duration of measurement in minutes.