Figure 5. Effects of antioxidants on RA-induced ROS production.

In A, HESC cells were preloaded with DCF-DA as in Fig. 4 and then treated with NAC (2.5 mm), PEG-catalase (100 U ml⁻¹), or GSH-MEE (2 mm) for 30 min before treatment with 10 μm RA. While NAC and GSH-MEE were potent inhibitors of ROS production, PEG-catalase unexpectedly showed an increase of DCF fluorescence in comparison to RA alone, indicative of increased ROS levels. B shows control experiments using H₂O₂ to rapidly increase ROS levels and the potent suppression of ROS by all three antioxidants. As in Fig. 4, results are shown in 20 min intervals for presentation purposes. Symbols without visible error bars indicate that the s.e.m. was less than the value represented by the width of the symbol.