Fig. 1. Antimycin A significantly lowers the threshold concentration and time necessary for maximal formation of ROS and DNA single-strand breaks in cells exposed to peroxynitrite. (A-D) The cells were first treated for 5 minutes with 0.5 µM rotenone, 5 µM myxothiazol or 20 µM ryanodine (Ry), as detailed in the figure, subsequently exposed for 3 minutes to increasing concentrations of peroxynitrite and finally incubated for a further 27 minutes in the absence (A,B) or presence (C,D) of 1 µM antimycin A. (E,F) Cells were exposed for 3 minutes to 0, 40 or 200 µM peroxynitrite and incubated for increasing time intervals in the absence or presence of 1 µM antimycin A. After treatment, cells were analyzed for DNA damage and dihydrorhodamine 123 (DHR)-fluorescence as detailed in the Materials and Methods. Results represent the means ± s.e.m. calculated from three to five experiments. ^*P<0.01; ^**P<0.001 compared with levels in untreated cells; (^*)P<0.01; (^**)P<0.001 compared with levels in cells treated with peroxynitrite alone (A,B) or associated with antimycin A (C,D) (ANOVA followed by Dunnett's test).