Figure 4. Rate of ROS production is higher in old cardiomyocytes and is attenuated with a mitochondrial ROS scavenger.

A, changes in DCFDA fluorescence signal at baseline and with ISO (30 nm) with cardiomyocytes from young and old rabbits and from cardiomyocytes pretreated with mito-TEMPO (MT, 25 μm) for 10 min from old rabbits. B, the mean data for rate of ROS production at baseline: young, 0.09 ± 0.01; old, 0.32 ± 0.04; and old + MT, 0.19 ± 0.03 F s⁻¹. ***P < 0.001 for young vs. old and **P < 0.01 for young vs. old + MT and for old vs. old + MT. C, the mean data for rate of ROS production with 30 nm ISO: young, 0.09 ± 0.01; old, 0.60 ± 0.12; and old + MT, 0.19 ± 0.04 F s⁻¹. ***P < 0.001 for young vs. old and for old vs. old + MT, and P = NS for young vs. old + MT. n= 8–20 cells from 2–4 heart preparations; all values are mean ± SEM.