Fig. (4) HLE B-3 cells were treated with hydrogen peroxide for 4 hours and the ratio of the fluorescence intensity of the calcium probe Indo-1 AM was used to measure changes in ionized intracellular calcium. A drop in the level of I400/I475 indicates hydrogen peroxide treatment caused intracellular calcium to rise. We estimate that calcium rose from 120 nM to 160 nM with 200 µM H2O2 treatment. Data are presented as mean ± standard error. Numbers next to the data points are the number of separate experiments