Figure 4: Effects of mercury exposure on caspase 3/7 activity expressed as a percent of control fluorescence measured at 48 hours. Control (0 ppm) values (RFU) for each cell line were MCF-12A, 3317 ± 167; MDA-MB-453, 2867 ± 18; and MCF-7, 4283 ± 252. Both MCF-12A and MDA-MB-453 cells showed decreased (p<0.01) caspase activity at 48 hours after exposure to 5 ppm CH3Hg+. Exposure to HgCl2 appeared to have the opposite effect, causing an increase in caspase 3/7 activity in MDA-MB-453 cells, but not MCF-12A cells. MCF-7 cells showed a robust increase in caspase activity when exposed to the 5 ppm CH3Hg+ and a decrease in caspase production when exposed to HgCl2. Non-transformed data were analyzed by one-way ANOVA (treatment X cell line) followed by Dunnett’s test for multiple comparisons to control (0 ppm) mean for each cell line. Data are expressed as mean ± SEM of N=4 in duplicate.