Figure 3: Effects of 48 hour mercury exposure (0.5 ppm) on cell number/proliferation. Relative cell number was determined by assessing the total number of live cells using lactate dehydrogenase (LDH) activity [Total cell LDH-Dead/Media LDH]. The concentration of 0.5 ppm was chosen based on its relative lack of effect on cell viability. Following exposure to mercury, MCF-12A cells were most sensitive to both CH3Hg+ and HgCl2 with significant increases (p<0.01) in cell number in both treatment groups. MDA-MB-453 cell number was significantly (p<0.01) reduced in both the CH3Hg+ and HgCl2 group compared to control. MCF-7 cells were the least sensitive, with only 0.5 ppm CH3Hg+ group showing a reduction in cell number (p<0.01). Collectively, each of the cells appeared to be most sensitive to the organic form of mercury. 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.