Figure 4: Particulate Cr(VI) Decreases Mad2 Protein Levels. This figure shows that zinc chromate decreased Mad2 protein levels after 24-120 h exposure. Protein expression was measured with western blotting. GAPDH was used as a loading control. A) Protein expression level in total population of cells. B) Representative western blot image of Mad2 expression in total population of cells. C) Protein expression level in mitotic population of cells. D) Representative western blot image of Mad2 expression in mitotic cells. Data represent an average of three independent experiments ± the standard error of the mean.*Statistically different from control (p<0.05). †Statistically different from control (p<0.01).