Research Paper Volume 8, Issue 11 pp 3131—3146

Figure 1. Age-dependent decline in the repair of DEN-induced DNA damage. (A) Mice at the indicated ages were injected with DEN and sacrificed after two and six days. Representative low power filed images of γH2AX staining in liver sections are shown (x4 objective). The percentage of DNA damage repair was calculated by dividing the amount of DNA damage at the peak of damage after 48h and the residual damage after the resolution phase 6 days after DEN treatment. The percentage of residual damage in 1-month compared to 6-month-old mice is shown (right panel). Insets (high power images -objective x40) depict γH2AX (green) in hepatocyte nuclei (DAPI; blue). (B) Six-month-old mice were injected with DEN and the levels of residual damage after 6, 9 and 12 days were determined as above. Insets depict the lower density and intensity of γH2AX staining in 9 and 12 days compared to 6 days post DEN. Graph (lower left panels) shows γH2AX staining areas 2-12 days after DEN injections in 6-month-old mice (average ± STD). The percentage of DNA damage repair was calculated as in A (lower right panel). An average of at least four mice in each group is shown. *** p<0.0005. (C) Representative image of γH2AX (green) and pKAP-1 (red) staining demonstrating pKAP-1 foci overlapping with γH2AX at sites of DSBs.