Figure 2. Aging mice exhibit higher cardiomyocytes apoptotic rates and Caspase-9 activity but lower cardiac systolic function. TUNEL labeling and apoptotic index of paraffin-embedded cardiac tissues (A). Evaluation of Caspase-3, Caspase-9, Caspase-8, Caspase-12 activity in mice of different ages (B–E), data are represented as mean +/- SEM. n = 6 per group. *P<0.05, **P<0.01 vs. 4m. m=month. The correlation analysis between the expression of Caspase- 9 activity and ejection fraction (EF, %) (F). The correlation analysis between the Caspase -9 activity and fractional shortening (FS, %) (G). n=32.