Effects of different concentrations and time points of DOX and PAP on H9c2 cell viability using the CCK-8 assay. (A) DOX treatment concentrations were 0.08, 0.16, 0.32, 0.63, 1.25, 2.5, 5, 10 and 20 μM, and DOX treatment time points were 6, 12, 24 and 48 h, respectively. (B) PAP treatment concentrations were 4.0, 8.0, 16.0, 32.0, 62.5, 125, 250, 500 and 1000 μg/ml, and PAP treatment time points were 24, 48 and 72 h, respectively.