Fig. 3

Long-term pacing induced the cardiac apoptosis. a Hoechst 33342 staining demonstrated that the intact nuclei containing aequalis chromatin were homogeneously distributed in the controls. By contrast, as the Cum%VP increased, the VCMs exhibited typical morphological features of apoptosis as revealed by shrunken cells with condensed or fragmented nuclei (arrow: apoptosis cell, scale bar 50 μm); cytometric analysis with annexin V and propidium iodide (AV/PI) double staining was further conducted to quantify the occurrence of apoptosis (b). The results illuminated that pacing significantly increased the apoptosis ratio in a Cum%VP-dependent manner (c). ^* p < 0.05, ^** p < 0.005, ^*** p < 0.001 according to a one-way ANOVA test