Figure 2. IP₃R2 activation alters Ca²⁺ wave occurrence in intact cardiomyocytes.

A, representative line‐scans of fluo‐3‐loaded intact cardiomyocytes with the corresponding fluorescence profiles upon pharmacological intervention with 100 nM ET‐1, 2 μM 2‐APB or 3 μM XeC. Cells were field stimulated for 30 s at 1 Hz to reach steady state prior to a 10 s rest period to assess Ca²⁺ wave occurrence as a measure for arrhythmogenicity at the single cell level. SR‐Ca²⁺ load was assessed by application of 10 mM caffeine. B, Ca²⁺ transient amplitude (ΔF/F ₀) and SR‐Ca²⁺ content (ΔF/F ₀) under the tested pharmacological interventions in WT (n of groups 1–4 = 13, 11, 16, 15; N of groups 1–4 = 4, 3, 3, 3) and TG myocytes (n of groups 1–4 = 14, 16, 14, 11; N of groups 1–4 = 4, 4, 3, 3; ^* P < 0.05, ^** P < 0.01 vs. control; ANOVA followed by Dunnett's test). C, Ca²⁺ wave occurrence (%) calculated as the portion of cardiomyocytes displaying Ca²⁺ waves within the 10 s rest period (^* P < 0.05, ^*** P < 0.001 vs. control; ^‡‡‡ P < 0.001 vs. WT; N = 3–4, n = 9–21; χ² test).