Figure 6.

Effects of endothelial-specific Tnf ablation on electrical properties on exercise-induced arrhythmias and electrical changes in isolated atria. (A) Representative field electrogram recordings from isolated (denervated) atria in Tie2-Cre+ and Cre− sedentary and exercised mice showing atrial arrhythmia inducibility, with evidence of sustained AF episodes in both Tie2-Cre+ and Cre− exercised mice only. (B) Endothelial-specific Tnf ablation (Tie2-Cre+) did not protect against sustained (>10 s) atrial arrhythmia inducibility (P value from 2 × 2 contingency table with Fisher’s exact test) in exercised mice. (C) Representative optically-mapped images of AF episodes from rapidly stimulated isolated atria in Tie2-Cre+ swim mice. (D and E) Typical isochrone activation maps and summary results of conduction velocity (CV) measured in right atrial appendages isolated from Tie2-Cre+ (n = 7) and Cre− (n = 8) swim-exercised mice revealed that CVs are slowed in Tie2-Cre+ and Cre− swim mice when compared to their sedentary counterparts (n = 7 and 8 per group, respectively). (F) In isolated atrial preparations, action potential duration at 90% of repolarization (APD₉₀) were similar between sedentary and exercised mice, in both Tie2-Cre+ and Cre− groups. The n value for individual groups is indicated on bar graphs. Data presented as mean ± S.e.m. P values from two-way ANOVA with Sidak’s multiple comparison tests. *P < 0.05; **P < 0.01.