Fig. 6

Increased expression of osteopontin, CD44 and Epac and inducibility of ventricular arrhythmias in heart failure mice. A–C ISO (30 mg/kg per day subcutaneously for 15 days) led to cardiac contractile dysfunction in mice. A Representative examples and mean ± SE analysis western blot for osteopontin, CD44, Epac1 and Epac2 in WT and CD44^−/− mice treated with ISO. N = 4 for each group. *P < 0.05 versus control (WT without ISO) by one-way ANOVA with Bonferroni’s post hoc test. B Representative examples and mean ± SE analysis for co-immunoprecipitation of CD44 and control IgG with Epac1 and Epac2. N = 3 for each group. C Representative examples and mean ± SE analysis for co-immunoprecipitation of CD44 and control IgG with PKAc and PKAIIα. N = 3 for each group. In B and C, the pictures are representation of blots from 3 independent experiments for each. The mean ± SE analysis was for precipitated protein-bound CD44 and Epac1 to precipitated protein ratio and cell input, both of which were quantified to GADPH and normalized to the control level, which was set at 1.0. *P < 0.05 versus control by one-way ANOVA with Bonferroni’s post hoc test. D and E Inducibility of ventricular arrhythmias (VAs). Inducibility of VAs was tested by intra-cardiac pacing via an internal jugular vein access. A rhythm with more than 5 consecutive ventricular beats after burst pacing for 5 times was considered to be VAs. D Representative examples of VAs in WT and CD44^−/− mice with heart failure induced by 15-d ISO. All the examples after on-spot single bolus of isoproterenol. E Mean ± SE analysis VA inducibility in WT and CD44^−/− mice at baseline and after treatment with ISO, and before and after on-spot single bolus of isoproterenol (0.5 mg/kg, i.p.). N = 6–9 mice for each group. *P < 0.05 between groups by Fisher’s exact test. VAs = ventricular arrhythmias, WT = wild-type control mice, CD44^−/− = CD44 knock-out mice, ISO = isoproterenol at 30 mg/kg per day subcutaneously for 15 days, (number) = number of the mice