Fig. 4

Effect of CD44 and β-AR signaling on the Ca²⁺ sparks and Ca²⁺ waves in myocytes. Representative examples and mean ± SE analysis for the frequency and amplitude of A Ca²⁺ sparks (arrow) in HL-1 myocytes transfected with CD44 siRNA or wild-type CD44 cDNA -containing plasmids. n = 17–28 cells for each group. B Ca²⁺ sparks (arrow) in ventricular myocytes from wild-type mice (WT) treated with CD44 blocking antibody and C Ca²⁺ waves in ventricular myocytes from WT after 3-Hz electrical stimulation. In B and C, n = 4–20 cells for each group. In A–C, all were obtained before and after isoproterenol (1 μmol/L) infusion with and without treatment with CD44 blocking antibody. *P < 0.05 versus control and between ISO and ISO + CD44 siRNA or CD44 blocking antibody by one-way ANOVA with Bonferroni’s post hoc test. CaSpF = Ca²⁺ spark frequency, ISO = isoproterenol, WT = wild-type mice