Figure 5.

Post-transcriptional SCN5A gene silencing results in functional reduction of the late Na⁺ current, I_NaL, and unmasks non-cardiac Na⁺ channel component in LV cardiomyocytes from dog with chronic heart failure

A, representative raw traces of I_NaL were recorded at membrane potentials V_m = −10 mV in freshly isolated cells, and in cells 5 days after infection with virus containing control non-silencing siRNA and cDNA for GFP and siRNA-Na_v1.5 (indicated by the arrows). Exponential fits to I_NaL decay are shown by continuous lines and are superimposed with traces. Values of slow exponent time constant, τ,  are given in the panel. B, summary data with statistics for I_NaL density. C, representative I_NaL–voltage relationship obtained in freshly isolated (•) and cultured cells for 5 days with virally delivered control siRNA (▴ control GFP), and Na_v1.5-siRNA (▪). Continuous lines show theoretical curves fitted to experimental current–voltage (I–V) data points to evaluate steady-state activation (SSA) parameters which are given in the panel. D, average experimental data of steady-state inactivation (SSI) data points in control (•, n = 17) and after SCN5A gene silencing by the siRNA (▪, n = 16) along with the fit to a Boltzmann function. E and F, statistical data for I_NaL decay time course evaluated by the double exponent fit. Difference between theoretical fits (C and D) was statistically significant (P < 0.05) evaluated by F test. Statistical significance, P < 0.05, between experimental data points presented as mean ± SEM (B, E and F) were evaluated by ANOVA followed by Bonferroni's post hoc test.