Figure 3

Representative potassium current recordings from wt (A, C) and αMHC^403/+ (B, D) ventricular myocytes under control conditions (A, B) or the presence of 100 nM ISO (C, D). Whole-cell voltage-gated outward K⁺ (K_V) currents were evoked in response to 500 ms depolarizing voltage steps to test potentials between − 60 and + 40 mV, in 10 mV increments, from a holding potential of − 70 mV (− 70, 0 mV and positive test potentials shown). Inward rectifying K⁺ currents (I_K1) evoked in response to hyperpolarization to − 120 mV. (E–F) Scatter plot with bar graphs show I_K density (pA/pF) values for different K_V current components as means ± SEM. wt n = 8–15, N = 5 αMHC^403/+ n = 10–16 N = 5*p < 0.05 control versus ISO, ^†p < 0.05 wt versus αMHC^403/+ (G) Representative immunofluorescence and corresponding Western blot images for K_V4.2, K_ir2.1, K_ir6.2 potassium channels from wt and αMHC^403/+ hearts as indicated. Relative optical density (Rel OD) values were calculated using VDAC (voltage dependent anion channel) as loading control. For further details please see section “Materials and methods”.