FIG. 5.

I_NCX contributes to E-C coupling of ventricular hESC-CMs. (A) Representative tracings of Ca²⁺ transients in 40-day and 90-day dsRed+ cells with and without external Na⁺. Normalized basal [Ca²⁺]_i (B), amplitude (C), and maximum decay velocity (V_max-decay, D) of Ca²⁺ transients in 7+40- and 7+90-day ventricular hESC-CMs after replacing with a Na⁺-free external solution. ^*P < 0.05; ^**P < 0.01. (E) Ca²⁺ transients were completely blocked in ventricular hESC-CMs treated with nifedipine and Na⁺-free solution.