Figure 2.

(A,B) Normalized isometric force response at different Ca²⁺ concentrations (given as pCa) of d-hESC-CMs (black circles and bars) and hvMFs (gray squares and bars), with (open symbols and bars) and without (filled symbols and bars) PKA-treatment prior to force measurements. Measured force at different pCa were normalized to the maximum force generated at saturating [Ca²⁺] (pCa 4.18; 15°C) and fitted by a dose-response Hill-type equation given in “Material and Methods.” (C) pCa at half maximum force generation (pCa₅₀; indicating Ca²⁺-sensitivity of force), and the steepness of the force-pCa relationship (n_H or Hill coefficient). Data are given as mean ± SD; ^***p < 0.001. n, number of d-hESC-CMs and hvMFs, respectively. Force parameters of hvMFs isolated from two different adult donor hearts were pooled together.