Figure 5.

Calcium Characteristics of Pacemaker-like Cardiomyocytes Obtained from iSABs

(A) Frequencies of spontaneous Ca²⁺ transients in iSAB cells significantly decrease after inhibition of HCN channels via ZD7288. The data represent four independent experiments and are presented as means ± SEM; n ≥ 7.

(B) Frequencies of spontaneous Ca²⁺ transients in iSAB cells significantly decrease after inhibition of T-type and L-type Ca²⁺ channels via mibefradil and nifedipine. The data represent four independent experiments and are presented as means ± SEM; n > 12; ^∗p < 0.05. See also Movie S6.

(C) Analysis of SR Ca²⁺ efflux as a characteristic of pacemaker-active cells reveals an enhanced rate of intracellular Ca²⁺ accumulation in iSAB-derived cells (red) in comparison with aCaBs (blue). Na⁺/Ca²⁺ exchanger blockade plus inhibition of SERCA caused an intracellular Ca²⁺ accumulation comparable to the reduction of the caffeine peak in iSAB-derived cells. The rate of cytosolic Ca²⁺ accumulation and amplitude of the caffeine peak in aCaBs do not show a difference. The data represent five independent experiments and are presented as means ± SEM; #p < 0.05 versus no SERCA inhibition; ^∗p < 0.05 versus controls.

See also Figure S3.