Fig. 3
Ca2+ imaging with GmNL(Ca2+) in hiPSC-CMs. a Bioluminescence and bright-field images of hiPSC-CMs expressing GmNL(Ca2+). Scale bar, 50 μm. b Representative time course of the signal of GmNL(Ca2+), and Fluo4 at 0 or 15 min. Images were taken at 20 Hz, 20 μM coelenterazine-h was added just before imaging. Excitation light at 62 mW cm−2 for Fluo4 was applied continuously for 15 min. The measurements were replicated (n ≥ 6) for each condition. c Relative change in beating parameters after 15 min continuous imaging. Data are presented as mean ± S.D.; n = 6–8. Ca2+ imaging with Fluo4 was conducted under four different power densities of excitation light, 62, 125, 250 and 500 mW cm−2 respectively. d Representative time course of the bioluminescence signal of GmNL(Ca2+) before and after treatment with either 1 μM isoproterenol or 40 μM propranolol. The measurements were triplicated for each drug. e Mean beat interval before and after treatment; data are presented as mean ± S.D. Two-tailed Student’s t test was performed. **p < 0.01; n = 3