Figure 3
From: Cardiac Pacemaker Cells Generate Cardiomyocytes from Fibroblasts in Long-Term Cultures
Electrophysiological and pharmacological characterisation of cardiomyocyte clusters in SANC cultures. (A) Action potentials were recorded from the centre of a spontaneously beating cardiomyocyte cluster after 3 weeks in culture using a whole-cell patch pipette (a). Intracellular Ca2+ transient from other clusters was recorded optically using Fluo-4 after 3 weeks of culture (b). (B) Analysis of ion channels and an exchanger during spontaneous beating of cardiomyocyte clusters in SANC cultures after 3 weeks; a) the If inhibitor ivabradine (0.1 µM,●; 1 µM, ▲) decreased beat rates gradually (n = 8) in a concentration-dependent manner, and addition of the ionic If inhibitor CsCl (3 mM) reduced beating rates completely. (b) The effects of the IKr, INa/Ca, ICaT and ICaL inhibitors E-4031 (3 µM), KB-R7943 (5 µM), Ni2+ (50 µM) and nicardipine (10 µM), respectively, on rates of spontaneous beating (n = 10); (c) Effects of tetrodotoxin (10 µM) on beating rates; horizontal lines indicate averages, and ticks indicate S.E.M. Tetrodotoxin-sensitive and tetrodotoxin-resistant clusters were present (n = 10). (d) Time-dependent increases in the proportions of tetrodotoxin-sensitive and tetrodotoxin-resistant cell clusters (n > 150) (chi-square test, P = 0.0413); data are expressed as mean ± S.E.M. Vertical bars denote S.E.M.; Dunnett’s test, *P < 0.05, **P < 0.01, ***P < 0.001, compared with control.
