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Figure 5 Composite data of the effect of propranolol (Prop, 1 µmol/L) to suppress the influence of isoproterenol (Iso, 100 nmol/L) on the QT interval (solid circle), the APD90 of M (open circle) and epicardial (Epi, open triangle) cells and TDR (solid circle) in the LQT1 (A and B), LQT2 (C and D) and LQT3 (E and F) models. In the LQT1 and the LQT2 models, propranolol completely prevented the influence of isoproterenol to persistently or transiently increase TDR. In the LQT3 model, propranolol completely suppressed the protective effect of isoproterenol to decrease TDR. The isoproterenol data reported here were recorded 10 min after addition of the catecholamine although similar results were obtained at 2 min in the presence of propranolol. *p < 0.0005 vs. control. APD90 = action potential duration measured at 90% repolarization; LQT1, 2, 3 = long QT syndrome 1, 2, 3; TDR = transmural dispersion of repolarization.
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