Figure 3.

(A, B) Effects of nebivolol (n=4) and bisoprolol (n=7) on isoprenaline (1 μmol l⁻¹) prestimulated force of contraction in human ventricular myocardium. Both β-blockers significantly inhibit the isoprenaline induced increase in force of contraction. (C) Cumulative dose-response curves of nebivolol (n=10) and bisoprolol (n=6) in the presence of forskolin (0.3 μmol l⁻¹). (D) Inotropic effect of nebivolol and bisoprolol at concentrations occupying 50% (K_i) and 100% (100×K_i) of β-adrenoceptors. Data are derived from cumulative dose-response curves (C), related to the respective dissociation constants determined in radioligand binding experiments (Table 1). Concentrations are as follows: nebivolol, 0.03 (K_i) and 3 μmol l⁻¹ (100×K_i); bisoprolol, 0.1 (K_i) and 10 μmol l⁻¹ (100×K_i).