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Figure 2 Radioligand binding assay for beta-adrenergic receptors in lung membrane preparations from rats with CHF after aortic banding and from control animals was performed using [¹²⁵I]iodocyanopindolol (A). Saturation isotherms established by the least-squares method are from single data referring to CHF and control animals 28 days after aortic banding. Nonspecific binding (bottom) was determined as the residual binding in the presence of 10 µmol/liter alprenolol. (B) Density (B_max) and affinity (K_D) of pulmonary adrenergic receptors from rats at 3 days (n = 6), 7 days (n = 11) and 28 days (n = 12) after aortic banding (hatched bars) are compared with respective controls (n = 5, 9 and 10, respectively) (open bars). Mean ± SEM; *p 0.001 (two-way ANOVA). K_D values (shown in numbers) were not significantly different. (C) Ratio of adrenergic receptor subtypes as determined by two-site competition curves obtained with the beta₁-selective receptor antagonist bisoprolol (Biso) and the beta₂-selective antagonist ICI 118,551 (ICI). No differences in the beta₁-/beta₂-subtype ratio of 20:80 were observed between lungs from rats with CHF (after 28 days; n = 3) and from sham-operated control animals (n = 3).