TABLE 1

Kinetic binding parameters of unlabeled ligands for human β₂-adrenoceptor receptors

Data are mean ± S.E.M. for three or more experiments performed in duplicate.

β₂ Ligand	k_off	k_on	pK_d	pK_i
	min⁻¹	ΜM⁻¹ min⁻¹
Bisoprolol	6.86 ± 2.09	4.61 ± 1.30 × 10⁷	6.83 ± 0.02	6.79 ± 0.05
Atenolol	1.27 ± 0.31	4.57 ± 0.73 × 10⁶	6.58 ± 0.06	6.29 ± 0.05
Labetalol	1.22 ± 0.08	2.03 ± 0.33 × 10⁸	8.20 ± 0.08	8.45 ± 0.18
Metoprolol	5.27 ± 0.82	4.39 ± 0.92 × 10⁷	6.90 ± 0.06	6.75 ± 0.02
Bucindolol	0.039 ± 0.007	1.39 ± 0.16 × 10⁹	10.56 ± 0.03	10.52 ± 0.03
Carvedilol	0.033 ± 0.006	1.85 ± 0.13 × 10⁹	10.77 ± 0.13	10.88 ± 0.08
Propranolol	0.46 ± 0.05	3.65 ± 0.42 × 10⁹	9.90 ± 0.03	9.76 ± 0.03
Salmeterol	1.16 ± 0.16	3.50 ± 0.57 × 10⁹	9.47 ± 0.01	9.49 ± 0.04
ICI 118,551	0.21 ± 0.03	7.63 ± 0.84 × 10⁸	9.56 ± 0.03	9.36 ± 0.14
Sotalol	3.10 ± 0.67	2.29 ± 0.46 × 10⁷	6.87 ± 0.02	6.66 ± 0.09
Nadolol	0.14 ± 0.04	1.01 ± 0.33 × 10⁸	8.87 ± 0.01	8.82 ± 0.05
Formoterol	3.00 ± 0.38	1.78 ± 0.21 × 10⁸	7.77 ± 0.01	7.28 ± 0.10^{^a}
Timolol	0.033 ± 0.003	3.76 ± 0.23 × 10⁸	10.06 ± 0.04	9.90 ± 0.03
Cyanopindolol	0.002 ± 0.001	1.83 ± 0.15 × 10⁹	12.04 ± 0.18	11.74 ± 0.42
CGP12177	0.048 ± 0.004	2.89 ± 0.34 × 10⁸	9.78 ± 0.02	9.67 ± 0.09
Isoprenaline^{^a}	3.06 ± 1.53	2.47 ± 1.39 × 10⁷	6.89 ± 0.08	6.73 ± 0.15
Salbutamol^{^a}	4.06 ± 1.19	2.05 ± 1.03 × 10⁷	6.65 ± 0.14	6.54 ± 0.07