Table 2

Relative efficacies of TMQ isomers at β-adrenoceptor subtypes expressed in CHO cells

Compound	β₁-Adrenoceptor Fractional Receptor Occupancy^2-a	e_r^2-b	β₂-Adrenoceptor Fractional Receptor Occupancy^2-a	e_r^2-b	β₃-Adrenoceptor Fractional Receptor Occupancy^2-a	e_r^2-b
(−)-Isoproterenol	0.13	1	0.26	1	0.21	1
(±)-Trimetoquinol	0.24	0.54	n.d.^2-c	n.d.^2-c	0.06	3.42
(+)-Trimetoquinol	1.68	0.08	5.61	0.05	6.1	0.03
(−)-Trimetoquinol	0.64	0.20	6.21	0.04	0.03	8.2

↵2-a Fractional receptor occupancy, fraction of the total population of receptors occupied by a drug to elicit a response equivalent to half-maximal response to (−)-isoproterenol calculated by the method of Furchgott and Bursztyn (1967).
↵2-b e_r, efficacy of drug relative to (−)-isoproterenol calculated as the ratio of fractional receptor occupancy of drug to fractional receptor occupancy of (−)-isoproterenol.
↵2-c n.d., not determined.