TABLE 5.
The ratio of the log KB value for CGP12177 (as an antagonist of cimaterol) and log EC50 value for CGP12177 for responses seen at the β2-WT and β2-TM chimeric receptors (data taken from Table 4)
Ratios of the affinity for antagonists at the two conformations are also given (i.e., log KB for antagonism of cimaterol/log KB for antagonism of CGP12177). This table examines the ratio of the affinities of ligands at the β2-adrenoceptor and thus allows for differences in absolute affinity. ICI118551 has lower affinity at the β2-TM4 receptor (Table 4), but this occurred both in the presence of cimaterol and CGP12177; thus, the ratio is similar to that at the other receptors. There is no large consistent change with any of the receptors.
| Ratio of Log KB CGP12177/Log EC50 CGP12177 | Ratio of Log KB (Cimaterol as Agonist)/Log KB (CGP12177 as Agonist) |
||||
|---|---|---|---|---|---|
| CGP20712A | Bisoprolol | ICI118551 | Propranolol | ||
| β2-WT | 0.65 | −0.09 | 0.25 | 0.25 | 0.63 |
| β2-TM1 | 0.26 | 0.46 | 0.19 | 0.23 | 0.49 |
| β2-TM2 | 0.81 | 0.41 | 0.25 | 0.27 | 0.55 |
| β2-TM3 | 0.81 | 0.36 | 0.52 | 0.24 | 0.86 |
| β2-TM4 | 0.63 | 0.04 | 0.41 | 0.45 | 1.00 |
| β2-TM5 | 0.51 | 0.16 | 0.06 | 0.19 | 0.71 |
| β2-TM6 | 0.78 | −0.26 | 0.33 | 0.47 | 0.41 |
| β2-TM7 | 0.01 | 0.35 | 0.47 | 0.09 | 0.28 |