Table 3.
Comparison of the kinetic rate constants, residence times (RT) and kinetic K D values of representative hA1R antagonists and (partial) agonists obtained from competition association experiments to hA1R expressed on CHO cell membranes at 28 °C by SPA assay and filtration assay. For (partial) agonists LUF5834, CCPA, and NECA, 1 mM GTP was present in the assay. The k on (k 3), k off (k 4) values of the unlabeled compounds were determined in [3H]-DPCPX (2.4 nM) competition association experiments. RTs and kinetic K Ds were determined in the same manner as described in Table 2
| Cmpd. | SPA | Filtration assay | ||||||
|---|---|---|---|---|---|---|---|---|
| k on (nM−1 · min−1) | k off (min−1) | RT (min) | Kinetic K D (nM) | k on (nM−1 · min−1) | k off (min−1) | RT (min) | Kinetic K D (nM) | |
| FSCPX | 0.0047 ± 0.0007 | 0.0064 ± 0.0013 | 156 ± 31 | 1.4 ± 0.3 | 0.0019 ± 0.0003 | 0.0060 ± 0.0020 | 167 ± 56 | 3.2 ± 0.4 |
| DPCPX | 0.72 ± 0.16 | 0.50 ± 0.01 | 2.0 ± 0.1 | 0.69 ± 0.15 | 0.19 ± 0. 04 | 0.27 ± 0.03 | 3.7 ± 0.4 | 1.4 ± 0.1 |
| LUF5834 | 0.13 ± 0.05 | 0.50 ± 0.05 | 2.0 ± 0.1 | 3.9 ± 1.5 | 0.062 ± 0.006 | 0.23 ± 0.03 | 4.4 ± 0.5 | 3.7 ± 0.5 |
| CCPA | 0.0094 ± 0.0022 | 0.73 ± 0.04 | 1.4 ± 0.1 | 78 ± 19 | 0.016 ± 0.002 | 1.5 ± 0.03 | 0.68 ± 0.01 | 92 ± 9 |
| NECA | 0.0014 ± 0.0004 | 0.54 ± 0.06 | 1.9 ± 0.02 | 386 ± 36 | 0.0012 ± 0.0001 | 0.60 ± 0.04 | 1.7 ± 0.1 | 500 ± 8 |