Association rate and dissociation kinetic parameters of [3H]aclidinium, [3H]ipratropium, and [3H]tiotropium to human M2 and M3 receptors
Data are reported as mean ± S.E.M. of three independent experiments.
| Compound | Kon | Koff | t1/2 | t1/2 Ratio | |||
|---|---|---|---|---|---|---|---|
| M2 Receptor | M3 Receptor | M2 Receptor | M3 Receptor | M2 Receptor | M3 Receptor | M3/M2 | |
| M−1 · min−1 | min −1 | h | |||||
| [3H]Aclidinium | NM | 1.4 × 108 ± 5.8 × 106 | 0.15 ± 0.01 | 0.02 ± 0.00 | 4.69 ± 0.29 | 29.24 ± 0.61 | 6.2 |
| [3H]Ipratropium | NM | 1.1 × 108 ± 9.1 × 106 | 9.72 ± 1.52 | 1.49 ± 0.06 | 0.08 ± 0.01 | 0.47 ± 0.02 | 5.9 |
| [3H]Tiotropium | NM | 5.5 × 107 ± 4.8 × 106 | 0.047 ± 0.00 | 0.011 ± 0.00 | 15.11 ± 1.57 | 62.19 ± 2.96 | 4.1 |
Kon, association rate constant of radiolabeled antagonist; Koff, rate constant of dissociation of radiolabeled antagonist; t1/2, residence half-life; NM, not measurable.