Effect of amiloride on the binding of [3H]yohimbine or [3H]rauwolscine to the human α2A-adrenergic receptor
| Ligand | Amiloride | Kd | Bmax |
|---|---|---|---|
| mm | nm | pmol/mg protein | |
| Yohimbine | 0 | 2.8 ± 0.1 | 14.4 ± 0.4 |
| 0.1 | 13.3 ± 1.0 | 14.5 ± 0.5 | |
| Rauwolscine | 0 | 2.4 ± 0.1 | 14.0 ± 0.1 |
| 0.1 | 11.5 ± 0.2 | 14.0 ± 0.1 | |
| 0.3 | 29.1 ± 1.0 | 13.8 ± 0.3 |
Values are mean ± standard error from three saturation binding assays, in which membranes containing the α2A-adrenergic receptor were incubated at 30° for 60 min with increasing concentrations of radioligand (0.2–50 nm) in a final volume of 0.4 ml of assay buffer. The Kd value (=1/KL, Fig. 1) is the dissociation constant of the antagonists in the absence or presence of amiloride at the α2A-adrenergic receptor.