Table 2.
Displacement by amiloride analogues of binding at A1, A2A, and A3 adenosine receptors
| Radioligand and receptor | ic50 (μM) | |||
|---|---|---|---|---|
| Amiloride | DMA | HMA | MIBA | |
| Antagonist [3H]DPCPX, 1 nM Rat A1 (slope) | 197 ± 23 (1.3 ± 0.1) | 7.9 ± 1.7 (1.2 ± 0.1) | 21.5 ± 3.7 (1.4 ± 0.2) | 12.6 ± 1.4 (1.4 ± 0.1) |
| Antagonist [3H]ZM241385, 1 nM Rat A2A | 9.7 ± 1.1a | NDb | 3.3 ± 0.5a | 3.0 ± 0.2a |
| Agonist [125I]I-AB-MECA, 1 nM Rat A3 (slope) | >100c | 19.7 ± 3.2 (1.1 ± 0.1) | 7.0 ± 1.4 (1.0 ± 0.2) | 7.1 ± 1.5 (1.2 ± 0.1) |
| Antagonist [3H]PSB-11, 5 nM Human A3 | 82.3 ± 7.2 | 12.8 ± 2.1 | 5.7 ± 0.9 | 8.2 ± 1.3 |
Concentrations of the radioligands used were close to their Kd values. Human A3 receptors were expressed in CHO cells, and the rat A3 receptor of RBL-2H3 cells was used. A1 and A2A receptors of rat brain (forebrain and striatum, respectively) were used. Results are expressed as mean ± SEM and are from at least three independent experiments performed in duplicate.
a
Ki values. Data from Ref. [19].
b
ND = not determined.
c
Displaced less than 15% of [125I]I-AB-MECA binding at 100 μM.