Table 2
Dissociation constants of antagonists for the canine A3(cA3 13.1) and canine A1 adenosine receptors determined in binding assays
| Xanthine | KI | A1/A3 | A3/A1 | ||||
|---|---|---|---|---|---|---|---|
| R1 | R2 | R3 | A3 | A1 | |||
| nm | |||||||
| I-ABOPX | Propyl | 3-Iodo-4-aminobenzyl | Phenyl-oxyacetate | 37.5 ± 11 | 601 ± 99 | 16.0 | |
| XAC | Propyl | Propyl | Phenyl-(2-aminoethyl)aminocarbonylmethyloxy | 138 ± 22 | 159 ± 12 | 1.2 | |
| 8-SPT | Methyl | Methyl | Phenyl-sulfol | 25,300 ± 4,200 | 6,460 ± 590 | 3.9 | |
| CPX | Propyl | Propyl | Cyclopentyl | 115 ± 10 | 11.4 ± 2.1 | 10.1 | |
| BW-A1433 | Propyl | Propyl | Phenyl-acrylate | 1,880 ± 190 | 132 ± 11 | 14.2 | |
| WRC-0571 | (Nonxanthine) | 17,200 ± 2,100 | 484 ± 41 | 35.4 | |||
| Theophylline | Methyl | Methyl | H | >100,000 | |||
| Enprofylline | H | Propyl | H | >100,000 | >100,000 | ||
All structures except WRC-0571 are xanthines.
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K I values obtained from competition experiments using [125I]ABA as the radioligand; all values are reported as mean ± standard error of three to six experiments.