Table 2.
Dissociation constants of adenosine receptor agonists for binding to sites present in NEM-pretreated cortical and cardiac membranes estimated by inhibition of [3H]XACa binding
| Compound | Cortexb
|
Heart
|
|
|---|---|---|---|
| Kd, nM | K1, nM (% total) |
K2, nM (% total) |
|
| R-PIA | 26 ± 6 | 17 ± 9 (86%) | 28 248 ± 30322 (14%) |
| IABA | 55 ± 10 | 98 ± 44 (90%) | 15480 ± 17421 (10%) |
| NECA | 6329 ±347 | 124 ± 80 (36%) | 16155 ± 3836 (64%) |
| NCCA | 6329 ± 336 | 107 ± 68 (33%) | 12121 ± 2159 (67%) |
a
[3H]XAC was present in concentrations of 0.6 – 0.7 nM for both cortical and cardiac membranes. The Kd values of [3H]XAC under these conditions was 0.20 ± 0.0.02 nM (Bmax 101 ± 14 fmol/mg, N = 3) for cardiac membranes and 0.09 ± 0.01 nM (Bmax 780 ± 75 fmol/mg, N=3) for cortical membranes
b
Inhibition curves were monophasic giving a single Kd value