Effect of amiloride analogs on [3H]UK14304 dissociation from the α2A-adrenergic receptor
| AmilorideY | k−1 | HMA (AmilorideX) | Amiloride Y | ||||||
|---|---|---|---|---|---|---|---|---|---|
| k−2 | Fold change | log αKX | log αobs | k−3 | Fold change | log βKY | log βobs | ||
| min−1 | min−1 | k−2/k−1 | min−1 | k−3/k−1 | |||||
| 0.043 ± 0.005 | 0.015 ± 0.002 | 0.37 ± 0.07 | 4.24 ± 0.05 | −2.50 ± 0.05 | |||||
| Amiloride | 0.036 ± 0.001 | 0.016 ± 0.001 | 0.45 ± 0.01 | 4.28 ± 0.03 | −2.46 ± 0.03 | 0.024 ± 0.002 | 0.67 ± 0.06 | 2.39 ± 0.05 | −2.21 ± 0.05 |
| DMA | 0.038 ± 0.001 | 0.015 ± 0.001 | 0.41 ± 0.01 | 4.20 ± 0.03 | −2.54 ± 0.03 | 0.029 ± 0.002 | 0.77 ± 0.02 | 3.39 ± 0.12 | −2.10 ± 0.12 |
The experiments were performed at 30°C, as described in the legend of Fig. 3. The data from each experiment were fitted to the single-exponential equations derived in a previous study (equations 10 and 9, respectively, Leppik et al., 1998). k −1,k −2, and k −3 are the dissociation constants for the dissociation of [3H]UK14304 from the unoccupied (k −1), HMA-occupied (k −2), or amiloride- or DMA-occupied (k −3) receptors. The log αobs and log βobs are the calculated differences between the log affinity of the amiloride analog at the agonist-occupied receptor (log αK X or log βK Y) and the log affinity at the unoccupied receptor (log K X, described in the second paragraph under Results). Values are means ± S.E. of three experiments.