Effect of (−)U50,488H pretreatment of the wild-type, chimeric, and mutant κ opioid receptors on [35S]GTPγS binding stimulated by the subsequent application of (−)U50,488H∶EC50values and maximal responses (E max) of (−)U50,488H
| Receptor Construct | Control | (−)U50,488H-Treated | n | ||
|---|---|---|---|---|---|
| EC50 | Emax | EC50 | Emax | ||
| nM | fmol/mg of protein | nM | fmol/mg of protein | ||
| hkor | 6.32 ± 0.97 | 258.0 ± 10.0 | 13.79 ± 3.072-a | 184.5 ± 9.62-b | 4 |
| rkor | 5.16 ± 0.38 | 144.3 ± 20.7 | 8.27 ± 0.64 | 141.3 ± 14.6 | 3 |
| Flag-hkor | 4.69 ± 0.91 | 287.7 ± 8.5 | 15.35 ± 4.172-a | 200.9 ± 18.52-b | 7 |
| Flag-rkor | 2.11 ± 0.25 | 143.4 ± 7.0 | 4.97 ± 0.53 | 156.6 ± 7.03 | 9 |
| Flag-h/rkor | 4.13 ± 0.82 | 175.1 ± 7.8 | 7.32 ± 1.61 | 190.8 ± 9.54 | 8 |
| Flag-r/hkor | 2.72 ± 0.59 | 332.8 ± 7.0 | 18.67 ± 3.962-b | 237.6 ± 28.42-b | 5 |
| Flag-rkorN358S | 3.64 ± 1.35 | 336.3 ± 29.2 | 1.25 ± 0.26 | 236.4 ± 13.52-b | 5 |
| Flag-hkorS358N | 3.30 ± 1.08 | 253.1 ± 27.6 | 1.84 ± 1.01 | 283.0 ± 36.6 | 7 |
Clonal CHO cells stably transfected with each of the receptor constructs were treated without (control) or with 1 μM (−)U50,488H at 37°C for 60 min and washed. Membranes were prepared and [35S]GTPγS binding was performed. Results are expressed as mean ± S.E.M. n = number of independent experiments in duplicate.