Agonist and antagonist affinities of hH1R, gpH1R and hH1R-F153L/I433V expressed in Sf9 membranes in the [3H]mepyramine competition binding assay
[3H]Mepyramine competition binding in Sf9 membranes expressing H1R constructs (+RGS4 or GAIP) was determined as described under Materials and Methods. Reaction mixtures contained 2 nM [3H]mepyramine and unlabeled H1R ligands at concentrations of 0.1 nM to 10 mM as appropriate to generate saturated competition curves. Data were analyzed by nonlinear regression and were best fit to one-site (monophasic) competition curves. Data shown are the means ± S.D. of three to five experiments performed in duplicates each. The relative affinity of histamine (Rel. Aff.) was set 100, and the affinities of other agonists were referred to this value. We also calculated the ratio of the Ki values for hH1R and gpH1R (Aff. Rat. gp/h) and the ratio of the Ki values for hH1R and hH1R-F153L/I433V (Aff. Rat. m/h).
Cpd. | Ligand | hH1R | gpH1R | Aff. Rat. gp/h | hH1R-F153L/I433V | Aff. Rat. m/h | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ki | Rel. Aff. | Ki | Rel. Aff. | Ki | Rel. Aff. | |||||||
| 1 | Histamine | 2.06 ± 0.18 μM | 100 | 4.65 ± 0.26 μM* | 100 | 0.44 | 3.30 ± 0.60 μM* | 100 | 0.62 | |||
| 3 | 2-(2-Thiazolyl)ethanamine | 4.60 ± 1.93 μM | 44.8 | 8.49 ± 3.53 μM | 54.8 | 0.54 | 12.7 ± 1.70 μM* | 26 | 0.36 | |||
| 12 | 2-(3-Chlorophenyl)histamine | 1.78 ± 0.30 μM | 115.7 | 0.60 ± 0.17 μM* | 775.0 | 2.97 | 1.53 ± 0.18 μM | 215.7 | 1.16 | |||
| 14 | 2-(3-Bromophenyl)histamine | 2.22 ± 0.30 μM | 107.8 | 0.70 ± 0.10 μM* | 668.1 | 3.19 | 1.43 ± 0.24 μM | 230.8 | 1.55 | |||
| 15 | 2-(3-Iodophenyl)histamine | 1.76 ± 0.24 μM | 117.1 | 0.61 ± 0.14 μM* | 759.8 | 2.88 | 1.38 ± 0.02 μM | 239.1 | 1.28 | |||
| 19 | Methylhistaprodifen | 0.37 ± 0.07 μM | 552.3 | 0.29 ± 0.06 μM | 1603.4 | 1.29 | 0.24 ± 0.04 μM* | 1375 | 1.54 | |||
| 20 | Dimethylhistaprodifen | 0.40 ± 0.06 μM | 509.9 | 0.31 ± 0.08 μM | 1480.9 | 1.29 | 0.36 ± 0.02 μM | 916.7 | 1.11 | |||
| 31 | Triprolidine | 3.01 ± 0.54 nM | — | 1.15 ± 0.02 nM* | — | 2.62 | 2.88 ± 0.15 nM | — | 1.05 | |||
| 35 | Arpromidine | 353 ± 71 nM | — | 33.3 ± 10.1 nM* | — | 10.6 | 282 ± 57 nM | — | 1.25 | |||
|
36
| BU-E 47 | 255 ± 68 nM | — | 53.9 ± 14.8 nM* | — | 4.73 | 321 ± 56 nM | — | 0.79 | |||
—, not applicable; Cpd., compound.
↵ * P < 0.05 for comparison of hH1R versus other H1R constructs