WT | N147→Y | S320 → F | ||||
---|---|---|---|---|---|---|
Agonist | EC50 | Efficacy | EC50 | Efficacy | EC50 | Efficacy |
μM | μM | μM | ||||
(R)-(–)-α-Methylhistamine | 0.27 ± 0.03 | 100 | 0.46 ± 0.7 | 76 | 12.4 ± 1.8 | 164 |
(S)-(+)-α-Methylhistamine | 6.97 ± 0.7 | 100 | 0.97 ± 0.3 | 50 | >1000 | >100 |
Imetit | 0.09 ± 0.01 | 100 | 0.19 ± 0.04 | 32 | 1.7 ± 0.14 | 219 |
Immepip | 0.13 ± 0.03 | 100 | 0.32 ± 0.03 | 31 | 0.76 ± 0.1 | 183 |
HEK-293 SFM cells expressing wild type, Ser320 → Phe, or Asn147 → Tyr mutant histamine H4 receptors were treated with increasing concentrations of the indicated histamine H4 receptor agonists. The resulting intracellular Ca2+ mobilization was measured by Fluorescent Imaging Plate Reader assay. Data were calculated as the mean ± S.E. of three independent experiments. Efficacy is expressed as percentage of the response of the wild-type receptor to each agonist.