TABLE 2

Pharmacological characterization of [3H]mepyramine and [3H]-(—)-trans-H2-PAT binding sites in wild-type H1R-expressing cells and in cells expressing both H1R Asp107Ala and H1R Phe432Ala mutant H1Rs (D107A + F432A)

The Hill coefficient (nH) for the displacement of the radioligand binding to the reconstituted ligand binding sites that are observed upon coexpression of the mutant H1Rs D107A and F432A are shown. Data shown are mean ± S.E.M. of three independent experiments, each performed in triplicate.



[3H]Mepyramine

[3H]-(—)-trans-H2-PAT
H1R: pKi
D107A + F432A
H1R: pKi
D107A + F432A

pKi
nH
pKi
nH
Histamine 4.1 ± 0.1 4.2 ± 0.1 -0.8 ± 0.1 4.1 ± 0.1 4.5 ± 0.1 -0.9 ± 0.1
Mepyramine 8.7 ± 0.1 8.0 ± 0.1 -1.1 ± 0.1 8.1 ± 0.1 6.3 ± 0.1 -0.5 ± 0.1
(—)-trans-H2-PAT 8.8 ± 0.2 8.5 ± 0.2 -0.8 ± 0.2 8.2 ± 0.1 7.3 ± 0.1 -1.0 ± 0.1
(R)-Cetirizine 7.8 ± 0.1 7.6 ± 0.1 -1.1 ± 0.1 7.5 ± 0.1 6.9 ± 0.1 -1.0 ± 0.1
(S)-Cetirizine
6.8 ± 0.1
6.3 ± 0.1
-1.1 ± 0.1
6.4 ± 0.1
5.6 ± 0.1
-1.2 ± 0.1