Left: ab118174 ligand (100 nM) binding to CHO cells expressing histamine H1 receptors. Center: Binding to CHO-H1 cells blocked by the unlabelled competitor triprolidine (1 µM). Right: No binding of ab118174 to host CHO cells (not expressing H1 receptors). Nuclei have been counter-stained with Hoechst.
To determine the apparent KD for ab118174 at histamine H1 receptors, cells were treated with varying concentrations of histamine agonist alone, or in the presence of 1 µM ab118174, and the serum-induced expression of SPAP measured. The apparent KD at H1 was calculated from the rightward shift of the agonist response curve in the presence of ab118174, compared to the response curve for the agonist alone. KD value for H1 = 8.07 Antagonist –log KD values
The KD for ab118174 ligand was assessed using a recombinant CHO cell line expressing the Human H2 receptor and a cyclic AMP-responsive SPAP reporter gene. The apparent KD at H2 was calculated in the same way to that calculated for the Human H1 receptor. The KD value for H2 was found to be 5.37 Antagonist -log KD