Left: ab118175 ligand (30 nM) binding to CHO cells expressing histamine H2 receptors. Right: Binding blocked by the unlabelled competitor ranitidine (10 µM). Nuclei have been counter-stained with Hoechst.
To determine the apparent KD for ab118175 at histamine H2 receptor, cells were treated with varying concentrations of histamine agonist alone, or in the presence of 1 µM ab118175, and the cyclic AMP-induced expression of SPAP measured. The apparent KD at H2 was calculated from the rightward shift of the agonist response curve in the presence of ab118175, compared to the response curve for the agonist alone. KD value for H2 was found to be 8.94 Antagonist -log KD.
To determine the apparent KD for ab118175 at histamine H3 receptor, cells were treated with varying concentrations of histamine agonist alone, or in the presence of 1 µM ab118175, and the cyclic AMP-induced expression of SPAP measured. The apparent KD at H3 was calculated from the rightward shift of the agonist response curve in the presence of ab118175, compared to the response curve for the agonist alone. The KD for ab118175 was found to be 7.3 Antagonist-log KD