Specific binding of [3H]mepyramine to histamine H1-receptors in vascular smooth muscle membranes

The antagonist-sensitive binding of ³H]mepyramine to beef aortic membranes was as expected for binding to histamine H₁-receptors. ³H]mepyramine binds rapidly and in saturable fashion to the specific receptor sites, specific binding reaching equilibrium in 3 min at 37°CScatchard's analysis of the binding data gave a dissociation constant of 3.0 nM for the radioligand-receptor complex and maximal number of binding sites: 31 fmol/mg protein. In the competition studies histamine H₁-antagonists are more potent inhibitors of radioligand binding than H₂-antagonist. They inhibit ³H]mepyramine binding in the following order: mepyramine >triprolidine