Re-examination of [3H]mepyramine binding assay for histamine H1 receptor using quinine. |
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| Authors: | Y Q Liu Y Horio H Mizuguchi K Fujimoto I Imamura Y Abe H Fukui |
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| Institution: | Department of Pharmacology II, Faculty of Medicine, Osaka University, Suita, Japan. |
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| Abstract: | 3H]Mepyramine, a potent antagonist of the histamine H1 receptor, has been widely used as a radioligand binding assay for the H1 receptor. Previously, we purified a mepyramine binding protein (MBP) from rat liver, but found that its partial amino acid sequences were very similar to those of debrisoquine 4-hydroxylase isozymes (P450 db1 and db2), which are members of the superfamily of cytochrome P450. Using cloned histamine H1 receptor cDNA, we found that 3H]mepyramine could bind only the H1 receptor and did not bind MBP in the presence of 10(-5) M quinine, an inhibitor of debrisoquine 4-hydroxylase isozymes. We developed a method to determine the contents of the H1 receptor and MBP separately using 3H]mepyramine and quinine and found that MBP is abundant in certain areas of bovine brain. |
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