title: Purification of histamine receptor (VI). An improved double labeling method with "double protection".
abstract: Studies were done on the specific labeling of the histaminergic H1-receptor of the longitudinal smooth muscle of cat small intestine. A procedure involving 'double protection' combined with the double labeling technique was developed. The first protection was the usual with a protective antihistamine, promethazine, and the second was cross protection of non-specific sites with non-hitaminergic drugs, thioriazine and atropine. Muscle tissue protected with promethazine against non-radioactive dibenamine was treated with 3H-dibenamine in the presence of these second protectors. The second protectors covered non-receptor sites which had been protected from non-radioactive dibenamine with promethazine. The dose-response curves were carefully checked in each experiment to confirm that the second protectors did not interfere with the specific coverage provided by the first protector. Finally 14C-dibenamine was applied to measure non-specific binding after which the labeled muscles were fractionated and the radioactivity was counted. The specificity of labeling achieved in the receptor-rich fraction by this method is discussed.
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002415:Cats; D003983:Dibenzylchlorethamine / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000032:analysis; D011398:Promethazine / Q000494:pharmacology; D011968:Receptors, Histamine / Q000302:isolation & purification*; D011969:Receptors, Histamine H1 / Q000187:drug effects / Q000302:isolation & purification*; D013881:Thioridazine / Q000494:pharmacology
chemical_list: D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D003983:Dibenzylchlorethamine; D001285:Atropine; D011398:Promethazine; D013881:Thioridazine