title: Characterization of muscarinic cholinergic receptor subtypes in human peripheral lung.
abstract: The authors have characterized the muscarinic cholinergic receptor subtypes in human peripheral lung membranes using the selective muscarinic antagonist [3H]pirenzepine [( 3H]PZ) and the classical muscarinic antagonist [3H](-)-quinuclidinyl benzilate. High-affinity binding with pharmacologic specificity was demonstrated for both radioligands. The high affinity Kd for [3H]PZ binding determined from saturation isotherms was 5.6 nM, and the Kd for [3H](-)-quinuclidinyl benzilate binding was 14.3 pM. Approximately 62% of the total muscarinic binding sites in human peripheral lung bind [3H]PZ with high affinity. There was no significant effect of the guanine nucleotide, guanyl-5'-yl imidodiphosphate, on the inhibition of [3H](-)-quinyclidinyl benzilate binding by the muscarinic agonist carbachol in peripheral lung membranes. If the muscarinic receptor with high affinity for PZ has an important role in bronchoconstriction, its characterization could result in the development of more selective bronchodilators.
authors.affiliation: Department of Internal Medicine, University of Arizona College of Medicine, Tucson.
authors.forename: J W
authors.initials: JW
authors.lastname: Bloom
authors.forename: M
authors.initials: M
authors.lastname: Halonen
authors.forename: H I
authors.initials: HI
authors.lastname: Yamamura
mesh_terms: D000328:Adult; D004305:Dose-Response Relationship, Drug; D005260:Female; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D010276:Parasympatholytics / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology; D010890:Pirenzepine / Q000378:metabolism / Q000494:pharmacology; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000032:analysis*; D013045:Species Specificity; D014316:Tritium
chemical_list: D010276:Parasympatholytics; D010277:Parasympathomimetics; D011976:Receptors, Muscarinic; D014316:Tritium; D006165:Guanylyl Imidodiphosphate; D010890:Pirenzepine; D011813:Quinuclidinyl Benzilate