title: A possibility that the ATP-sensitive potassium channel in coronary artery has a high-affinity internal binding site for tetraalkylammonium.
abstract: The functionally responsible sites for the blocking action of tetraalkylammonium ions (TAAs) in ATP-sensitive K+ (KATP) channels opened by levcromakalim were estimated in canine coronary artery. Tetraethylammonium (TEA) and tetrabutylammonium (TBA) inhibited the levcromakalim-induced relaxation in a noncompetitive manner. Analyses of the noncompetitive antagonism revealed that the binding constant of TBA was about 900 times lower than that of TEA, although the reported affinity of TBA for the internal binding site in various K+ channels was only 10 times higher than that of TEA. TBA is much more lipid-soluble and permeable through membranes than TEA. Thus, TBA blocks KATP channels by binding to a possible high-affinity internal site for TAAs, whereas TEA seems to bind to the external site.
authors.affiliation: Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Orito
authors.forename: T
authors.initials: T
authors.lastname: Yanagisawa
authors.forename: N
authors.initials: N
authors.lastname: Taira
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001578:Benzopyrans / Q000037:antagonists & inhibitors / Q000494:pharmacology; D001665:Binding Sites; D003331:Coronary Vessels / Q000378:metabolism*; D019806:Cromakalim; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D015221:Potassium Channels / Q000378:metabolism*; D011758:Pyrroles / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism* / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D001578:Benzopyrans; D015221:Potassium Channels; D011758:Pyrroles; D000644:Quaternary Ammonium Compounds; D013757:Tetraethylammonium Compounds; D019806:Cromakalim; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate; C009405:tetrabutylammonium