title: Endothelium-dependent relaxation by tetraoctylammonium ions in rat isolated aortic rings.
abstract: Quaternary ammonium ions are common pharmacological blockers of K+ channels. This study examined the vasorelaxant effect of tetraoctylammonium ions (TOA+) in rat isolated aortic rings. TOA+ caused a concentration-dependent transient relaxation of endothelium-intact tissues. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME, 3x10(-5) M) or methylene blue (3 x 10(-6) M) or removal of the endothelium abolished the TOA+-induced relaxation. L-arginine (10(-3) M ) partially antagonized the effect of L-NAME. Glibenclamide (3x10(-6) M), charybdotoxin (CTX, 10(-7) M), indomethacin (10(-5) M), or atropine (3x10(-6) M) had no effect. Both TOA+ (10(-5) M)- and acetylcholine (ACh, 10(-5) M)-induced increase in tissue content of cyclic GMP was significantly attenuated by NG-nitro-L-arginine (L-NNA, 10(-4) M) and abolished in endothelium-denuded arteries. These results indicate that TOA+ induced endothelium-dependent relaxation which is likely mediated through nitric oxide but not other endothelium-derived factors. This relaxant action seems unique for TOA+ since other quaternary ammonium ions did not cause nitric oxide-dependent relaxation.
authors.affiliation: Department of Physiology, Chinese University of Hong Kong, Shatin.
authors.forename: X
authors.initials: X
authors.lastname: Yao
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
mesh_terms: D000818:Animals; D001011:Aorta; D006152:Cyclic GMP / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D026902:Potassium Channel Blockers; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D026902:Potassium Channel Blockers; D000644:Quaternary Ammonium Compounds; D014665:Vasodilator Agents; D009569:Nitric Oxide; C027435:tetrapentylammonium; D006152:Cyclic GMP