title: The role of K+ channels in vasorelaxation induced by hypoxia and the modulator effects of lidocaine in the rat carotid artery.
abstract: Hypoxia induces vasodilation, partly via the activation of K(+) channels. Lidocaine impairs vasorelaxation mediated by a K(+) channel opener, suggesting that this antiarrhythmic drug may inhibit hypoxia-induced vasodilation mediated by K(+) channels. We designed the current study to determine whether, in the carotid artery, K(+) channels contribute to vasorelaxation in response to hypoxia and whether lidocaine modulates vasorelaxation induced by K(+) channels via pathophysiological and pharmacological stimuli. Rings of rat common carotid artery without endothelium were suspended for isometric force recording. During contraction to phenylephrine, hypoxia-induced vasorelaxation or concentration-response to an adenosine triphosphate-sensitive K(+) channel opener was obtained changing control gas to hypoxic gas and the cumulative addition of levcromakalim, respectively. Hypoxia-induced vasorelaxation was significantly reduced by glibenclamide (5 micro M) but not by iberiotoxin (0.1 micro M), apamin (0.1 micro M), BaCl(2) (10 micro M), or 4-aminopyridine (1 mM). Levcromakalim-induced vasorelaxation was completely abolished by glibenclamide. Lidocaine (10-100 micro M) concentration-dependently inhibited this vasodilation, whereas it did not affect hypoxia-induced vasodilation. These results suggest that adenosine triphosphate-sensitive K(+) channels play a role in hypoxia-induced vasodilation in the rat carotid artery and that lidocaine differentially modulates vasodilation via these channels activated by pathophysiological and pharmacological stimuli.
  
  
  CONCLUSIONS
  In rat carotid artery, levcromakalim produced vasorelaxation mediated by adenosine triphosphate (ATP)-sensitive K(+) channels, whereas hypoxia induced it partly via these channels. Lidocaine inhibited vasorelaxation induced by an ATP-sensitive K(+) channel opener but not by hypoxia, indicating the differential mechanisms of modulatory effects of this antiarrhythmic drug on vasodilation via ATP-sensitive K(+) channels activated by pathophysiological and pharmacological stimuli.
authors.affiliation: *Department of Anesthesia, Japanese Red Cross Society, Wakayama Medical Center, and †Department of Anesthesiology, Wakayama Medical University, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kinoshita
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kimoto
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Nakahata
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iranami
authors.forename: Mayuko
authors.initials: M
authors.lastname: Dojo
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hatano
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D017536:Carotid Artery, Common / Q000187:drug effects / Q000503:physiopathology*; D019806:Cromakalim / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000494:pharmacology; D000860:Hypoxia / Q000503:physiopathology*; D066298:In Vitro Techniques; D008012:Lidocaine / Q000494:pharmacology*; D008297:Male; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D014665:Vasodilator Agents; D019806:Cromakalim; C064719:iberiotoxin; D000255:Adenosine Triphosphate; D008012:Lidocaine; D005905:Glyburide