title: [Investigation of regulating effects of potassium channels on the tone of rat bronchial smooth muscle].
abstract: OBJECTIVE
  To investigate the role of three K+ channels-delayed rectifier K+ channel (Kv), large-conductance Ca(2+)-activated K+ channel (BK(Ca)) and ATP-sensitive K+ channel (K(ATP)) in the regulation of the resting and contracting tone of rat bronchial smooth muscle (BSM).
  
  
  METHODS
  By measuring the isometric tone of bronchial strips in vitro, the regulating effects of the three K+ channels on the tone of rat BSM were observed.
  
  
  RESULTS
  (1) Kv blocker 4-aminopyridine (4-AP) caused concentration dependent contraction in resting bronchial strips, but BK(Ca) blocker tetraethylammonium (TEA) and K(ATP) blocker glibenclamide (Glib) had no such effects. (2) The bronchial epithelium had no effects on the contraction induced by 4-AP, but nifedipine, a Ca2+ channel blocker, significantly suppressed it. (3) Before or after treatment with 0.1 mmol/L histamine or 50 mmol/L KCl, administration of TEA (1 or 5 mmol/L) or 0.1 mmol/L 4-AP could significantly increase the contraction induced by histamine and KCl in bronchial strips. But Glib (10 micromol/L) had no effect on it.
  
  
  CONCLUSIONS
  Not BK(Ca) and K(ATP) but Kv participated in the regulation of the resting tone in rat BSM. The closure of BK(Ca) or Kv increased the contracting tone induced by histamine or KCl in rat BSM in vitro, but K(ATP) had no such effect on it.
authors.affiliation: Department of Respiratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Xian-Shen
authors.initials: XS
authors.lastname: Liu
authors.forename: Yong-Jian
authors.initials: YJ
authors.lastname: Xu
authors.forename: Zhen-Xiang
authors.initials: ZX
authors.lastname: Zhang
authors.forename: Chao-Qian
authors.initials: CQ
authors.lastname: Li
authors.forename: Dan-Lei
authors.initials: DL
authors.lastname: Yang
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001980:Bronchi / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015221:Potassium Channels; D015761:4-Aminopyridine