title: [Regulating effects of delayed rectifier potassium channel on the tone of human passively sensitized bronchial smooth muscle].
abstract: OBJECTIVE
  To investigate the role of delayed rectifier K+ channel (Kv), Ca2+ -activated K+ channel (K(Ca)) and ATP-sensitive K+ channel (K(ATP)) in the regulation of the resting and contracting tone of human control and passively sensitized bronchial smooth muscle (BSM).
  
  
  METHODS
  The regulating effects of the three K+ channels on the tone of human BSM (HBSM) were observed by measuring the isometric tone of bronchial rings in vitro.
  
  
  RESULTS
  (1) The contraction of passively sensitized bronchial ring was significantly increased by histamine. (2) Kv blocker 4-aminopyridine (4-AP) caused concentration dependent contraction in resting bronchial rings of two groups, and the contraction sensitivity of the sensitized group rings was significantly stronger than that of control, that is, the negative logarithm of the drug concentration causing 50% of maximal effect (pD2) of the sensitized group rings were significantly larger than that of control rings, but there was no difference in the maximal effect (Emax) of two groups; Kca blocker tetraethylammonium (TEA) and K(ATP) blocker glibenclamide (Glib) had no such effects as those of 4-AP. (3) After pretreatment with 4-AP, the contraction of the control rings could significantly increased by histamine. After 4-AP treatment the Emax was significantly larger than that before 4-AP treatment. But the sensitized group rings had no such change, there was no significant difference in Emax before and after 4-AP treatment.
  
  
  CONCLUSIONS
  (1) Not K(Ca) and K(ATP) but Kv participated in regulation of the resting tone of HBSM. (2) The activity of Kv decreased in bronchial smooth muscle passively sensitized by asthmatic serum compared with that of nonsensitized group. This change might be involved in the mechanism of asthma.
authors.affiliation: Department of Respiratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Li-min
authors.initials: LM
authors.lastname: Zhao
authors.forename: Yong-jian
authors.initials: YJ
authors.lastname: Xu
authors.forename: Zhen-xiang
authors.initials: ZX
authors.lastname: Zhang
authors.forename: Dong-jun
authors.initials: DJ
authors.lastname: Cheng
authors.forename: Wang
authors.initials: W
authors.lastname: Ni
mesh_terms: D001249:Asthma / Q000378:metabolism / Q000503:physiopathology; D001980:Bronchi / Q000502:physiology; D051668:Delayed Rectifier Potassium Channels / Q000502:physiology*; D005260:Female; D006801:Humans; D007106:Immune Sera; D007116:Immunization, Passive; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009129:Muscle Tonus; D009130:Muscle, Smooth / Q000502:physiology*
chemical_list: D051668:Delayed Rectifier Potassium Channels; D007106:Immune Sera