title: Characteristics of transient outward K+ current in human atrial cardiomyocytes.
abstract: OBJECTIVE
  To study the properties of transient outward potassium current (Ito) in human atrial myocytes.
  
  
  METHODS
  The patch-clamp whole-cell recording techniques were used. When the calcium inward current was blocked by CdCl2 (0.1 mmol.L-1), the transient outward potassium current (Ito) was recorded by depolarizing cells.
  
  
  RESULTS
  The current was voltage dependent, it was activated quickly and inactivated rapidly too. 4-Aminopyridine (4-AP) 10 mmol.L-1 (a selective blocker of Ito) blocked the current completely. The IC50 (95% confidence limits) of 4-AP on Ito were 0.67 (0.58-0.80) mmol.L-1, 4-AP 1 mmol.L-1 shifted the activation curve of Ito to positive potential, therefore a higher membrane potential was required to activate Ito.
  
  
  CONCLUSIONS
  Ito, a major K+ channel current in human atrial cells, is blocked by 4-AP.
authors.affiliation: Department of Pharmacology, Peking Union Medical College, Beijing, China.
authors.forename: W H
authors.initials: WH
authors.lastname: Xu
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: H W
authors.initials: HW
authors.lastname: Yue
authors.forename: X L
authors.initials: XL
authors.lastname: Wang
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology*; D006325:Heart Atria / Q000166:cytology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects*
chemical_list: D015221:Potassium Channels; D015761:4-Aminopyridine