title: Characterization of transient outward K+ current and ultra-rapid delayed rectifier K+ current in isolated human atrial myocytes from patients with congestive heart failure.
abstract: OBJECTIVE
  To study the properties of transient outward K+ current (Ito) and ultra-rapid delayed rectifier K+ current (IKur) in isolated human atrial myocytes from patients with congestive heart failure (CHF).
  
  
  METHODS
  Single cells were isolated from CHF patients with collagenase and protease. Ito and IKur were recorded using whole cell patch-clamp technique.
  
  
  RESULTS
  The activation and inactivation of I(to) were voltage-dependent and time-dependent. The half-activation and half-inactivation voltage were (15 +/- 12) mV and (-45 +/- 4) mV respectively. When membrane potential went up from -40 mV to +60 mV, the activation time constant means decreased from (6.9 +/- 2.3) ms to (1.40 +/- 0.20) ms, while the inactivation time constant means decreased from (69 +/- 17) ms to (21 +/- 14) ms. Otherwise, the mean reactivation time constants was (125 +/- 65) ms when the membrane potential was held at -80 mV, but the recovery was not complete during the interval observed. Ito showed less frequency-dependent reduction at test frequency between 0.2-2 Hz. Compared with Ito, the activation of IKur only showed voltage-dependence, without time-dependence. Its mean current densities was (3.4 +/- 0.7) pA/pF when test potential was +60 mV. The half activation voltage of IKur was (23 +/- 14) mV. No clear frequency-dependence was observed at the same frequency range of Ito either.
  
  
  CONCLUSIONS
  I(to) and IKur are important outward potassium channel currents in isolated human atrial myocytes from CHF patients and they have different kinetic properties.
authors.affiliation: Department of Pharmacology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, China. xuzhengxin@yahoo.com
authors.forename: Zheng-Xin
authors.initials: ZX
authors.lastname: Xu
authors.forename: Man-Wen
authors.initials: MW
authors.lastname: Jin
mesh_terms: D000293:Adolescent; D000328:Adult; D002469:Cell Separation; D051668:Delayed Rectifier Potassium Channels; D006325:Heart Atria / Q000473:pathology; D006333:Heart Failure / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008875:Middle Aged; D032342:Muscle Cells / Q000378:metabolism* / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated
chemical_list: D051668:Delayed Rectifier Potassium Channels; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated