title: Adrenergic regulation of the rapid component of delayed rectifier K+ currents in guinea pig cardiomyocytes.
abstract: BACKGROUND
  Guinea pig ventricular cardiomyocytes display the rapid component of the delayed rectifier potassium current (Ikr) that contributes to ventricular repolarization and promotes stress-induced arrhythmias. Adrenergic stimulation favors ventricular arrhythmogenesis but its effects on Ikr are poorly understood.
  
  
  METHODS
  Adrenergic modulation of Ikr was studied in isolated guinea pig ventricular cardiomyocytes using whole-cell patch clamping.
  
  
  RESULTS
  We found that the Ikr amplitude was reduced to 0.66±0.02 and 0.62±0.03 in response to 0.1 µM phenylephrine (PE), an α1AR agonist, and 10 µM isoproterenol (ISO), a βAR agonist, respectively. The effect of PE can be blocked by the selective α1A-adrenoceptor antagonist 5-methylurapidil, but not by the α1B-adrenoceptor antagonist chloroethylclonidine or α1D-adrenoceptor antagonist BMY7378. Additionally, the effect of ISO can be blocked by the β1-selective AR antagonist CGP-20712A, but not by the β2-selective AR antagonist ICI-118551. Although PE and ISO was continuously added to cells, ISO did not decrease the current to a greater extent when cells were first given PE. In addition, PE's effect on Ikr was suppressed by β1AR stimulation.
  
  
  CONCLUSIONS
  Ikr can by regulated by both the α1 and β ARs system, and that in addition to direct regulation by each receptor system, crosstalk may exist between the two systems.
authors.affiliation: Department of Geriatric Cardiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China.
authors.forename: Sen
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Geriatric Cardiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Min
authors.affiliation: Department of Geriatric Cardiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China.
authors.forename: Si-Si
authors.initials: SS
authors.lastname: Pang
authors.affiliation: Department of Geriatric Cardiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Qian
authors.affiliation: Department of Geriatric Cardiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China.
authors.forename: Di
authors.initials: D
authors.lastname: Xu
authors.affiliation: Department of Geriatric Cardiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Guo
keywords: Adrenergic receptors (ARs); cardiomyocytes; crosstalk; potassium current