Effects of diltiazem and nifedipine on transient outward and ultra-rapid delayed rectifier potassium currents in human atrial myocytes

Br J Pharmacol. 2005 Feb;144(4):595-604. doi: 10.1038/sj.bjp.0706113.


1. It is unknown whether the widely used L-type Ca(2+) channel antagonists diltiazem and nifedipine would block the repolarization K(+) currents, transient outward current (I(to1)) and ultra-rapid delayed rectifier K(+) current (I(Kur)), in human atrium. The present study was to determine the effects of diltiazem and nifedipine on I(to1) and I(Kur) in human atrial myocytes with whole-cell patch-clamp technique. 2. It was found that diltiazem substantially inhibited I(to1) in a concentration-dependent manner, with an IC(50) of 29.2+/-2.4 microM, and nifedipine showed a similar effect (IC(50)=26.8+/-2.1 muM). The two drugs had no effect on voltage-dependent kinetics of the current; however, they accelerated I(to1) inactivation significantly, suggesting an open channel block. 3. In addition, diltiazem and nifedipine suppressed I(Kur) in a concentration-dependent manner (at +50 mV, IC(50)=11.2+/-0.9 and 8.2+/-0.8 microM, respectively). These results indicate that the Ca(2+) channel blockers diltiazem and nifedipine substantially inhibit I(to1) and I(Kur) in human atrial myocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium Channel Blockers / pharmacology*
  • Calcium Channels, L-Type / metabolism
  • Cells, Cultured
  • Delayed Rectifier Potassium Channels
  • Diltiazem / pharmacology*
  • Heart Atria / cytology
  • Heart Atria / drug effects
  • Heart Atria / metabolism
  • Humans
  • Middle Aged
  • Myocytes, Cardiac / drug effects*
  • Myocytes, Cardiac / metabolism
  • Nifedipine / pharmacology*
  • Patch-Clamp Techniques
  • Potassium Channels, Tandem Pore Domain / antagonists & inhibitors*
  • Potassium Channels, Voltage-Gated / antagonists & inhibitors*


  • Calcium Channel Blockers
  • Calcium Channels, L-Type
  • Delayed Rectifier Potassium Channels
  • Potassium Channels, Tandem Pore Domain
  • Potassium Channels, Voltage-Gated
  • Diltiazem
  • Nifedipine