title: Antiarrhythmic drug carvedilol inhibits HERG potassium channels.
abstract: OBJECTIVE
  The aryloxypropanolamine carvedilol is a multiple action cardiovascular drug with blocking effects on alpha-receptors, beta-receptors, Ca(2+)-channels, Na(+)-channels and various native cardiac K(+) channels, thereby prolonging the cardiac action potential. In a number of clinical trials with patients suffering from congestive heart failure, carvedilol appeared to be superior to other beta-blocking agents in reducing total mortality. Given the multiple pharmacological actions of carvedilol, this may be due to specific channel blockade rather than beta-antagonistic activity. Since human ether-a-go-go related gene (HERG) K(+)channels play a critical role in the pathogenesis of cardiac arrhythmias and sudden cardiac death, the effects of carvedilol on HERG K(+)channels were investigated.
  
  
  METHODS
  Double-electrode voltage-clamp experiments were performed on HERG potassium channels which were expressed heterologously in Xenopus oocytes.
  
  
  RESULTS
  Carvedilol at a concentration of 10 microM blocked HERG potassium tail currents by 47%. The electrophysiological characteristics of HERG, i.e. activation, steady-state inactivation and recovery from inactivation were not affected by carvedilol. Inhibition of current gradually increased from 0% immediately after the test pulse to about 80% at 600 ms with subsequent marginal changes of current kinetics during the resting 29 s, indicating a very fast open channel block by carvedilol as the major blocking mechanism.
  
  
  CONCLUSIONS
  This is the first study demonstrating that carvedilol blocks HERG potassium channels. The biophysical data presented in this study with a potentially antiarrhythmic effect may contribute to the positive outcome of clinical trials with carvedilol.
authors.affiliation: 3rd Department of Internal Medicine (Cardiology), University of Heidelberg Medical School, Bergheimerstrasse 58, D-69115, Heidelberg, Germany.
authors.forename: C A
authors.initials: CA
authors.lastname: Karle
authors.forename: V A
authors.initials: VA
authors.lastname: Kreye
authors.forename: D
authors.initials: D
authors.lastname: Thomas
authors.forename: K
authors.initials: K
authors.lastname: Röckl
authors.forename: S
authors.initials: S
authors.lastname: Kathöfer
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Kiehn
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002227:Carbazoles / Q000494:pharmacology*; D000077261:Carvedilol; D027682:Cation Transport Proteins; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D009865:Oocytes / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011412:Propanolamines / Q000494:pharmacology*; D014981:Xenopus
chemical_list: D000889:Anti-Arrhythmia Agents; D002227:Carbazoles; D027682:Cation Transport Proteins; D051638:Ether-A-Go-Go Potassium Channels; C092509:KCNH6 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011412:Propanolamines; D000077261:Carvedilol