Age-dependent changes in the effects of amiodarone on rabbit cardiac myocyte contractions

F. Chen, S. Naim, W. F. Friedman, T. S. Klitzner, G. T. Wetzel

Research output: Contribution to journalArticlepeer-review


Background: Intravenous amiodarone has increasingly been used to control life-threatening atrial and ventricular arrhythmias. In addition to its four antiarrhythmic properties, amiodarone may have complex effects on intracellular Ca2+ stores and myocyte contractility. Methods and Results: Contraction amplitude was recorded for cardiac ventricular myocytes isolated from neonatal and adult rabbits. Sarcoplasmic reticulum (SR) Ca2+ stores were loaded to steady-state levels by a train of eight electric field stimulations. The SR Ca2+ load was quantified by recording the contraction amplitude resulting from the complete depletion of SR Ca2+ stores by exposing the cell to a 1-second pulse of 10 mmol/L caffeine. After the cells were exposed to 1 μmol/L amiodarone for 10 minutes, electrically stimulated contraction amplitudes significantly decreased in both adult and neonatal cells. Caffeine-induced cell contraction amplitudes were not affected by amiodarone in adult ventricular myocytes. By contrast, amiodarone markedly inhibited caffeine-induced contractions in neonatal ventricular myocytes. The inhibitory effect of amiodarone on the caffeine-induced contractions was not replicated by Ca2+ channel blockade with diltiazem. Conclusions: Amiodarone markedly inhibits caffeine-induced contraction in neonatal myocytes but has no significant effect on adult myocytes. Ca2+ influx through amiodarone- sensitive Ca2+ channels may play a primary role in maintaining SR Ca2+ stores in neonatal heart.

Original languageEnglish (US)
Pages (from-to)23-32
Number of pages10
JournalJournal of Cardiovascular Pharmacology and Therapeutics
Issue number1
StatePublished - 1999
Externally publishedYes


  • Amiodarone
  • Antiarrhythmic agent
  • Arrhythmia
  • Ca channel blocker
  • Excitation- contraction coupling
  • Neonatal heart

ASJC Scopus subject areas

  • Pharmacology
  • Cardiology and Cardiovascular Medicine
  • Pharmacology (medical)


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