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Published on: July 25, 2019
Age-Dependent Changes in the Effects of Amiodarone on Rabbit Cardiac Myocyte Contractions
1School of Medicine, University of California at Los Angeles, Los Angeles, California, USA
Journal of Cardiovascular Pharmacology and Therapeutics
|February 23, 2000
Summary
Intravenous amiodarone impacts heart cell contractility differently in young and adult rabbits. Amiodarone significantly reduces contraction in neonatal cells but not adult cells, suggesting age-dependent effects on calcium handling.
Area of Science:
- Cardiology
- Pharmacology
- Cell Physiology
Background:
- Intravenous amiodarone is widely used for serious arrhythmias.
- Amiodarone's effects on intracellular calcium (Ca2+) and heart muscle contraction are complex.
- Its impact on cardiac myocytes requires further investigation.
Purpose of the Study:
- To investigate the effects of amiodarone on cardiac myocyte contractility and intracellular Ca2+ handling.
- To compare amiodarone's effects in neonatal versus adult rabbit ventricular myocytes.
Main Methods:
- Cardiac ventricular myocytes were isolated from neonatal and adult rabbits.
- Sarcoplasmic reticulum (SR) Ca2+ stores were loaded via electrical stimulation.
- SR Ca2+ load was quantified by caffeine-induced contractions after amiodarone exposure.
- Effects were compared with diltiazem (Ca2+ channel blockade).
Main Results:
- Amiodarone (1 µmol/L) significantly decreased electrically stimulated contraction amplitude in both neonatal and adult myocytes.
- Amiodarone did not affect caffeine-induced contractions in adult myocytes.
- Amiodarone markedly inhibited caffeine-induced contractions in neonatal myocytes.
- Diltiazem did not replicate amiodarone's inhibitory effect on neonatal contractions.
Conclusions:
- Amiodarone significantly inhibits caffeine-induced contractions in neonatal myocytes but not adult myocytes.
- Age-dependent differences in amiodarone's effects on cardiac contractility exist.
- Ca2+ influx via amiodarone-sensitive channels may be crucial for SR Ca2+ loading in neonatal hearts.
