Related Experiment Videos
Decreased sensitivity of neonatal rabbit sarcoplasmic reticulum to anthracycline cardiotoxicity
Brian E Burke1, Phillip S Mushlin, Barry J Cusack
1Medical Research Service, Department of Veterans Affairs Medical Center, Boise, ID 83702, USA. drq10@iglide.net
Abstract:
Anthracyclines are useful chemotherapeutic agents whose utility is limited by the development of irreversible cardiotoxicity. When tested, the pediatric population demonstrates an increased sensitivity to the cardiotoxicity of this class of agents, although the reasons for this increased sensitivity are unclear. The sarcoplasmic reticulum (SR) is a target for anthracycline cardiotoxicity in adults, but the effects of anthracycline on the SR in developing myocardium have not been examined. It may be possible to gain insight into the mechanisms of cardiotoxicity through a comparative approach. We compared the acute effects of doxorubicin, daunorubicin, and caffeine on contractile function in adult and neonatal rabbit myocardium. Frequency-dependent contractility, 90% relaxation times, and postrest potentiated contractions (a uniquely SR-dependent phenomenon) in adult myocardium were inhibited in a concentration- dependent manner. Neonatal myocardium, however, was resistant to the effects of these agents. The degree of contractile dysfunction was consistent with the difference in SR maturation between adult and developing myocardium. Anthracyclines exhibited effects similar to those of caffeine, an agent known to render the SR nonfunctional by the depletion of the releasable SR calcium pool. These results suggest that anthracyclines induce acute cardiac lesions through effects on the SR in adults, whereas cardiotoxic effects in the developing myocardium may proceed by a different mechanism.
Insights
Pediatric patients show increased sensitivity to anthracycline cardiotoxicity. This study found neonatal rabbit hearts resistant to anthracyclines, suggesting different mechanisms of cardiac damage in developing versus adult hearts.
Area of Science:
- Cardiovascular Pharmacology
- Pediatric Oncology
- Molecular Cardiology
Background:
- Anthracyclines are vital chemotherapy drugs, but their use is limited by cardiotoxicity.
- Pediatric patients exhibit heightened sensitivity to anthracycline-induced cardiotoxicity, with underlying mechanisms remaining unclear.
- The sarcoplasmic reticulum (SR) is implicated in adult anthracycline cardiotoxicity, but its role in developing myocardium is unexamined.
Purpose of the Study:
- To investigate the acute effects of anthracyclines on cardiac contractility in adult and neonatal rabbit models.
- To compare the impact of anthracyclines on sarcoplasmic reticulum (SR) function in developing versus mature myocardium.
- To elucidate potential differences in mechanisms of cardiotoxicity between pediatric and adult populations.
Main Methods:
- Compared acute effects of doxorubicin, daunorubicin, and caffeine on contractile function in adult and neonatal rabbit myocardium.
- Assessed concentration-dependent inhibition of frequency-dependent contractility, relaxation times, and post-rest potentiation.
- Evaluated the role of sarcoplasmic reticulum (SR) calcium stores and function.
Main Results:
- Adult myocardium showed concentration-dependent inhibition of contractile function and impaired SR function with anthracyclines and caffeine.
- Neonatal myocardium demonstrated resistance to the acute cardiotoxic effects of anthracyclines and caffeine.
- Contractile dysfunction correlated with differences in SR maturation between adult and neonatal hearts.
Conclusions:
- Anthracyclines induce acute cardiac lesions in adults via effects on the sarcoplasmic reticulum (SR).
- Developing myocardium appears resistant to anthracycline-induced SR dysfunction, suggesting alternative mechanisms for cardiotoxicity.
- Findings highlight potential age-dependent differences in anthracycline cardiotoxicity mechanisms, crucial for pediatric treatment strategies.