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Sodium-free contractures in frog myocardium damaged by catecholamines
R Volkmann1, A Carlsten, S Winell
1Department of Clinical Physiology, University of Göteborg, Sweden.
Summary
Frog heart muscle damaged by catecholamines resists sodium-free contractures, indicating intact sodium-calcium exchange. Cell injury does not impair this vital ion transport mechanism.
Area of Science:
- Cardiology
- Cell Physiology
- Pharmacology
Background:
- Catecholamines like adrenaline and isoproterenol can damage heart muscle.
- Sodium-calcium exchange is crucial for maintaining cellular ion balance in the heart.
Purpose of the Study:
- To investigate the effect of catecholamine-induced myocardial damage on sodium-free contractures in frog hearts.
- To determine if cell injury impacts sarcolemmal sodium-calcium exchange and calcium leakage.
Main Methods:
- Myocardial strips from Rana pipiens were subjected to sodium-free solutions with varying extracellular calcium (Ca2+o).
- Normal myocardium was compared to tissue damaged by in vivo adrenaline (ADR) or isoproterenol (ISO) injections.
- Potassium cyanide (KCN) was added to assess contractures in Na+/Ca2+-free solutions.
Main Results:
- Frog myocardium damaged by catecholamines remained relaxed in Na+/Ca2+-free solutions, with minimal contractures observed.
- Addition of KCN induced small contractures in damaged myocardium in Na+/Ca2+-free solutions.
- The time to maximum sodium-free contractures depended on Ca2+o but was unaffected by catecholamine-induced damage.
Conclusions:
- Cell injury in frog hearts from catecholamine injections does not impair sarcolemmal sodium-calcium exchange.
- The observed results suggest that catecholamine-induced cell damage is not associated with passive calcium leakage into the intracellular space.