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Effects of excessive noradrenaline on cardiac mitochondrial calcium transport and oxidative phosphorylation
Abstract:
Mitochondrial oxidative phosphorylation, calcium transport activity and calcium content were investigated in dog hearts injured by excessive noradrenaline (NA). Diffuse cardiac injury was produced by a 5-hour infusion of NA (2 or 5 micrograms/kg/min), and the injury was evaluated based on ECG and hemodynamic changes. Mitochondrial calcium uptake and binding activities measured in the presence of ATP showed no significant differences between the control and NA groups. However, the calcium content of heart mitochondria isolated from the NA groups, state 3 respiration and the respiratory control index were significantly depressed without any change in the ADP/O ratio. These results suggest that excessive NA causes the intracellular calcium overload and the depression of mitochondrial respiration, and the both of these changes may play a key role in the pathogenesis of myocardial injury through the insufficient control of cytosolic calcium levels.
Insights
Excessive noradrenaline (NA) causes heart injury by increasing intracellular calcium and impairing mitochondrial respiration. These changes are critical in the development of myocardial damage due to poor cytosolic calcium control.
Area of Science:
- Cardiovascular Physiology
- Mitochondrial Biology
- Biochemistry
Background:
- Excessive noradrenaline (NA) can lead to myocardial injury.
- Mitochondrial dysfunction is implicated in cardiac pathogenesis.
- Calcium homeostasis is crucial for cardiac function.
Purpose of the Study:
- To investigate the effects of excessive noradrenaline on mitochondrial function and calcium content in canine hearts.
- To evaluate the role of mitochondrial oxidative phosphorylation and calcium transport in NA-induced cardiac injury.
Main Methods:
- Induction of diffuse cardiac injury in dogs via a 5-hour infusion of noradrenaline (2 or 5 micrograms/kg/min).
- Evaluation of cardiac injury using electrocardiogram (ECG) and hemodynamic monitoring.
- Measurement of mitochondrial calcium uptake, binding, content, state 3 respiration, and respiratory control index (RCI).
- Assessment of ADP/O ratio to determine oxidative phosphorylation efficiency.
Main Results:
- No significant differences in mitochondrial calcium uptake and binding activities between control and NA groups.
- Significant depression in mitochondrial calcium content, state 3 respiration, and RCI in NA-treated groups.
- No alteration in the ADP/O ratio, indicating preserved phosphorylation efficiency despite impaired respiration.
Conclusions:
- Excessive noradrenaline leads to intracellular calcium overload and depressed mitochondrial respiration in the heart.
- These mitochondrial and calcium-related changes are key factors in the pathogenesis of myocardial injury.
- Impaired control of cytosolic calcium levels contributes significantly to NA-induced cardiac damage.