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Ischemic cardioprotection by ATP-sensitive K+ channels involves high-energy phosphate preservation
C D McPherson1, G N Pierce, W C Cole
1Department of Physiology, St. Boniface Research Centre, University of Manitoba, Winnipeg, Canada.
The American Journal of Physiology
|November 1, 1993
Summary
Activation of ATP-sensitive potassium channels (KATP) preserves high-energy phosphates and reduces cardiac injury during ischemia. These channels indirectly protect the heart by altering electrical activity, suggesting additional cardioprotective mechanisms.
Area of Science:
- Cardiovascular Physiology
- Cellular Electrophysiology
- Mitochondrial Function
Background:
- ATP-sensitive potassium channels (KATP) are known to protect the myocardium against ischemia-reperfusion injury.
- The precise cellular mechanisms by which KATP activation influences ischemic injury remain incompletely understood.
- Investigating the link between KATP activity and high-energy phosphate preservation during ischemia is crucial for understanding cardioprotection.
Purpose of the Study:
- To investigate the relationship between KATP channel activation and the preservation of high-energy phosphates during global no-flow ischemia.
- To elucidate the role of KATP in modulating cellular electrical and mechanical activity during ischemic conditions.
- To determine the effects of KATP modulators (pinacidil and glibenclamide) on myocardial energy status and function.
Main Methods:
- Global no-flow ischemia was induced in arterially perfused guinea pig right ventricular walls.
- Electrical and mechanical activity were monitored using intracellular microelectrodes and a force transducer.
- KATP channels were modulated using pinacidil (activator) and glibenclamide (blocker); ATP and creatine phosphate (CP) levels were measured enzymatically.
Main Results:
- Pinacidil (10 microM) preserved high-energy phosphates, prevented ischemic contracture, and attenuated changes in action potential duration (APD) and contractile function.
- Glibenclamide (50 microM) blocked the protective effects of pinacidil on electromechanical function and energy preservation.
- Glibenclamide alone exacerbated APD shortening and contracture, leading to enhanced ATP and CP depletion during ischemia.
Conclusions:
- KATP channel activation indirectly preserves high-energy phosphates by modulating electrical activity, thereby reducing ischemic injury.
- The findings support a role for KATP channels in maintaining myocardial energy homeostasis during ischemia.
- Additional, yet undefined, mechanisms may contribute to the overall cardioprotective effects of KATP channels.