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Catecholamines and preconditioning: studies of contraction and function in isolated rat hearts
1Cardiovascular Research, The King's Center for Cardiovascular Biology and Medicine, The Rayne Institute, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
The American Journal of Physiology
|July 17, 1999
Summary
Norepinephrine preconditioning, similar to ischemic preconditioning, paradoxically worsens heart muscle contracture during ischemia. This effect is stereospecific, with L-norepinephrine enhancing recovery, suggesting receptor-mediated protection.
Area of Science:
- Cardiology
- Pharmacology
- Physiology
Background:
- Ischemic preconditioning protects the heart from damage during ischemia.
- The role of norepinephrine in cardiac protection during ischemia is not fully understood.
Purpose of the Study:
- To investigate if norepinephrine exposure before ischemia exacerbates contracture, similar to ischemic preconditioning.
- To determine if the protective effects of norepinephrine are stereospecific, indicating receptor involvement.
Main Methods:
- Isolated perfused rat hearts were used.
- Five groups were studied: ischemic preconditioning, untreated control, vehicle control, d-norepinephrine, and l-norepinephrine.
- Hearts underwent 40 minutes of zero-flow ischemia followed by 50 minutes of reperfusion.
Main Results:
- Both ischemic preconditioning and l-norepinephrine significantly exacerbated contracture during ischemia compared to controls.
- Postischemic recovery of left ventricular developed pressure was significantly improved in the preconditioned and l-norepinephrine groups.
- D-norepinephrine did not offer protection and showed similar contracture to controls.
Conclusions:
- Norepinephrine preconditioning, like ischemic preconditioning, causes a paradoxical exacerbation of contracture.
- Enhanced postischemic recovery is stereospecific, with l-norepinephrine providing protection, suggesting a receptor-mediated mechanism.