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Ischemic preconditioning protects against infarction in rat heart
1Department of Physiology, University of South Alabama, Mobile 36688.
The American Journal of Physiology
|October 1, 1992
Summary
Ischemic preconditioning significantly reduces heart attack size in rats. This protective effect was not blocked by adenosine receptor or ATP-sensitive potassium channel blockers, suggesting a complex underlying mechanism.
Area of Science:
- Cardiology
- Physiology
- Biochemistry
Background:
- Ischemic preconditioning (IP) is a phenomenon where brief episodes of ischemia protect the heart against subsequent longer ischemic events.
- The precise molecular mechanisms underlying IP, particularly the roles of adenosine and ATP-sensitive potassium channels, remain incompletely understood.
Purpose of the Study:
- To investigate the anti-infarct effect of ischemic preconditioning in a rat heart model.
- To explore the involvement of adenosine receptors and ATP-sensitive potassium channels in mediating the protective effects of preconditioning.
Main Methods:
- Rat hearts were subjected to 30 minutes of regional coronary ischemia followed by 2 hours of reperfusion.
- Infarct size was quantified using tetrazolium staining.
- Pharmacological agents, including an adenosine receptor blocker (PD 115,199) and an ATP-sensitive potassium channel blocker (glibenclamide), were used to assess their impact on preconditioning-induced protection.
- An adenosine A1-receptor agonist (2-chloro-N6-cyclopentyladenosine) was administered to evaluate its protective potential.
Main Results:
- Three cycles of 5-minute preconditioning ischemia significantly reduced infarct size from 31% in control hearts to 3.7%.
- Neither PD 115,199 nor glibenclamide could block the anti-infarct protection afforded by preconditioning.
- Intracoronary administration of an adenosine A1-receptor agonist provided significant anti-infarct protection.
- A single 5-minute preconditioning cycle did not reduce infarct size but did attenuate arrhythmias.
Conclusions:
- The rat heart can be preconditioned, indicating that mitochondrial adenosinetriphosphatase is unlikely to be the sole mechanism.
- The threshold for achieving preconditioning protection appears higher in rats compared to rabbits or dogs.
- Adenosine plays a partially supported role in preconditioning, while ATP-sensitive potassium channels do not appear to be involved.