Related Experiment Videos
Potassium channel blocker dofetilide does not abolish ischaemic preconditioning
J Munch-Ellingsen1, E Bugge, J E Løkebø
1Department of Medical Physiology, University of Tromsø, Norway.
Scandinavian Journal of Clinical and Laboratory Investigation
|February 1, 1997
Summary
Ischaemic preconditioning (IP) protects the heart from infarcts. Blocking potassium channels with dofetilide during IP did not abolish this protective effect in a rabbit model.
Area of Science:
- Cardiology
- Pharmacology
- Physiology
Background:
- Ischaemic preconditioning (IP) is a potent mechanism for reducing heart infarct size.
- Enhanced K+ conductance and shortened action potential duration are proposed mechanisms for IP's infarct-reducing effects.
- The role of potassium channels in IP requires further investigation.
Purpose of the Study:
- To investigate if the potassium channel blocker dofetilide abolishes ischaemic preconditioning in an in situ rabbit heart infarct model.
- To determine the effect of dofetilide on action potential duration and heart rate in rabbits.
- To assess the impact of dofetilide administration on infarct size following IP.
Main Methods:
- Anesthetized, open-chest rabbits were used in an in situ heart infarct model.
- Regional ischemia (30 min) and reperfusion (180 min) were induced.
- Ischaemic risk zone was determined by fluorescent particles, and infarct size by TTC staining.
- Three groups were studied: control, IP, and IP with dofetilide (IPdof).
- The IP protocol involved 5 min ischemia and 10 min reperfusion.
- Dofetilide (20 µg/kg IV) was administered during the early reperfusion phase of the preconditioning protocol.
Main Results:
- Dofetilide significantly increased monophasic action potential duration (149.2 to 215.8 ms), confirming delayed rectifier potassium channel blockade.
- Heart rate decreased from 255.5 to 230.3 bpm after dofetilide administration.
- Infarct size as a percentage of the risk zone was 42.4% in controls, 7.6% in the IP group, and 12.3% in the IPdof group.
- The reduction in infarct size by IP was statistically significant compared to controls (p < 0.05).
Conclusions:
- The potassium channel-blocking agent dofetilide, administered after preconditioning ischemia but before sustained ischemia, does not abolish ischaemic preconditioning.
- These findings suggest that blockade of the delayed rectifier potassium channel during the early reperfusion phase of preconditioning does not negate its infarct-limiting effects.
- Further research is needed to fully elucidate the complex mechanisms underlying ischaemic preconditioning and the role of specific potassium channels.