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Acute extracellular magnesium deficiency and myocardial tolerance to ischemia
Abstract:
The present study was undertaken in order to assess the effects of an acute and purely extracellular depletion of Mg during subtotal global ischemia and/or during post-ischemic reperfusion in the isolated rat heart. Mg depletion during reperfusion only or during ischemia plus reperfusion induced a significant reduction in post-ischemic recovery of cardiac function. Mg depletion during ischemia alone induced only a minor reduction in inotropy and coronary flow. Myocardial ATP at the end of the experiment was lowered in the groups of hearts deprived of Mg during ischemia plus reperfusion or during reperfusion only. A secondary finding was the demonstration of positive chronotropic and negative inotropic effects of the removal of extracellular Mg in non-ischemic hearts. It is concluded that, in a minor to moderate ischemic injury as in the present study, acute removal of extracellular Mg may lead to impairment of post-ischemic cardiac function and metabolism.
Insights
Acute extracellular magnesium (Mg) depletion impairs post-ischemic cardiac function and metabolism in isolated rat hearts. This Mg deficiency during reperfusion significantly reduces cardiac recovery and myocardial ATP levels.
Area of Science:
- Cardiology
- Biochemistry
- Physiology
Background:
- Extracellular magnesium (Mg) plays a crucial role in cardiac function.
- Understanding Mg's impact during ischemia and reperfusion is vital for cardiac protection strategies.
Purpose of the Study:
- To assess the effects of acute extracellular Mg depletion on cardiac function and metabolism during ischemia and reperfusion in an isolated rat heart model.
- To determine if Mg depletion during ischemia, reperfusion, or both phases impacts recovery.
Main Methods:
- Isolated rat hearts were subjected to subtotal global ischemia and reperfusion.
- Extracellular Mg levels were acutely depleted during specific phases (ischemia, reperfusion, or both).
- Cardiac function (inotropy, chronotropy, coronary flow) and myocardial ATP levels were measured.
Main Results:
- Mg depletion during reperfusion, or during both ischemia and reperfusion, significantly reduced post-ischemic cardiac function recovery.
- Mg depletion during ischemia alone had minimal effects on inotropy and coronary flow.
- Myocardial ATP levels were decreased in hearts with Mg depletion during ischemia plus reperfusion or reperfusion only.
- Extracellular Mg removal induced positive chronotropic and negative inotropic effects in non-ischemic hearts.
Conclusions:
- Acute extracellular Mg depletion impairs post-ischemic cardiac function and metabolism, particularly when occurring during reperfusion.
- Mg's role is critical in maintaining cardiac function and energy metabolism following ischemic injury.
- These findings highlight the importance of maintaining adequate extracellular Mg levels for cardiac recovery after ischemia.