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Cellular compartmentation in ischemic myocardium: indirect analysis by electron probe.
1Department of Physiology, School of Medicine, University of California, Los Angeles 90024.
The American Journal of Physiology
|October 1, 1988
Summary
Electron probe microanalysis revealed that myocardial sarcoplasmic reticulum (SR) calcium stores are stable during ischemia but significantly decrease upon reperfusion, indicating altered SR function.
Area of Science:
- Biochemistry
- Cell Biology
- Cardiovascular Science
Background:
- Myocardial calcium handling is critical for cardiac function.
- Ischemia-reperfusion injury significantly impacts cellular calcium balance.
- The sarcoplasmic reticulum (SR) plays a key role in regulating intracellular calcium.
Purpose of the Study:
- To quantify calcium distribution within myocardial cells using electron probe microanalysis (EPMA).
- To investigate changes in subcellular calcium compartments, particularly the SR, during ischemia and reperfusion.
- To elucidate the role of SR calcium content in myocardial response to ischemic events.
Main Methods:
- Direct EPMA of myocardial cells, myofibrils, and mitochondria.
- Indirect measurement of calcium within the sarcoplasmic reticulum (SR) compartment.
- Calculation of SR calcium content by subtracting myofibril and mitochondrial data from total cell calcium.
- Quantification of other elements in control, ischemic, and reperfused myocardium.
Main Results:
- SR calcium content remained largely unchanged during global ischemia.
- A marked depletion of SR calcium was observed after 5 minutes of reperfusion.
- Other elemental compositions were also quantified across different conditions.
Conclusions:
- The sarcoplasmic reticulum (SR) is not significantly depleted of calcium during global ischemia.
- Reperfusion triggers a significant loss of calcium from the SR.
- These findings suggest that altered SR function contributes to myocardial dysfunction during reperfusion.