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Stunning does not change the relation between calcium and force in skinned rat trabeculae
D L Dietrich1, G R van Leeuwen, G J Stienen
1Laboratory for Physiology, Free University, Amsterdam, The Netherlands.
Journal of Molecular and Cellular Cardiology
|May 1, 1993
Summary
Myocardial stunning after ischemia-reperfusion does not alter myofibril sensitivity to calcium. This study found no difference in force-calcium relations in stunned versus control heart muscle, suggesting other mechanisms are involved.
Area of Science:
- Cardiology
- Physiology
- Biochemistry
Background:
- Myocardial stunning is a post-ischemic dysfunction.
- The role of altered myofibril calcium sensitivity in stunning is debated.
Purpose of the Study:
- To investigate if myocardial stunning results from decreased myofibril sensitivity to calcium.
- To compare the isometric force-calcium relationship in stunned and control heart trabeculae.
Main Methods:
- Hearts underwent 40 minutes of ischemia followed by 30 minutes of reperfusion.
- Skinned trabeculae were isolated to determine the force-calcium relationship using the Hill equation.
- Control trabeculae were from aerobically perfused hearts.
Main Results:
- Left ventricular developed pressure significantly decreased in stunned hearts post-ischemia.
- Nucleotide content was reduced in stunned hearts, but creatine kinase levels remained similar.
- Maximal isometric force, force-calcium midpoint, and curve steepness were not significantly different between stunned and control trabeculae.
Conclusions:
- The contractile apparatus of stunned myocardium shows normal isometric force and calcium sensitivity.
- Structural changes in contractile proteins leading to reduced calcium sensitivity are unlikely to cause myocardial stunning.