Calcium ion in cardiac contractility

Under physiological conditions where the intracellular Ca ion concentration does not exceed 3 X 10(-6) M, the sarcoplasmic reticulum plays a major role in the relaxation process of cardiac muscle; mitochondria do not take up a significant amount of Ca ion during this process. If cardiac muscle under...

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Bibliographic Details
Published inRecent advances in studies on cardiac structure and metabolism Vol. 11; p. 93
Main Authors Ebashi, S, Kitazawa, T, Kohama, K, Van Eerd, P C
Format Journal Article
LanguageEnglish
Published United States 26.05.1976
Subjects
Animals
Biological Transport, Active
Calcium - metabolism
Cations, Divalent
Hydrogen-Ion Concentration
Kinetics
Mitochondria, Heart - physiology
Muscles - metabolism
Myocardial Contraction - drug effects
Myocardium - metabolism
Protein Binding
Sarcoplasmic Reticulum - physiology
Troponin - metabolism
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Summary:Under physiological conditions where the intracellular Ca ion concentration does not exceed 3 X 10(-6) M, the sarcoplasmic reticulum plays a major role in the relaxation process of cardiac muscle; mitochondria do not take up a significant amount of Ca ion during this process. If cardiac muscle undergoes maximum contraction, in which the intracellular Ca ion concentration should reach 10(-4) M, the role of mitochondria in reducing intracellular Ca ion becomes appreciable. The relationship of the tension developed by cardiac glycerinated muscle fibers to the Ca ion concentration resembles the relationship of the amount of bound Ca of cardiac troponin to the Ca ion concentrations, being less steep in its slope compared with those of fast and slow skeletal muscles. This gentle slope seems to reflect the great diversity of affinities for Ca ion of the two Ca-binding sites of cardiac troponin, one being about 100 times that of the other.
ISSN:0363-5872