Advertisement

Variable Calcium Sensitivity of the Mammalian Cardiac Contractile System

  • Saul Winegrad
  • George McClellan
  • Andrea Weisberg
  • Steven Weindling
  • Lin Er Lin

Abstract

Activation of the contraction in cardiac muscle occurs as a result of a rise in the concentration of calcium in the immediate vicinity of the myofibrils. The sources of the calcium for this rise are the extracellular space and the sarcoplasmic reticulum. Within a specific range of concentration, in the vicinity of 1µ molar, the amount of force that is generated is dependent on the amplitude of the calcium concentration. The amplitude of the contraction, however, is also dependent on the affinity of the regulatory protein, troponin, for calcium. Developed force rises from zero to maximum with a change in concentration of calcium of approximately tenfold, but the specific concentration range at which this occurs is dependent upon the properties of troponin, in particular, the affinity of the calcium binding site on one of the three subunits of the regulatory protein. A change in the range of calcium concentration that initiates contraction as a result of modification of the calcium-binding characteristics of troponin can be considered an alteration in calcium sensitivity. This can occur without any change in maximum calcium activity (Figure 4-1).

Keywords

Sarcomere Length Calcium Sensitivity Cholinergic Stimulation Calcium Binding Site Contractile System 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Winegrad S (1971). Studies of cardiac muscle with a high permeability to calcium produced by treatment with ethylene diamine-tetraacetic acid. J Gen Physiol 58: 71–93.PubMedCrossRefGoogle Scholar
  2. 2.
    Fabiato A, Fabiato F (1979). Tension developed and intracellular free calcium concentration reached during the twitch of an isolated cardiac cell with closed sarcolemma. J Gen Physiol 74: 6a.Google Scholar
  3. 3.
    Robertson S, Johnson D, Holroyde M, et al (1982). The effect of troponin I phosphorylation on the Ca-binding properties of Ca-regulatory site of bovine cardiac troponin. J Biol Chem 257: 260–263.PubMedGoogle Scholar
  4. 4.
    Holroyde MJ, Bowe E, Solaro RJ (1979). Modification of calcium requirements for activation of cardiac myofibrillar ATPase by cAMP dependent phosphorylation. Biochim Biophys Acta 586: 63–69.CrossRefGoogle Scholar
  5. 5.
    Ray K, England P (1976). Phosphorylation of the inhibitory subunit of troponin and its effect on calcium dependence of cardiac myofibril adenosine triphosphatase, FEBS Lett 70: 11–17.PubMedCrossRefGoogle Scholar
  6. 6.
    Mope L, McClellan G, Winegrad S (1980). Calcium sensitivity of the contractile system and phosphorylation of troponin in hyperpermeable cardiac cells. J Gen Physiol 75: 271–282.PubMedCrossRefGoogle Scholar
  7. 7.
    McClellan G, Winegrad S (1978). The regulation of calcium sensitivity of the contractile system in mammalian cardiac muscle. J Gen Physiol 72: 734–764.CrossRefGoogle Scholar
  8. 8.
    Horowits R, Winegrad S (1983). Cholinergic regulation of calcium sensitivity in cardiac muscle. J Mol Cell Cardiol 16: 277–280.CrossRefGoogle Scholar
  9. 9.
    Huxley HE, Farugi AR, Kress M, et al (1982). Time resolved X-ray diffraction studies of the myosin layer-line reflections during muscle contraction. J Mol Biol 158: 637–684.PubMedCrossRefGoogle Scholar
  10. 10.
    Bremel R, Weber A (1972). Cooperation within actin filament in vertebrate skeletal muscle. Nature New Biology 238: 97–101.PubMedGoogle Scholar
  11. 11.
    Hibberd M, Jewell B (1982). Calcium and length dependent force production in rat ventricular muscle. J Physiol (Lond) 329: 527–540.Google Scholar
  12. 12.
    Fabiato A, Fabiato F (1978). Effects of pH on the myofilaments and the sarcoplasmic reticulum of skinned cells from cardiac and skeletal muscles. J Physiol (Lond) 276: 233–255.Google Scholar
  13. 13.
    Kentish J (1986). The effects of inorganic phosphate and creatine phosphate on force production in skinned muscles from rat ventricle. J Physiol 370: 585–604.PubMedGoogle Scholar

Copyright information

© Martinus Nijhoff Publishing 1987

Authors and Affiliations

  • Saul Winegrad
  • George McClellan
  • Andrea Weisberg
  • Steven Weindling
  • Lin Er Lin

There are no affiliations available

Personalised recommendations