The two components in the shortening of unloaded ventricular myocytes: Their voltage dependence

  • G. Isenberg
  • A. Beresewicz
  • D. Mascher
  • F. Valenzuela
Conference paper

Summary

In isolated myocytes from mammalian ventricles a fast and a slow component in the contractile response to depolarizing voltage clamp steps were identified. The potential dependence of the slow component was identical to the activation curve of iCa. The fast component, however, remained at its maximal amplitude at potentials positive to + 10 mV (up to + 100 mV), in which potential range iCa declined and eventually disappeared. The results suggest that the slow component may be activated by Ca + + entering through sarcolemmal Ca channels, whereas the fast component depends on Ca release from intracellular sites and may depend on both Cai and voltage.

Key words

contraction calcium electro-mechanical coupling sarcomere length isotonic contraction 

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References

  1. 1.
    Beeler GW, Reuter H (1970): The relation between membrane potential, membrane currents and activation of contraction in ventricular myocardial fibres. J Physiol 207: 211–229PubMedGoogle Scholar
  2. 2.
    Chapman RA (1983): Control of cardiac contractility at the cellular level. Am J Physiol H535 — H552Google Scholar
  3. 3.
    DeClerck NM, Claes VA, Brutssaert DL (1977): Force velocity relations of single cardiac muscle cells. J Gen Physiol 69: 221–241CrossRefGoogle Scholar
  4. 4.
    Endo M (1977): Calcium release from the sarcoplasmic reticulum. Physiol Rev 57: 71–108PubMedGoogle Scholar
  5. 5.
    Fabiato A (1983): Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum. Am J Physiol 245: Cl—C14Google Scholar
  6. 6.
    Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ (1981): Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflügers Arch 391: 85–100PubMedCrossRefGoogle Scholar
  7. 7.
    Isenberg G (1982): Ca entry and contraction as studied in isolated bovine ventricular myocytes. Z Naturforsch 37c: 502–512Google Scholar
  8. 8.
    Isenberg G, Klöckner U (1982): Calcium tolerant ventricular myocytes prepared by preincubation in a “KB medium”. Pflügers Arch 395: 6–18PubMedCrossRefGoogle Scholar
  9. 9.
    Isenberg G, Klöckner U (1982): Calcium currents of isolated bovine ventricular myocytes are fast and of large amplitude. Pflüglers Arch 395: 30–41CrossRefGoogle Scholar
  10. 10.
    King BW, Bose D (1983): Mechanism of biphasic contractions in strontium-treated ventricular muscle. Circ Res 52: 65–75PubMedCrossRefGoogle Scholar
  11. 11.
    Mascher D, Cruz A (1980): Electrical and mechanical responses of the guinea-pig ventricular muscle in the presence of histamine. XXVIII International Congress of Physiological Sciences. Budapest, 1980Google Scholar
  12. 12.
    Mullins LJ (1981): Ion transport in heart. Raven Press, New YorkGoogle Scholar
  13. 13.
    Reiter M, Vierling W, Seibel K (1984) Where is the origin of the activator calcium in cardiac ventricular contraction? Basic Res Cardiol 79: 1–8PubMedCrossRefGoogle Scholar
  14. 14.
    Reuter H, Scholz H (1977): A study of the ion selectivity and the kinetic properties of the calcium dependent slow inward current in mammalian cardiac muscle. J Physiol 264: 17–47PubMedGoogle Scholar
  15. 15.
    Tsien RW (1983): Calcium channels in excitable cell membranes. Ann Rev Physiol 45: 341–358CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1984

Authors and Affiliations

  • G. Isenberg
    • 2
  • A. Beresewicz
    • 1
  • D. Mascher
    • 1
  • F. Valenzuela
    • 1
  1. 1.II. Physiologisches InstitutUniversität des SaarlandesHomburgGermany
  2. 2.II. Physiologisches InstitutUniversität des SaarlandesHomburgGermany

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