Advertisement

The contribution of Ca++ ions to the current voltage relation in cardiac muscle (Purkinje fibers)

  • J. Dudel
  • K. Peper
  • W. Trautwein
Article

Summary

By a voltage clamp method in short Purkinje fibers membrane current was measured during stepwise or steady changes of membrane potential. The contribution of Ca++ to the total membrane current was investigated by measuring the effects of omission and increase of the extracellular Ca++. When Ca++ is omitted the transient current flowing after a depolarizing voltage step is little affected. However, after longer exposure to 0 Ca++ the membrane conductance increases throughout the potential range of −120 to +20 mV; furthermore the fiber depolarizes to about −30 mV. These effects of omission of Ca++ are the same in Tyrode and in sodium-free solutions using either choline chloride or saccharose. The high membrane conductance in 0 Ca++ is not due to an increase of the Na+, K+ or Cl conductance. All effects of Ca++ omission are reversible when Ca++ is readmitted. When extracellular Ca++ is increased to up to 108 mM/l no increase of a negative current is observed in the range of membrane potentials covered. There is no evidence of an increased flow of Ca++ ions. The shape of the action potentials in 0 Ca++ and 21.6 mM/l Ca++ is discussed in relation to the measured current voltage relationships. The experiments seem to exclude an appreciable contribution of Ca++ to the membrane current flowing during the action potential of the Purkinje fiber.

Keywords

Membrane Current Membrane Conductance Choline Chloride Current Voltage Purkinje Fiber 
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.

Zusammenfassung

An ca. 2 mm langen Purkinje-Fäden (Schaf) wurde das Membranpotential sprungweise oder stetig geändert und der dazu benötigte Membranstrom gemessen. Es wurde versucht, den etwaigen Anteil eines Calciumstromes am Membranstrom durch Weglassen oder drastische Erhöhung der extracellulären Calciumkonzentration zu ermitteln. Bei 0 Ca++ in der Außenlösung ändern sich bei einem Spannungssprung die phasischen Komponenten des Membranstroms kaum. Dagegen nimmt nach 20–60 min die Leitfähigkeit der Membran im Potentialbereich von −120 bis +20 mV zu, und die Faser depolarisiert auf einen Wert von etwa −30 mV. Diese Effekte treten in natriumhaltigen und natriumfreien Lösungen auf und sind bei Zugabe von Ca++ reversibel. Die hohe Membranleitfähigkeit in 0 Ca++ beruht nicht auf einer Erhöhung der Natrium-, Kalium- oder Chlorid-Leitfähigkeit. Bei Erhöhung des extracellulären Ca++ auf bis zu 108 mM/l tritt im untersuchten Spannungsbereich kein vergrößerter negativer Strom auf, ein vergrößerter Fluß von Calciumionen ist also nicht nachzuweisen. Die Veränderungen der Aktionspotentiale in 0 und 21,6 mM/l Ca++ werden an Hand der aufgenommenen Strom-Spannungsbeziehungen diskutiert. Die Versuche schließen eine wesentliche Beteiligung des Ca++ an den Ionenströmen aus, die während des Aktionspotentials der Purkinje-Fasern fließen.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Carmeliet, E.: Chloride ions and the membrane potential of Purkinje fibres. J. Physiol. (Lond.) 156, 375–388 (1961).Google Scholar
  2. Chang, J. J., and R. F. Schmidt: Prolonged action potentials and regenerative hyperpolarizing responses in Purkinje fibers of mammalian heart. Pflügers Arch. ges. Physiol. 272, 127–141 (1960).Google Scholar
  3. Deck, K. A., R. Kern, and W. Trautwein: Voltage clamp technique in mammalian cardiac fibres. Pflügers Arch. ges. Physiol. 280, 50–62 (1964).Google Scholar
  4. Deck, K. A., and W. Trautwein: Ionic currents in cardiac excitation. Pflügers Arch. ges. Physiol. 280, 63–80 (1964).Google Scholar
  5. Dudel, J., K. Peper, R. Rüdel, and W. Trautwein: (in preparation) (1966).Google Scholar
  6. —, u. W. Trautwein: Elektrophysiologische Messungen zur Strophanthinwirkung am Herzmuskel. Naunyn-Schmiedebergs Arch. exp. Path. Pharmak. 232, 393–407 (1958).Google Scholar
  7. Fatt, P., and B. L. Ginsborg: The ionic requirements for the production of action potentials in crustacean muscle fibres. J. Physiol. (Lond.) 142, 516–543 (1958).Google Scholar
  8. Frankenhaeuser, B.: The effect of calcium on the myelinated nerve fibre. J. Physiol. (Lond.) 137, 245–260 (1957).Google Scholar
  9. — The ionic currents in the myelinated nerve fibre. J. gen. Physiol. 48, 79–81 (1965).Google Scholar
  10. —, and A. L. Hodgkin: The action of calcium on the electrical properties of squid axons. J. Physiol. (Lond.) 137, 218–244 (1957).Google Scholar
  11. Hagiwara, S., and K. I. Naka: The initiation of spike potential in barnacle muscle fibers under low intracellular Ca++. J. gen. Physiol. 48, 141–162 (1964).Google Scholar
  12. Hasselbach, W.: Relaxing factor and the relaxation of muscle. Progress in Biophysics and Molecular Biology, Vol. 14, pp. 169–222. New York: Pergamon Press 1964.Google Scholar
  13. Hodgkin, A. L., and A. F. Huxley: A quantitative description of membrane current and its application to excitation and conduction in nerve. J. Physiol. (Lond.) 117, 500–544 (1952).Google Scholar
  14. Hoffman, B. F., and P. F. Cranefield: Electrophysiology of the Heart. New York: McGraw-Hill Book Company, Inc. 1960.Google Scholar
  15. —, and E. E. Suckling: Effect of several cations on transmembrane potential of cardiac muscle. Amer. J. Physiol. 186, 317–324 (1956).Google Scholar
  16. Hutter, O. F., and D. Noble: Anion conductance of cardiac muscle. J. Physiol. (Lond.) 157, 335–350 (1961).Google Scholar
  17. Kimizuka, H., and K. Koketsu: Changes in the membrane permeability of frog's sartorius muscle fibers in Ca-free EDTA solution. J. gen. Physiol. 47, 379–392 (1963).Google Scholar
  18. Langer, G. A., and A. J. Brady: Calcium flux in the mammalian ventricular myocardium. J. gen. Physiol. 46, 703–719 (1963).Google Scholar
  19. Niedergerke, R.: Movements of Ca in beating ventricles of the frog heart. J. Physiol. (Lond.) 167, 551–580 (1963).Google Scholar
  20. Noble, D.: A modification of the Hodgkin-Huxley equations applicable to Purkinje fiber action and pacemaker potential. J. Physiol. (Lond.) 160, 317–352 (1962).Google Scholar
  21. Orkand, R. K., and R. Niedergerke: Heart action potential: Dependence on external calcium and sodium ions. Science 146, 1176–1177 (1964).Google Scholar
  22. Portzehl, H., P. C. Caldwell, and J. C. Rüegg: The dependence of contraction and relaxation of muscle fibres from the crab maia squinado on the internal concentration of free calcium ions. Biochim. biophys. Acta (Amst.) 79, 581–591 (1964).Google Scholar
  23. Reiter, M., and J. Noe: Die Bedeutung von Calcium, Magnesium, Kalium und Natrium für die rhythmische Erregungsbildung im Sinusknoten des Warmblüterherzens. Pflügers Arch. ges. Physiol. 269, 366–374 (1959).Google Scholar
  24. Reuter, H.: Strom-Spannungsbeziehungen in Purkinje-Fasern bei verschiedenen extracellulären Ca-Konzentrationen. Pflügers Arch. ges. Physiol. 283, R 16 (1965).Google Scholar
  25. Stanley, E. J., and M. Reiter: The antagonistic effects of sodium and calcium on the action potential of guinea pig papillary muscle. Naunyn-Schmiedebergs Arch. exp. Path. Pharmak. 252, 159–172 (1965).Google Scholar
  26. Trautwein, W.: Generation and conduction of impulses in the heart as affected by drugs. Pharmacol. Rev. 15, 277–332 (1963).Google Scholar
  27. -- J. Dudel, and K. Peper: Stationary S-shaped current voltage relation and hysteresis in heart muscle fiber. Excitatory phenomena in Na+-free bathing solution. J. cell. comp. Physiol. 65, Suppl. 2 (in press) (1965).Google Scholar
  28. Verdonck, F., D. DeClerq, and E. Carmeliet: Intracellular Cl-concentration in frog ventricle as a function of the extracellular Na and Cl concentration. Arch. int. Physiol. 73, 381–382 (1965).Google Scholar
  29. Weber, A., and R. Hertz: The binding of calcium to actomyosin systems in relation to their biological function. J. biol. Chem. 238, 599–605 (1963).Google Scholar
  30. Weidmann, S.: Effects of calcium ions and local anaesthetics on electrical properties of Purkinje fibres. J. Physiol. (Lond.) 129, 568–582 (1955).Google Scholar
  31. Werman, R., and H. Grundfest: Graded and all-or-none electrogenesis in arthropod muscle. II. The effects of alkali-earth and onium ions on lobster muscle fibers. J. gen. Physiol. 44, 997–1027 (1961).Google Scholar
  32. Winegrad, S., and A. M. Shanes: Calcium flux and contractility in guinea pig atria. J. gen. Physiol. 45, 371–394 (1962).Google Scholar

Copyright information

© Springer-Verlag 1966

Authors and Affiliations

  • J. Dudel
    • 1
  • K. Peper
    • 1
  • W. Trautwein
    • 1
  1. 1.Institut für Allgemeine Physiologie der Universität HeidelbergGermany

Personalised recommendations