Skip to main content
PMC home page
The Journal of Physiology logoLink to The Journal of Physiology
. 1977 Jul;268(3):655–695. doi: 10.1113/jphysiol.1977.sp011876

Ionic membrane conductance during the time course of the cardiac action potential.

Y Goldman, M Morad
PMCID: PMC1283683  PMID: 560474

Abstract

1. Membrane ionic current-voltage (I-V) relations of the frog ventricular myocardium were measured during the action potential with a new single sucrose gap voltage clamp technique. 2. The I-V relation is linear during the plateau and rapid repolarization phases of the action potential and during the development of the regenerative threshold of repolarization. 3. Time dependent I-V relation during a series of voltage clamp pulses of clamp initiation. 4. The membrane conductance is remarkably constant during the plateau and is about 85 mumhos/muF of membrane capacitance. 5. Chloride conductance is about 18% of the total ionic conductance during the plateau and is not time dependent. Two inward Cl-movement during a normal action potential is sufficient to approximately halve the action potential duration. 6. Membrane conductance did not change significantly when Ca2+ was omitted from the bathing medium. 7. Epinephrine increased the duration of the action potential and the total ionic conductance during the platiau in normal and Ca-free media. 8. Separation of Na+ and K+ currents in muscles bathed in 'zero' Ca2+, 'zero' Cl- solution indicates that the inward and outward currents are balanced to within 2% during the slow repolarization. 9. The results indicates that a fine balance between conductance changes cardiac action potential. The possibility of a cross ionic interaction in the heart cell membrane is suggested.

Full text

PDF
655

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Armstrong C. M., Bezanilla F., Rojas E. Destruction of sodium conductance inactivation in squid axons perfused with pronase. J Gen Physiol. 1973 Oct;62(4):375–391. doi: 10.1085/jgp.62.4.375. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Beeler G. W., Jr, Reuter H. Membrane calcium current in ventricular myocardial fibres. J Physiol. 1970 Mar;207(1):191–209. doi: 10.1113/jphysiol.1970.sp009056. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Beeler G. W., Jr, Reuter H. Voltage clamp experiments on ventricular myocarial fibres. J Physiol. 1970 Mar;207(1):165–190. doi: 10.1113/jphysiol.1970.sp009055. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bezanilla F., Rojas E., Taylor R. E. Sodium and potassium conductance changes during a membrane action potential. J Physiol. 1970 Dec;211(3):729–751. doi: 10.1113/jphysiol.1970.sp009301. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Brady A. J., Woodbury J. W. The sodium-potassium hypothesis as the basis of electrical activity in frog ventricle. J Physiol. 1960 Dec;154(2):385–407. doi: 10.1113/jphysiol.1960.sp006586. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. GOLDMANN D. E. A MOLECULAR STRUCTURAL BASIS FOR THE EXCITATION PROPERTIES OF AXONS. Biophys J. 1964 May;4:167–188. doi: 10.1016/s0006-3495(64)86776-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Garnier D., Rougier O., Gargouïl Y. M., Coraboeuf E. Analyse électrophysiologique du plateau des réponses myocardiques, mise en évidence d'un courant lent entrant en absence d'ions bivalents. Pflugers Arch. 1969;313(4):321–342. doi: 10.1007/BF00593957. [DOI] [PubMed] [Google Scholar]
  8. Goldman Y., Morad M. Measurement of transmembrane potential and current in cardiac muscle: a new voltage clamp method. J Physiol. 1977 Jul;268(3):613–654. doi: 10.1113/jphysiol.1977.sp011875. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Goldman Y., Morad M. Regenerative repolarization of the frog ventricular action potential: a time and voltage-dependent phenomenon. J Physiol. 1977 Jul;268(3):575–611. doi: 10.1113/jphysiol.1977.sp011874. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. HODGKIN A. L., HUXLEY A. F. Currents carried by sodium and potassium ions through the membrane of the giant axon of Loligo. J Physiol. 1952 Apr;116(4):449–472. doi: 10.1113/jphysiol.1952.sp004717. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. HUTTER O. F., NOBLE D. Rectifying properties of heart muscle. Nature. 1960 Nov 5;188:495–495. doi: 10.1038/188495a0. [DOI] [PubMed] [Google Scholar]
  12. Hille B. Ionic channels in nerve membranes. Prog Biophys Mol Biol. 1970;21:1–32. doi: 10.1016/0079-6107(70)90022-2. [DOI] [PubMed] [Google Scholar]
  13. Katz A. M., Repke D. I. Control of myocardial contraction: the sensitivity of cardiac actomyosin to calcium ion. Science. 1966 May 27;152(3726):1242–1243. doi: 10.1126/science.152.3726.1242. [DOI] [PubMed] [Google Scholar]
  14. Keenan M. J., Niedergerke R. Intracellular sodium concentration and resting sodium fluxes of the frog heart ventricle. J Physiol. 1967 Jan;188(2):235–260. doi: 10.1113/jphysiol.1967.sp008136. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. LUTTGAU H. C., NIEDERGERKE R. The antagonism between Ca and Na ions on the frog's heart. J Physiol. 1958 Oct 31;143(3):486–505. doi: 10.1113/jphysiol.1958.sp006073. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Ladle R. O., Walker J. L. Intracellular chloride activity in frog heart. J Physiol. 1975 Oct;251(2):549–559. doi: 10.1113/jphysiol.1975.sp011107. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. MULLINS L. J. An analysis of conductance changes in squid axon. J Gen Physiol. 1959 May 20;42(5):1013–1035. doi: 10.1085/jgp.42.5.1013. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Morad M., Orkand R. K. Excitation-concentration coupling in frog ventricle: evidence from voltage clamp studies. J Physiol. 1971 Dec;219(1):167–189. doi: 10.1113/jphysiol.1971.sp009656. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Morad M., Rolett E. L. Relaxing effects of catecholamines on mammalian heart. J Physiol. 1972 Aug;224(3):537–558. doi: 10.1113/jphysiol.1972.sp009912. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. NOBLE D. A modification of the Hodgkin--Huxley equations applicable to Purkinje fibre action and pace-maker potentials. J Physiol. 1962 Feb;160:317–352. doi: 10.1113/jphysiol.1962.sp006849. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Noble D., Tsien R. W. Outward membrane currents activated in the plateau range of potentials in cardiac Purkinje fibres. J Physiol. 1969 Jan;200(1):205–231. doi: 10.1113/jphysiol.1969.sp008689. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Noble D., Tsien R. W. Reconstruction of the repolarization process in cardiac Purkinje fibres based on voltage clamp measurements of membrane current. J Physiol. 1969 Jan;200(1):233–254. doi: 10.1113/jphysiol.1969.sp008690. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Noble D., Tsien R. W. The kinetics and rectifier properties of the slow potassium current in cardiac Purkinje fibres. J Physiol. 1968 Mar;195(1):185–214. doi: 10.1113/jphysiol.1968.sp008454. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Novotny I., Bianchi C. P. Distribution and efflux of sodium from frog heart ventricles perfused with normal and sodium free Ringer's solution. Pflugers Arch. 1973 Mar 21;339(2):113–124. doi: 10.1007/BF00587178. [DOI] [PubMed] [Google Scholar]
  25. Reuter H. Localization of beta adrenergic receptors, and effects of noradrenaline and cyclic nucleotides on action potentials, ionic currents and tension in mammalian cardiac muscle. J Physiol. 1974 Oct;242(2):429–451. doi: 10.1113/jphysiol.1974.sp010716. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Rougier O., Vassort G., Garnier D., Gargouil Y. M., Coraboeuf E. Existence and role of a slow inward current during the frog atrial action potential. Pflugers Arch. 1969;308(2):91–110. doi: 10.1007/BF00587018. [DOI] [PubMed] [Google Scholar]
  27. Rougier O., Vassort G., Stämpfli R. Voltage clamp experiments on frog atrial heart muscle fibres with the sucrose gap technique. Pflugers Arch Gesamte Physiol Menschen Tiere. 1968;301(2):91–108. doi: 10.1007/BF00362729. [DOI] [PubMed] [Google Scholar]
  28. Tsien R. W. Effects of epinephrine on the pacemaker potassium current of cardiac Purkinje fibers. J Gen Physiol. 1974 Sep;64(3):293–319. doi: 10.1085/jgp.64.3.293. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. WEIDMANN S. Effect of current flow on the membrane potential of cardiac muscle. J Physiol. 1951 Oct 29;115(2):227–236. doi: 10.1113/jphysiol.1951.sp004667. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. WEIDMANN S. Resting and action potentials of cardiac muscle. Ann N Y Acad Sci. 1957 Aug 9;65(6):663–678. doi: 10.1111/j.1749-6632.1957.tb36674.x. [DOI] [PubMed] [Google Scholar]
  31. Walker J. L., Ladle R. O. Frog heart intracellular potassium activities measured with potassium microelectrodes. Am J Physiol. 1973 Jul;225(1):263–267. doi: 10.1152/ajplegacy.1973.225.1.263. [DOI] [PubMed] [Google Scholar]

Articles from The Journal of Physiology are provided here courtesy of The Physiological Society

RESOURCES