Skip to main content
PMC home page
The Journal of Physiology logoLink to The Journal of Physiology
. 1993 Jun;465:699–714. doi: 10.1113/jphysiol.1993.sp019701

Na+ pump current-voltage relationships of rabbit cardiac Purkinje cells in Na(+)-free solution.

F V Bielen 1, H G Glitsch 1, F Verdonck 1
PMCID: PMC1175454  PMID: 8229858

Abstract

1. The Na+ pump current (Ip) of isolated, single rabbit cardiac Purkinje cells in Na(+)-free solution was measured at 32-34 degrees C by means of whole-cell recording. 2. The Ip amplitude was studied as a function of clamp potential (Vc) and external concentration of various monovalent cations known to activate the Na(+)-K+ pump. 3. Under conditions which strongly activated Ip the Ip-Vc curve of the cells displayed a positive slope at membrane potentials negative to -20 mV and little variation at more positive potentials. 4. The Ip-Vc relationship showed an extended region of negative slope at positive and negative potentials in solutions containing low concentrations of activator cations which caused little Ip activation. A positive slope of the Ip-Vc curve was occasionally observed at clamp potentials negative to -60 mV under these conditions. 5. The shape of the Ip-Vc relation was independent of the cation species used as external Ip activator. 6. At zero membrane potential half-maximum Ip activation (K0.5(Vc = 0 mV) occurred at 0.05 mM Tl+, 0.08 mM K+, 0.4 mM NH4+ and 1.5 mM Cs+. The Hill coefficient derived amounted to 0.9 for Tl+, 1.2 for K+, 1.04 for NH4+ and 1.5 for Cs+. 7. The concentrations of external activator cations required for half-maximum Ip activation increased with depolarization. The voltage dependence of the K0.5 values could be described by a single exponential function for clamp potentials positive to -40 mV. 8. The steepness of the function is determined by a factor alpha, indicating the apparent fraction of an elementary charge which moves in the electrical field across the sarcolemma when external monovalent cations bind to the Na(+)-K+ pump. 9. The alpha values were calculated to be 0.32 for Tl+, 0.24 for K+, 0.29 for NH4+ and 0.18 for Cs+. Possible interpretations of the alpha values are considered. 10. It is suggested that binding of external monovalent activator cations to the Na(+)-K+ pump (or a process related to the binding) is voltage dependent. This potential-dependent process determines mainly the shape of the Ip-Vc curve in cardiac Purkinje cells superfused with Na(+)-free media containing low concentrations (< K0.5(Vc = 0 mV)) of K+ or its congeners.

Full text

PDF
713

Selected References

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

  1. Apell H. J. Electrogenic properties of the Na,K pump. J Membr Biol. 1989 Sep;110(2):103–114. doi: 10.1007/BF01869466. [DOI] [PubMed] [Google Scholar]
  2. Bahinski A., Nakao M., Gadsby D. C. Potassium translocation by the Na+/K+ pump is voltage insensitive. Proc Natl Acad Sci U S A. 1988 May;85(10):3412–3416. doi: 10.1073/pnas.85.10.3412. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bielen F. V., Glitsch H. G., Verdonck F. Changes of the subsarcolemmal Na+ concentration in internally perfused cardiac cells. Biochim Biophys Acta. 1991 Jun 18;1065(2):269–271. doi: 10.1016/0005-2736(91)90239-5. [DOI] [PubMed] [Google Scholar]
  4. Bielen F. V., Glitsch H. G., Verdonck F. Dependence of Na+ pump current on external monovalent cations and membrane potential in rabbit cardiac Purkinje cells. J Physiol. 1991 Oct;442:169–189. doi: 10.1113/jphysiol.1991.sp018788. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. De Weer P., Gadsby D. C., Rakowski R. F. Voltage dependence of the Na-K pump. Annu Rev Physiol. 1988;50:225–241. doi: 10.1146/annurev.ph.50.030188.001301. [DOI] [PubMed] [Google Scholar]
  6. Eisner D. A., Lederer W. J. The relationship between sodium pump activity and twitch tension in cardiac Purkinje fibres. J Physiol. 1980 Jun;303:475–494. doi: 10.1113/jphysiol.1980.sp013299. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Eisner D. A., Lederer W. J. The role of the sodium pump in the effects of potassium-depleted solutions on mammalian cardiac muscle. J Physiol. 1979 Sep;294:279–301. doi: 10.1113/jphysiol.1979.sp012930. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Gadsby D. C., Kimura J., Noma A. Voltage dependence of Na/K pump current in isolated heart cells. Nature. 1985 May 2;315(6014):63–65. doi: 10.1038/315063a0. [DOI] [PubMed] [Google Scholar]
  9. Gadsby D. C., Nakao M. Steady-state current-voltage relationship of the Na/K pump in guinea pig ventricular myocytes. J Gen Physiol. 1989 Sep;94(3):511–537. doi: 10.1085/jgp.94.3.511. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Gadsby D. C. The Na/K pump of cardiac cells. Annu Rev Biophys Bioeng. 1984;13:373–398. doi: 10.1146/annurev.bb.13.060184.002105. [DOI] [PubMed] [Google Scholar]
  11. Glitsch H. G., Krahn T., Pusch H. The dependence of sodium pump current on internal Na concentration and membrane potential in cardioballs from sheep Purkinje fibres. Pflugers Arch. 1989 May;414(1):52–58. doi: 10.1007/BF00585626. [DOI] [PubMed] [Google Scholar]
  12. Goldshlegger R., Karlish S. J., Rephaeli A., Stein W. D. The effect of membrane potential on the mammalian sodium-potassium pump reconstituted into phospholipid vesicles. J Physiol. 1987 Jun;387:331–355. doi: 10.1113/jphysiol.1987.sp016576. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
  14. Lafaire A. V., Schwarz W. Voltage dependence of the rheogenic Na+/K+ ATPase in the membrane of oocytes of Xenopus laevis. J Membr Biol. 1986;91(1):43–51. doi: 10.1007/BF01870213. [DOI] [PubMed] [Google Scholar]
  15. Nakao M., Gadsby D. C. [Na] and [K] dependence of the Na/K pump current-voltage relationship in guinea pig ventricular myocytes. J Gen Physiol. 1989 Sep;94(3):539–565. doi: 10.1085/jgp.94.3.539. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Omay H. S., Schwarz W. Voltage-dependent stimulation of Na+/K(+)-pump current by external cations: selectivity of different K+ congeners. Biochim Biophys Acta. 1992 Feb 17;1104(1):167–173. doi: 10.1016/0005-2736(92)90146-d. [DOI] [PubMed] [Google Scholar]
  17. POST R. L., MERRITT C. R., KINSOLVING C. R., ALBRIGHT C. D. Membrane adenosine triphosphatase as a participant in the active transport of sodium and potassium in the human erythrocyte. J Biol Chem. 1960 Jun;235:1796–1802. [PubMed] [Google Scholar]
  18. Rakowski R. F., Gadsby D. C., De Weer P. Stoichiometry and voltage dependence of the sodium pump in voltage-clamped, internally dialyzed squid giant axon. J Gen Physiol. 1989 May;93(5):903–941. doi: 10.1085/jgp.93.5.903. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Rakowski R. F., Vasilets L. A., LaTona J., Schwarz W. A negative slope in the current-voltage relationship of the Na+/K+ pump in Xenopus oocytes produced by reduction of external [K+]. J Membr Biol. 1991 Apr;121(2):177–187. doi: 10.1007/BF01870531. [DOI] [PubMed] [Google Scholar]
  20. Schwarz W., Gu Q. B. Characteristics of the Na+/K+-ATPase from Torpedo californica expressed in Xenopus oocytes: a combination of tracer flux measurements with electrophysiological measurements. Biochim Biophys Acta. 1988 Nov 22;945(2):167–174. doi: 10.1016/0005-2736(88)90479-8. [DOI] [PubMed] [Google Scholar]
  21. Schweigert B., Lafaire A. V., Schwarz W. Voltage dependence of the Na-K ATPase: measurements of ouabain-dependent membrane current and ouabain binding in oocytes of Xenopus laevis. Pflugers Arch. 1988 Oct;412(6):579–588. doi: 10.1007/BF00583758. [DOI] [PubMed] [Google Scholar]
  22. Stürmer W., Bühler R., Apell H. J., Läuger P. Charge translocation by the Na,K-pump: II. Ion binding and release at the extracellular face. J Membr Biol. 1991 Apr;121(2):163–176. doi: 10.1007/BF01870530. [DOI] [PubMed] [Google Scholar]
  23. Vasilets L. A., Schwarz W. Regulation of endogenous and expressed Na+/K+ pumps in Xenopus oocytes by membrane potential and stimulation of protein kinases. J Membr Biol. 1992 Jan;125(2):119–132. doi: 10.1007/BF00233352. [DOI] [PubMed] [Google Scholar]

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

RESOURCES