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. 1981 Feb;311:161–178. doi: 10.1113/jphysiol.1981.sp013579

A study of pace-maker potential in rabbit sino-atrial node: measurement of potassium activity under voltage-clamp conditions.

J Maylie, M Morad, J Weiss
PMCID: PMC1275404  PMID: 7264968

Abstract

1. A single sucrose-gap voltage-clamp technique was used to control the membrane potential and to measure current in rabbit sino-atrial (SA) strips. K+ activity in the extracellular space was simultaneously measured using K+-selective micro-electrodes. 2. Using double-barrelled K+ selective micro-electrodes it was possible to measure the time course of accumulation or depletion of K+ accompanying a single action potential without complications arising from mechanical or electrical artifacts. 3. K+ activity in the extracellular space increased during the action potential and then decreased to base-line levels during the diastolic depolarization phase. Single beat accumulations of 0.1-0.4 M could be measured. 4. The magnitude of accumulation or depletion of K+ depended upon the membrane potential such that K+ accumulated at potentials positive to -50 mV (K+ efflux greater than K+ uptake) and was depleted from the extracellular space at potentials negative to -50 mV (K+ efflux less than K+ uptake). 5. The rate of K+ depletion was fairly constant during the time course of a clamp step within the range of diastolic depolarization (-55 to -75 mV) even though the accompanying membrane current showed marked time-dependent kinetics. 6. The total membrane conductance measured during the time course of the diastolic depolarization or during the time course of activation of time-dependent 'pace-maker' current remained fairly constant or increased. 7. No reversal potential for the time-dependent 'pace-maker' current could be measured at EK in solutions containing 2.7, 5.4 and 8.1 mM-K+. 8. These results do not support the turn-off a K+ conductance as the primary mechanisms for the generation of the pace-maker potential in SA nodal tissue; rather the results are more consistent with the idea that activation of an inward current, with large positive equilibrium potential, is responsible for pace-making activity.

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Selected References

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

  1. Baumgarten C. M., Isenberg G. Depletion and accumulation of potassium in the extracellular clefts of cardiac Purkinje fibers during voltage clamp hyperpolarization and depolarization. Pflugers Arch. 1977 Mar 11;368(1-2):19–31. doi: 10.1007/BF01063450. [DOI] [PubMed] [Google Scholar]
  2. Brown H. F., Giles W., Noble S. J. Proceedings: Voltage clamp of frog sinus venosus. J Physiol. 1976 Jun;258(2):78P–79P. [PubMed] [Google Scholar]
  3. Cleemann L., Morad M. Extracellular potassium accumulation in voltage-clamped frog ventricular muscle. J Physiol. 1979 Jan;286:83–111. doi: 10.1113/jphysiol.1979.sp012608. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Cohen I., Daut J., Noble D. The effects of potassium and temperature on the pace-maker current, iK2, in Purkinje fibres. J Physiol. 1976 Aug;260(1):55–74. doi: 10.1113/jphysiol.1976.sp011504. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. 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]
  6. Goldman Y., Morad M. Ionic membrane conductance during the time course of the cardiac action potential. J Physiol. 1977 Jul;268(3):655–695. doi: 10.1113/jphysiol.1977.sp011876. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. 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]
  8. 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]
  9. Irisawa H. Comparative physiology of the cardiac pacemaker mechanism. Physiol Rev. 1978 Apr;58(2):461–498. doi: 10.1152/physrev.1978.58.2.461. [DOI] [PubMed] [Google Scholar]
  10. Isenberg G., Trautwein W. The effect of dihydro-ouabain and lithium-ions on the outward current in cardiac Purkinje fibers. Evidence for electrogenicity of active transport. Pflugers Arch. 1974;350(1):41–54. doi: 10.1007/BF00586737. [DOI] [PubMed] [Google Scholar]
  11. Kline R. P., Morad M. Potassium efflux in heart muscle during activity: extracellular accumulation and its implications. J Physiol. 1978 Jul;280:537–558. doi: 10.1113/jphysiol.1978.sp012400. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Kline R., Morad M. Potassium efflux and accumulation in heart muscle. Evidence from K +/- electrode experiments. Biophys J. 1976 Apr;16(4):367–372. doi: 10.1016/S0006-3495(76)85694-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. 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]
  14. 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]
  15. Noma A., Irisawa H. A time- and voltage-dependent potassium current in the rabbit sinoatrial node cell. Pflugers Arch. 1976 Nov 5;366(2-3):251–258. doi: 10.1007/BF00585886. [DOI] [PubMed] [Google Scholar]
  16. Noma A., Irisawa H. Membrane currents in the rabbit sinoatrial node cell as studied by the double microelectrode method. Pflugers Arch. 1976 Jun 29;364(1):45–52. doi: 10.1007/BF01062910. [DOI] [PubMed] [Google Scholar]
  17. Peper K., Trautwein W. A note on the pacemaker current in Purkinje fibers. Pflugers Arch. 1969 Jun 19;309(4):356–361. doi: 10.1007/BF00587758. [DOI] [PubMed] [Google Scholar]
  18. Seyama I. Characteristics of the rectifying properties of the sino-atrial node cell of the rabbit. J Physiol. 1976 Feb;255(2):379–397. doi: 10.1113/jphysiol.1976.sp011285. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Tsien R. W., Carpenter D. O. Ionic mechanisms of pacemaker activity in cardiac Purkinje fibers. Fed Proc. 1978 Jun;37(8):2127–2131. [PubMed] [Google Scholar]
  20. Vassalle M. Analysis of cardiac pacemaker potential using a "voltage clamp" technique. Am J Physiol. 1966 Jun;210(6):1335–1341. doi: 10.1152/ajplegacy.1966.210.6.1335. [DOI] [PubMed] [Google Scholar]
  21. 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]

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