Pflügers Archiv

, Volume 437, Issue 6, pp 831–838

A Na+-activated K+ current (IK,Na) is present in guinea-pig but not rat ventricular myocytes

  • C. Lawrence
  • G. C. Rodrigo
Original Article

DOI: 10.1007/s004240050852

Cite this article as:
Lawrence, C. & Rodrigo, G. Pflügers Arch (1999) 437: 831. doi:10.1007/s004240050852

Abstract

 The effects of removing extracellular Ca2+ and Mg2+ on the membrane potential, membrane current and intracellular Na+ activity (aiNa) were investigated in guinea-pig and rat ventricular myocytes. Membrane potential was recorded with a patch pipette and whole-cell membrane currents using a single-electrode voltage clamp. Both guinea-pig and rat cells depolarize when the bathing Ca2+ and Mg2+ are removed and the steady-state aiNa increases rapidly from a resting value of 6.4± 0.6 mM to 33±3.8 mM in guinea-pig (n=9) and from 8.9±0.8 mM to 29.3±3.0 mM (n=5) in rat ventricular myocytes. Guinea-pig myocytes partially repolarized when, in addition to removal of the bathing Ca2+ and Mg2+, K+ was also removed, however rat cells remained depolarized. A large diltiazem-sensitive inward current was recorded in guinea-pig and rat myocytes, voltage-clamped at –20 mV, when the bathing divalent cations were removed. When the bathing K+ was removed after Ca2+ and Mg2+ depletion, a large outward K+ current developed in guinea-pig, but not in rat myocytes. This current had a reversal potential of –80±0.7 mV and was not inhibited by high Mg2+ or glybenclamide indicating that it is not due to activation of non-selective cation or adenosine triphosphate (ATP)-sensitive K channels. The current was not activated when Li+ replaced the bathing Na+ and was blocked by R-56865, suggesting that it was due to the activation of KNa channels.

Key words Cardiac myocyte Ca2+ channels Ca2+ paradox Intracellular sodium K+ current Membrane potential 

Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • C. Lawrence
    • 1
  • G. C. Rodrigo
    • 1
  1. 1.Department of Physiology, School of Medical Sciences, University of Otago, Dunedin, New Zealand e-mail: glenn.rodrigo@stonebow.otago.ac.nz Fax: +64-34797323NZ

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