Pflügers Archiv

, Volume 403, Issue 2, pp 225–227 | Cite as

Block of sodium currents by the calcium antagonist D600 in human heart cell segments

  • J. Omar Bustamante
Excitable Tissues and Central Nervous Physiology Short Communication


The effects of micromolar concentrations of racemic D600 on the transmembrane inward sodium current (INa) were investigated in voltage clamped, intracellularly perfused, human heart cell segments. Extracellular D600 blocked INa in a ‘voltage- and ratedependent’ manner as shown by the enhanced INa depression with a reduction of the ‘resting’ transmembrane polarization (Vm) and stimulation interval (SI). D600 action was manifested as a voltage-dependent slowing down of the Na+ channels' recovery kinetics after a pulsed excitation, with greater recovery times during longer depolarized states, excited or non-excited. This phenomenon seems linked to the improved control of the intracellular environment normally influencing channel activity, and to the increased ratio of ‘non-sarcolemmal’ to ‘sarcolemmal’ cell membranes for this preparation.

Key words

human heart cell intercalated disc intracellular perfusion membrane sodium channels membrane capacitance calcium antagonism D600 


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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • J. Omar Bustamante
    • 1
  1. 1.Dalhousie University, School of Medicine, Department of Physiology and BiophysicsHalifaxCanada

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