Pflügers Archiv

, Volume 405, Supplement 1, pp S89–S94 | Cite as

Voltage dependence of the blocking rate constants of amiloride at apical Na channels

  • Jens Warncke
  • Bernd Lindemann
Characterization of Ion Channels


The overall rate constants of blockage of apical Na channels by amiloride, previously determined by noise analysis, were obtained in macroscopic relaxation experiments with toad urinary bladders exposed to a mucosal Na activity of 60 mM. By the use of step voltage perturbations and by admittance analysis we show that the on-rate constant of blockage increases, and the off-rate constant decreases when the outer membrane surface is made more positive. In the frame-work of a plug-type blocking model the results imply that the cationic amidino group of amiloride senses about 10% of the membrane voltage while invading the channel entrace and slightly more than 10% while leaving the entrance.

Key words

Amiloride Relaxation Admittance Current-voltage curves Epithelial Na channels Toad urinary bladder 


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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Jens Warncke
    • 1
  • Bernd Lindemann
    • 1
  1. 1.2nd Department of PhysiologyUniversity of the SaarlandHomburg (Saar)Federal Republic of Germany

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