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Pflügers Archiv

, Volume 431, Issue 4, pp 599–607 | Cite as

Characterization of a whole-cell Ca2+-blockable monovalent cation current in isolated ectodermal cells of chick embryo

  • Robert Sabovcik
  • Pavel Kucera
  • Blaise Prod'hom
Original Article

Abstract

The presence of a Ca2+-blockable monovalent cation current is demonstrated in isolated ectodermal cells of the chick embryo using the whole-cell patch-clamp method. In the absence of any stimulation, the whole-cell current is time independent and rectifies outwardly at membrane potentials higher than +40 mV The outward current is neither carried by Cl channels nor by K+ channels. Application of a Ca2+-free solution containing 1 mmol/l ethylenediaminetetraacetic acid (EDTA) elicits a large inward current and increases the outward current. The inward current can be carried by extracellular Li+, Na+, K+ and Cs+, but notN-methyl-d-glucamine. The Ca2+-blockable monovalent cation channel discriminates very poorly among these cations. The estimated number of channels per cell is around 2000. Extracellular protons block the inward Na+ current in the absence of extracellular Ca2+. The apparent negative logarithm of the dissociation constant for proton (pKH) at −100 mV is 5.8. Among 12 potential channel modulators, including verapamil and nifedipine, only quinine decreases the current. Quinine blocks this current with a dissociation constant,Kd, equal to 0.18 mmol/l, independent of the membrane potential. This study demonstrates the presence of a whole-cell Ca2+-blockade monovalent cation current in dissociated chick ectodermal cells with permeation properties similar to those observed at the single-channel level. Contrary to studies made of other tissues, we did not observe any blocking effect of verapamil and nifedipine on the Ca2+-blockable monovalent cation current.

Key words

Whole-cell recording Patch-clamp Embryo Ectoderm Cation channel Calcium Quinine Proton 

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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • Robert Sabovcik
    • 1
  • Pavel Kucera
    • 1
  • Blaise Prod'hom
    • 1
  1. 1.Institut de Physiologic, Faculté de MédecineUniversité de LausanneLausanneSwitzerland

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