Premium
Whole‐cell and single channel monovalent cation currents through the novel rabbit epithelial Ca 2+ channel ECaC
Author(s) -
Nilius Bernd,
Vennekens Rudi,
Prenen Jean,
Hoenderop Joost G. J,
Bindels René J. M.,
Droogmans Guy
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00239.x
Subject(s) - divalent , chemistry , conductance , permeation , analytical chemistry (journal) , membrane , biophysics , biochemistry , chromatography , physics , organic chemistry , biology , condensed matter physics
1 This study describes properties of monovalent cation currents through ECaC, a recently cloned epithelial Ca 2+ ‐permeable channel from rabbit. 2 The kinetics of currents through ECaC was strongly modulated by divalent cations. Currents were inhibited in the presence of extracellular Ca 2+ . They showed an initial voltage‐dependent decay in the presence of 1 m m Mg 2+ at hyperpolarizing steps in Ca 2+ ‐free solutions, which represents a voltage‐dependent Mg 2+ block through binding of Mg 2+ to a site localized in the electrical field of the membrane (δ= 0.31) and a voltage‐dependent binding constant (at 0 mV 3.1 m m Ca 2+ , obtained from a Woodhull type analysis). 3 Currents were only stable in the absence of divalent cations and showed under these conditions a small time‐ and voltage‐dependent component of activation. 4 Single channel currents in cell‐attached and inside‐out patches had a conductance of 77.5 ± 4.9 pS ( n = 11 ) and reversed at +14.8 ± 1.6 mV ( n = 9 ) in the absence of divalent cations. 5 The permeation sequence for monovalent cations through ECaC was Na + > Li + > K + > Cs + > NMDG + which is identical to the Eisenmann sequence X for a strong field‐strength binding site. 6 It is concluded that the permeation profile of ECaC for monovalent cations suggests a strong field‐strength binding site that may be involved in Ca 2+ permeation and Mg 2+ block.