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Biophysical characteristics of swelling-activated Cl- channels in human tracheal 9HTEo-cells.
Zegarra-Moran, O; Galietta, L J.
Afiliação
  • Zegarra-Moran O; Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, Genova, I-16148, Italy.
J Membr Biol ; 165(3): 255-64, 1998 Oct 01.
Article em En | MEDLINE | ID: mdl-9767679
The question of whether a single molecule can account for every observed swelling-activated Cl- current deserves to be addressed and biophysical description seems to be an adequate criterion to classify these channels. We studied the biophysical properties of swelling-activated Cl- currents in 9HTEo-cells using whole-cell and outside-out patch clamp recordings. Hypotonic shock activated outwardly rectifying currents that inactivated at potentials higher than 20 mV. The decay phase of the current was well fitted by two exponential functions and both time constants were voltage-dependent. Two voltage-dependent time constants were also necessary to describe reactivation. The midpoint of current inactivation was 54 mV. The voltage dependence of kinetics did not significantly change by modifying the extracellular NaCl concentration while the inactivation midpoint slightly shifted. In conclusion, our results indicate that the voltage-dependent properties of the swelling-activated Cl- currents in 9HTEo- cells are largely independent from the extracellular ionic strength and the extracellular Cl- concentration. Excised patches from cells exposed to hypotonic shock showed single channel currents that inactivated at positive membrane potentials and displayed chord conductance of approximately 60 pS at 100 mV and of approximately 20 pS at -80 mV. The permeability sequence for the single channel was I- > Br- > Cl- > gluconate and currents were blocked by Reactive blue 2. These properties indicate that intermediate conductance outwardly rectifying channels are responsible for the macroscopic swelling-activated current.
Assuntos
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Canais de Cloreto / Células Epiteliais Limite: Humans Idioma: En Revista: J Membr Biol Ano de publicação: 1998 Tipo de documento: Article País de afiliação: Itália País de publicação: Estados Unidos
Buscar no Google
Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Canais de Cloreto / Células Epiteliais Limite: Humans Idioma: En Revista: J Membr Biol Ano de publicação: 1998 Tipo de documento: Article País de afiliação: Itália País de publicação: Estados Unidos