Cl- currents activated by extracellular nucleotides in human bronchial cells

O. Zegarra-Moran, O. Sacco, L. Romano, G. A. Rossi, L. J V Galietta

Research output: Contribution to journalArticle

Abstract

The perforated-patch technique was used to study the response of human bronchial cells to extracellular nucleotides. ATP or UTP (100 μM) elicited a complex response consisting of a large transient membrane current increase followed by a relatively small sustained level. These two phases were characterized by different current kinetics. Throughout the transient phase (2-3 min) the membrane current (I(p)) displayed slow activation and deactivation kinetics at depolarizing and hyperpolarizing potentials respectively. At steady-state (I(s)) the relaxation at hyperpolarizing potential disappeared whereas at positive membrane potentials the current became slightly deactivating. The I(s) amplitude was dependent on the extracellular Ca2+ concentration, being completely inhibited in Ca2+-free medium. Cell preincubation with the membrane-permeable chelating agent BAPTA/AM prevented completely the response to nucleotides, thus suggesting that both I(p) and I(s) were dependent on intracellular Ca2+. The presence of a hypertonic medium during nucleotide stimulation abolished I(s) leaving I(p) unchanged. On the contrary, niflumic acid, a blocker of Ca2+-activated Cl- channels, prevented completely I(p) without reducing significantly I(s). 1,9-dideoxyforskolin fully inhibited I(s) but also reduced I(p). Replacement of extracellular Cl- with aspartate demonstrated that the currents activated by nucleotides were Cl- selective. I(p) resulted five times more Cl- selective than I(s) with respect to aspartate. Taken together, our results indicate that ATP and UTP activate two types of Cl- currents through a Ca2+-dependent mechanism.

Original languageEnglish
Pages (from-to)297-305
Number of pages9
JournalJournal of Membrane Biology
Volume156
Issue number3
DOIs
Publication statusPublished - 1997

Keywords

  • ATP
  • Bronchial epithelial cells
  • Cl channels
  • Cl currents
  • Intracellular Ca
  • Patch-clamp
  • UTP

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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