title: Separate taurine and chloride efflux pathways activated during regulatory volume decrease.
abstract: Organic osmolyte and halide permeability pathways activated in epithelial HeLa cells by cell swelling were studied by radiotracer efflux techniques and single-cell volume measurements. The replacement of extracellular Cl- by anions that are more permeant through the volume-activated Cl- channel, as indicated by electrophysiological measurements, significantly decreased taurine efflux. In the presence of less-permeant anions, an increase in taurine efflux was observed. Simultaneous measurement of the 125I, used as a tracer for Cl-, and [3H]taurine efflux showed that the time courses for the two effluxes differed. In Cl--rich medium the increase in I- efflux was transient, whereas that for taurine was sustained. Osmosensitive Cl- conductance, assessed by measuring changes in cell volume, increased rapidly after hypotonic shock. The influx of taurine was able to counteract Cl- conductance-dependent cell shrinkage but only approximately 4 min after triggering cell swelling. This taurine-induced effect was blocked by DIDS. Differences in anion sensitivity, the time course of activation, and sensitivity to DIDS suggest that the main cell swelling-activated permeability pathways for taurine and Cl- are separate.
authors.affiliation: Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago 6530499, Chile. astutzin@bitmed.med.uchile.cl
authors.forename: A
authors.initials: A
authors.lastname: Stutzin
authors.forename: R
authors.initials: R
authors.lastname: Torres
authors.forename: M
authors.initials: M
authors.lastname: Oporto
authors.forename: P
authors.initials: P
authors.lastname: Pacheco
authors.forename: A L
authors.initials: AL
authors.lastname: Eguiguren
authors.forename: L P
authors.initials: LP
authors.lastname: Cid
authors.forename: F V
authors.initials: FV
authors.lastname: Sepúlveda
mesh_terms: D000838:Anions / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D006367:HeLa Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D013654:Taurine / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000838:Anions; D002712:Chlorides; D013654:Taurine