Volume-activated taurine permeability in cells of the human erythroleukemic cell line K562

The effects of hypotonic shock on cell volume, taurine influx and efflux were examined in the human erythroleukemic cell line K562. Cells exposed to hypotonic solutions exhibited a regulatory volume decrease (RVD) following rapid increases in cell volume. Cell swelling was associated with a increased taurine influx and efflux. The volume-activated taurine pathway was Na+-independent, and increased in parallel with increasing cell volume. The chloride channel blocker, 2,5-dichlorodiphenylamine-2-carboxylic acid (DCDPC), completely blocked the volume-activated taurine influx and efflux, while [dihydroindenyl)oxy]alkanoic acids (DIOA) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), an anion exchanger and anion channel blocker, respectively, also inhibited significantly. These results suggest that taurine transport is increased in response to hypotonic stress, which may be mediated via a volume-activated, DCDPC-sensitive anion channel.