Extracellular acidification elicits a chloride current that shares characteristics with ICl(swell).
A Cl- current activated by extracellular acidification, ICl(pHac), has been characterized in various mammalian cell types. Many of the properties of ICl(pHac) are similar to those of the cell swelling-activated Cl- current ICl(swell): ion selectivity (I- > Br- > Cl- > F-), pharmacology [ICl(pHac) is inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 1,9-dideoxyforskolin (DDFSK), diphenylamine-2-carboxylic acid (DPC), and niflumic acid], lack of dependence on intra- or extracellular Ca2+, and presence in all cell types tested. ICl(pHac) differs from ICl(swell) in three aspects: 1) its rate of activation and inactivation is very much more rapid, currents reaching a maximum in seconds rather than minutes; 2) it exhibits a slow voltage-dependent activation in contrast to the fast voltage-dependent activation and time- and voltage-dependent inactivation observed for ICl(swell); and 3) it shows a more pronounced outward rectification. Despite these differences, study of the transition between the two currents strongly suggests that ICl(swell) and ICl(pHac) are related and that extracellular acidification reflects a novel stimulus for activating ICl(swell) that, additionally, alters the biophysical properties of the channel.
Nobles
Muriel
M
Medical Research Council, Clinical Sciences Centre, Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, London, United Kingdom. m.nobles@ucl.ac.uk
Higgins
Christopher F
CF
Sardini
Alessandro
A
D002460:Cell Line; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D045604:Extracellular Fluid / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D015398:Signal Transduction / Q000502:physiology*
D018118:Chloride Channels; D002712:Chlorides