Osmosensitive C1- currents and their relevance to regulatory volume decrease in human intestinal T84 cells: outwardly vs. inwardly rectifying currents.
1. The swelling-activated outwardly rectifying Cl- current (ICl(swell)) recorded in T84 human intestinal cells was completely blocked by 10 microM tamoxifen, while 300 microM Cd2+ had no effect. 2. A ClC-2-like, inwardly rectifying Cl- current was activated after strong hyperpolarization in T84 cells. This current was completely inhibited by 300 microM Cd2+, unaffected by 10 microM tamoxifen, and its magnitude increased slightly in response to cell swelling under hyposmotic conditions. However, the swelling-dependent modulation occurred only after prior activation by hyperpolarizing voltages. 3. T84 cells behaved initially close to perfect osmometers in response to changes in external osmolalities between +20 and -30 %. The cells underwent full regulatory volume decrease (RVD) within 16 min when exposed to 30 or 10 % hyposmotic shocks. 4. Pharmacological tools were used to determine the anionic pathway(s) involved in RVD in T84 cells. Tamoxifen (10 microM), 1,9-dideoxyforskolin (DDFSK; 100 microM) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 100 microM) blocked RVD while 300 microM Cd2+ had no effect upon RVD following a 30 % hyposmotic shock. The RVD response was similarly unaffected by Cd2+ when cells were exposed to a smaller (10 %) hyposmotic shock. 5. In conclusion, these data show that the anionic pathway primarily activated by cell swelling and relevant to RVD in T84 cells is the tamoxifen-, DDFSK- and DIDS-sensitive ICl(swell) and not the hyperpolarization-activated, Cd2+-sensitive Cl- current associated with the ClC-2 Cl- channel.
Bond
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Physiology Group, Biomedical Sciences Division, King's College London, Strand, London WC2R 2LS, UK.
Ambikapathy
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Mohammad
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Valverde
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D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000090007:CLC-2 Chloride Channels; D002104:Cadmium / Q000494:pharmacology; D002460:Cell Line; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D003110:Colonic Neoplasms; D006801:Humans; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000502:physiology*; D009994:Osmolar Concentration; D013629:Tamoxifen / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D009419:Nerve Tissue Proteins; D002104:Cadmium; D013629:Tamoxifen; D005576:Colforsin; C047983:1,9-dideoxyforskolin; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid