Cation regulation of anion current activated by cell swelling in two types of human epithelial cancer cells.
1. In epithelial cells, hyposmotic stress induces visible cell swelling and large Cl- currents, which deactivate on return to isotonic solutions and are abolished by 0.1-0.5 mM DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid). During depolarizing voltage clamp pulses, the currents activate rapidly and show time-dependent relaxation with associated tail currents on return to negative potentials. 2. We used whole-cell and outside-out patch recording to study volume activation of Cl- currents in the epithelial cancer cell lines H69AR and HeLa S5. In a 210 or 160 mosmol l-1 hyposmotic bathing solution containing 90 mM NaCl, 1 mM Ca2+ and 1 mM Mg2+, current relaxation was rapid, occurred positive to the Cl- reversal potential and reduced current to < 30% of its peak level at +100 mV. 3. Replacement of most bath inorganic cations by N-methyl-D-glucamine (NMDG) at constant Cl- concentration and osmolarity eliminated most of the current relaxation and caused an increase in steady-state current levels. Steady-state current was 85 +/- 6% of peak current at +100 mV in NMDG-Cl bath solution. This ratio fell to 55 +/- 2% (n = 5) when 1 mM Mg2+ was re-added to the bath. 4. Re-addition of Mg2+ or other Group II metals (Ca2+, Sr2+, Ba2+) induced immediate changes in current relaxation in a dose- and species-dependent manner. Concentrations of Mg2+ as low as 0.1 mM were effective in causing Cl- current relaxation. The IC50 for steady-state current block by external Mg2+ was 1.75 mM.(ABSTRACT TRUNCATED AT 250 WORDS)
Anderson
J W
JW
Department of Physiology, Queen's University, Kingston, Canada.
Jirsch
J D
JD
Fedida
D
D
D000838:Anions / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002412:Cations / Q000378:metabolism*; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology; D002712:Chlorides / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004594:Electrophysiology; D006367:HeLa Cells / Q000502:physiology; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D008536:Meglumine / Q000494:pharmacology; D009997:Osmotic Pressure; D014407:Tumor Cells, Cultured
D000838:Anions; D002412:Cations; D018118:Chloride Channels; D002712:Chlorides; D008536:Meglumine; D008274:Magnesium; D002118:Calcium