Chloride channels activated by osmotic stress in T lymphocytes.
We have used whole-cell and perforated-patch recording techniques to characterize volume-sensitive Cl- channels in T and B lymphocytes. Positive transmembrane osmotic pressure (intracellular osmolality > extracellular osmolality) triggers the slow induction of a Cl- conductance. Membrane stretch caused by cellular swelling may underlie the activation mechanism, as moderate suction applied to the pipette interior can reversibly oppose the induction of Cl- current by an osmotic stimulus. Intracellular ATP is required for sustaining the Cl- current. With ATP-free internal solutions, the inducibility of Cl- current declines within minutes of whole-cell recording, while in whole-cell recordings with ATP or in perforated-patch experiments, the current can be activated for at least 30 min. The channels are anion selective with a permeability sequence of I- > SCN- > NO3-, Br- > Cl- > MeSO3- > acetate, propionate > ascorbate > aspartate and gluconate. GCl does not show voltage- and time-dependent gating behavior at potentials between -100 and +100 mV, but exhibits moderate outward rectification in symmetrical Cl- solutions. Fluctuation analysis indicates a unitary chord conductance of approximately 2 pS at -80 mV in the presence of symmetrical 160 mM Cl-. The relationship of mean current to current variance during the osmotic activation of Cl- current implies that each cell contains on the order of 10(4) activatable Cl- channels, making it the most abundant ion channel in lymphocytes yet described. The current is blocked in a voltage-dependent manner by DIDS and SITS (Ki = 17 and 89 microM, respectively, at +40 mV), the degree of blockade increasing with membrane depolarization. The biophysical and pharmacological properties of this Cl- channel are consistent with a role in triggering volume regulation in lymphocytes exposed to hyposmotic conditions.
Lewis
R S
RS
Department of Physiology and Biophysics, University of California, Irvine 92717.
Ross
P E
PE
Cahalan
M D
MD
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000502:physiology; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009997:Osmotic Pressure; D013601:T-Lymphocytes / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D013997:Time Factors
D002712:Chlorides; D007473:Ion Channels; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000255:Adenosine Triphosphate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid