Mechanisms of chloride transport in thymic lymphocytes.
This study examined mechanisms of Cl- transport in rat lymphocytes under a variety of conditions. Basal intracellular Cl- concentration ([Cl-]i) was not different between cells assayed in the presence of HCO3- or its absence (HEPES). Removal of external Cl- resulted in a fall in [Cl-]i and a rapid rise in intracellular pH (pH(i)). Both Cl- efflux and the rise in pH(i) were blocked by DIDS or removal of external Na+ but were unaffected by furosemide. The mechanisms governing Cl- influx were assessed in cells that had been Cl- depleted for 1 h. Reexposure to Cl- resulted in a rapid rise in [Cl-]i that was partially inhibited by pretreatment with DIDS (57%) and partially inhibited by pretreatment with furosemide (45%). Pretreatment with both compounds together completely blocked Cl- influx. Cl- depletion caused a marked increase in pH(i) that rapidly declined toward normal when the cells were reexposed to Cl-. Preincubation with DIDS completely blocked this decrease in pH(i). In contrast, neither removal of Na+ nor preincubation with furosemide affected the decline in pH(i) when the cells were reexposed to Cl-. We conclude that, in thymic lymphocytes, Cl-/HCO3- (or Cl-/base exchange) regulates both Cl- influx and efflux. Cl- efflux is totally inhibited by DIDS and is mediated by a Na+-dependent Cl-/HCO3- exchanger. Cl- influx is partially DIDS sensitive and partially furosemide sensitive and is mediated by both a Na+-independent Cl-/HCO3- exchanger and by a Na+-K+-2Cl- cotransporter.
Stakisaitis
D
D
Division of Nephrology and Hypertension, Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Lapointe
M S
MS
Batlle
D
D
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D017920:Antiporters / Q000187:drug effects / Q000378:metabolism*; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism*; D005452:Fluoresceins / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D011806:Quinolinium Compounds / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*
D017920:Antiporters; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D005452:Fluoresceins; D005456:Fluorescent Dyes; D011806:Quinolinium Compounds; D028021:Sodium-Potassium-Chloride Symporters; C085493:N-(ethoxycarbonylmethyl)-6-methoxyquinolinium; D012965:Sodium Chloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid