Stakisaitis D, Lapointe M S, Batlle D
Division of Nephrology and Hypertension, Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Am J Physiol Renal Physiol. 2001 Feb;280(2):F314-24. doi: 10.1152/ajprenal.2001.280.2.F314.
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.
本研究考察了多种条件下大鼠淋巴细胞中氯离子（Cl⁻）转运的机制。在存在或不存在HCO₃⁻（用HEPES缓冲）的情况下检测细胞，基础细胞内Cl⁻浓度（[Cl⁻]i）并无差异。去除细胞外Cl⁻导致[Cl⁻]i下降以及细胞内pH（pH(i)）迅速升高。Cl⁻外流和pH(i)的升高均被二异丁基苯磺酸钠（DIDS）或去除细胞外Na⁺所阻断，但不受速尿影响。在已Cl⁻缺失1小时的细胞中评估Cl⁻内流的调控机制。重新暴露于Cl⁻导致[Cl⁻]i迅速升高，这一过程部分被DIDS预处理（57%）抑制，部分被速尿预处理（45%）抑制。两种化合物一起预处理则完全阻断Cl⁻内流。Cl⁻缺失导致pH(i)显著升高，当细胞重新暴露于Cl⁻时，pH(i)迅速向正常水平下降。用DIDS预孵育完全阻断了pH(i)的这种下降。相反，去除Na⁺或用速尿预孵育均不影响细胞重新暴露于Cl⁻时pH(i)的下降。我们得出结论，在胸腺淋巴细胞中，Cl⁻/HCO₃⁻（或Cl⁻/碱基交换）调节Cl⁻的内流和外流。Cl⁻外流被DIDS完全抑制，由一种Na⁺依赖性Cl⁻/HCO₃⁻交换体介导。Cl⁻内流部分对DIDS敏感，部分对速尿敏感，由一种非Na⁺依赖性Cl⁻/HCO₃⁻交换体和一种Na⁺-K⁺-2Cl⁻协同转运体介导。
