Chloride channels play an important role in regulating smooth muscle contraction and proliferation, and contribute to the enhanced constriction of pulmonary arteries (PAs) in pulmonary hypertension (PH). The intracellular Cl^- concentration ([Cl^-]_i), tightly regulated by various Cl^- transporters, determines the driving force for Cl^- conductance, thereby the functional outcome of Cl^- channel activation. This study characterizes for the first time the expression profile of Cl^- transporters/exchangers in PA smooth muscle and provides the first evidence that the intracellular Cl^- homeostasis is altered in PA smooth muscle cells (PASMCs) associated with chronic hypoxic PH (CHPH). Quantitative RT-PCR revealed that the endothelium-denuded intralobar PA of rats expressed Slc12a gene family-encoded Na-K-2Cl cotransporter 1 (NKCC1), K-Cl cotransporters (KCC) 1, 3 and 4, and Slc4a gene family-encoded Na⁺-independent and Na ⁺-dependent Cl^-/HCO₃^- exchangers. Exposure of rats to chronic hypoxia (10% O₂, 3 weeks) caused CHPH and selectively increased the expression of Cl^--accumulating NKCC1 and reduced the Cl^--extruding KCC4. The intracellular Cl^- concentration ([Cl^-]_i) averaged at 45 mM and 47 mM in normoxic PASMCs as determined by fluorescent indicator MEQ and by gramicidin perforated patch clamp technique, respectively, The ([Cl^-]_i was increased by ~ 10 mM in PASMCs of rats with CHPH. Future studies are warranted to further establish the hypothesis that the altered intracellular Cl^- homeostasis contributes to the pathogenesis of CHPH.

中文翻译：

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与慢性缺氧性肺动脉高压相关的肺动脉肌细胞中细胞内 Cl- 浓度增加

氯离子通道在调节平滑肌收缩和增殖中起重要作用，并有助于增强肺动脉高压 (PH) 中的肺动脉 (PA) 收缩。细胞内 Cl ^-浓度 ([Cl ^- ] _{i ) 受到各种 Cl} ^-转运蛋白的严格调节，决定了 Cl ^-电导的驱动力，从而决定了 Cl ^-通道激活的功能结果。该研究首次表征了PA 平滑肌中 Cl ^{-转运蛋白/交换蛋白的表达谱，并提供了第一个证据表明细胞内 Cl -}与慢性缺氧性 PH (CHPH) 相关的 PA 平滑肌细胞 (PASMCs) 的体内平衡发生了改变。定量 RT-PCR 显示大鼠去内皮叶内 PA 表达 Slc12a 基因家族编码的 Na-K-2Cl 协同转运蛋白 1 (NKCC1)、K-Cl 协同转运蛋白 (KCC) 1、3 和 4，以及 Slc4a 基因家族编码的Na ⁺ - 非依赖性和 Na ⁺ -依赖性 Cl ^- /HCO ₃ ^-交换剂。大鼠暴露于慢性缺氧（10% O ₂，​​3周）引起CHPH并选择性地增加Cl - 积累的NKCC1的表达^并减少Cl ^-挤出的KCC4。细胞内 Cl ^-浓度 ([Cl ^- ]_i ) 在含氧量正常的 PASMCs 中平均为 45 mM 和 47 mM，由荧光指示剂 MEQ 和短杆菌肽穿孔膜片钳技术分别测定，CHPH 大鼠的 PASMCs 中的 ([Cl ^- ] _i增加了 ~ 10 mM。未来的研究有必要进一步确立改变的细胞内 Cl ^-稳态有助于 CHPH 发病机制的假设。