Husted R F, Volk K A, Sigmund R D, Stokes J B
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
J Clin Invest. 1995 Feb;95(2):644-50. doi: 10.1172/JCI117709.
It is well established that the terminal renal collecting duct is capable of electrogenic Na+ absorption. The present experiments examined other active ion transport processes in primary cultures of the rat inner medullary collecting duct. When the amiloride analogue benzamil inhibited electrogenic Na+ absorption, cAMP agonists stimulated a transmonolayer short circuit current that was not dependent on the presence of Na+ in the apical solution, but was dependent on the presence of Cl- and HCO3-. This current was not inhibited by the loop diuretic bumetanide, but was inhibited by ouabain, an inhibitor of the Na+/K+ pump. The current was reduced by anion transport inhibitors, with a profile similar to that seen for inhibitors of the cystic fibrosis transmembrane conductance regulator (CFATR) Cl- channel. Using several PCR strategies, we demonstrated fragments of the predicted lengths and sequence identity with the rat CFTR. Using whole-cell patch-clamp analysis, we demonstrated a cAMP-stimulated Cl- current with characteristics of the CFTR. We conclude that the rat inner medullary collecting duct has the capacity to secrete anions. It is highly likely that the CFTR Cl- channel is involved in this process.
终末肾集合管能够进行电生性钠吸收，这一点已得到充分证实。本实验研究了大鼠内髓集合管原代培养物中的其他主动离子转运过程。当氨氯吡脒类似物苯甲酰咪抑制电生性钠吸收时，环磷酸腺苷（cAMP）激动剂刺激了跨单层短路电流，该电流不依赖于顶端溶液中钠的存在，但依赖于氯离子（Cl⁻）和碳酸氢根离子（HCO₃⁻）的存在。该电流不受髓袢利尿剂布美他尼的抑制，但受钠钾泵抑制剂哇巴因的抑制。该电流被阴离子转运抑制剂降低，其模式与囊性纤维化跨膜传导调节因子（CFTR）氯离子通道抑制剂所见相似。使用多种聚合酶链反应（PCR）策略，我们证明了预测长度的片段以及与大鼠CFTR的序列一致性。使用全细胞膜片钳分析，我们证明了具有CFTR特征的cAMP刺激的氯离子电流。我们得出结论，大鼠内髓集合管具有分泌阴离子的能力。CFTR氯离子通道极有可能参与了这一过程。
