PDF(Pubmed)
Abstract：
Inwardly rectifying K+ (Kir ) channels located on the basolateral membrane of epithelial cells of the distal nephron play a crucial role in K+ handling and BP control, making these channels an attractive target for the treatment of hypertension. The purpose of the present study was to determine how the inhibition of basolateral Kir 4.1/Kir 5.1 heteromeric K+ channel affects epithelial sodium channel (ENaC)-mediated Na+ transport in the principal cells of cortical collecting duct (CCD).
The effect of fluoxetine, amitriptyline and recently developed Kir inhibitor, VU0134992, on the activity of Kir 4.1, Kir 4.1/Kir 5.1 and ENaC were tested using electrophysiological approaches in CHO cells transfected with respective channel subunits, cultured polarized epithelial mCCDcl1 cells and freshly isolated rat and human CCD tubules. To test the effect of pharmacological Kir 4.1/Kir 5.1 inhibition on electrolyte homeostasis in vivo and corresponding changes in distal tubule transport, Dahl salt-sensitive rats were injected with amitriptyline (15 mg·kg-1 ·day-1 ) for 3 days.
We found that inhibition of Kir 4.1/Kir 5.1, but not the Kir 4.1 channel, depolarizes the cell membrane, induces the elevation of intracellular Ca2+ concentration and suppresses ENaC activity. Furthermore, we demonstrate that amitriptyline administration leads to a significant drop in plasma K+ level, triggering sodium excretion and diuresis.
The present data uncover a specific role of the Kir 4.1/Kir 5.1 channel in the modulation of ENaC activity and emphasize the potential for using Kir 4.1/Kir 5.1 inhibitors to regulate electrolyte homeostasis and BP.
The effect of fluoxetine, amitriptyline and recently developed Kir inhibitor, VU0134992, on the activity of Kir 4.1, Kir 4.1/Kir 5.1 and ENaC were tested using electrophysiological approaches in CHO cells transfected with respective channel subunits, cultured polarized epithelial mCCDcl1 cells and freshly isolated rat and human CCD tubules. To test the effect of pharmacological Kir 4.1/Kir 5.1 inhibition on electrolyte homeostasis in vivo and corresponding changes in distal tubule transport, Dahl salt-sensitive rats were injected with amitriptyline (15 mg·kg-1 ·day-1 ) for 3 days.
We found that inhibition of Kir 4.1/Kir 5.1, but not the Kir 4.1 channel, depolarizes the cell membrane, induces the elevation of intracellular Ca2+ concentration and suppresses ENaC activity. Furthermore, we demonstrate that amitriptyline administration leads to a significant drop in plasma K+ level, triggering sodium excretion and diuresis.
The present data uncover a specific role of the Kir 4.1/Kir 5.1 channel in the modulation of ENaC activity and emphasize the potential for using Kir 4.1/Kir 5.1 inhibitors to regulate electrolyte homeostasis and BP.
摘要：
位于远端肾单位上皮细胞基底外侧膜上的向内整流K（Kir）通道在K处理和BP控制中起着至关重要的作用。使这些通道成为治疗高血压的有吸引力的目标。本研究的目的是确定基底外侧Kir4.1/Kir5.1异聚K通道的抑制如何影响皮质集合管（CCD）主要细胞中上皮钠通道（ENaC）介导的Na转运。
氟西汀的作用，阿米替林和最近开发的Kir抑制剂，VU0134992，对Kir4.1，Kir4.1/Kir5.1和ENaC的活性使用电生理学方法在用各自通道亚基转染的CHO细胞中进行测试，培养的极化上皮mCCDcl1细胞和新鲜分离的大鼠和人CCD小管。为了测试药理Kir4.1/Kir5.1抑制对体内电解质稳态的影响以及远端小管运输的相应变化，Dahl盐敏感大鼠注射阿米替林（15mg·kg-1·day-1）3天。
我们发现抑制Kir4.1/Kir5.1，但不抑制Kir4.1通道，使细胞膜去极化，诱导细胞内Ca2+浓度升高并抑制ENaC活性。此外，我们证明阿米替林给药导致血浆K+水平显著下降，引发钠排泄和利尿。
目前的数据揭示了Kir4.1/Kir5.1通道在调节ENaC活性中的特定作用，并强调了使用Kir4.1/Kir5.1抑制剂调节电解质稳态和BP的潜力。
氟西汀的作用，阿米替林和最近开发的Kir抑制剂，VU0134992，对Kir4.1，Kir4.1/Kir5.1和ENaC的活性使用电生理学方法在用各自通道亚基转染的CHO细胞中进行测试，培养的极化上皮mCCDcl1细胞和新鲜分离的大鼠和人CCD小管。为了测试药理Kir4.1/Kir5.1抑制对体内电解质稳态的影响以及远端小管运输的相应变化，Dahl盐敏感大鼠注射阿米替林（15mg·kg-1·day-1）3天。
我们发现抑制Kir4.1/Kir5.1，但不抑制Kir4.1通道，使细胞膜去极化，诱导细胞内Ca2+浓度升高并抑制ENaC活性。此外，我们证明阿米替林给药导致血浆K+水平显著下降，引发钠排泄和利尿。
目前的数据揭示了Kir4.1/Kir5.1通道在调节ENaC活性中的特定作用，并强调了使用Kir4.1/Kir5.1抑制剂调节电解质稳态和BP的潜力。
