盐摄入量改变影响血管紧张素II调控肾远曲小管Kir4.1/Kir5.1通道活性机制的研究

The basolateral Kir4.1/Kir5.1 channels in the distal convoluted tubule (DCT) play an important role in the reabsorption of NaCl. We have proved that AngII stimulates the basolateral 50pS K channels and 10pS Cl channels in the thick ascending limb via AT1 receptor, which in turn increases the activity of Na-K-Cl cotransporter (NKCC2) and stimulates the reabsorption of NaCl. We have found that AngII significantly stimulated the DCT basolateral Kir4.1/Kir5.1 channels activity of the mice on normal diet, whereas the agonist of AT2R decreased the channel activity, but it is not clear that the regulate mechanism of AngII on the Kir4.1/Kir5.1 channels and the role of salt intake change in mediating the effect of AngII on the Kir4.1/Kir5.1 channels. We speculate that AngII would regulate the activity of Kir4.1/Kir5.1 channels via its receptors and the signal pathway, and affect the activity of apical Na/Cl cotransporter (NCC) in the DCT and furtherly alter the reabsorption of NaCl. We plan to use Patch-clamp technique and other experimental tools to explore the regulation mechanism of AngII on the Kir4.1/Kir5.1 channels in the DCT of C57BL/6 and kidney specific Kcnj10-/- on different salt intake (high, low and normal) from cellular, molecular and organic levels, and furtherly reveal the key role of Kir4.1/Kir5.1 channels in the salt and water balance in DCT regulated by AngII, and provide a new idea for the prevention of hypertension and possible mechanism of the abnormal tubule transport.

肾远曲小管(DCT)管周膜Kir4.1/Kir5.1通道在NaCl重吸收中扮演重要角色。我们曾证实，AngII在AT1R介导下刺激肾髓袢升支粗段管周膜50pS钾、10pS氯通道，增强管腔膜钠钾氯转运体活动及对NaCl转运。预实验中加入AngII可激活、AT2R激动剂可抑制正常盐饮食鼠DCT管周膜Kir4.1/Kir5.1通道活性，然尚不清楚AngII对其调节作用及盐摄入量改变时对其调控机制。推测：AngII经受体-信号转导通路介导调控Kir4.1/Kir5.1活性，调节DCT钠氯转运体对NaCl转运。本研究用C57BL/6小鼠及肾特异性Kcnj10-/-小鼠，采用膜片钳等技术在细胞、分子及器官层面，探讨盐摄入改变时AngII对Kir4.1/Kir5.1活性调控机制，揭示Kir4.1/Kir5.1通道在AngII调节肾远曲小管水盐转运中的重要作用，为探讨防治高血压及肾小管转运异常提供新思路。

盐摄入量的改变与RAS系统（尤其是 Ang II）的活性调节密切相关，而肾远曲小管(DCT)管周膜Kir4.1/Kir5.1通道是多种影响因素调节远曲小管重吸收NaCl 的作用靶点，因此，本研究致力于探讨AngII 对肾DCT管周膜Kir4.1/Kir5.1 通道的活性的调节，并是否以此影响远曲小管对 Na+、Cl-的吸收及转运，从而致血压发生改变。本研究应用膜片钳技术、分子生物学技术及肾脏清除率技术探讨了AngII 对正常、高及低盐饮食小鼠肾脏DCT管周膜Kir4.1/Kir5.1通道的调控机制。研究发现：AngII 能够降低DCT管周膜Kir4.1/Kir5.1通道的活性。其中正常盐饮食情况下，100nmol/L的AngII能明显降低正常盐饮食小鼠肾脏 DCT管周膜 Kir4.1/Kir5.1通道活性，AT2受体、NO/cGMP信号转导通路参与这一调控作用；高盐饮食情况下，1μmol/L的AngII能能明显降低高盐饮食小鼠肾脏 DCT管周膜 Kir4.1/Kir5.1通道活性，AT2受体、NO/cGMP信号转导通路参与这一调控作用；低盐饮食情况下，100nmol/L的Ang II能明显降低低盐饮食小鼠肾脏 DCT管周膜 Kir4.1/Kir5.1通道活性，AT1受体和AT2受体、PLC/PKC信号转导途径、PTK/c-Src信号转导途径可能参与这一调控作用；本实验还发现，Ang II可降低正常、高及低盐饮食小鼠NCC活性。实验结果证实，Ang II可降低正常、高及低盐饮食小鼠肾脏DCT管周膜Kir4.1/Kir5.1通道活性，进而降低NCC活性，导致DCT 对 NaCl 的转运重吸收将会减少。为盐饮食与高血压疾病的关联提供了一定理论依据，并为防治高血压及肾小管转运异常提供新思路。