Angiotensin II stimulates epithelial sodium channels in the cortical collecting duct of the rat kidney.
Angiotensin II stimulates epithelial sodium channels in the cortical collecting duct of the rat kidney.
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DOI：
10.1152/ajprenal.00368.2011
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发表时间：
2012-03
期刊：
影响因子：
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通讯作者：
Peng Sun;Peng Yue;Wen‐Hui Wang
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文献类型：
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作者：
Peng Sun;Peng Yue;Wen‐Hui Wang
我们采用单通道和穿孔全细胞膜片钳记录技术，研究了血管紧张素II（ANG II）对大鼠皮质集合管（CCD）上皮钠通道（ENaC）的影响。施加50 nM的ANG II可使ENaC活性增加（以NP(o)，即通道数量和开放概率的乘积衡量），并使阿米洛利敏感的全细胞钠电流增加一倍。在有氯沙坦存在的情况下，ANG II对ENaC的刺激作用消失，这表明ANG II对ENaC的作用是由血管紧张素II 1型受体介导的。此外，用1,2 - 双（2 - 氨基苯氧基）乙烷 - N,N,N',N' - 四乙酸（BAPTA - AM）消耗细胞内Ca(2+)未能消除ANG II对ENaC的刺激作用，但抑制蛋白激酶C（PKC）可消除ANG II的作用，这表明ANG II的作用是刺激不依赖Ca(2+)的PKC的结果。用佛波酯衍生物刺激PKC模拟ANG II的作用并增加主细胞中阿米洛利敏感的钠电流，且用BAPTA - AM处理CCD不能消除这种作用，这也支持了上述观点。此外，用氯化二亚苯基碘鎓抑制NADPH氧化酶（NOX）可消除ANG II对ENaC的刺激作用，而施加超氧化物供体（邻苯三酚或黄嘌呤及黄嘌呤氧化酶）可显著增加ENaC活性。而且，添加ANG II或H(2)O(2)可减弱花生四烯酸（AA）对CCD中ENaC的抑制作用。我们得出结论：ANG II通过不依赖Ca(2+)的PKC途径刺激CCD中的ENaC，该途径激活NOX，从而增加超氧化物的产生。ANG II对ENaC的刺激作用可能部分是由于阻断了AA对ENaC的抑制作用。
We examined the effect of angiotensin II (ANG II) on epithelial Na(+) channel (ENaC) in the rat cortical collecting duct (CCD) with single-channel and the perforated whole cell patch-clamp recording. Application of 50 nM ANG II increased ENaC activity, defined by NP(o) (a product of channel numbers and open probability), and the amiloride-sensitive whole cell Na currents by twofold. The stimulatory effect of ANG II on ENaC was absent in the presence of losartan, suggesting that the effect of ANG II on ENaC was mediated by ANG II type 1 receptor. Moreover, depletion of intracellular Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA)-AM failed to abolish the stimulatory effect of ANG II on ENaC but inhibiting protein kinase C (PKC) abolished the effect of ANG II, suggesting that the effect of ANG II was the result of stimulating Ca(2+)-independent PKC. This notion was also suggested by the experiments in which stimulation of PKC with phorbol ester derivative mimicked the effect of ANG II and increased amiloride-sensitive Na currents in the principal cell, an effect that was not abolished by treatment of the CCD with BAPTA-AM. Also, inhibition of NADPH oxidase (NOX) with diphenyleneiodonium chloride abolished the stimulatory effect of ANG II on ENaC and application of superoxide donors, pyrogallol or xanthine and xanthine oxidase, significantly increased ENaC activity. Moreover, addition of ANG II or H(2)O(2) diminished the arachidonic acid (AA)-induced inhibition of ENaC in the CCD. We conclude that ANG II stimulates ENaC in the CCD through a Ca(2+)-independent PKC pathway that activates NOX thereby increasing superoxide generation. The stimulatory effect of ANG II on ENaC may be partially the result of blocking AA-induced inhibition of ENaC.