Feedback inhibition of rat amiloride-sensitive epithelial sodium channels expressed in Xenopus laevis oocytes
Feedback inhibition of rat amiloride-sensitive epithelial sodium channels expressed in Xenopus laevis oocytes
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DOI：
10.1111/j.1469-7793.1999.031aa.x
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发表时间：
1999-04-01
影响因子：
5.5
通讯作者：
Horisberger, JD
中科院分区：
文献类型：
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作者：
Abriel, H;Horisberger, JD
1.阿米洛利敏感性上皮钠通道（ENaC）的调节对于控制体内钠稳态至关重要。当细胞内Na+浓度（[Na+]（i））增加时，这种Na+通道活性的下调被认为是这种现象的触发因素，即其反馈抑制。虽然细胞内Na+的细胞和分子介质尚不清楚.我们使用“切开卵母细胞”技术来控制表达大鼠ENaCs的非洲爪蟾卵母细胞的细胞内环境的组成，以使我们能够测试可能涉及反馈抑制的几个因素。通过电子显微镜研究证明了细胞内空间灌注的影响，并通过观察细胞内pH值的影响确定了细胞内溶液交换的时间过程：从pH 7.4降至6.5使阿米洛利敏感电流减少了约40% 2分钟内。4.当Na+进入诱导[Na+]（i）大量增加时，在未灌注卵母细胞中观察到反馈抑制。细胞内灌注阻止反馈调节，即使[Na+]（i）被允许增加到50 mM以上的值。在细胞内灌注液中Na+（从1到50 mM）、Ca2+（从10到1000 nM）或ATP（从名义上游离到1或5 mM）的浓度变化后，未观察到对阿米洛利敏感电流的影响。我们的结论是，反馈抑制需要细胞内的因素，可以通过细胞内灌注。虽然[Na+]（i）的升高可能是ENaC反馈抑制的触发因素，但这种作用不是由Na+、Ca2+或ATP对ENaC蛋白的直接作用介导的。
1. Regulation of the amiloride-sensitive epithelial sodium channel (ENaC) is essential for the control of body sodium homeostasis. The downregulation of the activity of this Na+ channel that occurs when the intracellular Na+ concentration ([Na+](i)) is increased is known as is the trigger for this phenomenon, its feedback inhibition. Although intracellular Na+ cellular and molecular mediators are unknown.2. We used the 'cut-open oocyte' technique to control the composition of the intracellular milieu of Xenopus oocytes expressing rat ENaCs to enable us to test several factors potentially involved in feedback inhibition.3. The effects of perfusion of the intracellular space were demonstrated by an electromicrographic study and the time course of the intracellular solution exchange was established by observing the effect of intracellular pH: a decrease from pH 7.4 to 6.5 reduced the amiloride-sensitive current by about 40% within 2 min.4. Feedback inhibition was observed in non-perfused oocytes when Na+ entry induced a large increase in [Na+](i). Intracellular perfusion prevented feedback regulation even though the [Na+](i) was allowed to increase to values above 50 mM.5. No effects on the amiloride-sensitive current were observed after changes in the concentration of Na+ (from 1 to 50 mM), Ca2+ (from 10 to 1000 nM) or ATP (from nominally free to 1 or 5 mM) in the intracellular perfusate.6. We conclude that feedback inhibition requires intracellular factors that can be removed by intracellular perfusion. Although a rise in [Na+](i) may be the trigger for the feedback inhibition of the ENaC, this effect is not mediated by a direct effect of Na+, Ca2+ or ATP on the ENaC protein.