Rat proximal NHE3 adapts to chronic acid-base disorders but not to chronic changes in dietary NaCl intake
Rat proximal NHE3 adapts to chronic acid-base disorders but not to chronic changes in dietary NaCl intake
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DOI：
10.1152/ajprenal.00188.2001
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发表时间：
2002-05-01
影响因子：
4.2
通讯作者：
Chambrey, R
中科院分区：
文献类型：
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作者：
Eladari, D;Leviel, F;Chambrey, R
在近端小管中，顶端Na+/H+交换剂NHE3介导了大部分NaCl和NaHCO3的吸收。本研究的目的是分析NHE3在饲粮NaHCO3负荷和NaCl摄入量变化引起的碱中毒过程中的长期调控。研究了Sprague-Dawley大鼠分别暴露于低盐、高盐或NaHCO3饮食6天。在治疗大鼠和正常大鼠肾皮质顶端膜囊（AMV）中制备。Na+/H+交换作为Na-22（+）在向外H+梯度存在下的初始吸收速率进行了测定。在高剂量的5-（n -乙基- n -异丙基）酰胺存在下测量的Na-22（+）摄取在模型之间没有差异。NaCl摄入量的变化不影响NHE3活性，而NaHCO3负荷抑制了30%的Na-22（+）吸收。Western blot检测的AMV NHE3蛋白丰度不受NaCl摄入量变化的影响。在NaHCO3加载过程中，NHE3蛋白丰度降低了65%。我们得出结论，近端NHE3适应慢性代谢性酸碱失调，但不适应膳食NaCl摄入量的变化。
In the proximal tubule, the apical Na+/H+ exchanger identified as NHE3 mediates most NaCl and NaHCO3 absorption. The purpose of this study was to analyze the long-term regulation of NHE3 during alkalosis induced by dietary NaHCO3 loading and changes in NaCl intake. Sprague-Dawley rats exposed to a low-NaCl, high-NaCl, or NaHCO3 diet for 6 days were studied. Renal cortical apical membrane vesicles (AMV) were prepared from treated and normal rats. Na+/H+ exchange was assayed as the initial rate of Na-22(+) uptake in the presence of an outward H+ gradient. Na-22(+) uptake measured in the presence of high-dose 5-(N-ethyl-N-isopropyl) amiloride was not different among models. Changes in NaCl intake did not affect NHE3 activity, whereas NaHCO3 loading inhibited Na-22(+) uptake by 30%. AMV NHE3 protein abundance assessed by Western blot analysis was unaffected during changes in NaCl intake. During NaHCO3 loading, NHE3 protein abundance was decreased by 65%. We conclude that proximal NHE3 adapts to chronic metabolic acid-base disorders but not to changes in dietary NaCl intake.