In rat inner medullary collecting duct, NH uptake by the Na,K-ATPase is increased during hypokalemia.
In rat inner medullary collecting duct, NH uptake by the Na,K-ATPase is increased during hypokalemia.
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在大鼠内髓集合管中，低钾血症期间 Na,K-ATP 酶对 NH 的吸收增加。
DOI：
10.1152/ajprenal.0141.2001
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Hassell,KathrynA
中科院分区：
文献类型：
--
作者：
Wall,SusanM;Fischer,MichaelP;Kim,Gheun-Ho;Nguyen,Bich-May;Hassell,KathrynA
在大鼠终末内髓集合管（tIMCD）中，Na，K-ATP酶介导NH摄取，从而增加净H+当量的分泌。K+和NH竞争Na，K-ATP酶上的一个共同结合位点。因此，在低钾血症期间，NH摄取应增加，因为间质K+浓度降低。我们想知道在低钾血症时Na，K-ATP酶的上调是否也会增加基底外侧的NH摄取。为了诱导低钾血症，大鼠吃低K+含量的饮食。与K+充足对照组相比，在给予3天饮食K+限制的大鼠的tIMCD小管中，Na，K-ATP酶β1亚基（NK-β1）蛋白表达增加，而NK-α 1蛋白表达和Na，K-ATP酶活性无变化。限钾7 d后，NK-α 1和NK-β 1亚基蛋白表达及Na，K-ATP酶活性均升高。在正常或限制K+饮食3天后，在体外灌注的大鼠tIMCD小管中测定Na，K-ATPase介导的跨基底外侧膜的NH摄取量（J）。然而，在任一处理组中，将K+浓度从10 mM增加到30 mM使J> 60%降低。总之，在3天的K+限制下，tIMCD中Na，K-ATP酶的NH摄取增加，主要来自减少的间质K+浓度。
In rat terminal inner medullary collecting duct (tIMCD), the Na,K-ATPase mediates NHuptake, which increases secretion of net H+equivalents. K+and NHcompete for a common binding site on the Na,K-ATPase. Therefore, NHuptake should increase during hypokalemia because interstitial K+concentration is reduced. We asked whether upregulation of the Na,K-ATPase during hypokalemia also increases basolateral NHuptake. To induce hypokalemia, rats ate a diet with a low K+content. In tIMCD tubules from rats given 3 days of dietary K+restriction, Na,K-ATPase β1-subunit (NK-β1) protein expression increased although NK-α1protein expression and Na,K-ATPase activity were unchanged relative to K+-replete controls. However, after 7 days of K+restriction, both NK-α1and NK-β1subunit protein expression and Na,K-ATPase activity increased. The magnitude of Na,K-ATPase-mediated NHuptake across the basolateral membrane (J) was determined in tIMCD tubules perfused in vitro from rats after 3 days of a normal or a K+-restricted diet.Jwas the same in tubules from rats on either diet when measured at the same extracellular K+concentration. However, in either treatment group, increasing K+concentration from 10 to 30 mM reducedJ>60%. In conclusion, with 3 days of K+restriction, NHuptake by Na,K-ATPase is increased in the tIMCD primarily from the reduced interstitial K+concentration.