rENaC is the predominant Na+ channel in the apical membrane of the rat renal inner medullary collecting duct.
rENaC is the predominant Na+ channel in the apical membrane of the rat renal inner medullary collecting duct.
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DOI：
10.1172/jci118344
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发表时间：
1995-12
期刊：
影响因子：
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通讯作者：
K. Volk;R. Sigmund;P. Snyder;F. McDonald;M. Welsh;J. Stokes
中科院分区：
文献类型：
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作者：
K. Volk;R. Sigmund;P. Snyder;F. McDonald;M. Welsh;J. Stokes
终末肾单位段，即内髓集合管（IMCD），通过一个涉及通过顶端（管腔）膜Na+通道进入的生电过程吸收Na+。为了了解这种Na+通道的性质，我们采用膜片钳技术对大鼠IMCD细胞生长在渗透性支持物上的原代培养物的顶膜。我们发现，所有的离子通道中检测到的细胞附着的配置是高度选择性的Na+（Li+）超过K+。开/关转换显示出缓慢的动力学，具有6-11 pS的斜率电导，并且对阿米洛利和苯扎明敏感。具有较高电导率（25-30 pS）的非选择性阳离子通道，已知存在于IMCD细胞中，在细胞附着配置中未检测到，但在切除的贴片中很容易检测到。高度选择性的通道具有类似于最近描述的大鼠上皮Na+通道复合物，rENaC的属性。因此，我们询问IMCD中是否存在rENaC mRNA。我们在大鼠肾乳头和IMCD的原代培养物中检测到所有三种rENaC亚基的mRNA。无论是糖皮质激素或盐皮质激素增加α-rENaC亚基mRNA的量，但对β-rENaC或γ-rENaC亚基的mRNA水平没有影响。从这些数据中，在其他研究的背景下的Na+选择性通道的特性和rENaC mRNA的分布，我们得出结论，类固醇刺激的Na+吸收的IMCD介导的主要是Na+通道的rENaC亚基复合物的属性。
The terminal nephron segment, the inner medullary collecting duct (IMCD), absorbs Na+ by an electrogenic process that involves the entry through an apical (luminal) membrane Na+ channel. To understand the nature of this Na+ channel, we employed the patch clamp technique on the apical membrane of primary cultures of rat IMCD cells grown on permeable supports. We found that all ion channels detected in the cell-attached configuration were highly selective for Na+ (Li+) over K+. The open/closed transitions showed slow kinetics, had a slope conductance of 6-11 pS, and were sensitive to amiloride and benzamil. Nonselective cation channels with a higher conductance (25-30 pS), known to be present in IMCD cells, were not detected in the cell-attached configuration, but were readily detected in excised patches. The highly selective channels had properties similar to the recently described rat epithelial Na+ channel complex, rENaC. We therefore asked whether rENaC mRNA was present in the IMCD. We detected mRNA for all three rENaC subunits in rat renal papilla and also in primary cultures of the IMCD. Either glucocorticoid hormone or mineralocorticoid hormone increased the amount of alpha-rENaC subunit mRNA but had no effect on the mRNA level of the beta-rENaC or gamma-rENaC subunits. From these data, taken in the context of other studies on the characteristics of Na+ selective channels and the distribution of rENaC mRNA, we conclude that steroid stimulated Na+ absorption by the IMCD is mediated primarily by Na+ channels having properties of the rENaC subunit complex.