Apical potassium channels in the rat connecting tubule
Apical potassium channels in the rat connecting tubule
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DOI：
10.1152/ajprenal.00169.2004
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发表时间：
2004-11-01
影响因子：
4.2
通讯作者：
Palmer, LG
中科院分区：
文献类型：
--
作者：
Frindt, G;Palmer, LG
用膜片钳技术研究了大鼠连接小管(CNT)顶膜K通道。肾小管从肾皮质迷路分离出来，并裂开以提供通向顶膜的通道。在假定的主要和/或连接的小管细胞上形成细胞贴附的斑块。观察到的主要通道类型具有52ps的单通道电导、高的开放概率和仅弱依赖于电压的动力学。这些通道与大脑皮层集合管中的“SK”型通道密切对应，与ROMK(Kir1.1)基因产物相一致。第二种通道类型较少被观察到，它介导更大的电流，并被顶膜电压的去极化强烈激活。这些被鉴定为BK或MAXI-K通道。活跃的SK通道密度表现出高度的聚集性。虽然不能排除小管的异质性或小管内细胞类型的异质性，但支持这种分布的主要因素似乎是单个细胞膜上存在通道簇。通道的总密度高于以前在皮质集合管(CCT)中发现的密度。与CCT的结果相反，我们没有检测到喂食高K饮食后动物顶膜SK通道的总体密度增加。然而，在对照条件下，阿米洛利敏感钠通道的活性未被检测到，但在钾负荷1d(90+/-24pA/cell)或7d(385+/-82pA/cell)后，该通道的活动均增强。因此，导致CNT中K分泌增加的一个重要因素是顶端Na电导的增加，导致顶膜电压的去极化和K向管腔内移动的驱动力增加。
Apical membrane K channels in the rat connecting tubule (CNT) were studied using the patch-clamp technique. Tubules were isolated from the cortical labyrinth of the kidney and split open to provide access to the apical membrane. Cell-attached patches were formed on presumed principal and/or connecting tubule cells. The major channel type observed had a single-channel conductance of 52 pS, high open probability and kinetics that were only weakly dependent on voltage. These correspond closely to the "SK"-type channels in the cortical collecting duct, identified with the ROMK (Kir1.1) gene product. A second channel type, which was less frequently observed, mediated larger currents and was strongly activated by depolarization of the apical membrane voltage. These were identified as BK or maxi-K channels. The density of active SK channels revealed a high degree of clustering. Although heterogeneity of tubules or of cell types within a tubule could not be excluded, the major factor underlying the distribution appeared to be the presence of channel clusters on the membrane of individual cells. The overall density of channels was higher than that previously found in the cortical collecting tubule (CCT). In contrast to results in the CCT, we did not detect an increase in the overall density of SK channels in the apical membrane after feeding the animals a high-K diet. However, the activity of amiloride-sensitive Na channels was undetectable under control conditions but was increased after both 1 day (90 +/- 24 pA/cell) or 7 days (385 +/- 82 pA/cell) of K loading. Thus one important factor leading to an increased K secretion in the CNT in response to increased dietary K is an increased apical Na conductance, leading to depolarization of the apical membrane voltage and an increased driving force for K movement out into the tubular lumen.