Physiologic role of BK channel in distal nephron

描述（由申请人提供）：远端肾单位（包括连接小管（CNT）和皮质集合管（CCD））中的流量刺激的钾分泌由位于顶膜的Ca 2+和牵张激活的BK通道介导; BK通道还关键性地参与肾脏对膳食钾摄入的适应。在酸碱转运的插入细胞中BK通道的密度超过了钠吸收的CNT/主细胞。然而，功能测量表明，插入细胞可能没有一个机制，负载细胞与K维持高速率的K分泌到尿液中。本申请的目的是确定嵌入和/或主细胞中的BK通道是否介导流动刺激的净K分泌，从而调节全身K（和Na）稳态。为此，我们提出了三个具体目标（SA）：（1）使用选择性BK通道阻断剂，证实从WT分离的微灌注CD和我们将用floxed slo 1产生的小鼠品系中的流动刺激的净K分泌，建议用于SA 2和3，是由BK通道介导的;（二）为了确定嵌入细胞中BK通道的1亚基在远端肾单位中K分泌的体内调节中的作用，通过产生仅在嵌入细胞内靶向缺失BK通道的1亚基的小鼠模型，远端肾单位;和（3）通过产生仅在远端肾单位内的主细胞中靶向缺失BK通道1亚基的小鼠模型，确定主细胞中BK通道1亚基在体内调节远端肾单位中K分泌中的作用。在一定程度上，远端K分泌的幅度部分决定了Na吸收，并且BK通道亚基整体缺失的动物存在血压变化，还将评价远端肾单位中BK通道的细胞特异性缺失对Na和K清除率和血压（遥测）的影响。拟议的研究结果将确定BK通道在调节肾脏K（和Na）排泄和维持正常血压中的重要性，并有望揭示参与高血压和K排泄障碍的发展和/或维持的机制。 公共卫生相关性：所提出的研究旨在确定BK钾通道在肾脏远端肾单位中的生理作用。这些研究将确定这些通道在调节肾脏钠和钾排泄以及维持正常血压方面的重要性。这项工作有可能揭示参与高血压和钾排泄障碍的发展和/或维持的机制。

DESCRIPTION (provided by applicant): Flow-stimulated K secretion in the distal nephron, including the connecting tubule (CNT) and cortical collecting duct (CCD), is mediated by a Ca2+ and stretch-activated BK channel located in the apical membrane; the BK channel is also critically involved in the renal adaptation to dietary K intake. The density of BK channels in acid-base transporting intercalated cells exceeds that in Na absorbing CNT/principal cells. However, functional measurements suggest that intercalated cells may not have a mechanism to load cells with K to sustain high rates of K secretion into the urinary fluid. The goal of this application is to determine whether BK channels in intercalated and/or principal cells mediate flow-stimulated net K secretion and thereby regulate total body K (and Na) homeostasis. To this end, we propose three Specific Aims (SAs): (1) to confirm, using a selective BK channel blocker, that flow-stimulated net K secretion in microperfused CDs isolated from WT and a mouse strain we will generate with floxed slo1, proposed to be used in SAs 2 and 3, is mediated by the BK channel; (2) to define the role of the 1 subunit of the BK channel in intercalated cells in the in vivo regulation of K secretion in the distal nephron by generating a mouse model with targeted deletion of the 1 subunit of the BK channel solely in intercalated cells within the distal nephron; and (3) to define the role of the 1 subunit of the BK channel in principal cells in the in vivo regulation of K secretion in the distal nephron by generating a mouse model with targeted deletion of the 1 subunit of the BK channel solely in principal cells within the distal nephron. To the extent that the magnitude of distal K secretion determines, in part, Na absorption, and animals with global deletion of BK channel subunits present with alterations in blood pressure, the impact of cell-specific deletion of the BK channel in the distal nephron on Na and K clearances and blood pressure (telemetry) will also be evaluated. The results of proposed studies will define the importance of BK channels in the regulation of renal K (and Na) excretion and maintenance of normal blood pressure, and promises to uncover mechanisms involved in the development and/or maintenance of hypertension and disorders of K excretion. PUBLIC HEALTH RELEVANCE: The proposed studies are designed to determine the physiologic role of BK potassium channels in the distal nephron of the kidney. The studies will define the importance of these channels in the regulation of kidney sodium and potassium excretion and maintenance of normal blood pressure. This work has the potential to uncover mechanisms involved in the development and/or maintenance of hypertension and disorders of potassium excretion.