Physiologic role of BK channel in distal nephron

描述(申请人提供)：在远端肾单位，包括连接小管(CNT)和皮质收集管(CCD)，流动刺激的钾分泌是由位于顶膜的钙和牵张激活的BK通道调节的；BK通道也在肾脏对饮食K摄入量的适应中起关键作用。酸碱转运插层细胞的BK通道密度高于钠吸收碳纳米管/主细胞。然而，功能测量表明，间质细胞可能没有一种机制来使细胞装载K以维持尿液中K的高分泌。这项应用的目的是确定BK通道是否参与调节血流刺激的净K分泌，从而调节全身K(和Na)的动态平衡。为此，我们提出了三个特定的目标(SAS)：(1)使用选择性的BK通道阻滞剂，证实从WT和我们将用SLO1产生的小鼠品系中分离的微灌流CDs的流动刺激净K分泌是由BK通道介导的；(2)通过建立靶向缺失BK通道1亚单位的小鼠模型，确定BK通道的1个亚单位在体内调节远端肾单位的K分泌中的作用；以及(3)通过建立仅在远端肾单位内的主细胞中定向缺失BK通道的1个亚单位的小鼠模型，确定主细胞中BK通道的1个亚基在体内调节远端肾单位K分泌中的作用。在一定程度上，远端钾分泌的大小部分决定了钠的吸收，存在血压变化的BK通道亚基整体缺失的动物，也将评估远端肾单位中BK通道的细胞特异性缺失对Na和K清除和血压(遥测)的影响。这些研究结果将明确BK通道在调节肾脏K(和Na)排泄和维持正常血压方面的重要性，并有望揭示高血压的发生和/或维持以及K排泄障碍的机制。 公共卫生相关性：拟议的研究旨在确定BK钾通道在肾脏远端肾单位的生理学作用。这些研究将确定这些通道在调节肾脏钠钾排泄和维持正常血压方面的重要性。这项工作有可能揭示高血压和钾排泄障碍的发生和/或维持机制。

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.