Salt Absorption by the THAL: Role of NKCC2 trafficking

性状（由申请方提供）：细胞膜中Na转运蛋白的数量通过转运蛋白的动态插入、回收和再循环来调节。这些过程统称为贩运。在某些形式的人类和实验性高血压中，盐潴留是由某些肾单位节段顶膜中异常高水平的Na转运蛋白引起的。粗的上升支（塔尔）吸收NaCl并有助于盐和水的体内平衡，从而影响血压。塔尔的NaCl吸收主要受NKCC 2调节，NKCC 2是介导Na和Cl进入细胞的顶端Na/K/2Cl共转运蛋白。迄今为止，尚不清楚NKCC 2的运输是否调节NaCl吸收。还不清楚刺激NaCl被塔尔吸收的血管活性激素和抑制NaCl被THAL吸收的自育激素是否通过影响其运输来调节顶端膜中的NKCC 2水平。我们推测，NaCl吸收的塔尔的调节部分是由运输NKCC 2到顶端膜，在一个过程中由cAMP刺激和一氧化氮抑制。在盐敏感性高血压模型中，NKCC 2插入心尖膜的增强有助于盐潴留。在目的I中，我们将检查顶端膜中的NKCC 2水平和NaCl吸收是否通过NKCC 2的插入和检索来调节。在目的II中，我们将研究刺激NKCC 2依赖性NaCl通过cAMP进入THL的激素是否增加顶端膜中的NKCC 2水平。在目的III中，我们将研究一氧化氮是否通过降低顶端膜中的NKCC 2水平来抑制NKCC 2依赖性NaCl进入。最后，我们将研究是否在盐敏感动物的THAL中，顶端膜中的基础和盐刺激的NKCC 2水平增强。我们将使用最先进的技术来测量NKCC 2在分离的大鼠THAL中的运输和活性。该提案的数据将增加我们对塔尔如何调节正常和盐敏感动物的盐吸收的理解，并将确定利尿剂开发的新靶点。

DESCRIPTION (provided by applicant): The number of Na-transporters in the cell membrane is regulated by dynamic insertion, retrieval and, recycling of transporters. Collectively these processes are known as trafficking. In some forms of human and experimental hypertension salt retention is caused by abnormally high levels of Na-transporters in the apical membrane of some nephron segments. The thick ascending limb (THAL) absorbs NaCI and contributes to salt and water homeostasis, thereby influencing blood pressure. NaCI absorption by the THAL is primarily regulated by NKCC2, an apical Na/K/2CI cotransporter that mediates Na and Cl entry into the cell. To date, it is not clear whether trafficking of NKCC2 regulates NaCI absorption. It is also not clear whether vasoactive hormones that stimulate and autacoids that inhibit NaCI absorption by the THAL regulate NKCC2 levels in the apical membrane by affecting its trafficking. We hypothesize that NaCI absorption by the THAL is regulated in part by trafficking of NKCC2 into the apical membrane, in a process stimulated by cAMP and inhibited by nitric oxide. Enhanced insertion of NKCC2 into the apical membrane contributes to salt retention in models of salt-sensitive hypertension. In Aim I we will examine whether NKCC2 levels in the apical membrane and NaCI absorption are regulated by insertion and retrieval of NKCC2. In Aim II we will study whether hormones that stimulate NKCC2-dependent NaCI entry into THALs via cAMP increase NKCC2 levels in the apical membrane. In Aim III we will study whether nitric oxide inhibits NKCC2-dependent NaCI entry by decreasing NKCC2 levels in the apical membrane. Finally we will examine whether basal and hormone-stimulated NKCC2 levels in the apical membrane are enhanced in THALs from salt-sensitive animals. We will use state-of-the-art techniques to measure NKCC2 trafficking and activity in isolated rat THALs. Data from this proposal will increase our understanding of how salt absorption by the THAL is regulated in normal and salt-sensitive animals, and will identify new targets for the development of diuretics.