RENAL NET ACID SECRETION AND THE NA/K/2C1 CONTRANSPORTER

两个不同的基因(BSC-1和BSC-2)编码NA/+-K/+-2CI-co- 传送器。BSC-1，或“吸收异构体”，是肾脏特有的， 定位于粗大的升肢的顶膜。BSC-2， “分泌型”亚型，广泛分布于BSC-1中，负责 逆流倍增器的“单一效应”，从而产生 骨髓间质中氨和其他物质的轴向梯度 溶质，促进净排酸和尿液浓缩。在……里面 粗大的上肢，Na/+-K/+-2CI-共转运体对NH/4的摄取 (BSC-1)受到高度监管。由于BSC-2定位于基底外侧 大鼠α-嵌合细胞膜，因为它既是NH/4 AMD是一种CO/转运蛋白，它可能介导净酸分泌。然而， BSC-2在肾脏中的调节及其在净酸分泌中的作用 未经测试。集合管对CI-和H/+净分泌的调节 要求对这些离子的传输进行并行调节 集合管细胞的顶膜和基侧膜。使用 酸碱平衡紊乱，如慢性代谢性酸中毒和 观察到顶端质子分泌的增加，这是由于向上- 心尖部H/+-ATPase的调节与基底外侧脑缺血的平行 HCO/3-交换器。然而，在CI-/HCO/3-交换的大鼠贡献中 对跨上皮净酸和CI的分泌尚未建立。 因此，另一种净H/+和/或CI-摄取机制 基侧膜可能在调节或调节中起重要作用 跨上皮网酸分泌。我们将确定捐款 BSC-2对跨上皮净酸和净CI分泌的影响。此外，我们 将确定共转运蛋白的活性是否在 一种适用于酸碱扰动校正的方式 平衡。随着最近共转运蛋白两种异构体的克隆， 已发表的结构已被用来提高抗体。 共转运蛋白多肽。这些抗体可以用来研究Long 联运公司的定期监管。蛋白质的变化 免疫反应性和信使核糖核酸可以与运输的变化相关 确定共转运体在酸碱中的作用的活性 动态平衡。具体目标是确定大鼠的以下各项 OMCD：1.如果BSC-2通过直接NH/4+调节净酸分泌 领悟。2.如果BSC-2是跨上皮网CI的主要贡献者- 分泌物。4.探讨BSC-2转运调控机制。 为了回答这些问题，体外灌流的孤立肾小管将 被研究。将用微量荧光测定法以及 PH值敏感的荧光探头。转运蛋白免疫反应性和 将使用免疫印迹、免疫细胞化学来研究消息丰度 和RT-PCR法。

Two distinct genes (BSC-1 and BSC-2) encode the NA/+-K/+-2CI- co- transporter. BSC-1, or the "absorptive isoform", is kidney-specific and localizes to the apical membrane of the thick ascending limb. BSC-2, the "secretory" isoform, is widely distributed BSC-1 is responsible for the "single effect" of the countercurrent multiplier, and thereby generates an axial gradient in the medullary interstitium for ammonium and other solutes, facilitating net acid secretion and urinary concentration. In the thick ascending limb, NH/4 uptake by the Na/+-K/+-2CI-co-transporter (BSC-1) is highly regulated. Since BSC-2 localizes to the basolateral membrane of the rat alpha intercalated cell and since it is both an NH/4 amd a CO/transporter, it likely mediates net acid secretion. However, regulation of BSC-2 in the kidney and its role in net acid secretion are untested. Regulation of net CI- and H/+ secretion by the collecting duct requires transport of these ions to be regulated in parallel across the apical and the basolateral membrane of the collecting duct cell. With perturbations in acid-base balance such as chronic metabolic acidosis an increase in apical proton secretion is observed which results from up- regulation of the apical H/+-ATPase in parallel with the basolateral CI- HCO/3-exchanger. However, in the rat contribution of CI-/HCO/3-exchange to transepithelial net acid and CI-secretion has not been established. Thus, another mechanism for net H/+ and/or CI-uptake across the basolateral membrane may be important in mediating or modulating transepithelial net acid secretion. We will determine the contribution of BSC-2 to transepithelial net acid and net CI-secretion. Moreover, we will determine if activity of the co-transporter is modulated in a fashion appropriate for correction of perturbations in acid-base balance. With the recent cloning of both isoforms of the co-transporter, the published structure has been exploited to raise antibodies against co-transporter peptides. These antibodies can be used to study the long term regulation of the co-transporter. Changes in protein immunoreactivity and mRNA can be correlated with changes in transport activity to determine the role of the co-transporter in acid-base homeostasis. Specific Aims are to determine the following in the rat OMCD: 1. If BSC-2 modulates net acid secretion through direct NH/4+ uptake. 2. If BSC-2 is a major contributor to transepithelial net CI- secretion. 4. To determine the mechanism of BSC-2 transport regulation. To answer these questions, isolated renal tubules perfused in vitro will be studied. Transport will be studied with microfluorimetry as well as pH sensitive fluorescent probes. Transporter immunoreactivity and message abundance will be studied using immunoblots, immunocytochemistry and RT PCR.