EXTRA-RENAL REGULATION OF POTASSIUM HOMEOSTASIS

钾稳态的肾外调节

• 批准号: 6635254
• 负责人: Alicia A. McDonough
• 金额: $ 27.02万
• 依托单位: UNIVERSITY OF SOUTHERN CALIFORNIA
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-01 至 2005-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6635254
• 关键词: dexamethasone; electrolyte balance; enzyme mechanism; hormone regulation /control mechanism; hypokalemia; insulin; laboratory rat; membrane transport proteins; muscle metabolism; potassium ion; protein localization; sodium potassium exchanging ATPase; thyroid hormones

DESCRIPTION (Adapted from the Applicant's Abstract): Extracellular fluid (ECF) +} must be maintained within a narrow range. If ECF +] falls too low (hypokalemia), cell membranes hyperpolarize, and if ECF +] increases too much (hyperkalemia) cell membranes depobrize, both disrupt normal electrical excitability and can have life threatening cardiac effects. Kidneys and muscle work in concert to maintain ECF ]. During hypokalemia muscle ICF K is redistributed to buffer the fall in ECF }. During hyperkalemia K+ is pumped into muscle ICF until renal adjustments can occur. These important muscle specific homeostatic processes are only beginning to be understood at the molecular level. Evidence supports the hypothesis that K loss from muscle during hypokalemia results from decreased active K+ influx mediated by sodium pump (Na,KATPase, NKA) inhibition, and that K+ uptake during hyperktilemia is mediated by sodium pump activation. Our lab has established that during low K+ diet abundance of NKA subunits are depressed in an isoform and muscle specific manner: 60-95 percent fall in a2, not a 1. Using a novel K+ clamp technique, we recently showed that early in K+ restriction, prior to fall in a2, there is a severe blunting of both insulin stimulated K+ uptake, and of insulin stimulated redistribution of NKA ct2 type pumps from endosomes to the plasma membrane (PM). Evidence is mounting that the bumetanide sensitive Na,K,2C1 cotransporter also accounts for a component of muscle K+ influx and, thus, could play a role in potassium homeostasis. The overall aims are to determine the molecular mechanisms responsible for tapping muscle K+ stores during hypokalemia, for clearing excess plasma +] into the ICF store after K+ restoration, and to understand how these processes are altered in a set of clinically relevant paradigms. The contribution of both Na,K-ATPase isoforms and NKCCI in both red oxidative white glycolytic muscle will be studied with a compartmental analysis approach in which the following are assessed: whole body K+ uptake, muscle specific K+ transport, subcellular distribution and activity of K+ transporters, and pool size regulation of K transporter protein and mRNA levels. Aim 1 will test the hypothesis that the shift of K+ to ECF during K restriction is mediated by decreased plasma membrane (PM) expression of both NKA a2 and NKCC1 coupled to resistance to insulin stimulated K+ uptake, and that this process is altered in uremia accompanying chronic renal failure. Aim 2 will test the hypothesis that thyroid hormone or dexamethasone, both of which increase NKA cx2 (and perhaps NKCC 1), alter extrarenal control of K+ horneostasis. Aim 3 will test the hypothesis that the uptake of K+ from ECF to ICF during K+ restoration (following K+ restriction) is mediated by normalizing surface expression of both NKA a2 and NKCC1. Accomplishing these aims will identify the cellular mechanisms responsible for tapping and repleting the muscle K+ reservoir, which will, ideally, suggest strategies to manipulate muscle K stores in clinical settings.

描述（改编自申请人的摘要）：细胞外流体（ECF） +}必须保持在狭窄范围内。如果ECF +]跌倒太低 （低钾血症），细胞膜超极化，如果ECF +]增加了太多 （高钾血症）细胞膜Depobrize，都破坏正常电气 兴奋性，可能会威胁生命的心脏影响。肾脏和肌肉 协同工作以维持ECF]。在低钾血症期间ICF K是 重新分布以缓冲ECF的下落。在高钾血症期间，K+抽水 进入肌肉ICF，直到进行肾脏调整。这些重要的肌肉 具体的稳态过程才开始在 分子水平。证据支持k肌丧失的假设 在低钾血症期间，由钠介导的活性K+涌入降低导致 泵（Na，Katpase，NKA）抑制作用，HyperKlilemia期间的K+摄取为 由钠泵激活介导。我们的实验室已经确定，在低k+期间 NKA亚基的饮食丰度在同工型和肌肉特异性 方式： 60-95％落在A2中，而不是1。使用新颖的K+夹具技术，我们 最近表明，在A2跌倒之前的K+限制初期，有一个 两种胰岛素的严重钝化刺激的K+摄取和胰岛素的刺激 NKA CT2型泵的重新分布从内体到质膜 （下午）。有证据表明bumetanide敏感的Na，K，2C1共转运蛋白 还解释了肌肉K+涌入的组成部分，因此可以发挥作用 在钾稳态中。总体目的是确定分子 低钾血症期间负责攻击肌肉K+商店的机制，用于 在K +修复后将多余的血浆 +]清除到ICF商店中，然后 了解一组临床相关的过程如何改变这些过程 范式。 Na，K-ATPase同工型和NKCCI在两个红色中的贡献 氧化白糖酵解肌肉将通过分室分析进行研究 评估以下内容的方法：全身K+吸收，肌肉 特定的K+转运，k+的亚细胞分布和活性 转运蛋白的转运蛋白调节k转运蛋白和mRNA的调节 水平。 AIM 1将检验以下假设：K+在K期间转移到ECF 两者的质膜（PM）表达降低介导限制 NKA A2和NKCC1与胰岛素的抗性刺激K+摄取，并且 伴随慢性肾衰竭的尿毒症的尿中，这一过程发生了变化。目的 2将检验甲状腺激素或地塞米松的假设，这两种假设 增加NKA CX2（也许还有NKCC 1），改变了K+的外部控制 Horneostasis。 AIM 3将检验以下假设：K+从ECF摄取 K+恢复期间的ICF（K+限制后）通过标准化介导 NKA A2和NKCC1的表面表达。完成这些目标将 确定负责窃听和补充的细胞机制 肌肉K+水库，理想情况下将提出操纵策略 肌肉K存储在临床环境中。