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）：细胞外液（ECF） +}必须维持在一个狭窄的范围内。如果 ECF +] 降得太低 （低钾血症），细胞膜超极化，如果 ECF +] 增加过多 （高钾血症）细胞膜脱氧，两者都会破坏正常的电 兴奋性并可能产生危及生命的心脏效应。肾脏和肌肉 共同努力维持 ECF]。低钾血症期间肌肉 ICF K 为 重新分配以缓冲 ECF 的下降}。高钾血症期间 K+ 被泵出 进入肌肉 ICF，直到可以发生肾脏调整。这些重要的肌肉 特定的稳态过程才刚刚开始被理解 分子水平。有证据支持这样的假设：肌肉中 K 的损失 低钾血症是由于钠介导的活性 K+ 流入减少所致 泵（Na，KATPase，NKA）抑制，高钾血症期间 K+ 的摄取是 由钠泵激活介导。我们的实验室已经确定，在低 K+ 期间 NKA 亚基的饮食丰度在异构体和肌肉特异性中被抑制 方式： a2 下降 60-95%，而不是 1。使用新颖的 K+ 钳位技术，我们 最近表明，在 K+ 限制的早期，在 a2 下降之前，有一个 胰岛素刺激的 K+ 摄取和胰岛素刺激的吸收严重减弱 NKA ct2 型泵从内体到质膜的重新分配 （下午）。越来越多的证据表明布美他尼敏感的 Na,K,2C1 协同转运蛋白 也解释了肌肉 K+ 流入的一个组成部分，因此可能发挥作用 钾稳态。总体目标是确定分子 低钾血症期间负责利用肌肉 K+ 储备的机制， K+ 恢复后将多余的血浆 +] 清除到 ICF 存储中，并 了解这些过程如何在一组临床相关的过程中改变 范式。 Na,K-ATPase 亚型和 NKCCI 在两种红色中的贡献 将通过区室分析研究氧化白色糖酵解肌 评估以下内容的方法：全身 K+ 吸收、肌肉 K+ 的特异性转运、亚细胞分布和 K+ 活性 转运蛋白以及 K 转运蛋白和 mRNA 池大小调节 水平。目标 1 将检验以下假设：K 期间 K+ 向 ECF 的转变 限制是由质膜（PM）表达减少介导的 NKA a2 和 NKCC1 与胰岛素刺激的 K+ 摄取抵抗相结合，并且 这一过程在尿毒症伴有慢性肾功能衰竭时发生改变。目的 2 将检验甲状腺激素或地塞米松的假设，两者 增加 NKA cx2（也许还有 NKCC 1），改变 K+ 的肾外控制 激素平衡。目标 3 将检验以下假设：从 ECF 摄取 K+ K+ 恢复期间（K+ 限制后）的 ICF 通过标准化介导 NKA a2 和 NKCC1 的表面表达。实现这些目标将 确定负责挖掘和补充的细胞机制 肌肉 K+ 储库，理想情况下，它将提出操纵策略 肌肉 K 储存在临床环境中。