Stable Isotope Approaches to the Understanding of Potassium Homeostasis

项目摘要 钾(K+)稳态对正常的心血管和神经肌肉功能至关重要， K+稳态紊乱(例如，高钾血症)可导致危及生命的心血管事件。 细胞外K+稳态是通过肾脏和肾外机制维持的。肾脏有一种非凡的 调节K+排泄以匹配K+摄取的能力，在维持慢性K+平衡中起主要作用。在……里面 此外，肾外组织(主要是骨骼肌，主要的K+储存库)通过移位提供K+缓冲能力 胞外液和胞内液之间的K+。此外，肠道对饮食中的K+的感觉似乎会产生 调节肾脏K+排泄和肾外K+移位的信号。因此，细胞外K+动态平衡包括 多个器官和组织，它们对饮食K+摄入量的适应，以及它们之间的串扰。尽管有标记 近几十年来在这一领域的进展，关于K+动态平衡机制的许多关键问题仍然存在 由于缺乏适当的方法而悬而未决。细胞外K+动态平衡研究的主要局限 是无法量化体内的K+流量。尽管之前的研究使用放射性的86Rb来量化K+通量， 86Rb的K+示踪剂、放射性暴露和较短的半衰期限制了其在体外研究中的应用。稳定 各种元素的同位素已被用来量化各种底物或血液的流量 体内的成分。然而，尽管自然界中存在两种稳定的K+同位素(39K，93.3%和41K， 6.7%)，由于分析的局限性，这种方法还没有应用于体内K+动态平衡的研究。 普林斯顿大学的地球化学家约翰·希金斯博士开发了确定这一比例的分析方法 用电感耦合等离子体质谱分析天然样品中稳定的K+同位素(41K/39K)。这 最先进的技术提供了使用稳定同位素在体内确定K+通量的机会(即， 而不使用放射性示踪剂)。当前提案的目标是开发和验证这一新的 体内K~+流通量的估算方法及其推广到个体K~+转运活性的评价 纸巾。如果开发成功，这些新的尖端方法将打开新的大门 体内K+动态平衡机制的重要问题和填补空白。这些稳定的同位素方法 将是高度创新的，因为他们允许进行全身和体外K+通量分析，这是任何 传统方法，包括86Rb的方法。

Project Summary Potassium (K+) homeostasis is critical for normal cardiovascular and neuromuscular function, and disturbances in K+ homeostasis (e.g., hyperkalemia) can lead to life-threatening cardiovascular events. Extracellular K+ homeostasis is maintained by renal and extrarenal mechanisms. The kidneys have a remarkable capacity to regulate K+ excretion to match K+ intake, playing the major role in maintaining chronic K+ balance. In addition, extrarenal tissues (mainly skeletal muscle, the major K+ store) provide K+ buffering capacity by shifting K+ between the extracellular and intracellular fluids. Furthermore, gut sensing of dietary K+ appears to generate signals for regulating renal K+ excretion and extrarenal K+ shift. Thus, extracellular K+ homeostasis involves multiple organs and tissues, their adaptation to dietary K+ intake, and crosstalk among them. Despite marked progress in this field in recent decades, many critical issues concerning K+ homeostatic mechanisms remain unresolved due to a lack of appropriate methodology. A main limitation in studies of extracellular K+ homeostasis is an inability to quantify K+ fluxes in vivo. Although previous studies quantified K+ fluxes using 86Rb, a radioactive tracer for K+, radioactivity exposure and short half-life of 86Rb have limited its use to in vitro studies. Stable isotopes of a wide range of elements have been used to quantify fluxes of various substrates or blood constituents in vivo. However, in spite of the existence of two stable isotopes of K+ in nature (39K, 93.3% and 41K, 6.7%), this approach has not been applied to the study of K+ homeostasis in vivo due to analytical limitations. Dr. John Higgins, a geochemist at Princeton University, developed analytical methods for determining the ratio of stable K+ isotopes (41K/39K) in natural samples using inductively coupled plasma mass spectrometry. This state-of-the-art technology provides the opportunity to determine K+ fluxes in vivo using stable isotopes (i.e., without using radioactive tracers). The objective of the current proposal is to develop and validate this new approach for estimating whole-body K+ fluxes in vivo and extend it to assess K+ transport activities in individual tissues. If successfully developed, these new cutting-edge approaches will open new doors to answering important questions and filling gaps in K+ homeostatic mechanisms in vivo. These stable isotope approaches will be highly innovative, as they allow whole-body and in vitro K+ flux analyses that were infeasible with any conventional approaches, including those with 86Rb.