Stable Isotope Approaches to the Understanding of Potassium Homeostasis

项目摘要 钾（K+）稳态对正常心血管和神经肌肉功能至关重要， K+稳态的紊乱（例如，高钾血症）可导致危及生命的心血管事件。 细胞外K+稳态由肾和肾外机制维持。肾脏有一个显著的 调节K+排泄以匹配K+摄入的能力，在维持慢性K+平衡中起主要作用。在 此外，肾外组织（主要是骨骼肌，主要的K+库）通过转移提供K+缓冲能力。 细胞外液和细胞内液之间的K+。此外，肠道对膳食K+的感知似乎会产生 调节肾K+排泄和肾外K+转移的信号。因此，细胞外K+稳态涉及 多器官和组织，它们对膳食K+摄入的适应，以及它们之间的串扰。尽管标记 尽管近几十年来这一领域的研究取得了很大进展，但有关K+稳态机制的许多关键问题仍然存在 由于缺乏适当的方法，这一问题尚未得到解决。细胞外钾稳态研究的一个主要局限 不能定量体内K+通量。虽然先前的研究使用放射性同位素86Rb定量K+通量， K+示踪剂、放射性暴露和86Rb的短半衰期限制了其在体外研究中的使用。稳定 广泛范围的元素的同位素已被用于量化各种基质或血液的通量 体内成分。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%），由于分析限制，该方法尚未应用于体内K+稳态的研究。 博士普林斯顿大学的地球化学家约翰·希金斯（John Higgins）开发了确定比例的分析方法 用电感耦合等离子体质谱法测定了天然样品中稳定的钾同位素（41K/39K）。这 现有技术提供了使用稳定同位素在体内测定K+通量的机会（即， 不使用放射性示踪剂）。本提案的目标是制定和验证这一新的 一种估算体内全身K+通量的方法，并将其扩展到评估个体K+转运活动 组织中如果开发成功，这些新的尖端方法将为回答 重要的问题和填补空白的K+体内稳态机制。这些稳定同位素方法 将是高度创新的，因为它们允许全身和体外K+通量分析，这是不可行的任何 常规方法，包括使用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.