NMR STUDIES OF SODIUM HOMEOSTASIS IN ISCHEMIC MYOCARDIUM

缺血心肌钠稳态的核磁共振研究

• 批准号: 2397037
• 负责人: MARTIN M PIKE
• 金额: $ 14.59万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-08-01 至 2000-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2397037
• 关键词: acidity /alkalinity; bicarbonates; bioenergetics; high energy compound; ion transport; laboratory rat; myocardial ischemia /hypoxia; nuclear magnetic resonance spectroscopy; reperfusion; rubidium; sarcolemma; sodium channel; sodium ion; sodium potassium exchanging ATPase

Previous studies have demonstrated that intracellular Cs2+ overload plays an important role in myocardial ischemic injury, and that an important determinant of Ca2+ homeostasis is the control of intracellular Na+ (Na+). However, Na+ homeostasis during ischemia is still poorly understood. The proposed project will employ a unique combination of state-of-the-art NMR techniques to obtain a comprehensive assessment of how Na+I is controlled in the myocardium, during ischemia and hypoxia. Using the intact perfused rat heart model, interleaved 23Na and 31P NMR spectra will monitor changes in Na+I and cellular energy. In the same preparations, 87Rb NMR spectroscopy will be used to monitor Rb+ uptake and Na+/K+ ATPase activity. Using 7Li NMR spectroscopy, Li+ uptake will be measured to monitor voltage- gated Na+ channel activity. This methodology not only measures net Na+ accumulation, but is designed to also provide simultaneous information concerning how changes in unidirectional Na+ fluxes induce it. The following specific aims will be addresses: 1. To measure sarcolemmal Na+/K+ ATPase activity during control normoxic perfusion, hypoxia, and low-flow ischemia. The experiments will determine whether Na+ extrusion decreases or increases under the latter two conditions. Also, to examine Na+/K+ ATP activity in the context of the various metabolic modulators such as Na+, cellular energy status, pH, etc., in order to assess how functional alteration may occur during ischemia/hypoxia. 2. To determine the rate of unidirectional Na+ influx, during control normoxic perfusion, hypoxia, and low-flow ischemia, by using the Na+ and Na+ extrusion rate measurements. These measurements will determine if unidirectional Na+ influx is altered under the various conditions, and in particular, if it is downregulated during low-flow ischemia, as compared to control normoxia and hypoxia. Also, to compare these Na+ influx alterations with those obtained from measurement of Li+ uptake, which has specificity for Na+ channel activity. 3. To measure the rates of Na+ influx which occur via Na+/H+ exchange, during control normoxic perfusion, hypoxia, and low- flow ischemia, and to assess the importance of this mechanism in contributing to Na+ accumulation under various ischemic/hypoxic conditions. 4. To measure the rates of unidirectional Na+ influx which occur via Na+-HCO3- cotransport, during control normoxic perfusion, hypoxia, and low-flow ischemia, and to assess the importance of this mechanism in contributing to Na+ accumulation under various ischemic/hypoxic conditions. Also, to assess the possible interaction of this pH regulatory mechanism with Na+/H+ exchange (whether inhibition of one stimulates the other). 5. To measure the rate of Na+ influx which occur via non- inactivating Na+ channel current, during control, normoxia, hypoxia, and low-flow ischemia, and to assess the importance of this mechanism in contributing to Na+ accumulation under various ischemic/hypoxic conditions.

先前的研究表明，细胞内 Cs2+ 超负荷在心肌缺血性损伤中起着重要作用 Ca2+稳态的一个重要决定因素是控制 细胞内Na+（Na+）。 然而，Na+稳态 对缺血的了解仍知之甚少。 拟议的项目将 采用最先进的 NMR 技术的独特组合 获得对 Na+I 的控制方式的全面评估 心肌缺血、缺氧时。 使用原封不动的 灌注大鼠心脏模型，交错 23Na 和 31P NMR 谱 将监测 Na+I 和细胞能量的变化。 在同一个 制剂，87Rb NMR光谱将用于监测 Rb+ 摄取和 Na+/K+ ATP 酶活性。 使用 7Li NMR 光谱学，将测量Li+的吸收以监测电压- 门控Na+通道活性。 该方法不仅测量 净 Na+ 积累，但旨在同时提供 有关单向 Na+ 通量如何变化的信息 诱发它。 将解决以下具体目标： 1. 测量肌膜Na+/K+ ATP酶活性 控制含氧量正常的灌注、缺氧和低流量缺血。 这 实验将确定 Na+ 挤出是否减少或 在后两种情况下会增加。 另外，要检查 各种代谢背景下的 Na+/K+ ATP 活性 调节剂，如 Na+、细胞能量状态、pH 等，以便 评估期间如何发生功能改变 缺血/缺氧。 2. 为了确定单向 Na+ 流入的速率， 控制含氧量正常的灌注、缺氧和低流量缺血，通过 使用 Na+ 和 Na+ 挤出速率测量。 这些 测量将确定单向 Na+ 流入是否改变 在各种条件下，特别是如果 与对照相比，低流量缺血期间下调 常氧和缺氧。 另外，为了比较这些 Na+ 流入 与测量 Li+ 吸收所获得的变化， 对 Na+ 通道活性具有特异性。 3. 测量通过 Na+/H+ 发生的 Na+ 流入速率 交换，在控制常氧灌注、缺氧和低氧 血流缺血，并评估该机制的重要性 在各种缺血/缺氧情况下有助于Na+积累 状况。 4. 测量发生的单向 Na+ 流入的速率 通过 Na+-HCO3- 共转运，在控制常氧灌注期间， 缺氧和低流量缺血，并评估其重要性 这种机制在不同的条件下有助于Na+的积累 缺血/缺氧条件。 另外，为了评估可能的 这种 pH 调节机制与 Na+/H+ 的相互作用 交换（抑制一种物质是否会刺激另一种物质）。 5. 测量通过非非离子通道发生的 Na+ 流入速率 灭活Na+通道电流，在控制期间，含氧量正常， 缺氧和低流量缺血，并评估其重要性 这种机制在不同的条件下有助于Na+的积累 缺血/缺氧条件。