Subcellular Origin of T-wave Alternans in the Beating Mouse Heart

小鼠跳动心脏中 T 波交替的亚细胞起源

• 批准号: 7345433
• 负责人: ARIEL L ESCOBAR
• 金额: $ 38万
• 依托单位: UNIVERSITY OF CALIFORNIA, MERCED
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-01 至 2012-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7345433
• 关键词: Action Potentials; Address; Animal Model; Binding; Binding Proteins; Biological Models; Buffers; Calsequestrin; Cardiac; Cell Line; Data; Defect; Diffusion; Electrocardiogram; Endocardium; Epicardium; Fluorescence Microscopy; Functional disorder; Heart; Heart Rate; Immune; Lead; Left; Link; Localized; Maps; Measurement; Measures; Membrane Potentials; Metabolic; Metabolic stress; Metabolism; Methods; Modeling; Molecular; Monitor; Mus; Organ; Pathology; Phase; Physiologic intraventricular pressure; Physiologic pulse; Predisposition; Process; Pulse taking; Pump; Rate; Reaction; Relaxation; Research Personnel; Residual state; Resolution; Sarcoplasmic Reticulum; Signal Transduction; Site; Surface; Tachycardia; Testing; Theoretical model; Thinking; Time; Transgenic Animals; Transgenic Mice; Ventricular; Work; novel; programs; reuptake; sudden cardiac death; uptake

DESCRIPTION (provided by applicant): Intracellular Ca signaling in heart is a highly integrated process defined by the concerted function of numerous channels, pumps, transporters and buffers. Although several pathologies are associated with defects in Ca2+ handling, the specific mechanisms that link the deficiency to organ-level cardiac dysfunction are generally not well defined. One example is T-wave alternans (TW-Alt). TW-Alt is observed as alternating beat- to-beat changes in the T-wave of the electrocardiogram (ECG) and constitutes an important arrhythmogenic mechanism that can lead to sudden cardiac death. Likelihood of TW-Alt increases with tachycardia and is thought to be associated with abnormalities in intracellular Ca2+ handling and/or cellular metabolism. Despite years of study and debate, the mechanistic links between TW-Alt, tachycardia, intracellular Ca2+ handling and cellular metabolism are still unclear. One obstacle has been the absence of an experimental model system where all the salient factors can be explored in an integrated context (i.e. the working heart). To address this obstacle, a novel method (pulsed local field fluorescence microscopy or PLFF) was developed. This method allows very localized, high-resolution measurements of surface membrane potential and intracellular Ca2+ handling in Langendorff-perfused beating hearts where organ-level parameters (like heart rate, ECG, ventricular pressure) can be manipulated and measured. Multiple parameter real-time recording, simultaneous monitoring at multiple sites on the heart, and an integrative theoretical model are combined here to identify the molecular mechanisms that generate TW-Alt. Mouse heart is used in this proposal to more definitively establish mechanism using existing transgenic animal models. Preliminary results have led to the following hypothesis: In the mouse heart, insufficient Ca2+ uptake by the sarcoplasmic reticulum (SR) during tachycardia (or metabolic stress) produces intracellular Ca2+ release alternans (Ca-Alt). This first occurs in cells lining the endocardium and then progresses transmurally across the ventricular wall. This Ca-Alt generates beat-to-beat changes in Na- Ca exchanger activity producing beat-to-beat alterations in action potential (AP) repolarization. The resulting transmural difference in AP repolarization creates the TW-Alt observed in the ECG waveform.

描述（由申请人提供）：心脏内的细胞内CA信号传导是一个由许多通道，泵，转运蛋白和缓冲区的协同功能定义的高度整合过程。尽管几种病理与CA2+处理中的缺陷有关，但将缺陷与器官水平心脏功能障碍联系起来的特定机制通常没有很好地定义。一个例子是T波替代品（TW-alt）。观察到Tw-alt是心电图（ECG）T波的交替拍打to-beat变化，并且构成了一种重要的心律失常机制，可导致心脏突然死亡。 Tw-alt的可能性随心动过速增加，被认为与细胞内Ca2+处理和/或细胞代谢异常有关。尽管进行了多年的研究和争论，但TW-ALT，心动过速，细胞内CA2+处理和细胞代谢之间的机械联系仍不清楚。一个障碍是缺乏实验模型系统，在该模型系统中，可以在集成的环境（即工作心脏）中探索所有显着因素。为了解决这一障碍，开发了一种新型方法（脉冲局部荧光显微镜或PLFF）。该方法允许在Langendorff陷入的跳动心脏中对表面膜电位和细胞内CA2+处理的非常局部的高分辨率测量，其中可以操纵和测量器官级参数（例如心率，ECG，心率，心室，心室，心室，心室压力）。多个参数实时记录，在心脏上的多个位点同时监测，并在此组合一个集成的理论模型，以识别产生TW-ALT的分子机制。在该提案中使用小鼠心脏使用现有的转基因动物模型更明确地建立机制。初步结果导致了以下假设：在小鼠心脏中，在心动过速（或代谢应激）期间，肌浆网（SR）的Ca2+摄取不足，会产生细胞内Ca2+释放的替代品（CA-ALT）。这首先发生在内膜内衬的细胞中，然后在心室壁上传播。该Ca-alt在Na-CA交换器活动中产生了Beat-to-Beat变化，从而在动作电位（AP）复极化中产生了beat-to-beat变化。 AP复极化的产生透壁差异会在ECG波形中观察到TW-ALT。