Effects of K+ Accumulation/Depletion in the Heart

心脏中钾积累/消耗的影响

基本信息

批准号：
8207238
负责人：
Guy Salama
金额：
$ 47.31万
依托单位：
UNIVERSITY OF PITTSBURGH AT PITTSBURGH
依托单位国家：
美国
项目类别：
财政年份：
2010
资助国家：
美国
起止时间：
2010-01-15 至 2013-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8207238
关键词：
Adrenergic Agents Affinity Arrhythmia Binding Cardiac Cations Cell membrane Cells Cleaved cell Coronary Vessels Crown Ethers Diffuse Dyes Ectopic beats Electric Countershock Electrophysiology (science)Epicardium Equilibrium Exhibits Fiber Fluorescence Fluorescent Dyes Fluorescent Probes Goals Heart Heart Atrium Heart Diseases Heterogeneity In Vitro Intervention Ischemia Kinetics Lead Ligation Lipid Bilayers Liquid substance Maps Measures Membrane Membrane Potentials Metabolic Methods Muscle Cells Myocardial Ischemia Myocardium Optics Pathology Physiological Physiology Potassium Channel Property Pump Recurrence Regulation Reperfusion Therapy Reporting Rest Role Tail Testing Time Ventricular adrenergic aqueous base extracellular heart electrical activity improved interstitial new therapeutic target novel strategies premature prevent public health relevance response stop flow technique success uptake

项目摘要

DESCRIPTION (provided by applicant): Regulation of K+ in cellular and extracellular compartments is of central importance to volume regulation, fluid transport, the resting membrane potential and electrical activity in excitable cells. In heart, extracellular [K+] in narrow clefts between cells and in T-tubules is not always in diffusional equilibrium with external K+ ([K+]o ) and can be depleted or accumulated and thereby differ from [K+]o during a wide range of physiological/pathological conditions. The central goal of the project is to elucidate the consequences of extracellular K+ accumulation ([K+]a) on cardiac electrical activity in physiological and pathological conditions. To do so, we developed new K+ sensitive fluorescent probes that can be anchored to plasma membranes and upon binding to K+ produce a fluorescence change that reports the local [K+]. We can calibrate the probe, measure rapid (1 ms) changes in [K+]a in ventricular myocytes and Langendorff hearts. The Specific Aims are: Aim 1: Improve our new K+ sensitive probes consisting of: i) hydrophobic groups to anchor the probe to lipid bilayers, ii) hydrophilic groups to dissolve and prevent the probe from diffusing across the membrane into cells, iii) a fluorescent dye that senses iv) the binding of K+ to a K+- selective organic crown ether ring and exhibits a fluorescence change as a function of [K+] in the range of 1-50 mM. Aim 2: To test the hypothesis that different K+ currents contribute differently to [K+]a under different physiological conditions( ?? heartrate, ?? 2-adrenergic activity) and metabolic states. [K+]a responses will be compared during pharmacological interventions of channels responsible for K+ efflux (IK1, It,o, IK,slow, IKr, IKs, IKATP) and during manipulations of K+ re-uptake via the Na/K pumps. [K+]a will be compared in atrial and ventricular myocytes to test the effects of differences in APDs, K+ currents and T-tubules. In perfused hearts, APs and [K+]a will be simultaneously mapped, and changes in [K+]a will be measured on a beat-to-beat basis. Aim 3: To test the hypothesis that in pathological conditions, the rise of [K+]a can lead to regions of myocardium with an increase in excitability and a greater propensity to focal activity or premature beats that initiate arrhythmias. Simultaneous optical mapping of APs and [K+]a in perfused hearts will be used to measure APs and beat-to- beat changes in [K+]a transients to elucidate the role of [K+]a during arrhythmias elicited by ischemia/reperfusion applied either globally (zero flow) or locally via an LAD ligation. [K+]a elevation will be correlated with coronary vessels, fiber orientation and the origins of premature impulses. Such a project will develop K+ sensitive dyes for applications to cardiac electrophysiology and for the first time characterize [K+]a on a beat-to-beat basis. Dual optical mapping of [K+]a and APs will determine the changes in [K+]a that occur during physiological and pathological interventions, will validate methods to reduce [K+]a to offer new targets to treat cardiac diseases. PUBLIC HEALTH RELEVANCE: Extracellular K+ accumulation in T-tubules and narrow invaginations of heart muscle has been implicated as a determinant of normal cardiac physiology and pathology. However, [K+] concentrations in narrow regions that are not in diffusional equilibrium with the surrounding aqueous medium have never been measured directly. The project will synthesize new K+ indicator probes, measure [K+] in t-tubules, and interstitial spaces and characterize local [K+] accumulation in normal physiological conditions and various pathologies. The role of K+ accumulation may lead to a new understanding of mechanisms that enhanced the likelihood of arrhythmias, provide novel approaches to reduce defibrillation threshold, reduce the recurrence of VF after defibrillation, improve the success rate of defibrillation past 5 min of fibrillation and may lead to new therapeutic targets for the treatment of ischemic heart disease.

描述（由申请人提供）：细胞和细胞外区室中 K+ 的调节对于可兴奋细胞中的容量调节、液体运输、静息膜电位和电活动至关重要。在心脏中，细胞间狭窄裂隙和 T 管中的细胞外 [K+] 并不总是与外部 K+ ([K+]o ) 处于扩散平衡，并且可能会耗尽或积累，从而在很宽的范围内与 [K+]o 不同生理/病理状况。该项目的中心目标是阐明生理和病理条件下细胞外 K+ 积累 ([K+]a) 对心电活动的影响。为此，我们开发了新的 K+ 敏感荧光探针，该探针可以锚定在质膜上，并在与 K+ 结合后产生荧光变化，报告局部 [K+]。我们可以校准探针，测量心室肌细胞和 Langendorff 心脏中 [K+]a 的快速 (1 ms) 变化。具体目标是：目标 1：改进我们的新型 K+ 敏感探针，包括：i) 将探针锚定到脂质双层的疏水基团，ii) 溶解并防止探针跨膜扩散到细胞中的亲水基团，iii) a荧光染料，感测 iv) K+ 与 K+- 选择性有机冠醚环的结合，并在 1-50 mM 范围内表现出随 [K+] 变化的荧光变化。目标 2：检验以下假设：不同的 K+ 电流在不同的生理条件（??心率、??2-肾上腺素能活动）和代谢状态下对 [K+]a 的贡献不同。 [K+]a 反应将在负责 K+ 流出的通道（IK1、It,o、IK、slow、IKr、IKs、IKATP）的药物干预期间和通过 Na/K 泵操作 K+ 再摄取期间进行比较。将比较心房和心室肌细胞中的 [K+]a，以测试 APD、K+ 电流和 T 管差异的影响。在灌注的心脏中，AP 和 [K+]a 将被同时绘制，并且 [K+]a 的变化将在每次心跳的基础上进行测量。目标 3：检验以下假设：在病理条件下，[K+]a 的升高可导致心肌区域兴奋性增加，并且更容易发生局灶性活动或引发心律失常的早搏。灌注心脏中 AP 和 [K+]a 的同步光学测绘将用于测量 AP 和 [K+]a 瞬变的逐搏变化，以阐明 [K+]a 在缺血/再灌注引起的心律失常中的作用全局（零流量）或通过 LAD 连接进行局部。 [K+]a 升高与冠状血管、纤维方向和过早冲动的起源相关。该项目将开发用于心脏电生理学的 K+ 敏感染料，并首次在逐次心跳的基础上表征 [K+]a。 [K+]a 和 AP 的双重光学测绘将确定生理和病理干预期间发生的 [K+]a 变化，将验证降低 [K+]a 的方法，为治疗心脏病提供新靶点。公共健康相关性：T 管和心肌狭窄内陷中细胞外 K+ 的积累被认为是正常心脏生理学和病理学的决定因素。然而，从未直接测量过与周围水介质不处于扩散平衡的狭窄区域中的 [K+] 浓度。该项目将合成新的 K+ 指示探针，测量 T 型小管和间质空间中的 [K+]，并表征正常生理条件和各种病理条件下的局部 [K+] 积累。 K+积累的作用可能会导致对增加心律失常可能性的机制有新的认识，提供降低除颤阈值的新方法，减少除颤后心室颤动的复发，提高除颤超过 5 分钟的除颤成功率，并可能导致治疗缺血性心脏病的新治疗靶点。