Effects of K+ Accumulation/Depletion in the Heart

心脏中钾积累/消耗的影响

• 批准号: 7782625
• 负责人: Guy Salama
• 金额: $ 48.59万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 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/7782625
• 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

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）：对细胞和细胞外室中K+的调节对于调节体积调节，流体转运，静止膜电位和可激发细胞的电活动至关重要。在心脏中，细胞外的细胞外[K+]在细胞和T管中的狭窄裂缝中并不总是以外部K+（[k+] O）为扩散平衡，并且可以耗尽或累积，从而在广泛的范围内与[K+] O不同生理/病理状况。 该项目的核心目的是阐明细胞外K+积累（[K+] A）对生理和病理条件下心脏电活动的后果。为此，我们开发了新的K+敏感荧光探针，可以锚定在质膜上并在与K+结合后产生荧光变化，以报告局部[K+]。我们可以校准探针，测量心室心肌和兰多德夫心脏中[K+] A的快速变化（1 ms）。具体目的是：目标1：改进我们的新的K+敏感探针，包括：i）疏水基团以将探针锚定为脂质双层，ii）亲水基团溶解并防止探针在整个膜中散布到细胞中，iii）iii）。荧光染料感应IV）K+与K+ - 选择性有机冠环的结合，并在1-50 mm的范围内表现出荧光变化，这是[K+]的函数。 目的2：检验以下假设：在不同的生理条件下对[K+] a的不同贡献不同（heftrate，是2-肾上腺素能活性）和代谢状态。 [k+]在药理学干预过程中，将比较A反应，负责K+外排的通道（IK1，IT，O，IK，slow，slow，ikr，IKR，IKR，IKR，IKR），以及通过Na/k泵进行K+重新摄取的操作。 [K+] A将在心房和心室肌细胞中进行比较，以测试APD，K+电流和T管的差异的影响。在灌注的心脏中，APS和[K+] A将同时映射，并且[K+] A的变化将以节拍对基础进行测量。 目的3：为了检验以下假设：在病理条件下，[K+] A的兴起可以导致心肌区域，并增加兴奋性和更大的局灶性活动或过早的节拍倾向，从而引发心律不齐。 APS的同时光学映射和[K+] A中的[K+]将用于测量AP并进行[K+] A瞬变的变化，以阐明在hardrythmias在缺血/再灌注引起的[K+] A的作用中，全球（零流）或通过LAD连接在本地。 [K+]高程将与冠状动脉血管，纤维取向和过早冲动的起源有关。 这样的项目将开发K+敏感的染料，以应用于心脏电生理学，并首次以Beat-Beat为基础来表征[K+] A。 [K+] A和AP的双光学映射将确定生理和病理干预期间发生的[K+] A的变化，将验证减少[K+] A提供新靶标以治疗心脏疾病的方法。 公共卫生相关性：细胞外K+在T管中的积累和心肌的狭窄起伏已被视为正常心脏生理和病理学的决定因素。然而，从未直接测量过与周围水介质的扩散平衡的狭窄区域的[K+]浓度。该项目将综合新的K+指示剂探针，在T管中测量[K+]以及间质空间，并在正常的生理条件和各种病理中表征局部[K+]积累。 K+积累的作用可能会导致对机制的新理解，从而增强心律不齐的可能性，提供新的方法来减少除颤阈值，减少除颤后VF的复发，提高过去5分钟的除颤成功率，并可能导致纤维化的成功率用于治疗缺血性心脏病的新治疗靶标。