Gender-Differences in Cardiac Repolarization/Arrhythmias

心脏复极/心律失常的性别差异

• 批准号: 6905058
• 负责人: Guy Salama
• 金额: $ 7.28万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6905058
• 关键词: action potentials; arrhythmia; calcium channel blockers; cardiac myocytes; dihydrotestosterone; disease /disorder model; electrical potential; electrophysiology; estradiol; gender difference; gene expression; hormone therapy; immunocytochemistry; ion channel blocker; laboratory rabbit; long QT syndrome; messenger RNA; myocardial ischemia /hypoxia; nonhuman therapy evaluation; northern blottings; ovariectomy; placebos; potassium channel; protein structure function; voltage /patch clamp; western blottings

The long-term goal is to elucidate gender differences in the expression and spatial distribution of cardiac ionic channels and their functional consequences on the electrical and intracellular free Ca2+ (Cai) handling properties of the heart. Clinical studies have shown that women have longer corrected QT intervals (QTc), a greater propensity to drug-induced long QT syndrome (LQTS) and a higher incidence of sudden cardiac death than men. Differences in APD diminish after menopause implicating a modulation of ion channels by estrogen and/or testosterone. The effect of estrogen-replacement in post- menopausal women on arrhythmia vulnerability remains unknown. Female rabbits have longer APDs and QT intervals than males and a greater vulnerability to LQT-related arrhythmias. Differences in the expression and spatial distribution of IKr, IKs and/or ICa most likely account for differences in repolarization sequence, QT prolongation and enhanced susceptibility of females to arrhythmias. To characterize gender differences in Cai handling and dispersion of repolarization (DR), we propose to apply imaging techniques at high spatial and temporal resolution to simultaneously map voltage and intracellular Ca2+ transients from perfused rabbit hearts. Optical maps of APs and Cai transients q selective blockers for IKr, IKs and ICa will elucidate gender differences in the spatial distribution of these channels and will be correlated with measurements of Ito, IKr, IKs and ICa, by voltage clamping of ventricular myocytes isolated from various regions of the heart. These data will also be correlated with distributions of mRNA and protein using selective probes and antibodies for individual ion channel subunits. The specific aims are: 1) To characterize gender differences in the spatial distribution of Ito, IKr, IKs, and ICa and their functional effects on APD, repolarization and Cai handling that can be attributed to gonadal hormones. Hearts from female (q ovariectomy (OVX)), and male (q orchiectomy (ORX)) rabbits will be optically mapped (approximately 1 month later) to obtain baseline values for electrical and Cai handling. Hearts will then be treated with an IKr, IKs, and/or ICa blockers to measure changes in APD, repolarization patterns, and susceptibility to arrhythmias. Optical maps will be correlated with the distribution of ionic currents, channel mRNA levels and channel protein distribution using voltage clamp, Northern and Western blot techniques. 2) To investigate the effects of hormone replacement on the dispersion of repolarization and arrhythmia susceptibility by treating OVX and ORX rabbits with 17-beta estradiol (EST), 5alpha-dihydroxy-testosterone (DHT) for 2-3 weeks. Hearts will be examined for altered electrical and Cai handling properties, which will be correlated with changes in the distribution of ion channel currents, mRNA and protein levels. 3) To study gender differences in response to ischemic injury by determining the effects of acute and chronic ischemia (rabbit infarct model) on dispersion of repolarization and arrhythmias on males (q ORX) compared to females (q OVX). 4) To determine possible protective effects of estrogen replacement on ischemic injury. Changes in APD, dispersion of repolarization and arrhythmia susceptibility will be measured in an acute and chronic infarct model using rabbit hearts from OVX females with or without estrogen replacement. Such an investigation will analyze the functional effects of cardiac repolarization, a parameter that has been implicated in an underlying mechanism for the initiation and maintenance of arrhythmias and thus, will address a fundamental problem in women's health.

长期目标是阐明心脏离子通道的表达和空间分布的性别差异及其对心脏的电和细胞内游离CA2+（CAI）处理特性的功能后果。临床研究表明，女性具有更长的QT间隔（QTC），对药物诱导的长QT综合征（LQT）的倾向更大，而心脏死亡的发生率高于男性。 更年期后APD的差异暗示雌激素和/或睾丸激素对离子通道的调节。 雌激素替代在绝经后女性对心律不齐脆弱性的影响尚不清楚。雌性兔子的APD和QT间隔比男性更长，并且对LQT相关心律不齐的脆弱性更大。 IKR，IK和/或ICA的表达和空间分布的差异很可能解释了女性对心律不齐的雌性的复极序列，QT延长和增强的敏感性的差异。 为了表征在CAI处理和复极化（DR）中的性别差异，我们建议在高空间和时间分辨率下应用成像技术，以同时映射灌注兔心脏的细胞内CA2+瞬变。 IKR，IKS和ICA的AP和CAI瞬变的光学图Q选择性阻滞剂将阐明这些通道的空间分布中的性别差异，并将与ITO，IKR，IKS，IKS和ICA的测量相关，并通过从心脏夹具的voltage夹具的测量心脏的各个地区。 这些数据还将使用单个离子通道亚基的选择性探针和抗体与mRNA和蛋白质的分布相关。 具体目的是：1）表征ITO，IKR，IK和ICA的空间分布中的性别差异及其对APD，重复化和CAI处理的功能效应，这可以归因于性腺激素。 雌性（Q卵巢切除术（OVX））和雄性（Q Orchioctomy（Orx））兔子的心脏将被光学映射（大约1个月后），以获得电气和CAI处理的基线值。 然后，心脏将用IKR，IKS和/或ICA阻滞剂进行处理，以测量APD的变化，复极模式以及对心律不齐的易感性。光学图将与使用电压夹，北部和蛋白质印迹技术的离子电流，通道mRNA水平和通道蛋白分布的分布相关。 2）研究激素替代对复极化和心律失常易感性的影响，通过用17-β雌二醇（EST），5alpha-dihydroxy-Tostosterone（DHT）处理OVX和ORX兔子2-3周。 心脏将检查改变的电气和CAI处理特性，这将与离子通道电流，mRNA和蛋白质水平的分布变化相关。 3）通过确定急性缺血和慢性缺血（兔梗死模型）对男性（Q ORX）相比（Q OVX）对男性（Q ORX）的分散性，研究对缺血性损伤的性别差异。 4）确定雌激素替代对缺血性损伤的可能保护作用。 APD的变化，复极化的分散和心律不齐的敏感性将在急性和慢性梗塞模型中使用有或没有雌激素替代的OVX女性的兔心脏进行测量。这样的研究将分析心脏复极化的功能效应，心脏复极化的功能效应与基本机制有关心律失常的启动和维持，因此将解决妇女健康中的基本问题。