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表达和空间分布的性别差异及其对心脏电和细胞内游离 Ca2+ (Cai) 处理特性的功能影响。临床研究表明，与男性相比，女性的校正 QT 间期 (QTc) 更长，更容易出现药物引起的长 QT 综合征 (LQTS)，心源性猝死的发生率更高。 绝经后 APD 的差异减少，这表明雌激素和/或睾酮对离子通道的调节。 绝经后妇女补充雌激素对心律失常易感性的影响仍不清楚。雌性兔子的 APD 和 QT 间期比雄性兔子更长，并且更容易出现 LQT 相关的心律失常。 IKr、IKs 和/或 ICa 的表达和空间分布的差异最有可能解释复极序列、QT 延长和女性对心律失常的易感性增强的差异。 为了表征 Cai 处理和复极分散 (DR) 的性别差异，我们建议应用高空间和时间分辨率的成像技术来同时绘制灌注兔心脏的电压和细胞内 Ca2+ 瞬变图。 AP 和 Cai 瞬变的光学图 q IKr、IKs 和 ICa 的选择性阻断剂将阐明这些通道空间分布的性别差异，并将通过对从心脏的各个区域。 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。 具体目标是： 1) 描述 Ito、IKr、IKs 和 ICa 空间分布的性别差异及其对 APD、复极和 Cai 处理的功能影响，这些影响可归因于性腺激素。 对雌性（q 卵巢切除术（OVX））和雄性（q 睾丸切除术（ORX））兔子的心脏进行光学绘图（大约 1 个月后）以获得电和 Cai 处理的基线值。 然后用 IKr、IKs 和/或 ICa 阻滞剂治疗心脏，以测量 APD、复极模式和心律失常易感性的变化。使用电压钳、Northern 和 Western blot 技术将光学图谱与离子电流的分布、通道 mRNA 水平和通道蛋白分布相关联。 2)用17-β雌二醇(EST)、5α-二羟基睾酮(DHT)治疗OVX和ORX兔2-3周，探讨激素替代对复极分散和心律失常易感性的影响。 将检查心脏的电和蔡处理特性的改变，这将与离子通道电流分布、mRNA 和蛋白质水平的变化相关。 3) 通过确定急性和慢性缺血（兔梗塞模型）对男性（q ORX）与女性（q OVX）相比的复极和心律失常离散度的影响，研究对缺血性损伤反应的性别差异。 4) 确定雌激素替代对缺血性损伤可能的保护作用。 将使用 OVX 雌性兔心脏（有或没有补充雌激素）在急性和慢性梗塞模型中测量 APD 的变化、复极离散度和心律失常易感性。这样的研究将分析心脏复极的功能影响，该参数与心律失常的引发和维持的潜在机制有关，因此将解决女性健康的基本问题。