Sex Hormones and Cardiac Arrhythmia in Transgenic LQT2 Rabbits

心脏性猝死（SCD）每年夺去大约35万美国人的生命。新兴 有证据表明SCD的遗传易感性具有重要作用;然而， 仍然难以捉摸本提案的总体目标是研究SCD的新机制 通过创新技术的应用和新的长QT基因模型的新用途， 综合征2（LQT 2）。这种多管齐下的方法包括对青春期前， 卵巢切除的LQT 2兔，以探索性别影响的新机制范例 激素对心律失常的影响，使用体外和计算机实验方法， 新的分子、细胞、组织和理论模型。因为性别和交感神经 LQT 2中的一个系统在触发SCD中起关键作用，性激素和自主神经因素的影响 将详细研究SCD风险。该提案由四个具体目标组成：目标1： 性激素诱导的心脏复极化（QT间期和心脏复极化）变化的特征 不应期）、使用遥测ECG的自发TdP和心源性猝死发生率 监测和体内侵入性电生理学研究;目的2：分析动作电位持续时间， 复极化、传导、触发活动和电/机械不均匀性的分散 恢复和传导阻滞，使用动作电位和钙瞬变的光学映射。目标3： 定义（基于光学研究）心脏性别差异的分子决定因素 复极和兴奋通过分析性别或性激素相关的差异表达， 编码复极化钾电流、钙电流和蛋白质的或亚基的基因 控制Ca++循环和肾上腺素能受体的蛋白质表达研究， 定量实时PCR和细胞电生理学研究;目的4：进行比较 分析从经血管紧张素Ⅱ处理的心肌细胞中分离的肌细胞的动作电位和钙处理特性 在对照条件下和在自主神经受体刺激期间，使用膜片钳和 荧光指示剂技术。B）使用计算机建模来检查实验如何定义 这些LQT 2模型中的细胞/分子改变影响后去极化和促心律失常 模拟心脏组织中的基质形成。这些研究将有助于了解 机制，触发和维持心律失常的兔子，因此导致更好的 了解长QT综合征中的性别相关性心律失常。

Sudden cardiac death (SCD) claims the lives of approximately 350,000 Americans each year. Emerging evidence indicates an important role for genetic predisposition to SCD; however, the molecular determinants have remained elusive. The overall goal of this proposal is to investigate new mechanisms that underlie SCD through the application of innovative technology and the novel use of new genetic models of long QT syndrome 2 (LQT2). This multi-pronged approach includes the investigation of hormone-treated prepubertal, ovariectomized LQT2 rabbits to explore new mechanistic paradigms that underlie the effects of sex hormones on cardiac arrhythmias using in vitro and in silico experimental approaches that will integrate novel molecular, cellular, tissue, and theoretical models. Because gender and the sympathetic nervous system plays a key role in triggering SCD in LQT2, the influence of sex hormones and the autonomic factors on SCD risk will be studied in detail. The proposal is composed of Four Specific Aims: Aim 1: To characterize of the sex hormone induced changes in cardiac repolarization (QT duration and cardiac refractory periods), incidence of spontaneous TdP and sudden cardiac death with the use of telemetric ECG monitoring and in vivo invasive electrophysiological studies; Aim 2: To analyze the action potential duration, dispersion of repolarization, conduction, triggered activity and the heterogeneities in electrical/mechanical restitution, and conduction block using optical mapping of action potential and calcium transients. Aim 3: To define (based on the optical studies) the molecular determinants of the gender differences in cardiac repolarization and excitation by analyzing the gender or sex hormone related differences in the expression of genes coding for the or subunits of the repolarizing potassium currents, calcium currents, and proteins that control Ca++ cycling, and the adrenergic receptors with the use of protein expression studies and quantitative real-time PCR, and cellular electrophysiological studies; and Aim 4: To perform a comparative analysis of action potential and calcium-handling properties in myocytes isolated from hormone-treated LQT2 rabbits under control conditions and during autonomic receptor stimulation, using patch-clamp and fluorescent-indicator techniques. b) To use computer modeling to examine how experimentally defined cellular/molecular alterations in these LQT2 models influence afterdepolarizations and arrhythmogenic substrate formation in simulated cardiac tissue. These studies will contribute to the understanding of the mechanisms that trigger and maintain arrhythmias in hormone-treated rabbits, and therefore lead to a better understanding of gender-related arrhythmias in long QT syndrome.