MECHANISMS OF ALTERED CONTRACTILITY IN HEART FAILURE

拟议研究的总体目标是调查细胞 心脏收缩和舒张期异常的机制 心肌肥厚和衰竭时的收缩感受器。中的异常现象 钙稳态先前已经在动物模型中得到证实。 肥大和衰竭，以及从衰竭的人心脏中分离出来的细胞。 然而，这些研究未能确定单个的细胞过程 是这些反常现象的根源。重要的问题是走什么步(S) 在膜兴奋与随后的收缩和 在肥大和衰竭中，松弛会改变。在 钙稳态定量方案的理论框架 激发-收缩-松弛耦合的各个步骤将被 用电流法分别探测电压钳位(全电池和 单通道)、细胞内荧光钙(钙离子)指示剂，以及 笼状化合物的闪光光解。建议的具体目标 研究内容包括：1)检验一种假设，即钙离子通过 “触发”细胞内钙释放所需的L型钙通道 肌浆网(SR)在肥大和衰竭时发生改变。这 将涉及空穴细胞电流和单一钙电流的测量。2.) 检验肌浆网钙释放分级为L型的假说 钙电流在心肌肥厚和衰竭时发生改变。这将涉及到 单通道钙电流的测量及其同步测量 全细胞钙电流、细胞内钙离子的测定 瞬变和细胞缩短。3)检验一般假设 肌质网对钙离子的处理在肥大和衰竭时发生改变。 具体地说，3.1)测试心脏收缩功能异常的假设 肌浆网钙离子外流异常引起的收缩 释放通道，以及3.2)测试舒张压或 在肥厚和衰竭中看到的松弛异常是 肌浆网钙离子=三磷酸腺苷酶泵对钙离子的封存功能受损。4.)测试 假设钙离子结合配体(包括可收缩的 调节蛋白(肌钙蛋白C和钙调蛋白)在肥厚中发生改变 和失败。这些具体目标将在单个独立的 来自心肌肥厚和衰竭动物模型的肌细胞以及来自 人类的心脏衰竭。这项研究解决了根本问题 关于导致这种改变的确切细胞机制(S) 定量研究肥大和衰竭的收缩特性 道路。

The overall aim of the proposed research is to investigate the cellular mechanisms responsible for the systolic and diastolic abnormalities of contraction sen in myocardial hypertrophy and failure. Abnormalities in calcium homeostasis have previously been demonstrated in animal models of hypertrophy and failure and in cells isolated from failing human hearts. However, these studies fail to identify the individual cellular processes that underlie these abnormalities. The important question is what step(s) in the coupling of membrane excitation with subsequent contraction and relaxation is (are) altered in hypertrophy and failure. Within the theoretical framework of a quantitative scheme of calcium homeostasis, the various steps of excitation-contraction-relaxation coupling will be individually probed by current methods in voltage clamping (whole-cell & single-channel), intracellular fluorescent calcium (Ca2+) indicators, and the flash photolysis of caged compounds. The specific aims of the proposed research include: 1.) Test the hypothesis that the influx of Ca2+ through the L-type Ca2+-channel required to "trigger" the release of Ca2+ from the sarcoplasmic reticulum (SR) is altered in hypertrophy and failure. This will involve measurement of both hole-cell and unitary Ca2+-currents. 2.) Test the hypothesis that the grading of the SR calcium release b the L-type Ca2+-current is altered in hypertrophy and failure. This will involve the measurement of single-channel Ca2+-currents and the simultaneous measurement of whole-cell calcium currents, intracellular calcium transients, and cell shortening. 3) Test the general hypothesis that the handling of Ca2+ by the SR is altered in hypertrophy and failure. Specifically, 3.1) test the hypothesis that the systolic abnormalities of contraction result from abnormalities of Ca2=-efflux from the SR Ca2+- release channel, and 3.2) test the hypothesis that the diastolic or relaxation abnormalities seen in hypertrophy and failure are the result of impaired sequestration of Ca2+ by athe SR Ca2+=ATP-ase pump. 4.) Test the hypothesis that the Ca2+-binding ligands (including the contractile regulatory proteins troponin C and calmodulin) are altered in hypertrophy and failure. These specific aims will be investigated in single isolated myocytes from animal models of cardiac hypertrophy and failure and from failing human heart. This research addresses the fundamental question regarding the precise cellular mechanism(s) responsible for the altered contractility characteristic of hypertrophy and failure in a quantitative way.