MECHANISMS OF ALTERED CONTRACTILITY IN HEART FAILURE

这项研究的总体目标是研究细胞内的 导致心脏收缩和舒张异常的机制 心肌肥厚和衰竭中收缩感觉。 异常 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类心脏中分离的细胞中。 然而，这些研究未能确定单个细胞过程 这些异常现象背后的原因 重要的问题是采取哪些步骤 在膜兴奋与随后的收缩的耦合中， 松弛在肥大和衰竭时改变。 内 钙稳态定量方案的理论框架， 各种兴奋-收缩-松弛耦合步骤将 通过电压箝位中的电流方法单独探测（全细胞& 单通道）、细胞内荧光钙（Ca 2+）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Ca 2+通过 L型Ca 2+通道需要“触发”Ca 2+从细胞中释放， 肌浆网（SR）在肥大和衰竭中改变。 这 将涉及测量空穴电池和单位钙电流。 2.）的情况。 验证SR钙释放的分级为B型的假设 Ca 2+电流在肥大和衰竭中改变。 这将涉及 单通道Ca ~（2+）电流的测量和同步 全细胞钙电流的测量，细胞内钙 瞬变和细胞缩短。 3)检验一般假设，即 SR对Ca 2+的处理在肥大和衰竭中改变。 具体而言，3.1）检验以下假设： 收缩是由于SR Ca 2 +-流出异常所致。 3.2）检验舒张或舒张压升高的假设， 在肥大和衰竭中观察到的松弛异常是 受损的螯合钙+由Ca 2 + SR钙= ATP酶泵。 4.） 测试 假设Ca 2+结合配体（包括收缩性配体） 调节蛋白肌钙蛋白C和钙调蛋白）在肥大中改变 和失败 这些具体的目标将在一个单独的研究 来自心脏肥大和衰竭动物模型的肌细胞以及来自 人类心脏衰竭 这项研究解决了一个根本问题， 关于负责改变的精确细胞机制， 收缩性特征的肥大和失败，在一个定量的 路上了

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.