CELLULAR ELECTROPHYSIOLOGY OF REPOLARIZATION

本课题的总体目标是获得关于心室复极的细胞方面及其与细胞内Ca ~（2+）调节和电子相互作用的关系的新见解。将对正常和疾病心脏的左心室肌细胞进行研究。项目3包括三个分项目。子项目3.1关注慢性心肌梗死后存活的心肌细胞（MI后心肌细胞）的复极异常。实验的目的是确定心肌梗死后诱导的复极化变化及其逆转的甲状腺激素类似物，DITPA的离子基础。核心假设是复极异常及其恢复是由肌浆网（SR）、I/Ca和I/NaCa摄取的I/Kp Ca 2+变化介导的。将使用细胞内Ca 2+（Ca/i）的电压钳位和荧光测量（共聚焦和常规落射荧光）来检验该假设。主题3.2关注Ca+内流和SR触发的Ca 2+释放之间的关系。中心假设是，促进Na+内流的条件（如长QT综合征的一种遗传形式中发生的情况）将增加兴奋-矛盾偶联的增益，从而促进CaI诱导的心律失常。电压钳和荧光技术将被用来测试这一假设，在暴露于anthopleurin-A的肌细胞中，其中caseI/Na失活。子项目3.3关注细胞间通讯与复极化之间的关系。其中心假设是复极调制过程中细胞间电偶联作用于动作电位的传播和早期后去极化的形成。该假设将用电子电路进行测试，该电子电路使我们能够将物理上分离的肌细胞与可变电阻电连接，从而模拟间隙功能电阻的体外变化。

The overall objective of this project is to obtain new insight concerning the cellular aspects of ventricular repolarization and their relationship to intracellular Ca2_ regulation and electronic interactions. Studies will be performed on left ventricular myocytes from both normal and disease hearts. Project 3 contains three subprojects. Subproject 3.1 focuses on repolarization abnormalities in myocytes surviving chronic myocardial infarction (post-MI myocytes). The experiments are designed to determine the ionic basis of post-MI-induced changes in repolarization and their reversal by the thyroid hormone analogue, DITPA. The central hypothesis is that repolarization abnormalities and their recovery are mediated by changes in I/Kp Ca2+ uptake by the sarcoplasmic reticulum (SR), I/Ca and I/NaCa. Voltage clamping and fluorescence measurements of intracellular Ca2+ (Ca/i) (confocal and conventional epifluorescence) will be used to test this hypothesis. Subject 3.2 focuses on the relationship between Ca+ influx and triggered Ca2+ release from SR. The central hypotheses is that conditions which promote Na+ entry, as occur in one inherited form of the long QT syndrome, will increase the gain of excitation-contradiction coupling and thus promote Cai-induced arrhythmias. Voltage clamp and fluorescence techniques will be used to test this hypothesis in myocytes exposed to anthopleurin-A which prolongs I/Na inactivation. Subproject 3.3 focuses on the relationship between intercellular communication and repolarization. The central hypothesis is that cell-cell electrical coupling during repolarization modulation action potential propagation and the formation of early after-depolarizations. This hypothesis will be tested with an electronic circuit which enables us to electrically connect physically separate myocytes with a variable resistance and thus simulate in vitro change in gap functional resistance.