ELECTROPHYSIOLOGY OF DEVELOPING HEART CELLS

重要的电生理学、药理学和生化变化 在心脏发育过程中发生在心肌细胞中， 影响其功能特性。 幼雏的胚胎心脏 自发性缓慢升高、Na和Ca依赖性、抗TTX作用 潜力 快钠通道和IK 1通道数量增加 在发育过程中，老的鸡胚心脏有一个典型的快速- 钠依赖性动作电位升高 因此， 渠道在发展过程中不断变化。 通道特性和动力学可以 在发育过程中也会发生变化（ 年轻与年老的鸡胚心脏）。 的标识和属性， 在动作期间传导内向电流的心脏Ca通道 将在不同的发展阶段审查潜力。 在这些 研究中，将使用全细胞电压钳和膜片钳技术 在不同时期鸡胚和胎鼠心脏的单个细胞中 发展质量和 在成人心脏中，cAMP依赖性磷酸化 调节慢钙通道的功能。 其他磷酸化 激酶也可以调节通道功能。 例如，cGMP-， 钙调蛋白和磷脂依赖性磷酸化调节 慢钙通道的功能。 其他激酶的磷酸化也可能 调节通道功能。 拟议的实验旨在确定 蛋白质磷酸化在鸡胚发育中的作用 心 cAMP和cGMP水平的变化发生在发育过程中。 钙调素水平、cGMP水平和各种蛋白激酶活性将 在不同的发展阶段进行衡量。 肌膜调节 将通过各种蛋白激酶检测蛋白质以确定 磷酸化的模式是否在发育过程中发生变化， 显示cAMP依赖性磷酸化。 的作用 还将检查去磷酸化的电生理学， 生物化学 G蛋白对阳离子通道的调节也将是 评估。 生化和电生理实验将 相关，以便更好地了解信道特性， 在发展过程中发挥作用。 这些研究很重要，因为 心脏对病理状态的反应（例如，心肌 缺血）和心脏活性药物的作用主要取决于类型和 通道的属性。

Important electrophysiological, pharmacological, and biochemical changes occur in myocardial cells during development of the heart, which obviously affect its functional properties. Young embryonic chick hearts have spontaneous slowly-rising, Na- and Ca-dependent, TTX-resistant action potentials. The number of fast Na channels and IK1 channels increases during development so that old embryonic chick hearts have a typical fast- rising Na-dependent action potential. Thus, the types and number of channels changes during development. Channel properties and kinetics may also change during development (long-lasting openings of Ca channels in young vs. old embryonic chick hearts). The identity and properties of the cardiac Ca channels which conduct inward current during the action potential will be examined at different stages of development. In these studies, whole-cell voltage clamp and patch clamp techniques will be used in single cells of embryonic chick and fetal rat hearts at different stages of development. In the adult heart, cAMP-dependent phosphorylation regulates the function of slow Ca channels. Phosphorylation by other kinases may also regulate channel function. For example, cGMP-, calmodulin- and phospholipid-dependent phosphorylation regulates the function of slow Ca channels. Phosphorylation by other kinases may also regulate channel function. The proposed experiments seek to determine the role of protein phosphorylation during development of the embryonic chick heart. Changes in cAMP and cGMP levels occur during development. Calmodulin levels, cGMP levels and various protein kinase activities will be measured at different stages of development. Regulation of sarcolemmal proteins by the various protein kinases will be examined to determine whether the pattern of phosphorylation changes during development, as has been shown for cAMP-dependent phosphorylation. The role of dephosphorylation will also be examined electrophysiologically and biochemically. Regulation of cation channels by G-proteins will also be evaluated. Biochemical and electrophysiological experiments will be correlated to give a better understanding of channel properties and function during development. These studies are important, since the response of the heart to pathological conditions (e.g., myocardial ischemia) and to cardioactive drugs is largely determined by the types and properties of channels present.