ELECTROPHYSIOLOGY OF DEVELOPING HEART CELLS

重要的电生理、药理和生化变化 在心脏发育过程中发生在心肌细胞中，这显然 影响其功能属性。年轻的胚胎雏鸡的心脏 自发缓慢上升、钠和钙依赖、河豚毒素抵抗作用 潜力。快Na通道和Ik1通道的数量增加 在发育过程中，老的胚胎雏鸡的心脏有一个典型的快速- 钠依赖动作电位升高。因此，它们的类型和数量 渠道在发展过程中会发生变化。通道属性和动力学可以 在发育过程中也会发生变化(钙通道的长期开放 年轻的和老的胚胎雏鸡的心脏)。对象的标识和属性 在动作过程中传导内向电流的心脏钙通道 潜力将在不同的发展阶段进行审查。在这些 研究，将使用全细胞电压钳和膜片钳技术 鸡胚心和胎鼠心脏不同发育阶段的单个细胞 关于发展的问题。在成人心脏中，cAMP依赖的磷酸化 调节慢钙通道的功能。其他蛋白的磷酸化 激酶也可能调节通道功能。例如，cGMP-， 钙调素和磷脂依赖的磷酸化调节 慢钙通道的功能。其他激酶的磷酸化也可能 调节经络功能。拟议中的实验试图确定 蛋白质磷酸化在鸡胚胎期发育中的作用 心。CAMP和cGMP水平在发育过程中会发生变化。 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。肌膜的调节 通过对各种蛋白质的蛋白激酶进行检测，以确定 在发育过程中，磷酸化模式是否会发生变化 被证明是cAMP依赖的磷酸化。的作用 去磷酸化也将进行电生理学和 生化方面的。G蛋白对阳离子通道的调节也将是 已评估。生化和电生理实验将被 相互关联，以便更好地了解通道属性和 在发育过程中发挥作用。这些研究很重要，因为 心脏对病理条件的反应(例如，心肌炎 缺血)和对心脏活性药物的使用在很大程度上取决于药物的类型和 存在的频道属性。

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.