ADRENERGIC REGULATION OF CARDIAC MUSCLE CONTRACTION

拟议研究的长期目标是阐明 儿茶酚胺刺激增强的分子机制 收缩力和因此哺乳动物心脏的功输出。 的 待检验的假设是α 1和β肾上腺素能受体 与已知的涉及环AMP的第二信使途径偶联， 肌醇1，4，5-三磷酸，钙和甘油二酯，其介导 直接修改（e. e.磷酸化）的收缩装置 及其相关的钙调节系统。 先前的研究 集中在肾上腺素能机制有关的兴奋性的心脏 细胞膜 拟议的实验利用机械 单个离体心肌实验的测量利用 单个分离的心肌细胞（肌细胞）的机械测量 结合用于产生ATP的新颖的光化学技术， 钙、肌醇1，4，5-三磷酸和环磷酸腺苷快速均匀 在细胞内。 这允许严格控制第二信使 皮肤和活肌细胞中的浓度以及时间分辨 测量跨桥循环和收缩的激活， 皮肤肌细胞中的钙。 单个肌细胞的凝胶分析 电泳将用于鉴定特定的磷酸化， 收缩和调节蛋白，并表征同工酶 收缩蛋白的组成。 的主要目标 建议的研究是确定收缩的速率限制步骤， 明确的心肌准备，并了解 肾上腺素能调节这些步骤。 所用信息均来自 提出的测量方法可能会导致治疗方法， 心力衰竭期间的心肌收缩力，并将为 了解慢性疾病条件下心脏功能的变化 如高血压、糖尿病和甲状腺功能减退症。

The long range goals of the proposed research are to elucidate the molecular mechanisms by which catecholamine stimulation enhances contractility and hence the work output of the mammalian heart. The hypotheses to be tested are that both alpha1- and beta-adrenergic receptors are coupled to known second messenger pathways involving cyclic AMP, inositol 1,4,5-triphosphate, calcium and diacylglycerol, which mediate direct modifications (e.e. phosphorylation) of the contractile apparatus and its associated calcium regulatory system. Previous investigations have concentrated on adrenergic mechanisms related to excitability of cardiac cell membranes. The proposed experiments make use of mechanical measurements of single isolated cardiac muscle experiments make use of mechanical measurements of single isolated cardiac muscle cells (myocytes) in conjunction with a novel photochemical technique for generating ATP, calcium, inositol 1,4,5-triphosphate and cyclic AMP rapidly and uniformly within the cell. This permits rigorous control of second messenger concentrations in skinned and living myocytes as well as time-resolved measurements of cross-bridge cycling and the activation of contraction by calcium in skinned myocytes. Analysis of single myocytes by gel electrophoresis will be used to identify specific phosphorylations of contractile and regulatory proteins and to characterize the isozyme composition of contractile proteins. The principal objectives of the proposed research are to identify the rate limiting steps of contraction in a well-defined cardiac muscle preparation and to understand mechanisms of adrenergic regulation of these steps. Information obtained from the proposed measurements may lead to therapeutic approaches for enhancing myocardial contractility during heart failure and will provide a basis for understanding changes in cardiac performance in chronic disease conditions such as hypertension, diabetes and hypothyroidism.