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 收缩能力，因此是哺乳动物心脏的功输出。这个 有待检验的假设是，α1和β肾上腺素能受体 连接到涉及环状AMP的已知第二信使通路， 肌醇1，4，5-三磷酸，钙和二酰甘油，它们介导 直接修改(e.E.收缩装置的磷酸化) 及其相关的钙调节系统。此前的调查显示 集中于与心脏兴奋性相关的肾上腺素能机制 细胞膜。拟议的实验利用了机械 单个离体心肌的测量实验利用 单个分离心肌细胞(肌细胞)的力学测量 结合用于产生三磷酸腺苷的新的光化学技术， 钙、1，4，5-三磷酸肌醇和环磷酸腺苷快速均匀 在细胞内。这允许对第二信使进行严格控制 皮肤和活的心肌细胞中的浓度以及时间分辨 跨桥骑行的测量和收缩的激活 皮肤心肌细胞中的钙。凝胶法分析单个心肌细胞 电泳法将用于鉴定特定的磷酸化 收缩和调节蛋白及其同工酶的研究 收缩蛋白的组成。该计划的主要目标 拟议的研究是确定收缩的速度限制步骤 一种定义明确的心肌准备并了解其机制 肾上腺素能调节这些步骤。从以下网站获得的信息 建议的测量方法可能会导致治疗方法的加强 并将为心力衰竭时心肌收缩功能的研究提供依据 了解慢性病患者心脏功能的变化 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.