CALCIUM AND SODIUM TRANSPORT IN VASCULAR SMOOTH MUSCLE

“主动”(上坡)挤压的机制 来自肌细胞的钙及其在稳定期钙调节中的作用 平衡，是不完全理解的。许多类型的细胞， 包括无脊椎动物的肌肉和脊椎动物的平滑和心脏 肌肉，采用一种钙转运机制，其中钠离子 以钙交换(“钠/钙交换”)。因此，纳尔逊人 电化学梯度可以提供至少一部分能量 对于钙排出，Na/Ca交换也可能介导钙 当Na的电化学梯度减小时进入。ATP也 部分通过对Na/Ca交换动力学的影响发挥作用， 部分作为平行的钙-三磷酸腺苷酶驱动的“钙泵”的燃料。 内部灌流的单个巨型藤壶肌细胞 作为模型系统用于研究钙的转运和 肌肉的新陈代谢。在即将到来的项目期间， 藤壶Na/Ca交换系统的特征 肌肉应完成，包括直接测定的肌肉 交换化学计量学，以及 正向(钠进/钙出)和反向(钙进/钠出)模式 以及“无效模式” (Ca/Ca和Na/Na)交换。特别值得关注的是， 内源性钙、钠在交换器周转调节中的作用。这个 从该模型系统获得的信息将应用于 动脉平滑过程中钙转运与代谢的研究 肌肉(ASM)细胞。牛尾环的初步研究 动脉(进展报告)表明钠/钙交换在 在调节细胞内游离钙离子中的重要作用 钙离子浓度，在这个组织中。在拟议的实验中，一个 钙敏感荧光染料(Fura-2)及其数字成像方法 将被用来测量单个分离的牛尾巴中的(钙)i ASM细胞。(Ca~(2+))i将在静息和激活的细胞中测量， 随着Na电化学梯度的减小。这个 后者应提供有关钠/钙的直接信息 这些细胞中的交换系统。膜片钳方法，在 结合成像方法，将被用于测量 与Na/Ca交换有关的离子流，以及 确定调节ASM中Na/Ca交换的因素。这个 这些实验的结果应该会提供关于 Na/Ca交换和其他(平行)交换的相对重要性 钙转运系统在调节这些细胞内的(钙离子)i。 这些结果可能适用于病理生理过程。 例如那些与高血压相关的疾病。

The mechanisms involved in the "active" (uphill) extrusion of calcium from muscle cells, and in the regulation of steady Ca balance, are incompletely understood. Many types of cells, including invertebrate muscle and vertebrate smooth and cardiac muscle, employ a Ca transport mechanism in which Na ions exchange for Ca ("Na/Ca exchange"). Thus, the Na electrochemical gradient may provide at least some of the energy for Ca extrusion; moreover, Na/Ca exchange may also mediate Ca entry when Na electrochemical gradient is reduced. ATP also plays a role, in part via an effect on the Na/Ca exchange kinetics, and in part as fuel for a parallel Ca-ATPase driven "Ca pump". Internally perfused single giant barnacle muscle cells are employed as a model system to study Ca transport and metabolism in muscle. During the forthcoming project period, characterization of the Na/Ca exchange system in barnacle muscle should be completed, including direct determination of the exchange stoichiometry, and the comparative properties of the forward (Na entry/Ca exit) and reverse (Ca entry/Na exit) modes of operation of the exchanger as well as the "futile modes" (Ca/Ca and Na/Na) exchange. Of particular interest is the role of internal Ca and Na in the regulation of exchanger turnover. The information obtained from this model system will be applied to the study of Ca transport and metabolism in arterial smooth muscle (ASM) cells. Preliminary studies on rings of bovine tail artery (Progress Report) indicate that Na/Ca exchange plays a prominent role in the regulation of (Ca2+)i, the intracellular free Ca concentration, in this tissue. In the proposed experiments, a Ca-sensitive fluorescent dye (fura-2) and digital imaging methods will be used to measure (Ca2+)i in single, dissociated bovine tail ASM cells. (Ca2+)i will be measured in resting and activated cells, and following reduction of Na electrochemical gradient. The latter should provide direct information about the Na/Ca exchange system in these cells. Patch clamp methods, in conjunction with the imaging methods, will be used to measure the ionic currents associated with Na/Ca exchange, and to determine the factors that regulate Na/Ca exchange in ASM. The results of these experiments should provide new information about the relative importance of Na/Ca exchange and other (parallel) Ca transport systems in the regulation of (Ca2+)i in these cells. The results may be applicable to pathophysiological processes such as those associated with hypertension.