CELLULAR MAGNESIUM ION HOMEOSTASIS IN THE MYOCARDIUM

在上一个供资期间进行的研究和其他机构进行的研究 实验室表明，特定的激素刺激或细胞内 信号快速地从肌细胞（或其它细胞）动员大量的Mg 2+， 细胞）到细胞外空间，反之亦然。 另一方面 由实验数据支持的一般理解假定， 胞浆游离Mg 2+保持相对恒定在毫摩尔- 亚毫摩尔浓度。 因此，本组件项目研究的主要假设是： 表明激素刺激心肌细胞可诱导 Mg 2+在细胞内细胞器和细胞外空间之间， 胞质Mg 2+几乎不变。 假设的关键是 证明特定的细胞内信号诱导大通量的 Mg 2+穿过细胞器，如线粒体、肌浆网和细胞膜。 细胞质，这些流量与强大的激活相结合， 肌膜Mg ~（2+）转运蛋白。 拟议的五个具体目标将界定 心肌细胞转运Mg 2+的各种机制 肌膜、肌浆网和线粒体。 一些目标 建议进行广泛和系统的调查，而其他人则非常 特定. 后者的一个例子是对环磷酸腺苷的研究 结合腺嘌呤核苷酸转位酶和腺嘌呤核苷酸转位酶的两种同工酶， 当cAMP被结合时，导致Mg-ATP从线粒体转运。 各种各样的模型（麻醉动物、灌注心脏、肌细胞， 其他分离的细胞，透化细胞，分离的细胞器，纯化的 蛋白质，脂质体）和实验方法（31 P NMR，电子探针 微量分析、细胞成像、同位素、电位测量技术）。 用于确认或整合已获得的关于肌细胞Mg 2+的知识 体内平衡 在目标1中，通过从以下方面获得的信息提出了额外的积分： 使用麻醉动物的实验。 使用这个模型， Mg 2+在组织和血浆之间重新分布的结果和后果 将被调查。 最后，在与本计划项目的其他研究人员的合作下， 结果显示，心肌细胞内Mg ~（2+）的再分布和 细胞器Mg 2+将与细胞器的功能相关， 在ATP合成和利用方面，以及在离子调节方面， 梯度。

Studies conducted during the previous funding period and by other laboratories indicate that specific hormonal stimulation or intracellular signals rapidly mobilize large amounts of Mg2+ from myocytes (or other cells) to the extracellular space, and vice versa. On the other hand, the general understanding, supported by experimental data, assumes that cytosolic free Mg2+ is held relatively constant at a millimolar- submillimolar concentration. Hence, the main hypothesis of the research of this Component Project is to demonstrate that hormonal stimulation of myocytes induces redistribution of Mg2+ between intracellular organelles and the extracellular space, leaving cytosolic Mg2+ virtually unchanged. Key to athe hypothesis is the demonstration that specific intracellular signals induce large fluxes of Mg2+ across organelles such as mitochondria, sarcoplasmic reticulum and the cytosol, and that these fluxes are coupled with the activation of powerful sarcolemma Mg2+ transporter(s). The five specific aims proposed will define the operation and regulation of various mechanisms used by the myocardial cell to translocate Mg2+ across the sarcolemma, sarcoplasmic reticulum and mitochondria. Some of the aims proposed a broad and systemic investigation, whereas others are very specific. One example of the latter is the investigation of the cAMP binding to two isozymes of the adenine nucleotide translocase and the resulting Mg-ATP transport from mitochondrial when cAMP is bound. A large variety of models (anesthetized animals, perfused hearts, myocytes, other isolated cells, permeabilized cells, isolated organelles, purified proteins, liposomes) and experimental approaches (31P NMR, Electron Probe Microanalysis, cell imaging, isotopic, potentiometric techniques) will be used to confirm or to integrate the acquired knowledge on myocyte Mg2+ homeostasis. Additional integration is proposed in Aim 1 by information derived from experiments using anesthetized animals. Using this model, the overall results and consequences of Mg2+ redistribution between tissues and plasma will be investigated. Finally, in collaboration with other investigators of this Program Project, the results of Mg2+ redistribution within the myocyte and the changes in organelle Mg2+ will be correlated with the function of the organelles or myocytes in terms of ATP synthesis and utilization, and regulation of ion gradients.