ACID-BASE HOMEOSTASIS IN BRAIN INJURY

脑损伤中的酸碱稳态

• 批准号: 6336718
• 负责人: MITCHELL CHESLER
• 金额: $ 19.33万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2003-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6336718
• 关键词: acid base balance; astrocytes; bicarbonates; brain injury; carbonate dehydratase; cerebral ischemia /hypoxia; disease /disorder model; enzyme activity; homeostasis; interstitial; laboratory rat; lactic acidosis; microelectrodes; microspectrophotometry; sectioning; spinal cord injury; voltage /patch clamp

Disturbances in acid-base homeostasis have long been implicated in the pathophysiology of ischemic and traumatic brain injury. The deleterious effects of acidosis have received particular attention. Numerous studies indicate that excessive production of lactic acid is particularly harmful to astrocytes. Although the basis of this susceptibility is not understood, studies of astrocyte pH regulation suggest that acid transport mechanisms of these cells are implicated in these pathophysiological responses. Of particular interest are voltage-dependent acid secretory mechanisms which are activated by glial depolarization. A principal aim of this proposal is to elucidate the role of these astrocytic regulatory processes in acute injuries to the CNS. Astrocyte pH regulation will be investigated with pH microelectrodes, optical recording methods and whole cell patch clamp techniques. The intracellular pH studies will be performed at the level of the whole animal, brain slice and isolated cell, capitalizing on the unique experimental advantages offered by each preparation. Neurons, by contrast, can be protected by acidosis in the injury setting, since external hydrogen ions block NMDA receptor-mediated activity. However, spreading depression and others forms of excessive excitory synaptic activity, are associated with extracellular alkalinization, capable of relieving the H+ block of the NMDA receptor. The magnitude of these pH shifts depends upon the speed of buffering, which is governed by the extracellular activity of carbonic anhydrase. These studies will determine the role of this enzyme in ischemic and traumatic injury to the CNS. Experiments will employ recently-developed microelectrode techniques, which will permit the first real-time determination of pH, bicarbonate and carbon dioxide in injured brain. The microelectrode studies will be conducted in anesthetized rats, in models of cardiac arrest (complete cortical ischemia), stroke (middle cerebral artery occlusion), and spinal cord injury. These experiments will provide a complete description of extracellular acid base status in these afflictions. In conjunction with these measurements, we will determine whether the kinetics of H+ buffering can be enhanced by treatment with buffers or by modulation of carbonic anhydrase activity. Experiments will be extended to the study of spreading depression, and hypoxia, in order to determine the role of extracellular buffering in the manifestation of these pathologies. These studies capitalize upon recent conceptual and technological developments in the study of brain pH regulation. The broad goal of this work is to extend our progress in basic research to the pathophysiological setting. Our efforts will provide insights and understanding into how elemental regulatory processes affect injuries arising from cardiac arrest, stroke, and CNS trauma.

长期以来，酸碱稳态的障碍一直与 缺血性和创伤性脑损伤的病理生理学。 有害的 酸中毒的影响受到了特别的关注。 许多研究 表明过量产生乳酸特别有害 到星形胶质细胞。 尽管这种敏感性的基础不是 理解，星形胶质细胞pH调节的研究表明酸转运 这些细胞的机制与这些病理生理学有关 回答。 特别感兴趣的是电压依赖性酸分泌 通过神经胶质去极化激活的机制。 一个主要目的 该建议是阐明这些星形细胞调节的作用 中枢神经系统急性伤害的过程。 星形胶质细胞pH调节将是 用pH微电极，光学记录方法和整体研究 细胞贴片夹技术。 细胞内pH研究将是 在整个动物，脑切片和孤立细胞的水平上进行， 利用每个人提供的独特实验优势 准备。 相比之下，神经元可以在损伤环境中受酸中毒的保护， 由于外部氢离子阻断了NMDA受体介导的活性。 但是，散布抑郁症和其他形式的表现过多 突触活动与细胞外碱化有关， 能够缓解NMDA受体的H+块。 大小的 这些pH值转移取决于缓冲的速度，该缓冲速度由 碳赤铁酶的细胞外活性。 这些研究会 确定该酶在缺血性和创伤性损伤中的作用 CNS。 实验将采用最近开发的微电极技术， 这将允许第一个实时确定pH，碳酸氢盐和 受伤的大脑中的二氧化碳。 微电极研究将是 用麻醉大鼠进行心脏骤停模型进行（完全 皮质缺血），中风（中大脑动脉闭塞）和脊柱 绳索受伤。 这些实验将提供完整的描述 这些苦难中的细胞外酸基碱状态。 结合 这些测量值，我们将确定H+缓冲的动力学是否 可以通过缓冲液处理或通过碳调制来增强 赤铁酶活性。 实验将扩展到扩散的研究 抑郁症和缺氧，以确定细胞外的作用 在这些病理的表现中缓冲。 这些研究利用了最新的概念和技术 脑pH调节研究的发展。 这个广泛的目标 工作是将我们的基础研究进展扩展到病理生理学 环境。 我们的努力将提供见解，并了解如何 元素调节过程会影响心脏骤停引起的伤害， 中风和中枢神经系统创伤。