ACID-BASE HOMEOSTASIS IN BRAIN INJURY

脑损伤中的酸碱稳态

• 批准号: 6205051
• 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: 1999
• 资助国家: 美国
• 起止时间: 1999-06-01 至 2000-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6205051
• 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.

酸碱平衡的紊乱长期以来一直与 缺血性和创伤性脑损伤的病理生理学。 有害的 酸中毒的影响受到特别关注。 大量研究 表明乳酸产生过多特别有害 星形胶质细胞。 虽然这种敏感性的基础不是 据了解，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 回应。 特别令人感兴趣的是电压依赖性酸分泌 神经胶质去极化激活的机制。 一个主要目标是 该提案旨在阐明这些星形胶质细胞调节的作用 中枢神经系统急性损伤的过程。 星形胶质细胞 pH 调节将 采用 pH 微电极、光学记录方法和整体研究 细胞膜片钳技术。 细胞内 pH 值研究将 在整个动物、脑切片和分离细胞的水平上进行， 利用每个人提供的独特的实验优势 准备。 相比之下，神经元在受伤时可以受到酸中毒的保护， 因为外部氢离子会阻断 NMDA 受体介导的活性。 然而，抑郁症和其他形式的过度兴奋的蔓延 突触活动，与细胞外碱化有关， 能够解除 NMDA 受体的 H+ 阻断。 的大小 这些 pH 值变化取决于缓冲速度，缓冲速度受以下因素控制 碳酸酐酶的细胞外活性。 这些研究将 确定该酶在缺血性和创伤性损伤中的作用 中枢神经系统。 实验将采用最近开发的微电极技术， 这将允许首次实时测定 pH 值、碳酸氢盐和 受伤大脑中的二氧化碳。 微电极研究将 在麻醉大鼠的心脏骤停模型中进行（完全 皮质缺血）、中风（大脑中动脉闭塞）和脊髓 脊髓损伤。 这些实验将提供完整的描述 这些疾病中的细胞外酸碱状态。 结合 通过这些测量，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调节碳酸来增强 脱水酶活性。 实验将扩展到传播的研究 抑郁和缺氧，以确定细胞外的作用 缓冲这些病症的表现。 这些研究利用了最新的概念和技术 脑 pH 调节研究的进展 此次活动的总体目标是 我们的工作是将基础研究的进展扩展到病理生理学领域 环境。 我们的努力将提供关于如何 基本调节过程影响心脏骤停引起的伤害， 中风和中枢神经系统创伤。