MECHANISMS OF HEPATIC ELECTROLYTE TRANSPORT

正常的肝功能依赖于离子的快速和精确的运动。 和其他溶质以速率穿过每个细胞的质膜 大于1010离子秒-1。离子的数量和类型都是 每分钟调整一次，以适应不断变化的生理 由循环激素、底物可获得性或 代谢压力。运输方面的这些动态变化直接影响到 跨膜水运动和肝细胞体积。的确，荷尔蒙 诱导的细胞体积增加最近被认为是一种 强大的信号，通过对细胞的影响来调节肝功能 激酶、基因表达、胆汁形成和胞吐作用。这些研究 本提案中描述的将评估耦合细胞的机制 新陈代谢、离子运输和细胞体积 细胞内外信号调节细胞体积的假说 通过阳离子开放动态调节Na+内流- 选择性通道，细胞体积增加的刺激，以及K+和Cl- 外流，刺激细胞体积减少。具体目标是i) 评价细胞外三磷酸腺苷作为自分泌/旁分泌的作用 介导细胞肿胀恢复的信号分子；ii)评估 蛋白激酶C和蛋白激酶C的生理作用及靶点 肌醇磷脂3-激酶作为细胞内信号分子 转导细胞体积变化以调节通道；iii)确定 体积敏感氯离子外流的分子基础，以及IV)鉴定 钠离子内流和恢复的通道及其调控机制 细胞萎缩所致。中寻址的通道和信号通路 这些研究代表了荷尔蒙和其他物质的基本作用部位 利用细胞体积作为中间信号来调制的信号 肝脏代谢和分泌功能。此外，对 相关机制可能为肝脏的治疗提供新的策略 在细胞体积调节受损的情况下的损伤， 包括酒精中毒、缺血和肝脏炎症。

Normal liver function depends upon rapid and precise movement of ions and other solutes across the plasma membrane of each cell at rates greater that 1010 ions sec -1. Both the number and types of ions are regulated on a minute-to-minute basis to meet changing physiologic demands caused by circulating hormones, substrate availability, or metabolic stress. These dynamic changes in transport directly influence transmembrane water movement and liver cell volume. Indeed, hormone- induced cell volume increases have recently been recognized to be a potent signal, regulating liver function through effects on cellular kinases, gene expression, bile formation, and exocytosis. The studies described in this proposal will evaluate the mechanisms that couple cell metabolism, ion transport, and cell volume by addressing the Working Hypothesis that intra- and extracellular signals regulate cell volume through dynamic modulation of Na+ influx through opening of cation- selective channels, a stimulus for cell volume increases, and K+ and Cl- efflux, a stimulus for cell volume decreases. The Specific Aims are i) to evaluate the role of extracellular ATP as an autocrine/paracrine signaling molecule mediating recovery from cell swelling; ii) to assess the physiologic roles and targets of protein kinase C and phosphoinositide 3-kinase as intracellular signaling molecules transducing cell volume changes to channel regulation; iii) to determine the molecular basis of volume-sensitive Cl- efflux, and iv) to identify the channels and regulatory mechanisms governing Na+ influx and recovery from cell shrinkage. The channels and signaling pathways addressed in these studies represent essential sites of action for hormones and other signals that utilize cell volume as an intermediary signal to modulate liver metabolic and secretory functions. In addition, definition of the mechanisms involved may provide new strategies for treatment of liver injury under conditions where cell volume regulation is impaired, including alcohol toxicity, ischemia, and liver inflammation.