VOLUME REGULATION OF RENAL CELLS

细胞体积的维持对于正常的 大多数哺乳动物细胞的功能。运输过程存在 在高溶质率之间实现精确的平衡 流入和流出，以及强制耦合的水传输 质膜。细胞肿胀是一个特别的问题 对健康和疾病都有影响的细胞，必须持续看守 反对。降低细胞外液渗透压，如 在低钠血症中观察到，或溶质的细胞净积累， 例如在血浆溶质水平或荷尔蒙水平改变时可能发生 不平衡，导致水分进入细胞，从而导致细胞 肿胀。肿胀激活了血浆中的转运过程 膜的体积恢复正常，这个过程指的是 随着监管量的减少。这些过程特别是 明显见于肾脏近端的直管 肿胀激活钾和氯化物传导通路 基底膜允许钾和钙的外流 氯化物从细胞中排出，伴随着强制的水排出 将音量恢复到接近正常的水平。当前的总目标 建议阐明这些机制和信号通路。 近端直肌潜在的调节量减少 兔肾小管。这将首先完成 充分阐明细胞肿胀对基底外侧的影响 膜的钾和氯化物电导 电生理技术，以及激活机制 在这些传导通路中，即胞外插入通路 与质膜中已经存在的潜在通路的激活相比， 用荧光探针法研究细胞膜的周转。 于是，控制这些的调控通路 传导性将被阐明。重点将放在 钙，基于细胞内钙活性的测量 使用荧光钙探针。与钙的相互作用 和钙调蛋白受体蛋白来调节这些途径， 以及磷脂酰肌醇代谢途径的作用--如 初步研究将在细胞肿胀期间激活--将 直接评估。这些研究将为我们提供对 细胞内的体积调节机制及其潜在的 调节这些过程的生化途径。

Maintenance of cell volume is critically important for normal functioning of most mammalian cells. Transport processes exist to bring about a precise balance between high rates of solute influx and efflux, and obligatorily coupled water transport, across the plasma membrane. Cell swelling is a particular problem for cells in both health and disease and must be continually guarded against. Reduction of extracellular fluid osmolarity, such as observed in hyponatremia, or net cellular accumulation of solute, such as may occur with altered plasma solute levels or hormonal imbalances, results in water movement into cells and hence cell swelling. Swelling activates transport processes at the plasma membrane to return volume towards normal, a process referred to as regulatory volume decrease. These processes are particularly evident in the proximal straight tubule of the kidney where swelling activates potassium and chloride conductive pathways in the basolateral membrane to allow efflux of potassium and chloride from the cell, accompanied by obliged water efflux, to return volume to near normal. The overall goal of the present proposal is to elucidate the mechanisms and signalling pathways underlying regulatory volume decrease in the proximal straight tubule of the rabbit kidney. This will be accomplished by first fully elucidating the effect of cell swelling on the basolateral membrane potassium and chloride conductances using electrophysiological techniques, and the mechanism of activation of these conductive pathways, i.e. exocytic insertion of pathways vs activation of latent pathways already in the plasma membrane, using fluorescent probes to study membrane turnover. Whereupon, the regulatory pathways controlling these conductances will be elucidated. Focus will be on the role of calcium, based on measurements of intracellular calcium activity using fluorescent calcium probes. The interaction with calcium and calmodulin acceptor proteins in regulating these pathways, and the role of phosphatidylinositol turnover pathway--shown in preliminary studies to be activated during cell swelling--will be directly assessed. The studies will provide new insights into the mechanisms of volume regulation in cells and the underlying biochemical pathways that regulate these processes.