Axial Flow Effects in Proximal Tubule

近端小管的轴流效应

• 批准号: 8135544
• 负责人: Tong Wang Wang
• 金额: $ 34.98万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-05-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8135544
• 关键词: Actins; Angiotensin II; Animal Model; Apical; Bicarbonates; Blood Pressure; Brush Border; Calcium; Calcium Signaling; Calmodulin; Cells; Chelating Agents; Cilia; Collaborations; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cytoskeletal Modeling; Cytoskeleton; Data; Dopamine; Equilibrium; F-Actin; Fimbrin; Health; Immunofluorescence Immunologic; In Vitro; Ions; Kidney; Knockout Mice; Length; Liquid substance; MDCK cell; Maintenance; Measures; Mechanics; Mediating; Membrane Transport Proteins; Microtubules; Modeling; Mus; Myosin ATPase; Na(+)-K(+)-Exchanging ATPase; Nephrons; Neurons; PKA inhibitor; Perfusion; Permeability; Physiological; Play; Proton-Translocating ATPases; Regulation; Relative (related person); Role; Second Messenger Systems; Signal Transduction; Sodium; Sodium Chloride; Structure; Sulpiride; Tight Junctions; Torque; Water; Western Blotting; Work; absorption; autocrine; cellular microvillus; data modeling; hormone regulation; inhibitor/antagonist; kidney cell; knockout animal; luminal membrane; mathematical model; research study; response; second messenger; sensor; shear stress; theories; trafficking; villin

DESCRIPTION (provided by applicant): The physiological importance of flow-activated salt and water transport in proximal tubules has been recognized for more than four decades, however the mechanism of this regulation is still not well defined. Recently we have demonstrated that a) Perfusion-absorption balance is present in the isolated perfused proximal tubule of the mouse. b) Both luminal membrane NHE3 and H-ATPase are regulated by flow; c) Changes in tight junction permeabilities do not play a role in flow-modulated transport. We have developed a theory for calculating the forces and torques on the microvilli, and demonstrated that flow-induced changes of proximal tubule absorption are torque dependent, and that an intact actin cytoskeleton is required to transduce the signal to the cell. Experimental data and modeling calculations provide strong evidence that brush border microvilli function as flow sensors in the proximal tubule. However, whether the primary cilium also functions as flow sensor and whether peritubular ion transporters can also be regulated by axial flow has not been examined. In the work proposed, in vitro microperfusion experiments, immunofluorescence, and Western blotting will be conducted with the following three aims: 1) To study the controversy of whether central cilia or microvilli are the flow sensors in proximal tubules by comparing model predictions with flow-induced changes on Na+ and HCO3- absorption in wild-type, and villin, fimbrin, myosins and cilia-deficient mice; 2) To study the role of flow-induced actin cytoskeletal reorganization in modulating transporter trafficking and function in mouse proximal tubules; 3) To examine the role of second messengers, calcium signals, cAMP- and PKA- modulated mechanisms and the role of dopamine in flow-dependent proximal tubule transport. The unique features of our proposed collaboration are: 1) the comparison of flow-dependent proximal tubule transport in intact tubules in mice and in knockout animals; 2) the representation of reabsorptive fluxes as a function of the hydrodynamic forces and torques on microvilli and cilia; and 3) the assessment of flow-induced actin cytoskeletal reorganization, ion transporter localization, and functional changes within a mathematical model of proximal tubule transport. These studies will provide new information on mechanisms of glomerulotubular balance (GTB) and aspects of renal fluid and HCO3- transport in physiological and pathophysiological conditions. PUBLIC HEALTH RELEVANCE: The maintenance of systemic blood pressure depends upon the rate of sodium reabsorption within the kidney, along the entire nephron, and about 2/3 of this occurs in the proximal tubule. The proposed studies will provide direct information on the regulation of proximal tubule sodium transport. Possible benefits include identification of target molecules, which may be blocked or modified in order to modulate sodium reabsorption by the kidney.

描述（由申请人提供）：近端小管中流动盐和水运输的生理重要性已被确​​认已有40多年了，但是该调节的机制仍然没有很好地定义。最近，我们证明了a）在小鼠的孤立灌注近端小管中存在灌注 - 吸收平衡。 b）腔膜NHE3和HATPase均由流量调节； c）紧密连接渗透率的变化在流动调制的传输中不起作用。我们已经开发了一种用于计算微绒毛上力和扭矩的理论，并证明流动诱导的近端小管吸收的变化是扭矩依赖性的，并且需要完整的肌动蛋白细胞骨架才能将信号转传为细胞。实验数据和建模计算提供了有力的证据，表明将边界微绒毛作为近端小管中的流动传感器的作用。但是，尚未检查一级纤毛是否还充当流动传感器以及周围离子转运蛋白是否也可以受到轴向流的调节。 In the work proposed, in vitro microperfusion experiments, immunofluorescence, and Western blotting will be conducted with the following three aims: 1) To study the controversy of whether central cilia or microvilli are the flow sensors in proximal tubules by comparing model predictions with flow-induced changes on Na+ and HCO3- absorption in wild-type, and villin, fimbrin, myosins and缺乏纤毛的小鼠； 2）研究流动诱导的肌动蛋白细胞骨架重组在调节小鼠近端小管中的转运蛋白运输和功能中的作用； 3）检查第二使者，钙信号，cAMP和PKA调制机制的作用以及多巴胺在流动依赖性近端小管转运中的作用。我们提出的合作的独特特征是：1）比较小鼠和基因敲除动物中完整小管中流动近端小管的比较； 2）在微绒毛和纤毛上的流体动力和扭矩的函数的函数； 3）评估流动诱导的肌动蛋白细胞骨架重组，离子转运蛋白定位以及在近端小管转运的数学模型中的功能变化。这些研究将提供有关肾小球平衡机制（GTB）的新信息，以及生理和病理生理条件下肾脏液和HCO3-转运的方面。公共卫生相关性：系统性血压的维持取决于肾脏内，整个肾单位的钠重吸收率，其中约2/3发生在近端小管中。拟议的研究将提供有关调节近端钠转运的直接信息。可能的好处包括鉴定靶分子，这些分子可能会被阻断或修饰，以通过肾脏调节钠的重吸收。