Renal Oxalate Secretion

肾草酸分泌

• 批准号: 6733606
• 负责人: ROBERT W FREEL
• 金额: $ 14.54万
• 依托单位: UNIVERSITY OF FLORIDA
• 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 2006-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6733606
• 关键词: Xenopus oocyte; calcium ion; cell line; chloride channels; cyclic AMP; disease /disorder model; drug delivery systems; electrophysiology; excretion; gene expression; kidney; kidney function; kidney metabolism; laboratory rat; membrane transport proteins; microarray technology; oxalates; primary hyperoxalurias; radiotracer; renal cortex; renal tubular transport; renal tubule; secretion; vesicle /vacuole

DESCRIPTION (provided by applicant): Hyperoxaluria is one of the principal risk factors in the etiology of renal stone disease and in hyperoxaluric diseases like Primary Hyperoxaluria the renal excretory pathways are continuously challenged to excrete the oxalate load. While it has long been agreed that the kidney actively secretes oxalate and a number of membrane transport proteins have been identified that may transport the oxalate anion, it is remarkable that no vectorial transport mechanism for secretion has emerged from these studies. The research aims described in this proposal are directed at extending our understanding of the mechanisms and regulation of transepithelial oxalate secretion by the renal tubule in hyperoxaluric rats where oxalate excretion is elevated. Hyperoxaluria generated by oxalate-loaded osmotic pumps implanted in rats will be used to assess (using differential gene expression techniques) the nature and degree of up-regulation of transport systems that may participate in oxalate transport along the nephron in the hyperoxaluric state. Our previous studies concerning intestinal oxalate secretion, together with new findings regarding chloride secretion in the nephron, have led us to test the hypothesis that mechanistically similar, cAMP-dependent pathways can mediate oxalate secretion along the renal tubule. This hypothesis will be evaluated by measuring camp stimulated, radioisotope-labeled oxalate fluxes across confluent monolayers of cell lines derived from the proximal tubule and the inner medullary collecting duct. Additionally, a specific aspect of the cAMPdependent secretory mechanism (i.e., presence of an apical membrane conductive pathway for oxalate) will be assessed using membrane vesicles derived from the renal cortex of the hyperoxaluric animals. Finally, the hypothesis that oxalate permeates chloride channels will be explicitly tested by using the heterologous expression of CFTR gene product in Xenopus laevis oocytes. Oxalate flux through CFTR can be examined in the nominal absence of other oxalate transport pathways using efflux of labeled oxalate together with electrophysiological measurements in control and CFTR expressing oocytes. The hyperoxaluric/osmotic pump animal model, the novel transport perspectives, and the new experimental approaches that will be developed and explored in this proposal will provide specific answers regarding renal oxalate secretion and they will offer a foundation and a direction for future studies of renal oxalate.

描述（由申请方提供）：高尿酸是肾结石病病因学中的主要风险因素之一，在高尿酸疾病（如原发性高尿酸）中，肾脏排泄途径持续受到挑战，以排泄草酸负荷。虽然长期以来人们一致认为肾脏积极分泌草酸盐，并且已经鉴定了许多可能转运草酸盐阴离子的膜转运蛋白，但值得注意的是，这些研究中没有出现分泌的载体转运机制。本研究的目的是扩大我们对高尿酸大鼠肾小管经上皮细胞分泌草酸盐的机制和调节的理解，其中草酸盐排泄升高。通过植入大鼠体内的草酸盐负载渗透泵产生的高尿酸将用于评估（使用差异基因表达技术）可能参与高尿酸状态下沿着肾单位的草酸盐转运的转运系统的上调性质和程度。我们先前关于肠草酸盐分泌的研究，以及关于肾单位中氯化物分泌的新发现，使我们验证了这样的假设，即机制相似的cAMP依赖性途径可以介导沿肾小管的草酸盐分泌沿着。将通过测量cAMP刺激的放射性同位素标记的草酸盐穿过来自近端小管和内髓集合管的细胞系的汇合单层的通量来评价该假设。此外，cAMP依赖性分泌机制的一个具体方面（即，草酸盐的顶端膜传导途径的存在）将使用来源于高尿酸动物的肾皮质的膜囊泡进行评估。最后，草酸盐渗透氯离子通道的假设将明确测试通过使用CFTR基因产物在非洲爪蟾卵母细胞中的异源表达。通过CFTR的草酸通量可以在标称不存在其他草酸转运途径的情况下使用标记草酸的流出以及对照和CFTR表达卵母细胞中的电生理测量来检查。高尿酸/渗透泵动物模型、新的转运观点和新的实验方法将为肾脏草酸盐分泌提供具体答案，并为肾脏草酸盐的未来研究提供基础和方向。