Integrated Tubular and Vascular Structure and Function in Renal Inner Medulla

描述（由申请人提供）：内髓尿液浓缩机制是一种重要但仍知之甚少的肾功能。该项目的目标是增进我们对哺乳动物肾髓质结构组织和功能之间关系的理解，包括无机离子、尿素和水的通量以及尿液浓缩机制。三维结构强调了这样一种范式：内部髓质间质不是一个混合良好的隔室。对 Henle 环上皮 NaCl、尿素和水渗透性的不完全了解是创建解释 IM 渗透梯度和 UCM 生成的高级模型的最关键障碍。只有考虑肾 IM 的三维结构和功能架构才能充分理解 UCM。基于其他人的工作以及我们之前在确定功能组织以及溶质和水通量方面的工作，将研究以下三个具体目标。目标 1，测定中等浓度大鼠的 Henle 肌内环的水、尿素和 NaCl 渗透性。目标 2，确定 IM 中 Henle 环和 CD、血管网络和间质节点空间 (INS) 的功能结构。目标 3，测定利尿剂和抗利尿剂大鼠的亨利袢的尿素和氯化钠渗透性，以及体内和体外加压素治疗后的尿素和氯化钠渗透性。实验方法将包括：1) 从连续切片中对亨利氏环、CD 和直肠血管的所有 IM 薄肢进行三维重建，使用生理功能的免疫细胞化学标记来识别小管和血管段、细胞运输功能的位点和间质区室并确定结构与结构的相互作用，以及 2) 通过体外微灌注直接测量所定义的特定薄肢段的 NaCl、尿素和水渗透率在重建中。将在体外研究有或没有加压素的肾小管渗透性，并且将在体内水利尿、抗利尿和暴露于加压素后研究渗透性。

DESCRIPTION (provided by applicant): The inner medullary urinary concentrating mechanism is an important yet poorly understood renal function. The goal of this project is to advance our understanding of the relationships between structural organization and function, including fluxes of inorganic ions, urea, and water, and the urine concentrating mechanism in the mammalian renal medulla. Three-dimensional architecture underscores the paradigm that the inner medullary interstitium is not one single well-mixed compartment. Incomplete knowledge of loop of Henle transepithelial NaCl, urea, and water permeabilities is the single most critical barrier to creating advanced models that explain generation of the IM osmotic gradient and the UCM. The UCM can only be fully understood by taking into consideration three-dimensional structural and functional architecture of the renal IM. Based on the work of others and on our previous work in determining the functional organization and solute and water fluxes, the three following specific aims will be investigated. Aim 1, determination of water, urea, and NaCl permeabilities of IM loops of Henle from moderately-concentrating rats. Aim 2, determination of functional architecture of loops of Henle and CDs, vascular networks, and interstitial nodal spaces (INSs) in the IM. Aim 3, determination of urea, and NaCl permeabilities of loops of Henle from diuretic and antidiuretic rats, and following vasopressin treatment in vivo and in vitro. Experimental approaches will include: 1) production of three-dimensional reconstruction of all IM thin limbs of Henle's loops, CDs, and vasa recta from serial sections, using immunocytochemical markers of physiological function to identify tubule and vessel segments, sites of cellular transport functions, and interstitial compartments and determination of structure-to-structure interactions, and 2) direct measurements, by in vitro microperfusions, of the NaCl, urea, and water permeabilities of specific thin limb segments defined in the reconstructions. Tubule permeabilities will be investigated with and without vasopressin in vitro, and permeabilities will be investigated following water diuresis, antidiuresis, and exposure to vasopressin in vivo.