Integrated Tubular and Vascular Structure and Function in Renal Inner Medulla

描述（由申请人提供）：髓内尿浓缩机制是一种重要但尚不清楚的肾功能。本项目旨在进一步了解哺乳动物肾髓质的结构、组织和功能之间的关系，包括无机离子、尿素和水的通量，以及尿液在哺乳动物肾髓质的浓缩机制。三维结构强调了内髓间质不是一个单一的混合良好的隔间。对Henle透皮细胞NaCl、尿素和水渗透性的不完全了解是建立解释IM渗透梯度和UCM产生的先进模型的最关键障碍。只有考虑到肾脏IM的三维结构和功能结构，才能充分理解UCM。根据其他人的工作和我们以前在确定功能组织和溶质和水通量方面的工作，我们将研究以下三个具体目标。目的1，测定中度浓缩大鼠Henle IM环的水、尿素和NaCl渗透性。目的2，确定IM中Henle和CDs回路、血管网络和间质结空间（INSs）的功能结构。目的3：利尿和抗利尿大鼠体内和体外抗利尿素处理后Henle袢尿素和NaCl渗透率的测定。实验方法包括：1)利用生理功能的免疫细胞化学标记物对Henle’s袢、CDs和直血管的所有IM细肢进行三维重建，以识别小管和血管段、细胞运输功能位点和间质室，并确定结构与结构之间的相互作用；2)通过体外微灌注直接测量NaCl、尿素、以及在重建中定义的特定细肢段的透水性。小管的渗透性将在体外使用和不使用抗利尿素时进行研究，渗透性将在水利尿、抗利尿和体内使用抗利尿素后进行研究。

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.