Integrated Tubular and Vascular Structure and Function in Renal Inner Medulla

描述(由申请人提供)：内髓质尿浓缩机制是一个重要但知之甚少的肾功能。该项目的目的是促进我们对哺乳动物肾髓质结构组织和功能之间的关系的理解，包括无机离子、尿素和水的通量以及尿液浓缩机制。三维结构强调的是，内髓间质不是一个单一的、混合良好的隔室。对Henle跨上皮环的不完全了解是创建解释IM渗透梯度和UCM产生的高级模型的唯一最关键的障碍。只有考虑到肾脏IM的三维结构和功能结构，才能完全理解UCM。在前人工作的基础上，以及我们以前在确定功能组织以及溶质和水通量的工作的基础上，将调查以下三个具体目标。目的1、测定中等浓度大鼠肌间充盈环的水、尿素和氯化钠通透性。目的2，确定IM内Henle环、CDs环、血管网络和间质结节间隙(INSS)的功能构筑。目的3测定利尿剂和抗利尿剂大鼠及加压素治疗后大鼠Henle环对尿素和氯化钠的通透性。实验方法将包括：1)从连续切片中建立Henle‘s环、CDs和Vasa recta的所有IM细肢的三维重建，使用生理功能的免疫细胞化学标记物来识别小管和血管段、细胞运输功能的位置和间质间隔室，并确定结构与结构的相互作用；以及2)通过体外微灌流直接测量重建中所定义的特定细肢段的氯化钠、尿素和水的渗透性。体外研究有无血管加压素的肾小管通透性，体内观察利水、抗利尿和暴露于血管加压素后的肾小管通透性。 公共卫生相关性：细胞外液和溶质动态平衡对于维持全身正常的细胞功能非常重要。肾脏在维持液体和溶质动态平衡方面起着至关重要的作用，而浓缩机制是完成这一作用的关键过程。这些研究的主要目的是为了更清楚地了解集中的机制。

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. PUBLIC HEALTH RELEVANCE: Extracellular fluid and solute homeostasis is important for maintaining normal cell function throughout the body. The kidney plays a critical role in maintaining fluid and solute homeostasis and the concentrating mechanism is an essential process in accomplishing this role. The major goal of these studies is to more clearly understand the concentrating mechanism.