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Vasa recta Henle loop

Yael Kenig-Kozlovsky, Rizaldy P Scott, Tuncer Onay, Isabel Anna Carota, Benjamin R Thomson, Hyea Jin Gil, Veronica Ramirez, Shinji Yamaguchi, Christine E Tanna, Stefan Heinen, Christine Wu, Radu V Stan, Janet D Klein, Jeff M Sands, Guillermo Oliver, Susan E Quaggin
Urinary concentrating ability is central to mammalian water balance and depends on a medullary osmotic gradient generated by a countercurrent multiplication mechanism. Medullary hyperosmolarity is protected from washout by countercurrent exchange and efficient removal of interstitial fluid resorbed from the loop of Henle and collecting ducts. In most tissues, lymphatic vessels drain excess interstitial fluid back to the venous circulation. However, the renal medulla is devoid of classic lymphatics. Studies have suggested that the fenestrated ascending vasa recta (AVRs) drain the interstitial fluid in this location, but this function has not been conclusively shown...
April 2018: Journal of the American Society of Nephrology: JASN
Miriam Zacchia, Valentina Di Iorio, Francesco Trepiccione, Marianna Caterino, Giovambattista Capasso
BACKGROUND: The ciliopathies are a growing number of disorders caused by mutations in genes involved in the function of the primary cilium. Bardet-Biedl syndrome (BBS) belongs to this group of disorders. In this setting, kidney dysfunction is highly variable, and urine concentrating defect, a common feature of multiple ciliopathies, has been described as the most frequent defect. Here we review the mechanism of urine concentration and describe the possible mechanism underling this defect in ciliopathies and especially BBS, based on the current body of literature...
July 2017: Kidney Diseases
Michele Andreucci, Teresa Faga, Raffaele Serra, Giovambattista De Sarro, Ashour Michael
An important side effect of diagnostic contrast drugs is contrast-induced acute kidney injury (CI-AKI; a sudden decrease in renal function) occurring 48-72 hours after injection of a contrast drug that cannot be attributed to other causes. Its existence has recently been challenged, because of some retrospective studies in which the incidence of AKI was not different between subjects who received a contrast drug and those who did not, even using propensity score matching to prevent selection bias. For some authors, only patients with estimated glomerular filtration rate <30 mL/min/1...
2017: Drug, Healthcare and Patient Safety
Jennifer P Ngo, Connie P C Ow, Bruce S Gardiner, Saptarshi Kar, James T Pearson, David W Smith, Roger G Evans
Countercurrent systems have evolved in a variety of biological systems that allow transfer of heat, gases, and solutes. For example, in the renal medulla, the countercurrent arrangement of vascular and tubular elements facilitates the trapping of urea and other solutes in the inner medulla, which in turn enables the formation of concentrated urine. Arteries and veins in the cortex are also arranged in a countercurrent fashion, as are descending and ascending vasa recta in the medulla. For countercurrent diffusion to occur, barriers to diffusion must be small...
November 1, 2016: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Cécile Verrier, Dominique Bazin, Léa Huguet, Odile Stéphan, Alexandre Gloter, Marie-Christine Verpont, Vincent Frochot, Jean-Philippe Haymann, Isabelle Brocheriou, Olivier Traxer, Michel Daudon, Emmanuel Letavernier
PURPOSE: Randall identified calcium phosphate plaques in renal papillae as the origin of kidney stones. However, little is known about the early steps of Randall plaque formation preceding the onset of urolithiasis. Our objective was to characterize the composition and the initial formation site of incipient Randall plaque in nonstone forming, living patients. MATERIALS AND METHODS: Median patient age was 67.7 years. A total of 54 healthy papillae from kidneys removed for cancer and without stones were analyzed by immunohistochemistry and von Kossa staining, field emission-scanning electron microscopy with energy dispersive x-ray analysis, μ-Fourier transform infrared spectroscopy, cryo-transmission electron microscopy coupled to selected area electron diffraction and electron energy loss spectroscopy...
November 2016: Journal of Urology
Kristen K Evans, C Michele Nawata, Thomas L Pannabecker
Outer medullary isolated descending vasa recta have proven to be experimentally tractable, and consequently much has been learned about outer medullary vasa recta endothelial transport, pericyte contractile mechanisms, and tubulovascular interactions. In contrast, inner medullary vasa recta have never been isolated from any species, and therefore isolated vasa recta function has never been subjected to in vitro quantitative evaluation. As we teased out inner medullary thin limbs of Henle's loops from the Munich-Wistar rat, we found that vasa recta could be isolated using similar protocols...
August 15, 2015: American Journal of Physiology. Renal Physiology
Dong-Un Kim
To produce a concentrated urine, the renal medulla needs hypertonicity for the reabsorption of free water from collecting duct. The single effect that increases interstitial tonicity in the outer medulla is the active NaCl reabsorption in the thick ascending limb, while the single effect in the inner medulla is the passive efflux of NaCl through the thin ascending limb. The passive mechanism in the inner medulla requires high interstitial urea concentration. Two main groups of urea transporters (UT-A, UT-B) are present in the kidney, which maintains the high concentration of urea in the deepest portion of the inner medulla by intra-renal urea recycling...
March 2006: Electrolyte & Blood Pressure: E & BP
Hao Ren, Ling Gu, Arne Andreasen, Jesper S Thomsen, Liu Cao, Erik I Christensen, Xiao-Yue Zhai
The vascular bundle (VB) is a complex structure that resides in the inner stripe of the outer medulla. At present, the tubulovascular spatial organization of the VB, which is crucial for the formation of the osmolarity gradient and for solute transport, is still under debate. In this study, we used computer-assisted digital tracing combined with aquaporin-1 immunohistochemistry to reconstruct all tubules and vessels in the VB of the mouse kidney. We found, first, that the descending and ascending vasa recta travelled exclusively through the VB...
February 1, 2014: American Journal of Physiology. Renal Physiology
C Crawford, S S P Wildman, M C Kelly, T M Kennedy-Lydon, C M Peppiatt-Wildman
Pericyte cells are now known to be a novel locus of blood flow control, being able to regulate capillary diameter via their unique morphology and expression of contractile proteins. We have previously shown that exogenous ATP causes constriction of vasa recta via renal pericytes, acting at a variety of membrane bound P2 receptors on descending vasa recta (DVR), and therefore may be able to regulate medullary blood flow (MBF). Regulation of MBF is essential for appropriate urine concentration and providing essential oxygen and nutrients to this region of high, and variable, metabolic demand...
2013: Frontiers in Physiology
Magali Tournus, Nicolas Seguin, Benoît Perthame, S Randall Thomas, Aurélie Edwards
We developed a mathematical model of calcium (Ca(2+)) transport along the rat nephron to investigate the factors that promote hypercalciuria. The model is an extension of the flat medullary model of Hervy and Thomas (Am J Physiol Renal Physiol 284: F65-F81, 2003). It explicitly represents all the nephron segments beyond the proximal tubules and distinguishes between superficial and deep nephrons. It solves dynamic conservation equations to determine NaCl, urea, and Ca(2+) concentration profiles in tubules, vasa recta, and the interstitium...
October 1, 2013: American Journal of Physiology. Renal Physiology
Thomas L Pannabecker
The thin limbs of the loop of Henle, which comprise the intermediate segment, connect the proximal tubule to the distal tubule and lie entirely within the renal medulla. The descending thin limb consists of at least two or three morphologically and functionally distinct subsegments and participates in transepithelial transport of NaCl, urea, and water. Only one functionally distinct segment is recognized for the ascending thin limb, which carries out transepithelial transport of NaCl and urea in the reabsorptive and/or secretory directions...
July 2012: Comprehensive Physiology
Thomas L Pannabecker
Comparative studies of renal structure and function have potential to provide insights into the urine-concentrating mechanism of the mammalian kidney. This review focuses on the tubular transport pathways for water and urea that play key roles in fluid and solute movements between various compartments of the rodent renal inner medulla. Information on aquaporin water channel and urea transporter expression has increased our understanding of functional segmentation of medullary thin limbs of Henle's loops, collecting ducts, and vasa recta...
April 1, 2013: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Kristen Y Westrick, Bradley Serack, William H Dantzler, Thomas L Pannabecker
In the inner medulla, radial organization of nephrons and blood vessels around collecting duct (CD) clusters leads to two lateral interstitial regions and preferential intersegmental fluid and solute flows. As the descending (DTLs) and ascending thin limbs (ATLs) pass through these regions, their transepithelial fluid and solute flows are influenced by variable transepithelial solute gradients and structure-to-structure interactions. The goal of this study was to quantify structure-to-structure interactions, so as to better understand compartmentation and flows of transepithelial water, NaCl, and urea and generation of the axial osmotic gradient...
February 1, 2013: American Journal of Physiology. Renal Physiology
William H Beierwaltes
No abstract text is available yet for this article.
January 1, 2013: American Journal of Physiology. Renal Physiology
Mauricio M Sendeski, Anja Bondke Persson, Zhi Zhao Liu, Jonas F Busch, Steffen Weikert, Pontus B Persson, Stefan Hippenstiel, Andreas Patzak
Contrast-induced acute kidney injury is an important clinical event with a worldwide increasing number of cases. Medullary hypoperfusion and hypoxia due to constriction of vasa recta are main factors in the pathophysiology of acute kidney injury. However, the mechanism of contrast media (CM)-induced vessel constriction is not known. We tested the hypothesis that vasa recta constriction is a consequence of endothelial dysfunction due to the cytotoxicity of CM. Human and rat descending vasa recta (DVR) were isolated and perfused with CM, and the luminal diameter was analyzed...
December 15, 2012: American Journal of Physiology. Renal Physiology
Renfang Song, Ihor V Yosypiv
The mature renal medulla, the inner part of the kidney, consists of the medullary collecting ducts, loops of Henle, vasa recta and the interstitium. The unique spatial arrangement of these components is essential for the regulation of urine concentration and other specialized kidney functions. Thus, the proper and timely assembly of medulla constituents is a crucial morphogenetic event leading to the formation of a functioning metanephric kidney. Mechanisms that direct renal medulla formation are poorly understood...
January 2012: Organogenesis
Anita T Layton, Rebecca L Gilbert, Thomas L Pannabecker
Recent anatomic findings indicate that in the upper inner medulla of the rodent kidney, tubules, and vessels are organized around clusters of collecting ducts (CDs). Within CD clusters, CDs and some of the ascending vasa recta (AVR) and ascending thin limbs (ATLs), when viewed in transverse sections, form interstitial nodal spaces, which are arrayed at structured intervals throughout the inner medulla. These spaces, or microdomains, are bordered on one side by a single CD, on the opposite side by one or more ATLs, and on the other two sides by AVR...
April 1, 2012: American Journal of Physiology. Renal Physiology
Takefumi Mori, Susumu Ogawa, Allen W Cowely, Sadayoshi Ito
1. Salt-sensitive hypertension is commonly associated with diabetes, obesity and chronic kidney disease. The present review focuses on renal mechanisms involved in the development of this type of hypertension. 2. The renal medullary circulation plays an important role in the development of salt-sensitive hypertension. In vivo animal studies have demonstrated that the balance between nitric oxide (NO) and reactive oxygen species (ROS) in the renal medulla is an important element of salt-sensitive hypertension...
January 2012: Clinical and Experimental Pharmacology & Physiology
Anita T Layton, William H Dantzler, Thomas L Pannabecker
We extended a region-based mathematical model of the renal medulla of the rat kidney, previously developed by us, to represent new anatomic findings on the vascular architecture in the rat inner medulla (IM). In the outer medulla (OM), tubules and vessels are organized around tightly packed vascular bundles; in the IM, the organization is centered around collecting duct clusters. In particular, the model represents the separation of descending vasa recta from the descending limbs of loops of Henle, and the model represents a papillary segment of the descending thin limb that is water impermeable and highly urea permeable...
March 1, 2012: American Journal of Physiology. Renal Physiology
Tianluo Lei, Lei Zhou, Anita T Layton, Hong Zhou, Xuejian Zhao, Lise Bankir, Baoxue Yang
Urea transporters UT-A2 and UT-B are expressed in epithelia of thin descending limb of Henle's loop and in descending vasa recta, respectively. To study their role and possible interaction in the context of the urine concentration mechanism, a UT-A2 and UT-B double knockout (UT-A2/B knockout) mouse model was generated by targeted deletion of the UT-A2 promoter in embryonic stem cells with UT-B gene knockout. The UT-A2/B knockout mice lacked detectable UT-A2 and UT-B transcripts and proteins and showed normal survival and growth...
December 2011: American Journal of Physiology. Renal Physiology
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