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Solenov EI, Baturina GS, Katkova LE, Yang B, Zarogiannis SG. Methods to Measure Water Permeability. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:343-361. [PMID: 36717506 DOI: 10.1007/978-981-19-7415-1_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Water permeability is a key feature of the cell plasma membranes, and it has seminal importance for several cell functions such as cell volume regulation, cell proliferation, cell migration, and angiogenesis to name a few. The transport of water occurs mainly through plasma membrane water channels, aquaporins. Aquaporins have very important function in physiological and pathophysiological states. Due to the above, the experimental assessment of the water permeability of cells and tissues is necessary. The development of new methodologies of measuring water permeability is a vibrant scientific field that constantly develops during the last three decades along with the advances in imaging mainly. In this chapter we describe and critically assess several methods that have been developed for the measurement of water permeability both in living cells and in tissues with a focus in the first category.
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Affiliation(s)
- Evgeniy I Solenov
- Institute of Cytology and Genetics, SB RAS, Novosibirsk, Russia.
- Novosibirsk State Technical University, Novosibirsk, Russia.
| | | | | | - Baoxue Yang
- School of Basic Medical Sciences, Peking University, Beijing, China
| | - Sotirios G Zarogiannis
- Department of Physiology, Faculty of Medicine, University of Thessaly, BIOPOLIS, Larissa, Greece
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2
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Marcoux AA, Tremblay LE, Slimani S, Fiola MJ, Mac-Way F, Haydock L, Garneau AP, Isenring P. Anatomophysiology of the Henle's Loop: Emphasis on the Thick Ascending Limb. Compr Physiol 2021; 12:3119-3139. [PMID: 34964111 DOI: 10.1002/cphy.c210021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The loop of Henle plays a variety of important physiological roles through the concerted actions of ion transport systems in both its apical and basolateral membranes. It is involved most notably in extracellular fluid volume and blood pressure regulation as well as Ca2+ , Mg2+ , and acid-base homeostasis because of its ability to reclaim a large fraction of the ultrafiltered solute load. This nephron segment is also involved in urinary concentration by energizing several of the steps that are required to generate a gradient of increasing osmolality from cortex to medulla. Another important role of the loop of Henle is to sustain a process known as tubuloglomerular feedback through the presence of specialized renal tubular cells that lie next to the juxtaglomerular arterioles. This article aims at describing these physiological roles and at discussing a number of the molecular mechanisms involved. It will also report on novel findings and uncertainties regarding the realization of certain processes and on the pathophysiological consequences of perturbed salt handling by the thick ascending limb of the loop of Henle. Since its discovery 150 years ago, the loop of Henle has remained in the spotlight and is now generating further interest because of its role in the renal-sparing effect of SGLT2 inhibitors. © 2022 American Physiological Society. Compr Physiol 12:1-21, 2022.
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Affiliation(s)
- Andrée-Anne Marcoux
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Laurence E Tremblay
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Samira Slimani
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Marie-Jeanne Fiola
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Fabrice Mac-Way
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Ludwig Haydock
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Alexandre P Garneau
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada.,Cardiometabolic Axis, School of Kinesiology and Physical Activity Sciences, University of Montréal, Montréal, QC, Canada
| | - Paul Isenring
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
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Agarwal S, Sudhini YR, Polat OK, Reiser J, Altintas MM. Renal cell markers: lighthouses for managing renal diseases. Am J Physiol Renal Physiol 2021; 321:F715-F739. [PMID: 34632812 DOI: 10.1152/ajprenal.00182.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Kidneys, one of the vital organs in our body, are responsible for maintaining whole body homeostasis. The complexity of renal function (e.g., filtration, reabsorption, fluid and electrolyte regulation, and urine production) demands diversity not only at the level of cell types but also in their overall distribution and structural framework within the kidney. To gain an in depth molecular-level understanding of the renal system, it is imperative to discern the components of kidney and the types of cells residing in each of the subregions. Recent developments in labeling, tracing, and imaging techniques have enabled us to mark, monitor, and identify these cells in vivo with high efficiency in a minimally invasive manner. In this review, we summarize different cell types, specific markers that are uniquely associated with those cell types, and their distribution in the kidney, which altogether make kidneys so special and different. Cellular sorting based on the presence of certain proteins on the cell surface allowed for the assignment of multiple markers for each cell type. However, different studies using different techniques have found contradictions in cell type-specific markers. Thus, the term "cell marker" might be imprecise and suboptimal, leading to uncertainty when interpreting the data. Therefore, we strongly believe that there is an unmet need to define the best cell markers for a cell type. Although the compendium of renal-selective marker proteins presented in this review is a resource that may be useful to researchers, we acknowledge that the list may not be necessarily exhaustive.
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Affiliation(s)
- Shivangi Agarwal
- Department of Internal Medicine, Rush University, Chicago, Illinois
| | | | - Onur K Polat
- Department of Internal Medicine, Rush University, Chicago, Illinois
| | - Jochen Reiser
- Department of Internal Medicine, Rush University, Chicago, Illinois
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Gee MT, Kurtz I, Pannabecker TL. Expression of SLC4A11 protein in mouse and rat medulla: a candidate transporter involved in outer medullary ammonia recycling. Physiol Rep 2019; 7:e14089. [PMID: 31124301 PMCID: PMC6533174 DOI: 10.14814/phy2.14089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Accepted: 04/10/2019] [Indexed: 01/27/2023] Open
Abstract
SLC4A11 is a multifunctional membrane transporter involved with H+ transport, NH3 and alkaline pH stimulated H+ transport, and water transport. The role of SLC4A11 in the kidney is not well understood. A prior study has shown that in murine kidney, SLC4A11/LacZ staining is primarily in the long-looped descending thin limb (DTL) as determined by colocalization with aquaporin 1 (AQP1), a protein that is expressed in some, but not all, descending thin limb segments. Using a previously characterized polyclonal antibody, we demonstrate the selective expression of SLC4A11 in the upper DTLs (which are AQP1-positive) in the outer medulla and inner medulla with little or no expression in the lower DTLs (which are AQP-1-null). SLC4A11 also colocalized with AQP1 and the urea transporter UT-B in the mouse descending vasa recta, but was absent in mouse and rat ascending vasa recta. Mouse, but not rat, outer medullary collecting duct cells also labeled for SLC4A11. Our results are compatible with the hypothesis that in the inner stripe of the outer medulla, SLC4A11 plays a role in the countercurrent transport of ammonia absorbed from the outer medullary thick ascending limb and secreted into the long-looped DTLs. SLC4A11 can potentially modulate the rate of ammonia transport in the mouse outer medullary collecting duct. Our data suggest functionally unique SLC4A11 pathways in mouse and rat and complement previous studies of DTL Na+ , urea and water permeability indicating that the upper and lower DTLs of long-looped nephrons are functionally distinct.
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Affiliation(s)
- Michael T. Gee
- Department of PhysiologyBanner‐University Medical CenterUniversity of ArizonaTucsonAZ85724
| | - Ira Kurtz
- Division of NephrologyDavid Geffen School of MedicineUniversity of California, Los Angeles (UCLA)Los AngelesCA
- Brain Research InstituteDavid Geffen School of MedicineUniversity of California, Los Angeles (UCLA)Los AngelesCA
| | - Thomas L. Pannabecker
- Department of PhysiologyBanner‐University Medical CenterUniversity of ArizonaTucsonAZ85724
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Nawata CM, Pannabecker TL. Mammalian urine concentration: a review of renal medullary architecture and membrane transporters. J Comp Physiol B 2018; 188:899-918. [PMID: 29797052 PMCID: PMC6186196 DOI: 10.1007/s00360-018-1164-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 04/23/2018] [Accepted: 05/14/2018] [Indexed: 01/10/2023]
Abstract
Mammalian kidneys play an essential role in balancing internal water and salt concentrations. When water needs to be conserved, the renal medulla produces concentrated urine. Central to this process of urine concentration is an osmotic gradient that increases from the corticomedullary boundary to the inner medullary tip. How this gradient is generated and maintained has been the subject of study since the 1940s. While it is generally accepted that the outer medulla contributes to the gradient by means of an active process involving countercurrent multiplication, the source of the gradient in the inner medulla is unclear. The last two decades have witnessed advances in our understanding of the urine-concentrating mechanism. Details of medullary architecture and permeability properties of the tubules and vessels suggest that the functional and anatomic relationships of these structures may contribute to the osmotic gradient necessary to concentrate urine. Additionally, we are learning more about the membrane transporters involved and their regulatory mechanisms. The role of medullary architecture and membrane transporters in the mammalian urine-concentrating mechanism are the focus of this review.
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Affiliation(s)
- C Michele Nawata
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA.
| | - Thomas L Pannabecker
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA
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Sonntag SR, Ziemens A, Wulfmeyer VC, Milatz S, Bleich M, Himmerkus N. Diuretic state affects ascending thin limb tight junctions. Am J Physiol Renal Physiol 2018; 314:F190-F195. [PMID: 28971992 DOI: 10.1152/ajprenal.00419.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nephron segments in the inner medulla are part of the urine concentrating mechanism. Depending on the diuretic state, they are facing a large range of extracellular osmolality. We investigated whether water homeostasis affects tubular transport and permeability properties in inner medullary descending thin limb (IMdTL) and ascending thin limb (IMaTL). Three experimental groups of rats under different diuretic states were investigated on metabolic cages: waterload, furosemide-induced diuresis, and control (antidiuresis). Urine production and osmolalities reflected the 3-day treatment. To functionally investigate tubular epithelial properties, we performed experiments in freshly isolated inner medullary thin limbs from these animals. Tubular segments were acutely dissected and investigated for trans- and paracellular properties by in vitro perfusion and electrophysiological analysis. IMdTL and IMaTL were distinguished by morphological criteria. We confirmed absence of transepithelial electrogenic transport in thin limbs. Although diffusion potential measurements showed no differences between treatments in IMdTLs, we observed increased paracellular cation selectivity under waterload in IMaTLs. NaCl diffusion potential was -5.64 ± 1.93 mV under waterload, -1.99 ± 1.72 mV under furosemide-induced diuresis, and 0.27 ± 0.40 mV under control. The corresponding permeability ratio PNa/Cl was 1.53 ± 0.21 (waterload), 1.22 ± 0.18 (furosemide-induced diuresis), and 0.99 ± 0.02 (control), respectively. Claudins are main constituents of the tight junction responsible for paracellular selectivity; however, immunofluorescence did not show qualitative differences in claudin 4, 10, and 16 localization. Our results show that IMaTLs change tight junction properties in response to diuretic state to allow adaptation of NaCl reabsorption.
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Affiliation(s)
| | - Annalisa Ziemens
- Institute of Physiology, Christian Albrechts University of Kiel , Kiel , Germany
| | | | - Susanne Milatz
- Institute of Physiology, Christian Albrechts University of Kiel , Kiel , Germany
| | - Markus Bleich
- Institute of Physiology, Christian Albrechts University of Kiel , Kiel , Germany
| | - Nina Himmerkus
- Institute of Physiology, Christian Albrechts University of Kiel , Kiel , Germany
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7
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Zacchia M, Di Iorio V, Trepiccione F, Caterino M, Capasso G. The Kidney in Bardet-Biedl Syndrome: Possible Pathogenesis of Urine Concentrating Defect. KIDNEY DISEASES 2017; 3:57-65. [PMID: 28868293 DOI: 10.1159/000475500] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 04/05/2017] [Indexed: 12/16/2022]
Abstract
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. SUMMARY Active Na+ absorption along the thick ascending limb of the loop of Henle (TAL) is critical for generating the corticomedullary osmotic gradient, and the countercurrent anatomical arrangement of the 2 branches of the loop of Henle enhances this gradient. The vasa recta, paralleling the loop of Henle, operate into the countercurrent mechanism, minimizing washout of solutes from the interstitium. Final water reabsorption is mediated by the aquaporin 2 (AQP2) water channels along the distal nephron, and it is under hormonal control. Several studies demonstrated that hyposthenuria in BBS patients relies on kidney resistance to desmopressin, suggesting a renal origin. We recently showed that the majority of hyposthenuric BBS patients have also a defect regarding maximal urine dilution. Independent studies showed that BBS10 deficiency caused AQP2 mistrafficking in vitro; accordingly, we demonstrated impaired urinary AQP2 excretion in BBS patients with combined concentrating and diluting defect. Whether receptor signaling pathways or downstream events cause AQP2 deregulation is still unclear. In addition, reduced urinary uromodulin excretion in BBS patients opens the possibility that TAL dysfunction may also play a pathogenic role. KEY MESSAGE Impaired water handling in BBS is associated with AQP2 mistrafficking. The potential role of additional factors, such as the dissipation of the medullary osmotic gradient due to TAL dysfunction and/or structural anomalies, remains to be elucidated.
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Affiliation(s)
- Miriam Zacchia
- Division of Nephrology, Department of Cardiothoracic and Respiratory Sciences, University of Campania "Luigi Vanvitelli," Naples, Italy
| | - Valentina Di Iorio
- Eye Clinic, Multidisciplinary Department of Medical, Surgical, and Dental Sciences, University of Campania "Luigi Vanvitelli," Naples, Italy
| | - Francesco Trepiccione
- Division of Nephrology, Department of Cardiothoracic and Respiratory Sciences, University of Campania "Luigi Vanvitelli," Naples, Italy
| | - Marianna Caterino
- Department of Molecular Biology and Medical Biotechnologies, Università degli Studi di Napoli "Federico II," Naples, Italy
| | - Giovambattista Capasso
- Division of Nephrology, Department of Cardiothoracic and Respiratory Sciences, University of Campania "Luigi Vanvitelli," Naples, Italy
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Layton AT, Vallon V, Edwards A. A computational model for simulating solute transport and oxygen consumption along the nephrons. Am J Physiol Renal Physiol 2016; 311:F1378-F1390. [PMID: 27707705 DOI: 10.1152/ajprenal.00293.2016] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 09/28/2016] [Indexed: 11/22/2022] Open
Abstract
The goal of this study was to investigate water and solute transport, with a focus on sodium transport (TNa) and metabolism along individual nephron segments under differing physiological and pathophysiological conditions. To accomplish this goal, we developed a computational model of solute transport and oxygen consumption (QO2 ) along different nephron populations of a rat kidney. The model represents detailed epithelial and paracellular transport processes along both the superficial and juxtamedullary nephrons, with the loop of Henle of each model nephron extending to differing depths of the inner medulla. We used the model to assess how changes in TNa may alter QO2 in different nephron segments and how shifting the TNa sites alters overall kidney QO2 Under baseline conditions, the model predicted a whole kidney TNa/QO2 , which denotes the number of moles of Na+ reabsorbed per moles of O2 consumed, of ∼15, with TNa efficiency predicted to be significantly greater in cortical nephron segments than in medullary segments. The TNa/QO2 ratio was generally similar among the superficial and juxtamedullary nephron segments, except for the proximal tubule, where TNa/QO2 was ∼20% higher in superficial nephrons, due to the larger luminal flow along the juxtamedullary proximal tubules and the resulting higher, flow-induced transcellular transport. Moreover, the model predicted that an increase in single-nephron glomerular filtration rate does not significantly affect TNa/QO2 in the proximal tubules but generally increases TNa/QO2 along downstream segments. The latter result can be attributed to the generally higher luminal [Na+], which raises paracellular TNa Consequently, vulnerable medullary segments, such as the S3 segment and medullary thick ascending limb, may be relatively protected from flow-induced increases in QO2 under pathophysiological conditions.
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Affiliation(s)
- Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina;
| | - Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego, La Jolla, California, and San Diego Veterans Affairs Healthcare System, San Diego, California
| | - Aurélie Edwards
- Sorbonne Universités, UPMC Univ Paris 06, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and
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Abstract
PURPOSE OF REVIEW Urea is transported by urea transporter proteins in kidney, erythrocytes, and other tissues. Mice in which different urea transporters have been knocked out have urine-concentrating defects, which has led to the development and testing of urea transporters Slc14A2 (UT-A) and Slc14A1 (UT-B) inhibitors as urearetics. This review summarizes the knowledge gained during the past year on urea transporter regulation and investigations into the clinical potential of urearetics. RECENT FINDINGS UT-A1 undergoes several posttranslational modifications that increase its function by increasing UT-A1 accumulation in the apical plasma membrane. UT-A1 is phosphorylated by protein kinase A, exchange protein activated by cyclic AMP, protein kinase Cα, and AMP-activated protein kinase, all at different serine residues. UT-A1 is also regulated by 14-3-3, which contributes to UT-A1 removal from the membrane. UT-A1 is glycosylated with various glycan moieties in animal models of diabetes mellitus. Transgenic expression of UT-A1 into UT-A1/UT-A3 knockout mice restores urine-concentrating ability. UT-B is present in descending vasa recta and urinary bladder, and is linked to bladder cancer. Inhibitors of UT-A and UT-B have been developed that result in diuresis with fewer abnormalities in serum electrolytes than conventional diuretics. SUMMARY Urea transporters play critical roles in the urine-concentrating mechanism. Urea transport inhibitors are a promising new class of diuretic agent.
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Affiliation(s)
- Janet D Klein
- Renal Division, Department of Medicine, and Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, USA
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Nawata CM, Dantzler WH, Pannabecker TL. Alternative channels for urea in the inner medulla of the rat kidney. Am J Physiol Renal Physiol 2015; 309:F916-24. [PMID: 26423860 PMCID: PMC4669356 DOI: 10.1152/ajprenal.00392.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 09/24/2015] [Indexed: 11/22/2022] Open
Abstract
The ascending thin limbs (ATLs) and lower descending thin limbs (DTLs) of Henle's loop in the inner medulla of the rat are highly permeable to urea, and yet no urea transporters have been identified in these sections. We hypothesized that novel, yet-unidentified transporters in these tubule segments could explain the high urea permeability. cDNAs encoding for Na(+)-glucose transporter 1a (SGLT1a), Na(+)-glucose transporter 1 (NaGLT1), urea transporter (UT)-A2c, and UT-A2d were isolated and cloned from the Munich-Wistar rat inner medulla. SGLT1a is a novel NH2-terminal truncated variant of SGLT1. NaGLT1 is a Na(+)-dependent glucose transporter primarily located in the proximal tubules and not previously described in the thin limbs. UT-A2c and UT-A2d are novel variants of UT-A2. UT-A2c is truncated at the COOH terminus, and UT-A2d has one exon skipped. When rats underwent water restriction for 72 h, mRNA levels of SGLT1a increased in ATLs, NaGLT1 levels increased in both ATLs and DTLs, and UT-A2c increased in ATLs. [(14)C]urea uptake assays performed on Xenopus oocytes heterologously expressing these proteins revealed that despite having structural differences from their full-length versions, SGLT1a, UT-A2c, and UT-A2d enhanced urea uptake. NaGLT1 also facilitated urea uptake. Uptakes were Na(+) independent and inhibitable by phloretin and/or phloridzin. Our data indicate that there are several alternative channels for urea in the rat inner medulla that could potentially contribute to the high urea permeabilities in thin limb segments.
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Affiliation(s)
- C Michele Nawata
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona
| | - William H Dantzler
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona
| | - Thomas L Pannabecker
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona
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11
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Wei G, Rosen S, Dantzler WH, Pannabecker TL. Architecture of the human renal inner medulla and functional implications. Am J Physiol Renal Physiol 2015; 309:F627-37. [PMID: 26290371 DOI: 10.1152/ajprenal.00236.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/10/2015] [Indexed: 11/22/2022] Open
Abstract
The architecture of the inner stripe of the outer medulla of the human kidney has long been known to exhibit distinctive configurations; however, inner medullary architecture remains poorly defined. Using immunohistochemistry with segment-specific antibodies for membrane fluid and solute transporters and other proteins, we identified a number of distinctive functional features of human inner medulla. In the outer inner medulla, aquaporin-1 (AQP1)-positive long-loop descending thin limbs (DTLs) lie alongside descending and ascending vasa recta (DVR, AVR) within vascular bundles. These vascular bundles are continuations of outer medullary vascular bundles. Bundles containing DTLs and vasa recta lie at the margins of coalescing collecting duct (CD) clusters, thereby forming two regions, the vascular bundle region and the CD cluster region. Although AQP1 and urea transporter UT-B are abundantly expressed in long-loop DTLs and DVR, respectively, their expression declines with depth below the outer medulla. Transcellular water and urea fluxes likely decline in these segments at progressively deeper levels. Smooth muscle myosin heavy chain protein is also expressed in DVR of the inner stripe and the upper inner medulla, but is sparsely expressed at deeper inner medullary levels. In rodent inner medulla, fenestrated capillaries abut CDs along their entire length, paralleling ascending thin limbs (ATLs), forming distinct compartments (interstitial nodal spaces; INSs); however, in humans this architecture rarely occurs. Thus INSs are relatively infrequent in the human inner medulla, unlike in the rodent where they are abundant. UT-B is expressed within the papillary epithelium of the lower inner medulla, indicating a transcellular pathway for urea across this epithelium.
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Affiliation(s)
- Guojun Wei
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - Seymour Rosen
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - William H Dantzler
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - Thomas L Pannabecker
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
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12
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Wang Y, Bu J, Zhang Q, Chen K, Zhang J, Bao X. Expression pattern of aquaporins in patients with primary nephrotic syndrome with edema. Mol Med Rep 2015; 12:5625-32. [PMID: 26261083 PMCID: PMC4581814 DOI: 10.3892/mmr.2015.4209] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 04/20/2015] [Indexed: 01/10/2023] Open
Abstract
The association between the expression of aquaporins (AQPs) in kidney tissues and the occurrence of edema in nephrotic syndrome (NS) remains unclear. The current study aimed to investigate this association. A total of 54 patients with primary glomerular disease, diagnosed by renal biopsy, were divided into three groups: Control, NS without edema and NS with edema. The expression of AQP1, AQP2, AQP3 and AQP4 in kidney tissues from these patients was assessed using immunohistochemistry, and urinary AQP concentrations were quantified by ELISA. Comparison of the three groups was conducted using one way analysis of variance, independent samples t-test or the Chi-square test. AQP1 was strongly expressed in the proximal tubules. The proportion of the AQP1-positive area in kidney tissues from patients with NS with edema was significantly reduced, in comparison with the other two groups. By contrast, the proportion of the AQP2-positive area in the NS with edema group was significantly higher than that of the other two groups; significant differences were also observed between the control and NS without edema groups for this parameter. Urinary AQP2 concentrations in patients with NS (with and without edema) were significantly higher than that of the control group, and exhibited a significant positive correlation with kidney tissue AQP2 concentrations. The present study demonstrated the abnormal expression pattern of AQP1-AQP4 in the kidney tissues of patients with NS, providing a basis for an improved understanding of the role of AQP in the pathogenesis of NS.
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Affiliation(s)
- Yu Wang
- Department of Nephrology, Jinshan Hospital Affiliated to Fudan University, Shanghai 201508, P.R. China
| | - Jimei Bu
- Department of Nephrology, Jinshan Hospital Affiliated to Fudan University, Shanghai 201508, P.R. China
| | - Qing Zhang
- Department of Nephrology, Jinshan Hospital Affiliated to Fudan University, Shanghai 201508, P.R. China
| | - Kai Chen
- Department of Nephrology, Jinshan Hospital Affiliated to Fudan University, Shanghai 201508, P.R. China
| | - Jihong Zhang
- Department of Nephrology, Jinshan Hospital Affiliated to Fudan University, Shanghai 201508, P.R. China
| | - Xiaorong Bao
- Department of Nephrology, Jinshan Hospital Affiliated to Fudan University, Shanghai 201508, P.R. China
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Abstract
Desert rodents face a sizeable challenge in maintaining salt and water homeostasis due to their life in an arid environment. A number of their organ systems exhibit functional characteristics that limit water loss above that which occurs in non-desert species under similar conditions. These systems include renal, pulmonary, gastrointestinal, nasal, and skin epithelia. The desert rodent kidney preserves body water by producing a highly concentrated urine that reaches a maximum osmolality nearly three times that of the common laboratory rat. The precise mechanism by which urine is concentrated in any mammal is unknown. Insights into the process may be more apparent in species that produce highly concentrated urine. Aquaporin water channels play a fundamental role in water transport in several desert rodent organ systems. The role of aquaporins in facilitating highly effective water preservation in desert rodents is only beginning to be explored. The organ systems of desert rodents and their associated AQPs are described.
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Affiliation(s)
- Thomas L Pannabecker
- Department of Physiology, AHSC 4128, University of Arizona Health Sciences Center, 1501 N. Campbell Avenue, Tucson, Arizona 85724-5051
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14
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Evans KK, Nawata CM, Pannabecker TL. Isolation and perfusion of rat inner medullary vasa recta. Am J Physiol Renal Physiol 2015; 309:F300-4. [PMID: 26062876 DOI: 10.1152/ajprenal.00214.2015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 06/04/2015] [Indexed: 11/22/2022] Open
Abstract
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. We isolated ∼30 inner medullary vasa recta from 23 adult male Munich-Wistar rats and prepared them for brightfield or electron microscopy, gene expression analysis by RT-PCR, or isolated tubule microperfusion. Morphological characteristics include branching and nonbranching segments exhibiting a thin endothelium, axial surface filaments radiating outward giving vessels a hairy appearance, and attached interstitial cells. Electron microscopy shows multiple cells, tight junctions, and either continuous or fenestrated endothelia. Isolated vasa recta express genes encoding the urea transporter UT-B and/or the fenestral protein PV-1, genes expressed in descending or ascending vasa recta, respectively. The transepithelial NaCl permeability (383.3 ± 60.0 × 10(-5) cm/s, mean ± SE, n = 4) was determined in isolated perfused vasa recta. Future quantitative analyses of isolated inner medullary vasa recta should provide structural and functional details important for more fully understanding fluid and solute flows through the inner medulla and their associated regulatory pathways.
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Affiliation(s)
- Kristen K Evans
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona
| | - C Michele Nawata
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona
| | - Thomas L Pannabecker
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona
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Weinstein AM. A mathematical model of rat proximal tubule and loop of Henle. Am J Physiol Renal Physiol 2015; 308:F1076-97. [PMID: 25694479 DOI: 10.1152/ajprenal.00504.2014] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 02/10/2015] [Indexed: 01/11/2023] Open
Abstract
Proximal tubule and loop of Henle function are coupled, with proximal transport determining loop fluid composition, and loop transport modulating glomerular filtration via tubuloglomerular feedback (TGF). To examine this interaction, we begin with published models of the superficial rat proximal convoluted tubule (PCT; including flow-dependent transport in a compliant tubule), and the rat thick ascending Henle limb (AHL). Transport parameters for this PCT are scaled down to represent the proximal straight tubule (PST), which is connected to the thick AHL via a short descending limb. Transport parameters for superficial PCT and PST are scaled up for a juxtamedullary nephron, and connected to AHL via outer and inner medullary descending limbs, and inner medullary thin AHL. Medullary interstitial solute concentrations are specified. End-AHL hydrostatic pressure is determined by distal nephron flow resistance, and the TGF signal is represented as a linear function of end-AHL cytosolic Cl concentration. These two distal conditions required iterative solution of the model. Model calculations capture inner medullary countercurrent flux of urea, and also suggest the presence of an outer medullary countercurrent flux of ammonia, with reabsorption in AHL and secretion in PST. For a realistically strong TGF signal, there is the expected homeostatic impact on distal flows, and in addition, a homeostatic effect on proximal tubule pressure. The model glycosuria threshold is compatible with rat data, and predicted glucose excretion with selective 1Na(+):1glucose cotransporter (SGLT2) inhibition comports with observations in the mouse. Model calculations suggest that enhanced proximal tubule Na(+) reabsorption during hyperglycemia is sufficient to activate TGF and contribute to diabetic hyperfiltration.
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Affiliation(s)
- Alan M Weinstein
- Department of Physiology and Biophysics, Department of Medicine, Weill Medical College of Cornell University, New York, New York
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16
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Pannabecker TL, Layton AT. Targeted delivery of solutes and oxygen in the renal medulla: role of microvessel architecture. Am J Physiol Renal Physiol 2014; 307:F649-55. [PMID: 25056344 DOI: 10.1152/ajprenal.00276.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Renal medullary function is characterized by corticopapillary concentration gradients of various molecules. One example is the generally decreasing axial gradient in oxygen tension (Po2). Another example, found in animals in the antidiuretic state, is a generally increasing axial solute gradient, consisting mostly of NaCl and urea. This osmolality gradient, which plays a principal role in the urine concentrating mechanism, is generally considered to involve countercurrent multiplication and countercurrent exchange, although the underlying mechanism is not fully understood. Radial oxygen and solute gradients in the transverse dimension of the medullary parenchyma have been hypothesized to occur, although strong experimental evidence in support of these gradients remains lacking. This review considers anatomic features of the renal medulla that may impact the formation and maintenance of oxygen and solute gradients. A better understanding of medullary architecture is essential for more clearly defining the compartment-to-compartment flows taken by fluid and molecules that are important in producing axial and radial gradients. Preferential interactions between nephron and vascular segments provide clues as to how tubular and interstitial oxygen flows contribute to safeguarding active transport pathways in renal function in health and disease.
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Affiliation(s)
- Thomas L Pannabecker
- Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona; and
| | - Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina
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