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Ralph DL, Ha D, Lei H, Priver TS, Smith SD, McFarlin BE, Schwindt S, Pandya D, Koepsell H, Pastor-Soler NM, Edwards A, McDonough AA. Potassium-Alkali-Enriched Diet, Hypertension, and Proteinuria following Uninephrectomy. J Am Soc Nephrol 2024:00001751-990000000-00357. [PMID: 38913441 DOI: 10.1681/asn.0000000000000420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Accepted: 06/10/2024] [Indexed: 06/26/2024] Open
Abstract
Key Points
A K-alkali–enriched diet blunted post-uninephrectomy hypertension and facilitated acid clearance by suppressing Na+ reabsorption.Uninephrectomy-associated proteinuria could be attributed to elevated single-nephron GFR and downregulation of megalin, which reduced fractional protein endocytosis.
Background
Losing or donating a kidney is associated with risks of developing hypertension and albuminuria. Few studies address mechanisms or interventions. We investigate the potential benefits of a K+- alkali–enriched diet and the mechanisms underlying proteinuria.
Methods
Male Sprague Dawley rats were fed either a 2% NaCl+0.95% KCl diet (HNa-LK) or a 0.74% NaCl+3% K+-alkali diet (HK-alk) for 3 weeks before uninephrectomy and then maintained on respective diets for 12 weeks. BP (by tail-cuff), urine, blood, and kidney proteins were analyzed before and after uninephrectomy.
Results
Before uninephrectomy, HK-alk–fed versus HNa-LK–fed rats exhibited similar BPs and plasma [K+], [Na+], but lower proximal (NHE3, sodium bicarbonate cotransporter 1, NaPi2) and higher distal (NCC, ENaC, and pendrin) transporter abundance, a pattern facilitating K+ and HCO3
− secretion. After uninephrectomy, single-nephron GFR increased 50% and Li+ clearance doubled with both diets; in HK-alk versus HNa-LK, the increase in BP was less and ammoniagenesis was lower, abundance of proximal tubule transporters remained lower, ENaC-α fell, and NCCp increased, consistent with K+ conservation. After uninephrectomy, independent of diet, albuminuria increased eight-fold and abundance of endocytic receptors was reduced (megalin by 44%, disabled homolog 2 by 25%–35%) and kidney injury molecule-1 was increased.
Conclusions
The K-alkali–enriched diet blunted post-uninephrectomy hypertension and facilitated acid clearance by suppressing proximal Na+ transporters and increasing K+-alkali secretion. Furthermore, uninephrectomy-associated proteinuria could be attributed, at least in part, to elevated single-nephron GFR coupled with downregulation of megalin, which reduced fractional protein endocytosis and Vmax.
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Affiliation(s)
- Donna L Ralph
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Darren Ha
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hillmin Lei
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Taylor S Priver
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Scotti D Smith
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Brandon E McFarlin
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Seth Schwindt
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Drishti Pandya
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hermann Koepsell
- Institute for Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany
| | - Nuria M Pastor-Soler
- Division of Nephrology, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Aurelie Edwards
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
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Just A, Mallmann RT, Grossmann S, Sleman F, Klugbauer N. Two-pore channel protein TPC1 is a determining factor for the adaptation of proximal tubular phosphate handling. Acta Physiol (Oxf) 2023; 237:e13914. [PMID: 36599408 DOI: 10.1111/apha.13914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 10/27/2022] [Accepted: 01/02/2023] [Indexed: 01/06/2023]
Abstract
AIM Two-pore channels (TPCs) constitute a small family of cation channels expressed in endo-lysosomal compartments. TPCs have been characterized as critical elements controlling Ca2+ -mediated vesicular membrane fusion and thereby regulating endo-lysosomal vesicle trafficking. Exo- and endocytotic trafficking and lysosomal degradation are major mechanisms of adaption of epithelial transport. A prime example of highly regulated epithelial transport is the tubular system of the kidney. We therefore studied the localization of TPC protein 1 (TPC1) in the kidney and its functional role in the dynamic regulation of tubular transport. METHODS Immunohistochemistry in combination with tubular markers were used to investigate TPC1 expression in proximal and distal tubules. The excretion of phosphate and ammonium, as well as urine volume and pH were studied in vivo, in response to dynamic challenges induced by bolus injection of parathyroid hormone or acid-base transitions via consecutive infusion of NaCl, Na2 CO3 , and NH4 Cl. RESULTS In TPC1-deficient mice, the PTH-induced rise in phosphate excretion was prolonged and exaggerated, and its recovery delayed in comparison with wildtype littermates. In the acid-base transition experiment, TPC1-deficient mice showed an identical rise in phosphate excretion in response to Na2 CO3 compared with wildtypes, but a delayed NH4Cl-induced recovery. Ammonium-excretion decreased with Na2 CO3 , and increased with NH4 Cl, but without differences between genotypes. CONCLUSIONS We conclude that TPC1 is expressed subapically in the proximal but not distal tubule and plays an important role in the dynamic adaptation of proximal tubular phosphate reabsorption towards enhanced, but not reduced absorption.
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Affiliation(s)
- Armin Just
- Institut für Physiologie I, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Robert T Mallmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Sonja Grossmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Faten Sleman
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Norbert Klugbauer
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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Berg P, Svendsen SL, Sorensen MV, Schreiber R, Kunzelmann K, Leipziger J. The molecular mechanism of CFTR- and secretin-dependent renal bicarbonate excretion. J Physiol 2021; 599:3003-3011. [PMID: 33963548 DOI: 10.1113/jp281285] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 04/12/2021] [Indexed: 11/08/2022] Open
Abstract
This review summarizes the newly discovered molecular mechanism of secretin-stimulated urine HCO3 - excretion and the role of cystic fibrosis transmembrane conductance regulator (CFTR) in renal HCO3 - excretion. The secretin receptor is functionally expressed in the basolateral membrane of the HCO3 - -secreting β-intercalated cells of the collecting duct. Here it activates a fast and efficient secretion of HCO3 - into the urine serving to normalize metabolic alkalosis. The ability to acutely increase renal base excretion is entirely dependent on functional pendrin (SLC26A4) and CFTR, and both proteins localize to the apical membrane of the β-intercalated cells. In cystic fibrosis mice and patients, this function is absent or markedly reduced. We discuss that the alkaline tide, namely the transient urine alkalinity after a meal, has now received a clear physiological explanation.
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Affiliation(s)
- Peder Berg
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
| | - Samuel L Svendsen
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
| | - Mads Vaarby Sorensen
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
| | - Rainer Schreiber
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Jens Leipziger
- Department of Biomedicine, Physiology, Health, Aarhus University, Aarhus, Denmark
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4
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Berg P, Svendsen SL, Hoang TTL, Praetorius HA, Sorensen MV, Leipziger J. Impaired renal HCO 3 - secretion in CFTR deficient mice causes metabolic alkalosis during chronic base-loading. Acta Physiol (Oxf) 2021; 231:e13591. [PMID: 33270356 DOI: 10.1111/apha.13591] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 11/27/2020] [Accepted: 11/27/2020] [Indexed: 12/11/2022]
Abstract
AIM Cystic fibrosis patients have an increased risk of developing metabolic alkalosis presumably as a result of altered renal HCO3 - handling. In this study, we directly assess the kidneys' ability to compensate for a chronic base-load in the absence of functional CFTR. METHODS Comprehensive urine and blood acid-base analyses were done in anaesthetized WT mice or mice lacking either CFTR or pendrin, with or without 7 days of oral NaHCO3 loading. The in vivo experiments were complemented by a combination of immunoblotting and experiments with perfused isolated mouse cortical collecting ducts (CCD). RESULTS Base-loaded WT mice maintained acid-base homeostasis by elevating urinary pH and HCO3 - excretion and decreasing urinary net acid excretion. In contrast, pendrin KO mice and CFTR KO mice were unable to increase urinary pH and HCO3 - excretion and unable to decrease urinary net acid excretion sufficiently and thus developed metabolic alkalosis in response to the same base-load. The expression of pendrin was increased in response to the base-load in WT mice with a paralleled increased pendrin function in the perfused CCD. In CFTR KO mice, 7 days of base-loading did not upregulate pendrin expression and apical Cl- /HCO3 - exchange function was strongly blunted in the CCD. CONCLUSION CFTR KO mice develop metabolic alkalosis during a chronic base-load because they are unable to sufficiently elevate renal HCO3 - excretion. This can be explained by markedly reduced pendrin function in the absence of CFTR.
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Affiliation(s)
- Peder Berg
- Department of Biomedicine, Physiology Faculty of Health Aarhus University Aarhus C Denmark
| | - Samuel L. Svendsen
- Department of Biomedicine, Physiology Faculty of Health Aarhus University Aarhus C Denmark
| | - Thi Thuy Linh Hoang
- Department of Biomedicine, Physiology Faculty of Health Aarhus University Aarhus C Denmark
| | - Helle A. Praetorius
- Department of Biomedicine, Physiology Faculty of Health Aarhus University Aarhus C Denmark
| | - Mads V. Sorensen
- Department of Biomedicine, Physiology Faculty of Health Aarhus University Aarhus C Denmark
| | - Jens Leipziger
- Department of Biomedicine, Physiology Faculty of Health Aarhus University Aarhus C Denmark
- Aarhus Institute of Advanced Studies Aarhus University Aarhus C Denmark
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5
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Whittamore JM, Hatch M. Oxalate transport by the mouse intestine in vitro is not affected by chronic challenges to systemic acid-base homeostasis. Urolithiasis 2018; 47:243-254. [PMID: 29947993 DOI: 10.1007/s00240-018-1067-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 06/10/2018] [Indexed: 12/15/2022]
Abstract
In rats, we recently showed how a chronic metabolic acidosis simultaneously reduced urinary oxalate excretion and promoted oxalate secretion by the distal colon leading to the proposition that acid-base disturbances may trigger changes to renal and intestinal oxalate handling. The present study sought to reproduce and extend these observations using the mouse model, where the availability of targeted gene knockouts (KOs) would offer future opportunities to reveal some of the underlying transporters and mechanisms involved. Mice were provided with a sustained load of acid (NH4Cl), base (NaHCO3) or the carbonic anhydrase inhibitor acetazolamide (ATZ) for 7 days after which time the impacts on urinary oxalate excretion and its transport by the intestine were evaluated. Mice consuming NH4Cl developed a metabolic acidosis but urinary oxalate was only reduced 46% and not statistically different from the control group, while provision of NaHCO3 provoked a significant 2.6-fold increase in oxalate excretion. For mice receiving ATZ, the rate of urinary oxalate excretion did not change significantly. Critically, none of these treatments altered the fluxes of oxalate (or chloride) across the distal ileum, cecum or distal colon. Hence, we were unable to produce the same effects of a metabolic acidosis in mice that we had previously found in rats, failing to find any evidence of the 'gut-kidney axis' influencing oxalate handling in response to various acid-base challenges. Despite the potential advantages offered by KO mice, this model species is not suitable for exploring how acid-base status regulates oxalate handling between the kidney and intestine.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, PO Box 100275, 1600 SW Archer Rd, Gainesville, FL, 32610, USA.
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, PO Box 100275, 1600 SW Archer Rd, Gainesville, FL, 32610, USA
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Fenton RA, Poulsen SB, de la Mora Chavez S, Soleimani M, Dominguez Rieg JA, Rieg T. Renal tubular NHE3 is required in the maintenance of water and sodium chloride homeostasis. Kidney Int 2017; 92:397-414. [PMID: 28385297 DOI: 10.1016/j.kint.2017.02.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 01/25/2017] [Accepted: 02/02/2017] [Indexed: 11/30/2022]
Abstract
The sodium/proton exchanger isoform 3 (NHE3) is expressed in the intestine and the kidney, where it facilitates sodium (re)absorption and proton secretion. The importance of NHE3 in the kidney for sodium chloride homeostasis, relative to the intestine, is unknown. Constitutive tubule-specific NHE3 knockout mice (NHE3loxloxCre) did not show significant differences compared to control mice in body weight, blood pH or bicarbonate and plasma sodium, potassium, or aldosterone levels. Fluid intake, urinary flow rate, urinary sodium/creatinine, and pH were significantly elevated in NHE3loxloxCre mice, while urine osmolality and GFR were significantly lower. Water deprivation revealed a small urinary concentrating defect in NHE3loxloxCre mice on a control diet, exaggerated on low sodium chloride. Ten days of low or high sodium chloride diet did not affect plasma sodium in control mice; however, NHE3loxloxCre mice were susceptible to low sodium chloride (about -4 mM) or high sodium chloride intake (about +2 mM) versus baseline, effects without differences in plasma aldosterone between groups. Blood pressure was significantly lower in NHE3loxloxCre mice and was sodium chloride sensitive. In control mice, the expression of the sodium/phosphate co-transporter Npt2c was sodium chloride sensitive. However, lack of tubular NHE3 blunted Npt2c expression. Alterations in the abundances of sodium/chloride cotransporter and its phosphorylation at threonine 58 as well as the abundances of the α-subunit of the epithelial sodium channel, and its cleaved form, were also apparent in NHE3loxloxCre mice. Thus, renal NHE3 is required to maintain blood pressure and steady-state plasma sodium levels when dietary sodium chloride intake is modified.
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Affiliation(s)
- Robert A Fenton
- InterPrET Center, Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Søren B Poulsen
- InterPrET Center, Department of Biomedicine, Aarhus University, Aarhus, Denmark; VA San Diego Healthcare System, San Diego, California, USA
| | | | - Manoocher Soleimani
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio, USA; Research Services, Veterans Affairs Medical Center, Cincinnati, Ohio, USA
| | - Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida, USA
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida, USA.
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7
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Guo YM, Liu Y, Liu M, Wang JL, Xie ZD, Chen KJ, Wang DK, Occhipinti R, Boron WF, Chen LM. Na +/HCO 3- Cotransporter NBCn2 Mediates HCO 3- Reclamation in the Apical Membrane of Renal Proximal Tubules. J Am Soc Nephrol 2017; 28:2409-2419. [PMID: 28280139 DOI: 10.1681/asn.2016080930] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 01/23/2017] [Indexed: 12/31/2022] Open
Abstract
The kidney maintains systemic acid-base balance by reclaiming from the renal tubule lumen virtually all HCO3- filtered in glomeruli and by secreting additional H+ to titrate luminal buffers. For proximal tubules, which are responsible for about 80% of this activity, it is believed that HCO3- reclamation depends solely on H+ secretion, mediated by the apical Na+/H+ exchanger NHE3 and the vacuolar proton pump. However, NHE3 and the proton pump cannot account for all HCO3- reclamation. Here, we investigated the potential contribution of two variants of the electroneutral Na+/HCO3- cotransporter NBCn2, the amino termini of which start with the amino acids MCDL (MCDL-NBCn2) and MEIK (MEIK-NBCn2). Western blot analysis and immunocytochemistry revealed that MEIK-NBCn2 predominantly localizes at the basolateral membrane of medullary thick ascending limbs in the rat kidney, whereas MCDL-NBCn2 localizes at the apical membrane of proximal tubules. Notably, NH4Cl-induced systemic metabolic acidosis or hypokalemic alkalosis downregulated the abundance of MCDL-NBCn2 and reciprocally upregulated NHE3 Conversely, NaHCO3-induced metabolic alkalosis upregulated MCDL-NBCn2 and reciprocally downregulated NHE3 We propose that the apical membrane of the proximal tubules has two distinct strategies for HCO3- reclamation: the conventional indirect pathway, in which NHE3 and the proton pump secrete H+ to titrate luminal HCO3-, and the novel direct pathway, in which NBCn2 removes HCO3- from the lumen. The reciprocal regulation of NBCn2 and NHE3 under different physiologic conditions is consistent with our mathematical simulations, which suggest that HCO3- uptake and H+ secretion have reciprocal efficiencies for HCO3- reclamation versus titration of luminal buffers.
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Affiliation(s)
- Yi-Min Guo
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Ying Liu
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Mei Liu
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Jin-Lin Wang
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Zhang-Dong Xie
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Kang-Jing Chen
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
| | - Deng-Ke Wang
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and.,Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Li-Ming Chen
- Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, Hubei, China; and
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Petrenko AG, Zozulya SA, Deyev IE, Eladari D. Insulin receptor-related receptor as an extracellular pH sensor involved in the regulation of acid–base balance. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2170-5. [DOI: 10.1016/j.bbapap.2012.11.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/16/2012] [Accepted: 11/19/2012] [Indexed: 12/25/2022]
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9
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Hennings JC, Picard N, Huebner AK, Stauber T, Maier H, Brown D, Jentsch TJ, Vargas-Poussou R, Eladari D, Hübner CA. A mouse model for distal renal tubular acidosis reveals a previously unrecognized role of the V-ATPase a4 subunit in the proximal tubule. EMBO Mol Med 2012; 4:1057-71. [PMID: 22933323 PMCID: PMC3491836 DOI: 10.1002/emmm.201201527] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Revised: 06/19/2012] [Accepted: 07/10/2012] [Indexed: 11/09/2022] Open
Abstract
The V-ATPase is a multisubunit complex that transports protons across membranes. Mutations of its B1 or a4 subunit are associated with distal renal tubular acidosis and deafness. In the kidney, the a4 subunit is expressed in intercalated cells of the distal nephron, where the V-ATPase controls acid/base secretion, and in proximal tubule cells, where its role is less clear. Here, we report that a4 KO mice suffer not only from severe acidosis but also from proximal tubule dysfunction with defective endocytic trafficking, proteinuria, phosphaturia and accumulation of lysosomal material and we provide evidence that these findings may be also relevant in patients. In the inner ear, the a4 subunit co-localized with pendrin at the apical side of epithelial cells lining the endolymphatic sac. As a4 KO mice were profoundly deaf and displayed enlarged endolymphatic fluid compartments mirroring the alterations in pendrin KO mice, we propose that pendrin and the proton pump co-operate in endolymph homeostasis. Thus, our mouse model gives new insights into the divergent functions of the V-ATPase and the pathophysiology of a4-related symptoms.
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10
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Deyev IE, Sohet F, Vassilenko KP, Serova OV, Popova NV, Zozulya SA, Burova EB, Houillier P, Rzhevsky DI, Berchatova AA, Murashev AN, Chugunov AO, Efremov RG, Nikol'sky NN, Bertelli E, Eladari D, Petrenko AG. Insulin receptor-related receptor as an extracellular alkali sensor. Cell Metab 2011; 13:679-89. [PMID: 21641549 PMCID: PMC3119365 DOI: 10.1016/j.cmet.2011.03.022] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 12/18/2010] [Accepted: 03/23/2011] [Indexed: 11/29/2022]
Abstract
The insulin receptor-related receptor (IRR), an orphan receptor tyrosine kinase of the insulin receptor family, can be activated by alkaline media both in vitro and in vivo at pH >7.9. The alkali-sensing property of IRR is conserved in frog, mouse, and human. IRR activation is specific, dose-dependent and quickly reversible and demonstrates positive cooperativity. It also triggers receptor conformational changes and elicits intracellular signaling. The pH sensitivity of IRR is primarily defined by its L1F extracellular domains. IRR is predominantly expressed in organs that come in contact with mildly alkaline media. In particular, IRR is expressed in the cell subsets of the kidney that secrete bicarbonate into urine. Disruption of IRR in mice impairs the renal response to alkali loading attested by development of metabolic alkalosis and decreased urinary bicarbonate excretion in response to this challenge. We therefore postulate that IRR is an alkali sensor that functions in the kidney to manage metabolic bicarbonate excess.
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Affiliation(s)
- Igor E Deyev
- Laboratory of Receptor Cell Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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11
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Good DW, George T, Watts BA. High sodium intake increases HCO(3)- absorption in medullary thick ascending limb through adaptations in basolateral and apical Na+/H+ exchangers. Am J Physiol Renal Physiol 2011; 301:F334-43. [PMID: 21613418 DOI: 10.1152/ajprenal.00106.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A high sodium intake increases the capacity of the medullary thick ascending limb (MTAL) to absorb HCO(3)(-). Here, we examined the role of the apical NHE3 and basolateral NHE1 Na(+)/H(+) exchangers in this adaptation. MTALs from rats drinking H(2)O or 0.28 M NaCl for 5-7 days were perfused in vitro. High sodium intake increased HCO(3)(-) absorption rate by 60%. The increased HCO(3)(-) absorptive capacity was mediated by an increase in apical NHE3 activity. Inhibiting basolateral NHE1 with bath amiloride eliminated 60% of the adaptive increase in HCO(3)(-) absorption. Thus the majority of the increase in NHE3 activity was dependent on NHE1. A high sodium intake increased basolateral Na(+)/H(+) exchange activity by 89% in association with an increase in NHE1 expression. High sodium intake increased apical Na(+)/H(+) exchange activity by 30% under conditions in which basolateral Na(+)/H(+) exchange was inhibited but did not change NHE3 abundance. These results suggest that high sodium intake increases HCO(3)(-) absorptive capacity in the MTAL through 1) an adaptive increase in basolateral NHE1 activity that results secondarily in an increase in apical NHE3 activity; and 2) an adaptive increase in NHE3 activity, independent of NHE1 activity. These studies support a role for NHE1 in the long-term regulation of renal tubule function and suggest that the regulatory interaction whereby NHE1 enhances the activity of NHE3 in the MTAL plays a role in the chronic regulation of HCO(3)(-) absorption. The adaptive increases in Na(+)/H(+) exchange activity and HCO(3)(-) absorption in the MTAL may play a role in enabling the kidneys to regulate acid-base balance during changes in sodium and volume balance.
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Affiliation(s)
- David W Good
- Departments of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas 77555-0562, USA.
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12
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Jang HR, Kim S, Heo NJ, Lee JH, Kim HS, Nielsen S, Jeon US, Oh YK, Na KY, Joo KW, Han JS. Effects of thiazide on the expression of TRPV5, calbindin-D28K, and sodium transporters in hypercalciuric rats. J Korean Med Sci 2009; 24 Suppl:S161-9. [PMID: 19194547 PMCID: PMC2633179 DOI: 10.3346/jkms.2009.24.s1.s161] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 11/28/2008] [Indexed: 11/20/2022] Open
Abstract
TRPV5 is believed to play an important role in the regulation of urinary calcium excretion. We assessed the effects of hydrochlorothiazide (HCTZ) on the expression of TRPV5, calbindin-D(28K), and several sodium transporters in hypercalciuric rats. Sprague-Dawley rats were divided into 4 groups; control, HCTZ, high salt, and high salt with HCTZ group in experiment 1; control, HCTZ, high calcium (Ca), and high Ca with HCTZ group in experiment 2. To quantitate the expression of TRPV5, calbindin-D(28K), and sodium transporters, western blotting was performed. In both experiments, HCTZ significantly decreased urinary calcium excretion. TRPV5 protein abundance decreased in all hypercalciuric rats, and restored by HCTZ in both high salt with HCTZ and high Ca with HCTZ group. Calbindin-D(28K) protein abundance increased in the high salt and high salt with HCTZ groups, but did not differ among groups in experiment 2. Protein abundance of NHE3 and NKCC2 decreased in all hypercalciuric rats, and were restored by HCTZ in only high Ca-induced hypercalciuric rats. In summary, protein abundance of TRPV5, NHE3, and NKCC2 decreased in all hypercalciuric rats. The hypocalciuric effect of HCTZ is associated with increased protein abundance of TRPV5 in high salt or calcium diet-induced hypercalciuric rats.
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Affiliation(s)
- Hye Ryoun Jang
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Sejoong Kim
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Nam Ju Heo
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Jeong Hwan Lee
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Hyo Sang Kim
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Søren Nielsen
- Institute of Anatomy, University of Aarhus, The Water and Salt Research Center, Aarhus, Denmark
| | - Un Sil Jeon
- Postech Biotech Center, Pohang University of Science & Technology, Pohang, Korea
| | - Yun Kyu Oh
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Ki Young Na
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Kwon Wook Joo
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Jin Suk Han
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
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Blanchard A, Vargas-Poussou R, Peyrard S, Mogenet A, Baudouin V, Boudailliez B, Charbit M, Deschesnes G, Ezzhair N, Loirat C, Macher MA, Niaudet P, Azizi M. Effect of hydrochlorothiazide on urinary calcium excretion in dent disease: an uncontrolled trial. Am J Kidney Dis 2008; 52:1084-95. [PMID: 18976849 DOI: 10.1053/j.ajkd.2008.08.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Accepted: 08/01/2008] [Indexed: 11/11/2022]
Abstract
BACKGROUND Thiazide doses equivalent to 1 to 2 mg/kg/d of hydrochlorothiazide (HCTZ) have been proposed to correct hypercalciuria and prevent kidney failure in patients with Dent disease. However, they can cause adverse metabolic effects in the long term. In treating hypertension in children, lower thiazide doses have been shown to be as effective and well tolerated. STUDY DESIGN Uncontrolled trial, with forced-titration sequential open-label study design. SETTING & PARTICIPANTS 7 boys with genetically confirmed Dent disease and mild phenotype (neither overt sodium wasting nor kidney failure). INTERVENTION After a 1-month run-in period, patients sequentially received amiloride (5 mg/d) alone (1 month) and then for 3 periods of 2 months in association with increasing doses of HCTZ (<0.2, 0.2 to 0.4, and 0.4 to 0.8 mg/kg/d). OUTCOMES Urinary calcium excretion and extracellular volume indicators. MEASUREMENTS At the end of each period, 2 daily 24-hour urinary collections were performed on the days preceding admission. Blood and spot urine samples also were collected. RESULTS A greater HCTZ dose increased renin, aldosterone, and plasma protein concentrations. Amiloride alone had no effect on calcium excretion. The greatest HCTZ doses decreased spot urinary calcium excretion by 42% compared with baseline (median, 0.3; minimum, maximum, 0.2, 0.8 versus median, 0.8; minimum, maximum, 0.4, 1.1, respectively; P = 0.03). However, patients developed adverse reactions, including muscle cramps (n = 2), biological (n = 7) or symptomatic hypovolemia (n = 1), hypokalemia (n = 4), and hyponatremia (n = 1), which all corrected after treatment withdrawal. LIMITATION Small sample size and absence of a control group. CONCLUSION HCTZ doses greater than 0.4 mg/kg/d decreased calcium excretion, but were associated with significant adverse events. Thiazide diuretic therapy should be considered with caution in children with Dent disease.
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Affiliation(s)
- Anne Blanchard
- Université Paris 5, Faculté de Médecine Paris Descartes, Paris, France.
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14
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Yang LE, Sandberg MB, Can AD, Pihakaski-Maunsbach K, McDonough AA. Effects of dietary salt on renal Na+ transporter subcellular distribution, abundance, and phosphorylation status. Am J Physiol Renal Physiol 2008; 295:F1003-16. [PMID: 18653479 DOI: 10.1152/ajprenal.90235.2008] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
During high-salt (HS) diet the kidney increases urinary Na+ and volume excretion to match intake. We recently reported that HS provokes a redistribution of distal convoluted tubule Na+-Cl- cotransporter (NCC) from apical to subapical vesicles and decreases NCC abundance. This study aimed to test the hypothesis that the other renal Na+ transporters' abundance and or subcellular distribution is decreased by HS diet. Six-week-old Sprague-Dawley rats were fed a normal (NS) 0.4% NaCl diet or a HS 4% NaCl diet for 3 wk or overnight. Kidneys excised from anesthetized rats were fractionated on density gradients or analyzed by microscopy; transporters and associated regulators were detected with specific antibodies. Three-week HS doubled Na+/H+ exchanger (NHE)3 phosphorylation at serine 552 and provoked a redistribution of NHE3, dipeptidyl peptidase IV (DPPIV), myosin VI, Na+-Pi cotransporter (NaPi)-2, ANG II type 2 receptor (AT2R), aminopeptidase N (APN), Na+-K+-2Cl- cotransporter (NKCC2), epithelial Na+ channel (ENaC) beta-subunit, and Na+-K+-ATPase (NKA) alpha1- and beta1-subunits from low-density plasma membrane-enriched fractions to higher-density intracellular membrane-enriched fractions. NHE3, myosin VI, and AT2R retraction to the base of the microvilli (MV) during HS was evident by confocal microscopy. HS did not change abundance of NHE3, NKCC, or NKA alpha1- or beta1-subunits but increased ENaC-beta in high-density intracellular enriched membranes. Responses to HS were fully apparent after just 18 h. We propose that retraction of NHE3 to the base of the MV, driven by myosin VI and NHE3 phosphorylation and accompanied by redistribution of the NHE3 regulator DPPIV, contributes to a decrease in proximal tubule Na+ reabsorption during HS and that redistribution of transporters out of low-density plasma membrane-enriched fractions in the thick ascending limb of the loop of Henle and distal nephron may also contribute to the homeostatic natriuretic response to HS diet.
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Affiliation(s)
- Li E Yang
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, 1333 San Pablo St., MMR 626, Los Angeles, CA 90089-9142, USA
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15
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Kulick A, Panico C, Gill P, Welch WJ. Low salt intake increases adenosine type 1 receptor expression and function in the rat proximal tubule. Am J Physiol Renal Physiol 2008; 295:F37-41. [PMID: 18480183 DOI: 10.1152/ajprenal.00061.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine mediates Na+ reabsorption in the proximal tubule (PT) and other segments by activating adenosine type 1 receptors (A1-AR). We tested the hypothesis that A1-AR in the PT is regulated by salt intake and participates in the kidney adaptation to changes in salt intake. Absolute fluid reabsorption (Jv) was measured by direct in vivo microperfusion and recollection in rats maintained on low (LS; 0.03% Na, wt/wt)-, normal (NS; 0.3% Na)-, and high-salt (HS; 3.0% Na) diets for 1 wk. The effect of microperfusion of BG9719 a highly selective inhibitor of A1-ARs or adenosine deaminase (AD), which metabolizes adenosine, was measured in each group. Jv was higher in PT from LS rats (LA: 2.8 +/- 0.2 vs. NS: 2.1 +/- 0.2 nl.min(-1).mm(-1), P < 0.001). Jv in HS rats was not different from NS. BG9719 reduced Jv in LS rats by 66 +/- 6% (LS: 2.8 +/- 0.2 vs LS+CVT: 1.3 +/- 0.3 nl.min(-1).mm(-1), P < 0.001), which was greater than its effect in NS (45 +/- 4%) or HS (41 +/- 4%) rats. AD reduced Jv similarly, suggesting that A1-ARs are activated by local production of adenosine. Expression of A1-AR mRNA and protein was higher (P < 0.01) in microdissected PTs in LS rats compared with NS and HS. We conclude that A1-ARs in the PT are increased by low salt intake and that A1-AR participates in the increased PT reabsorption of solute and fluid in response to low salt intake.
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Affiliation(s)
- Aaron Kulick
- Department of Medicine, Division of Nephrology and Hypertension, Georgetown University, Washington, DC 20057, USA
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16
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Abstract
Acute kidney injury (AKI) is a common condition with a high risk of death. The standard metrics used to define and monitor the progression of AKI, such as serum creatinine and blood urea nitrogen levels, are insensitive, nonspecific, and change significantly only after significant kidney injury and then with a substantial time delay. This delay in diagnosis not only prevents timely patient management decisions, including administration of putative therapeutic agents, but also significantly affects the preclinical evaluation of toxicity thereby allowing potentially nephrotoxic drug candidates to pass the preclinical safety criteria only to be found to be clinically nephrotoxic with great human costs. Studies to establish effective therapies for AKI will be greatly facilitated by two factors: (a) development of sensitive, specific, and reliable biomarkers for early diagnosis/prognosis of AKI in preclinical and clinical studies, and (b) development and validation of high-throughput innovative technologies that allow rapid multiplexed detection of multiple markers at the bedside.
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Affiliation(s)
- Vishal S Vaidya
- Renal Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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18
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Kiwull-Schöne H, Kiwull P, Frede S, Wiemann M. Role of Brainstem Sodium/Proton Exchanger 3 for Breathing Control during Chronic Acid–Base Imbalance. Am J Respir Crit Care Med 2007; 176:513-9. [PMID: 17600278 DOI: 10.1164/rccm.200703-347oc] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE The sodium/proton exchanger (NHE) 3 is expressed in brainstem areas with prevalence for central chemosensitivity. Selective NHE3 inhibitors can evoke CO(2) mimetic responses both in vitro and in vivo, demonstrating the functional significance of this pH-regulating protein. Moreover, levels of NHE3 expression are inversely correlated to interindividual differences of baseline ventilation in conscious rabbits. OBJECTIVES We explored the influence of chronic acid-base disturbances on mRNA levels of brainstem NHE3 in relation to breathing control. METHODS Alveolar ventilation (Va), blood gases, systemic base excess (BE), and metabolic Vco(2) were determined in rabbits shortly after exposure to either CO(2)-enriched air for 3 days (n = 5) or to ammonium chloride with drinking water for 2 days (n = 6). Untreated animals served as controls (n = 24). NHE3 mRNA within the obex region was quantified by real-time reverse transcription-polymerase chain reaction. MEASUREMENTS AND MAIN RESULTS After chronic hypercapnia, we found a compensatory rise of BE (mean +/- SEM) to 5.3 +/- 0.5 mmol x L(-1) with slightly elevated Pa(CO(2)). Brainstem NHE3 mRNA as well as Va were not significantly different from control levels. In the NH(4)Cl group, arterial pH was approximately 0.09 units lower than control, and BE decreased to -6.5 +/- 1.6 mmol x L(-1) with slightly decreased Pa(CO(2)), but considerably reduced Va (by approximately 25%; P < 0.05) and Vco(2). Concomitantly, brainstem NHE3 mRNA had increased from control level of 1.45 +/- 0.19 to 3.64 +/- 0.37 fg cDNA/mug RNA; P < 0.01. CONCLUSIONS Expression of brainstem NHE3 is up-regulated by chronic metabolic acidosis but not by prolonged hypercapnia. It is proposed that elevated brainstem NHE3 expression contributes to limit maladaptive hyperventilation during metabolic acidosis.
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Abstract
Acute renal failure (ARF) is a frequent problem in the intensive care unit and is associated with a high mortality. Early recognition could help clinical management, but current indices lack sufficient predictive value for ARF. Therefore, there might be a need for biomarkers in detecting renal tubular injury and/or dysfunction at an early stage before a decline in glomerular filtration rate is noted by an increased serum creatinine. A MEDLINE/PubMed search was performed, including all articles about biomarkers for ARF. All publication types, human and animal studies, or subsets were searched in English language. An extraction of relevant articles was made for the purpose of this narrative review. These biomarkers include tubular enzymes (alpha- and pi-glutathione S-transferase, N-acetyl-glucosaminidase, alkaline phosphatase, gamma-glutamyl transpeptidase, Ala-(Leu-Gly)-aminopeptidase, and fructose-1,6-biphosphatase), low-molecular weight urinary proteins (alpha1- and beta2-microglobulin, retinol-binding protein, adenosine deaminase-binding protein, and cystatin C), Na+/H+ exchanger, neutrophil gelatinase-associated lipocalin, cysteine-rich protein 61, kidney injury molecule 1, urinary interleukins/adhesion molecules, and markers of glomerular filtration such as proatrial natriuretic peptide (1-98) and cystatin C. These biomarkers, detected in urine or serum shortly after tubular injury, have been suggested to contribute to prediction of ARF and need for renal replacement therapy. However, excretion of these biomarkers may also increase after reversible and mild dysfunction and may not necessarily be associated with persistent or irreversible damage. Large prospective studies in human are needed to demonstrate an improved outcome of biomarker-driven management of the patient at risk for ARF.
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Affiliation(s)
- Ronald J Trof
- Department of Intensive Care, Vrije Universiteit Medical Center, Amsterdam, The Netherlands
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20
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McCulloch F, Chambrey R, Eladari D, Peti-Peterdi J. Localization of connexin 30 in the luminal membrane of cells in the distal nephron. Am J Physiol Renal Physiol 2005; 289:F1304-12. [PMID: 16077080 DOI: 10.1152/ajprenal.00203.2005] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Several isoforms of the gap junction protein connexin (Cx) have been identified in a variety of tissues that communicate intercellular signals between adjacent cells. In the kidney, Cx37, Cx40, and Cx43 are localized in the vasculature, glomerulus, and tubular segments in a punctuate pattern, typical of classic gap junction channels. We performed immunohistochemistry in the mouse, rat, and rabbit kidney to study the localization of Cx30 protein, a new member of the Cx family. The vasculature, glomerulus, and proximal nephron segments were devoid of staining in all three species. Unexpectedly, Cx30 was found throughout the luminal membrane of select cells in the distal nephron. Expression of Cx30 was highest in the rat, which also showed some diffuse cytosolic labeling, continuous from the medullary thick ascending limb to the collecting duct system, and with the highest level in the distal convoluted tubule. Labeling in the mouse and rabbit was much less, limited to intercalated cells in the connecting segment and cortical collecting duct, where the apical signal was particularly strong. A high-salt-containing diet and culture medium upregulated Cx30 expression in the rat inner medulla and in M1 cells, respectively. The distinct, continuous labeling of the luminal plasma membrane and upregulation by high salt suggest that Cx30 may function as a hemichannel involved in the regulation of salt reabsorption in the distal nephron.
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Affiliation(s)
- Fiona McCulloch
- Zilkha Neurogenetic Institute, Department of Physiology and Biophysics, University of Southern California, Los Angeles, 90033, USA
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21
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Wiemann M, Frede S, Bingmann D, Kiwull P, Kiwull-Schöne H. Sodium/Proton Exchanger 3 in the Medulla Oblongata and Set Point of Breathing Control. Am J Respir Crit Care Med 2005; 172:244-9. [PMID: 15947281 DOI: 10.1164/rccm.200411-1567oc] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE In vivo inhibition of the sodium/proton exchanger 3 (NHE3) in chemosensitive neurons of the ventrolateral brainstem augments central respiratory drive in anesthetized rabbits. OBJECTIVES To further explore the possible role of this exchanger for the control of breathing, we examined the individual relationship between brainstem NHE3 abundance and ventilation in rabbits during wakefulness. METHODS In 32 adult male rabbits on standard nutritional alkali load, alveolar ventilation, metabolic CO2 production, and blood gases were determined, together with arterial and urinary acid-base status and renal base control functions. Expression of NHE3 in brainstem tissue from the obex region was determined by quantitative real-time reverse-transcription polymerase chain reaction analysis. MEASUREMENTS AND MAIN RESULTS Regarding the distribution above and below the median, we classified high and low brainstem NHE3 animals, expressing a mean (+/- SEM) NHE3 mRNA of 2.08 +/- 0.28 and 0.72 +/- 0.06 fg cDNA/mg RNA, respectively. Alveolar ventilation of high brainstem NHE3 animals was lower than that of low brainstem NHE3 animals (715 +/- 36 vs. 919 +/- 41 ml . minute(-1); p < 0.01), a finding also reflected by a marked difference in Pa(CO2) (5.24 +/- 0.16 vs. 4.44 +/- 0.15 kPa; p < 0.01). Among possible secondary factors, CO2 production, systemic base excess, and fractional renal base reabsorption were not found to be different. CONCLUSIONS We conclude that the level of brainstem NHE3 expression-most likely via intracellular pH modulation-contributes to the individual control of breathing and Pa(CO2) in conscious rabbits by adjusting the set point and the loop gain of the system.
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Affiliation(s)
- Martin Wiemann
- Department of Physiology, University of Duisburg-Essen, 45122 Essen, Germany.
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Kiwull-Schöne H, Kalhoff H, Manz F, Kiwull P. Food mineral composition and acid-base balance in rabbits. Eur J Nutr 2005; 44:499-508. [PMID: 15696401 DOI: 10.1007/s00394-005-0553-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2004] [Accepted: 12/20/2004] [Indexed: 10/25/2022]
Abstract
BACKGROUND Alkali-rich diets are often recommended in human medicine to prevent the pathological consequences of nutritional acid load in conditions of impaired renal function. AIM OF THE STUDY This study was undertaken in rabbits as common laboratory animals for basic medical research to explore the impact of high versus low dietary alkali intake on systemic acid-base balance and renal control in a typical herbivore. METHODS Male rabbits (2.3-4.8 kg) were kept in a metabolism cage. The 24h urine and arterial blood samples were analysed for acid-base data. The metabolic CO2 production was measured to calculate alveolar ventilation. Three randomized groups of animals were fed ad libitum with rabbit chow providing sufficient energy but variable alkali load, assessed by the ashes' cation-anion difference. RESULTS The average daily nutritional alkali load (+/- SEM) was 67.1 +/- 2.2 mEq x kg(-1) (N = 58) in the group on high, 45.4 +/- 2.5 mEq x kg(-1) (N = 31) in the group on normal and 1.7 +/- 0.5 mEq x kg(-1) (N = 11) in the group on low alkali food. Respective mean arterial base excess values (BE) were 1.4 +/- 0.3 mM, 0.3 +/- 0.4 mM and 0.0 +/- 0.3 mM, being significantly higher on high alkali food (P < 0.05) than in the other groups. Arterial PCO2, alveolar ventilation and metabolic CO2 production were not significantly different between groups. On normal and high-alkali chow, an alkaline urine (pH(u) > 8.0) with 18-20 mmol x kg(-1) bicarbonate/carbonate was excreted daily, typically containing an insoluble precipitate of 35-60% carbonate. On low-alkali diet, the mean pH(u) decreased to 6.26 +/- 0.14, due to a strong reduction of daily excreted soluble bicarbonate and precipitated carbonate to 1.2 +/- 0.6 and 0.7 +/- 0.2 mmol x kg(-1), respectively. Thereby, nearly complete fractional base reabsorption of 97.8 +/- 0.7 % was reached. CONCLUSION Herbivore nutritional alkali-load elicited large rates of renal base excretion including precipitates, to which the urinary tract of the rabbits appeared to be adapted. Dietary base variations were more accurately reflected in the urine than by the blood acid-base status. A strongly base-deficient diet exerted maximum impact on renal base saving mechanisms, implying a critical precondition for growing susceptibility to metabolic acidosis also in the rabbit.
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Quentin F, Chambrey R, Trinh-Trang-Tan MM, Fysekidis M, Cambillau M, Paillard M, Aronson PS, Eladari D. The Cl−/HCO3−exchanger pendrin in the rat kidney is regulated in response to chronic alterations in chloride balance. Am J Physiol Renal Physiol 2004; 287:F1179-88. [PMID: 15292050 DOI: 10.1152/ajprenal.00211.2004] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pendrin (Pds; Slc26A4) is a new anion exchanger that is believed to mediate apical Cl−/HCO3−exchange in type B and non-A-non-B intercalated cells of the connecting tubule and cortical collecting duct. Recently, it has been proposed that this transporter may be involved in NaCl balance and blood pressure regulation in addition to its participation in the regulation of acid-base status. The purpose of our study was to determine the regulation of Pds protein abundance during chronic changes in chloride balance. Rats were subjected to either NaCl, NH4Cl, NaHCO3, KCl, or KHCO3loading for 6 days or to a low-NaCl diet or chronic furosemide administration. Pds protein abundance was estimated by semiquantitative immunoblotting in renal membrane fractions isolated from the cortex of treated and control rats. We observed a consistent inverse relationship between Pds expression and diet-induced changes in chloride excretion independent of the administered cation. Conversely, NaCl depletion induced by furosemide was associated with increased Pds expression. We conclude that Pds expression is specifically regulated in response to changes in chloride balance.
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Affiliation(s)
- Fabienne Quentin
- Institut National de la Santé et de la Recherche Médicale Unité 356, Institut Fédératif de Recherche 58, Université René Descartes, Paris, France
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du Cheyron D, Daubin C, Poggioli J, Ramakers M, Houillier P, Charbonneau P, Paillard M. Urinary measurement of Na+/H+ exchanger isoform 3 (NHE3) protein as new marker of tubule injury in critically ill patients with ARF. Am J Kidney Dis 2003; 42:497-506. [PMID: 12955677 DOI: 10.1016/s0272-6386(03)00744-3] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND It has been shown that apical sodium transporters of the renal tubule can be detected by immunoblotting of urine membrane fraction from rats. We raised the hypothesis that protein levels of the Na+/H+ exchanger isoform 3 (NHE3), the most abundant apical sodium transporter in renal tubule, should be increased in urine of patients presenting with acute renal failure (ARF) with severe tubular cell damage and thus might be a noninvasive marker of acute tubular necrosis (ATN). METHODS Sixty-eight patients admitted to the intensive care unit were studied prospectively (54 patients with ARF, 14 controls without renal dysfunction). Patients with ARF were divided into 3 subgroups as follows: prerenal azotemia, ATN, and intrinsic ARF other than ATN. Urinary NHE3 protein abundance was estimated from semiquantitative immunoblots of urine membrane fraction samples collected from patients. The amount of urinary NHE3 was compared with the fractional excretion of sodium (FeNa) and urinary retinol-binding protein (RBP). RESULTS NHE3 was not detected in urine from controls. Levels of urinary NHE3 normalized to urinary creatinine level were increased in patients with prerenal azotemia and 6 times as much in patients with ATN, without overlap (ATN, 0.78 +/- 0.36; prerenal azotemia, 0.12 +/- 0.08; P < 0.001). Conversely, urinary NHE3 protein was not detected in patients with intrinsic ARF other than ATN. Normalized NHE3 level correlated positively with serum creatinine level in patients with tubular injury (R2 = 0.305; P = 0.0003). Values for FeNa and normalized urinary RBP did not discriminate ATN from intrinsic ARF other than ATN and prerenal azotemia, respectively. CONCLUSION In patients with ARF, urinary NHE3 abundance might be a novel noninvasive marker of renal tubule damage, helping to differentiate prerenal azotemia, ATN, and intrinsic ARF other than ATN.
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Affiliation(s)
- Damien du Cheyron
- Institut National de la Santé et de la Recherche Médicale U356, Université Pierre et Marie Curie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France.
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