scholarly journals Collecting duct-specific Rh C glycoprotein deletion alters basal and acidosis-stimulated renal ammonia excretion

2009 ◽  
Vol 296 (6) ◽  
pp. F1364-F1375 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Jill W. Verlander ◽  
Jesse M. Bishop ◽  
Peter Igarashi ◽  
Mary E. Handlogten ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Pcr Analysis ◽  
Lipid Phase ◽  
Urine Ph ◽  
Phase Diffusion ◽  
Ammonia Transport ◽  
Lipid Diffusion ◽  
Rh Glycoproteins

NH3movement across plasma membranes has traditionally been ascribed to passive, lipid-phase diffusion. However, ammonia-specific transporters, Mep/Amt proteins, are present in primitive organisms and mammals express orthologs of Mep/Amt proteins, the Rh glycoproteins. These findings suggest that the mechanisms of NH3movement in mammalian tissues should be reexamined. Rh C glycoprotein (Rhcg) is expressed in the collecting duct, where NH3secretion is necessary for both basal and acidosis-stimulated ammonia transport. To determine whether the collecting duct secretes NH3via Rhcg or via lipid-phase diffusion, we generated mice with collecting duct-specific Rhcg deletion (CD-KO). CD-KO mice had loxP sites flanking exons 5 and 9 of the Rhcg gene (Rhcgfl/fl) and expressed Cre-recombinase under control of the Ksp-cadherin promoter (Ksp-Cre). Control (C) mice were Rhcgfl/flbut Ksp-Cre negative. We confirmed kidney-specific genomic recombination using PCR analysis and collecting duct-specific Rhcg deletion using immunohistochemistry. Under basal conditions, urinary ammonia excretion was less in KO vs. C mice; urine pH was unchanged. After acid-loading for 7 days, CD-KO mice developed more severe metabolic acidosis than did C mice. Urinary ammonia excretion did not increase significantly on the first day of acidosis in CD-KO mice, despite an intact ability to increase urine acidification, whereas it increased significantly in C mice. On subsequent days, urinary ammonia excretion slowly increased in CD-KO mice, but was always significantly less than in C mice. We conclude that collecting duct Rhcg expression contributes to both basal and acidosis-stimulated renal ammonia excretion, indicating that collecting duct ammonia secretion is, at least in part, mediated by Rhcg and not solely by lipid diffusion.

scholarly journals Effect of collecting duct-specific deletion of both Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg) on renal response to metabolic acidosis

2014 ◽  
Vol 306 (4) ◽  
pp. F389-F400 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Jill W. Verlander ◽  
Mary E. Handlogten ◽  
Ki-Hwan Han ◽  
I. David Weiner
Keyword(s):  
Metabolic Acidosis ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Severe Metabolic Acidosis ◽  
Urine Ph ◽  
Renal Response ◽  
Rh Glycoproteins ◽  
Acid Loading ◽  
Specific Deletion

The Rhesus (Rh) glycoproteins, Rh B and Rh C Glycoprotein (Rhbg and Rhcg, respectively), are ammonia-specific transporters expressed in renal distal nephron and collecting duct sites that are necessary for normal rates of ammonia excretion. The purpose of the current studies was to determine the effect of their combined deletion from the renal collecting duct (CD-Rhbg/Rhcg-KO) on basal and acidosis-stimulated acid-base homeostasis. Under basal conditions, urine pH and ammonia excretion and serum HCO3− were similar in control (C) and CD-Rhbg/Rhcg-KO mice. After acid-loading for 7 days, CD-Rhbg/Rhcg-KO mice developed significantly more severe metabolic acidosis than did C mice. Acid loading increased ammonia excretion, but ammonia excretion increased more slowly in CD-Rhbg/Rhcg-KO and it was significantly less than in C mice on days 1–5. Urine pH was significantly more acidic in CD-Rhbg/Rhcg-KO mice on days 1, 3, and 5 of acid loading. Metabolic acidosis increased phosph enolpyruvate carboxykinase (PEPCK) and Na+/H+ exchanger NHE-3 and decreased glutamine synthetase (GS) expression in both genotypes, and these changes were significantly greater in CD-Rhbg/Rhcg-KO than in C mice. We conclude that 1) Rhbg and Rhcg are critically important in the renal response to metabolic acidosis; 2) the significantly greater changes in PEPCK, NHE-3, and GS expression in acid-loaded CD-Rhbg/Rhcg-KO compared with acid-loaded C mice cause the role of Rhbg and Rhcg to be underestimated quantitatively; and 3) in mice with intact Rhbg and Rhcg expression, metabolic acidosis does not induce maximal changes in PEPCK, NHE-3, and GS expression despite the presence of persistent metabolic acidosis.

scholarly journals Role of NH3 and NH4+ transporters in renal acid-base transport

2011 ◽  
Vol 300 (1) ◽  
pp. F11-F23 ◽  
Author(s):  
I. David Weiner ◽  
Jill W. Verlander
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Collecting Duct ◽  
Critical Role ◽  
Ammonia Excretion ◽  
Thick Ascending Limb ◽  
Acid Base ◽  
Predominant Component ◽  
Ammonia Transport ◽  
Basolateral Plasma Membrane

Renal ammonia excretion is the predominant component of renal net acid excretion. The majority of ammonia excretion is produced in the kidney and then undergoes regulated transport in a number of renal epithelial segments. Recent findings have substantially altered our understanding of renal ammonia transport. In particular, the classic model of passive, diffusive NH3 movement coupled with NH4+ “trapping” is being replaced by a model in which specific proteins mediate regulated transport of NH3 and NH4+ across plasma membranes. In the proximal tubule, the apical Na+/H+ exchanger, NHE-3, is a major mechanism of preferential NH4+ secretion. In the thick ascending limb of Henle's loop, the apical Na+-K+-2Cl− cotransporter, NKCC2, is a major contributor to ammonia reabsorption and the basolateral Na+/H+ exchanger, NHE-4, appears to be important for basolateral NH4+ exit. The collecting duct is a major site for renal ammonia secretion, involving parallel H+ secretion and NH3 secretion. The Rhesus glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), are recently recognized ammonia transporters in the distal tubule and collecting duct. Rhcg is present in both the apical and basolateral plasma membrane, is expressed in parallel with renal ammonia excretion, and mediates a critical role in renal ammonia excretion and collecting duct ammonia transport. Rhbg is expressed specifically in the basolateral plasma membrane, and its role in renal acid-base homeostasis is controversial. In the inner medullary collecting duct (IMCD), basolateral Na+-K+-ATPase enables active basolateral NH4+ uptake. In addition to these proteins, several other proteins also contribute to renal NH3/NH4+ transport. The role and mechanisms of these proteins are discussed in depth in this review.

scholarly journals More actors in ammonia absorption by the thick ascending limb

2012 ◽  
Vol 302 (3) ◽  
pp. F293-F297 ◽  
Author(s):  
Pascal Houillier ◽  
Soline Bourgeois
Keyword(s):  
Current Knowledge ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Hydrogen Ion ◽  
Thick Ascending Limb ◽  
Loop Of Henle ◽  
Transport Mechanisms ◽  
Sodium Hydrogen ◽  
Ammonia Transport ◽  
Ammonia Absorption

This review will briefly summarize current knowledge on the basolateral ammonia transport mechanisms in the thick ascending limb (TAL) of the loop of Henle. This segment transports ammonia against a concentration gradient and is responsible for the accumulation of ammonia in the medullary interstitium, which, in turn, favors ammonia secretion across the collecting duct. Experimental data indicate that the sodium/hydrogen ion exchanger isoform 4 (NHE4; Scl9a4) is a sodium/ammonia exchanger and plays a major role in this process. Disruption of murine NHE4 leads to metabolic acidosis with inappropriate urinary ammonia excretion and decreases the ability of the TAL to absorb ammonia and to build the corticopapillary ammonia gradient. However, NHE4 does not account for the entirety of ammonia absorption by the TAL, indicating that, at least, one more transporter is involved.

pCO2 in regulating ammonia excretion by renal tubules of dogs

1961 ◽  
Vol 200 (4) ◽  
pp. 881-884 ◽  
Author(s):  
Robert Cade ◽  
Robert J. Shalhoub ◽  
Klaus Hierholzer
Keyword(s):  
Intracellular Ph ◽  
Diffusion Theory ◽  
Ammonia Excretion ◽  
Respiratory Acidosis ◽  
Passive Diffusion ◽  
Urine Flow ◽  
Potassium Depletion ◽  
Renal Tubules ◽  
Urine Ph ◽  
Ammonia Transport

The importance of urine pH, urine flow, availability of substrate and activity of cellular enzymes on the production and excretion of ammonia have been investigated in several species. Little information concerning the effect of intracellular pH on ammonia excretion is available. To investigate this problem we have altered intracellular pH by inducing respiratory acidosis and alkalosis in dogs. An elevated pCO2 uniformly depresses excretion of ammonia while a fall in pCO2 is associated with increased ammonia excretion at any given urine pH. When animals are depleted of potassium, the degree of depression by 10% CO2 is far greater than in the same animals studied before potassium depletion. The data are interpreted in the context of the passive diffusion theory of ammonia transport.

scholarly journals Marine, freshwater and aerially acclimated mangrove rivulus (Kryptolebias marmoratus) use different strategies for cutaneous ammonia excretion

2013 ◽  
Vol 304 (8) ◽  
pp. R599-R612 ◽  
Author(s):  
Christopher A. Cooper ◽  
Jonathan M. Wilson ◽  
Patricia A. Wright
Keyword(s):  
Immunofluorescence Microscopy ◽  
Ammonia Excretion ◽  
Teleost Fishes ◽  
Ammonia Gas ◽  
Ammonia Transport ◽  
Paracellular Pathways ◽  
Kryptolebias Marmoratus ◽  
Rh Glycoproteins ◽  
Mangrove Rivulus ◽  
Ammonia Flux

Rhesus (Rh) glycoproteins are ammonia gas (NH3) channels known to be involved in ammonia transport in animals. Because of the different osmoregulatory and ionoregulatory challenges faced by teleost fishes in marine and freshwater (FW) environments, we hypothesized that ammonia excretion strategies would differ between environments. Also, we hypothesized that cutaneous NH3 volatilization in air-acclimated fish is facilitated by base secretion. To test these hypotheses, we used the skin of the euryhaline amphibious mangrove rivulus ( Kryptolebias marmoratus). The skin excretes ammonia and expresses Rh glycoproteins. Serosal-to-mucosal cutaneous ammonia flux was saturable (0–16 mmol/l ammonia, Km of 6.42 mmol/l). In FW, ammonia excretion increased in response to low mucosal pH but decreased with pharmacological inhibition of Na+/H+ exchangers (NHE) and H+ ATPase. Conversely, in brackish water (BW), lowering the mucosal pH significantly decreased ammonia excretion. Inhibitors of NHE also decreased ammonia excretion in BW fish. Immunofluorescence microscopy demonstrated that both the Rh isoform, Rhcg1, and NHE3 proteins colocalized in Na+/K+ ATPase expressing mitochondrion-rich cells in the gills, kidney, and skin. We propose that the mechanisms of cutaneous ammonia excretion in FW K. marmoratus are consistent with the model for branchial ammonia excretion in FW teleost fish. NH4+ excretion appeared to play a stronger role in BW. NH4+ excretion in BW may be facilitated by apical NHE and/or diffuse through paracellular pathways. In aerially acclimated fish, inhibition of NHE and H+ ATPase, but not the Cl−/HCO3− exchanger, significantly affected cutaneous surface pH, suggesting that direct base excretion is not critical for NH3 volatilization. Overall, K. marmoratus use different strategies for excreting ammonia in three different environments, FW, BW, and air, and Rh glycoproteins and NHE are integral to all.

scholarly journals Immunolocalization and tissue-specific splicing of AE2 anion exchanger in mouse kidney.

1998 ◽  
Vol 9 (6) ◽  
pp. 946-959 ◽  
Author(s):  
A K Stuart-Tilley ◽  
B E Shmukler ◽  
D Brown ◽  
S L Alper
Keyword(s):  
Epithelial Cells ◽  
Anion Exchanger ◽  
Plasma Membranes ◽  
Collecting Duct ◽  
Sodium Dodecyl ◽  
Mouse Kidney ◽  
Pcr Analysis ◽  
Cortical Collecting Duct ◽  
Principal Cells ◽  
Reverse Transcription Pcr

In this study, an epitope-unmasking technique was used to immunolocalize AE2 anion exchanger polypeptide to basolateral plasma membranes of tubular epithelial cells in mouse kidney. Kidney AE2 immunostaining in mouse kidney was less prominent than in rat, consistent with the relative levels of AE2 mRNA and polypeptide in these two species. Glomeruli showed faint but consistent AE2 immunostaining, whereas proximal tubules were generally unstained. Macula densa epithelial cells displayed bright AE2 immunostaining, and cortical thick limbs were stained at a lower intensity. AE2 immunostaining was weak or absent in type B intercalated cells and principal cells of the cortical collecting duct, but increased in intensity in principal cells of the inner stripe of the outer medulla. AE2 staining in medullary thick limbs was also of greater intensity than in cortical thick limbs. AE2 staining was strong and uniform in the epithelial cells of the inner medullary collecting duct, and in epithelial cells of the papillary surface, the ureter, and the urinary bladder. Extratubular and epithelial cells of the inner medulla also showed punctate intracellular AE2 staining in a Golgi-like distribution that, in contrast to cell surface staining, was sodium dodecyl sulfate-sensitive. Golgi localization of AE2 epitope was confirmed by immunoperoxidase electron microscopy. Reverse transcription-PCR analysis of mouse kidney RNA detected AE2a, AE2b, and an AE2c2 transcript, but an AE2c1 transcript was absent. Unlike in rat, the mouse AE2c2 mRNA splice variant encoded a polypeptide with a novel predicted N-terminal amino acid sequence.

scholarly journals Mechanism of Hyperkalemia-Induced Metabolic Acidosis

2018 ◽  
Vol 29 (5) ◽  
pp. 1411-1425 ◽  
Author(s):  
Autumn N. Harris ◽  
P. Richard Grimm ◽  
Hyun-Wook Lee ◽  
Eric Delpire ◽  
Lijuan Fang ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Proximal Tubule ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Molecular Mechanisms ◽  
Genetic Model ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Wild Type ◽  
Urine Ph ◽  
Transporter Family

Background Hyperkalemia in association with metabolic acidosis that are out of proportion to changes in glomerular filtration rate defines type 4 renal tubular acidosis (RTA), the most common RTA observed, but the molecular mechanisms underlying the associated metabolic acidosis are incompletely understood. We sought to determine whether hyperkalemia directly causes metabolic acidosis and, if so, the mechanisms through which this occurs.Methods We studied a genetic model of hyperkalemia that results from early distal convoluted tubule (DCT)–specific overexpression of constitutively active Ste20/SPS1-related proline-alanine–rich kinase (DCT-CA-SPAK).Results DCT-CA-SPAK mice developed hyperkalemia in association with metabolic acidosis and suppressed ammonia excretion; however, titratable acid excretion and urine pH were unchanged compared with those in wild-type mice. Abnormal ammonia excretion in DCT-CA-SPAK mice associated with decreased proximal tubule expression of the ammonia-generating enzymes phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase and overexpression of the ammonia-recycling enzyme glutamine synthetase. These mice also had decreased expression of the ammonia transporter family member Rhcg and decreased apical polarization of H+-ATPase in the inner stripe of the outer medullary collecting duct. Correcting the hyperkalemia by treatment with hydrochlorothiazide corrected the metabolic acidosis, increased ammonia excretion, and normalized ammoniagenic enzyme and Rhcg expression in DCT-CA-SPAK mice. In wild-type mice, induction of hyperkalemia by administration of the epithelial sodium channel blocker benzamil caused hyperkalemia and suppressed ammonia excretion.Conclusions Hyperkalemia decreases proximal tubule ammonia generation and collecting duct ammonia transport, leading to impaired ammonia excretion that causes metabolic acidosis.

scholarly journals Role of the Rhesus glycoprotein, Rh B glycoprotein, in renal ammonia excretion

2010 ◽  
Vol 299 (5) ◽  
pp. F1065-F1077 ◽  
Author(s):  
Jesse M. Bishop ◽  
Jill W. Verlander ◽  
Hyun-Wook Lee ◽  
Raoul D. Nelson ◽  
Arthur J. Weiner ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Glutamine Synthetase ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Acid Excretion ◽  
Urine Ph ◽  
Outer Medulla ◽  
Intercalated Cell ◽  
Titratable Acid ◽  
Acid Loading

Rh B glycoprotein (Rhbg) is a member of the Rh glycoprotein family of ammonia transporters. In the current study, we examine Rhbg's role in basal and acidosis-stimulated acid-base homeostasis. Metabolic acidosis induced by HCl administration increased Rhbg expression in both the cortex and outer medulla. To test the functional significance of increased Rhbg expression, we used a Cre-loxP approach to generate mice with intercalated cell-specific Rhbg knockout (IC-Rhbg-KO). On normal diet, intercalated cell-specific Rhbg deletion did not alter urine ammonia excretion, pH, or titratable acid excretion significantly, but it did decrease glutamine synthetase expression in the outer medulla significantly. After metabolic acidosis was induced, urinary ammonia excretion was significantly less in IC-Rhbg-KO than in control (C) mice on days 2–4 of acid loading, but not on day 5. Urine pH and titratable acid excretion and dietary acid intake did not differ significantly between acid-loaded IC-Rhcg-KO and C mice. In IC-Rhbg-KO mice, acid loading increased connecting segment (CNT) cell and outer medullary collecting duct principal cell Rhbg expression. In both C and IC-Rhbg-KO mice, acid loading decreased glutamine synthetase in both the cortex and outer medulla; the decrease on day 3 was similar in IC-Rhbg-KO and C mice, but on day 5 it was significantly greater in IC-Rhbg-KO than in C mice. We conclude 1) intercalated cell Rhbg contributes to acidosis-stimulated renal ammonia excretion, 2) Rhbg in CNT and principal cells may contribute to renal ammonia excretion, and 3) decreased glutamine synthetase expression may enable normal rates of ammonia excretion under both basal conditions and on day 5 of acid loading in IC-Rhbg-KO mice.

A Mathematical Model of the Rat Kidney. III. Ammonia Transport

2021 ◽  
Author(s):  
Alan M. Weinstein
Keyword(s):  
Renal Vein ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Ammonia Excretion ◽  
Ammonia Concentration ◽  
Systemic Circulation ◽  
Blood Flows ◽  
Peritubular Capillaries ◽  
Ammonia Transport ◽  
Principal Finding

Ammonia generated within the kidney is partitioned into a urinary fraction (the key buffer for net acid excretion), and an aliquot delivered to the systemic circulation. The physiology of this partitioning has yet to be examined in a kidney model, and that is undertaken in this work. This involves explicit representation of the cortical labyrinth, so that cortical interstitial solute concentrations are computed, rather than assigned. A detailed representation of cortical vasculature has been avoided by making the assumption that solute concentrations within interstitium and peritubular capillaries are likely to be identical, and that there is little to no modification of venous composition as blood flows to the renal vein. The model medullary ray has also been revised to include a segment of proximal straight tubule, which supplies ammonia to this region. The principal finding of this work is that cortical labyrinth interstitial ammonia concentration is likely to be several-fold higher than systemic arterial ammonia. This elevation of interstitial ammonia enhances ammonia secretion in both PCT and DCT, with uptake by Na,K-ATPases of both segments. Model prediction of urinary ammonia excretion is concordant with measured values, but at the expense of greater ammoniagenesis, with high rates of renal venous ammonia flux. This derives from a limited capability of the model medulla to replicate the high interstitial ammonia concentrations that are required to drive collecting duct ammonia secretion. Thus, renal medullary ammonia trapping appears key to diverting ammonia from renal vein to urine, but capturing the underlying physiology remains a challenge.

Localization of ammonia transporter Rhcg1 in mitochondrion-rich cells of yolk sac, gill, and kidney of zebrafish and its ionic strength-dependent expression

2007 ◽  
Vol 293 (4) ◽  
pp. R1743-R1753 ◽  
Author(s):  
Tsutomu Nakada ◽  
Kazuyuki Hoshijima ◽  
Masahiro Esaki ◽  
Saori Nagayoshi ◽  
Koichi Kawakami ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Fluorescent Protein ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Distal Tubule ◽  
Yolk Sac ◽  
Renal Tubules ◽  
Larval Stages ◽  
Ammonia Transport ◽  
Green Fluorescent

Members of the Rh glycoprotein family have been shown to be involved in ammonia transport in a variety of species. Here we show that zebrafish Rhcg1, a member of the Rh glycoprotein family, is highly expressed in the yolk sac, gill, and renal tubules. Molecular cloning and characterization indicate that zebrafish Rhcg1 shares 82% sequence identity with the pufferfish ortholog fRhcg1. RT-PCR, combined with in situ hybridization, revealed that Rhcg1 is first expressed in vacuolar-type H+-ATPase/mitochondrion-rich cells (vH-MRC) on the yolk sac of larvae at 3 days postfertilization (dpf) and later in vH-MRC-like cells in the gill at 4–5 dpf. Ammonia excretion from zebrafish larvae increased in parallel with the expression of Rhcg1. At larval stages, Rhcg1 mRNA was detected only on the yolk sac and gill; however, the kidney, as well as the gill, becomes a major site of Rhcg1 expression in adults. Using a zebrafish Tol2 transgenic line whose vH-MRC are labeled with green fluorescent protein (GFP) and an antibody against zebrafish Rhcg1, we demonstrate that Rhcg1 is located in the apical regions of 1) vH-MRC on the yolk sac and vH-MRC-like cells (cell population with the expression of Rhcg1 and GFP) in the gill and 2) cells in the renal distal tubule and intercalated cell-like cells in the collecting duct of the kidney. Remarkably, expression of Rhcg1 mRNA at the larval stage was changed by environmental ionic strength. These results suggest that roles of zebrafish Rhcg1 are not solely ammonia secretion to eliminate nitrogen from the gill.

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