Effect of reduced renal mass on renal ammonia transporter family, Rh C glycoprotein and Rh B glycoprotein, expression

2007 ◽  
Vol 293 (4) ◽  
pp. F1238-F1247 ◽  
Author(s):  
Hye-Young Kim ◽  
Chris Baylis ◽  
Jill W. Verlander ◽  
Ki-Hwan Han ◽  
Sirirat Reungjui ◽  
...  
Keyword(s):  
Creatinine Clearance ◽  
Renal Mass ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Sham Operation ◽  
Acid Base ◽  
Ammonia Metabolism ◽  
Adaptive Changes ◽  
Predominant Component ◽  
Transporter Family

Kidneys can maintain acid-base homeostasis, despite reduced renal mass, through adaptive changes in net acid excretion, of which ammonia excretion is the predominant component. The present study examines whether these adaptations are associated with changes in the ammonia transporter family members, Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg). We used normal Sprague-Dawley rats and a 5/6 ablation-infarction model of reduced renal mass; control rats underwent sham operation. After 1 wk, glomerular filtration rate, assessed as creatinine clearance, was decreased, serum bicarbonate was slightly increased, and Na+ and K+ were unchanged. Total urinary ammonia excretion was unchanged, but urinary ammonia adjusted for creatinine clearance, an index of per nephron ammonia metabolism, increased significantly. Although reduced renal mass did not alter total Rhcg protein expression, both light microscopy and immunohistochemistry with quantitative morphometric analysis demonstrated hypertrophy of both intercalated cells and principal cells in the cortical and outer medullary collecting duct that was associated with increased apical and basolateral Rhcg polarization. Rhbg expression, analyzed using immunoblot analysis, immunohistochemistry, and measurement of cell-specific expression, was unchanged. We conclude that altered subcellular localization of Rhcg contributes to adaptive changes in single-nephron ammonia metabolism and maintenance of acid-base homeostasis in response to reduced renal mass.

scholarly journals Effect of hypokalemia on renal expression of the ammonia transporter family members, Rh B Glycoprotein and Rh C Glycoprotein, in the rat kidney

2011 ◽  
Vol 301 (4) ◽  
pp. F823-F832 ◽  
Author(s):  
Ki-Hwan Han ◽  
Hyun-Wook Lee ◽  
Mary E. Handlogten ◽  
Jesse M. Bishop ◽  
Moshe Levi ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Metabolic Alkalosis ◽  
Collecting Duct ◽  
Family Members ◽  
Ammonia Excretion ◽  
Intercalated Cells ◽  
Acid Base ◽  
Ammonia Metabolism ◽  
Transporter Family ◽  
Base Disorder

Hypokalemia is a common electrolyte disorder that increases renal ammonia metabolism and can cause the development of an acid-base disorder, metabolic alkalosis. The ammonia transporter family members, Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg), are expressed in the distal nephron and collecting duct and mediate critical roles in acid-base homeostasis by facilitating ammonia secretion. In the current studies, the effect of hypokalemia on renal Rhbg and Rhcg expression was examined. Normal Sprague-Dawley rats received either K+-free or control diets for 2 wk. Rats receiving the K+-deficient diet developed hypokalemia and metabolic alkalosis associated with significant increases in both urinary ammonia excretion and urine pH. Rhcg expression increased in the outer medullary collecting duct (OMCD). In OMCD intercalated cells, hypokalemia resulted in more discrete apical Rhcg expression and a marked increase in apical plasma membrane immunolabel. In principal cells, in the OMCD, hypokalemia increased both apical and basolateral Rhcg immunolabel intensity. Cortical Rhcg expression was not detectably altered by immunohistochemistry, although there was a slight decrease in total expression by immunoblot analysis. Rhbg protein expression was decreased slightly in the cortex and not detectably altered in the outer medulla. We conclude that in rat OMCD, hypokalemia increases Rhcg expression, causes more polarized apical expression in intercalated cells, and increases both apical and basolateral expression in the principal cell. Increased plasma membrane Rhcg expression in response to hypokalemia in the rat, particularly in the OMCD, likely contributes to the increased ammonia excretion and thereby to the development of metabolic alkalosis.

scholarly journals Differences in acidosis-stimulated renal ammonia metabolism in the male and female kidney

2019 ◽  
Vol 317 (4) ◽  
pp. F890-F905 ◽  
Author(s):  
Autumn N. Harris ◽  
Hyun-Wook Lee ◽  
Lijuan Fang ◽  
Jill W. Verlander ◽  
I. David Weiner
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Volume Density ◽  
Male Mice ◽  
Ammonia Metabolism ◽  
Female Mice ◽  
Predominant Component ◽  
Acid Load ◽  
Acid Loading

Renal ammonia excretion is a critical component of acid-base homeostasis, and changes in ammonia excretion are the predominant component of increased net acid excretion in response to metabolic acidosis. We recently reported substantial sex-dependent differences in basal ammonia metabolism that correlate with sex-dependent differences in renal structure and expression of key proteins involved in ammonia metabolism. The purpose of the present study was to investigate the effect of sex on the renal ammonia response to an exogenous acid load. We studied 4-mo-old C57BL/6 mice. Ammonia excretion, which was less in male mice under basal conditions, increased in response to acid loading to a greater extent in male mice, such that maximal ammonia excretion did not differ between the sexes. Fundamental structural sex differences in the nonacid-loaded kidney persisted after acid loading, with less cortical proximal tubule volume density in the female kidney than in the male kidney, whereas collecting duct volume density was greater in the female kidney. To further investigate sex-dependent differences in the response to acid loading, we examined the expression of proteins involved in ammonia metabolism. The change in expression of phosphoenolpyruvate carboxykinase and Rh family B glycoprotein with acid loading was greater in male mice than in female mice, whereas Na+-K+-2Cl– cotransporter and inner stripe of the outer medulla intercalated cell Rh family C glycoprotein expression were significantly greater in female mice than in male mice. There was no significant sex difference in glutamine synthetase, Na+/H+ exchanger isoform 3, or electrogenic Na+-bicarbonate cotransporter 1 variant A protein expression in response to acid loading. We conclude that substantial sex-dependent differences in the renal ammonia response to acid loading enable a similar maximum ammonia excretion response.

scholarly journals Expression of ammonia transporter family members, Rh B glycoprotein and Rh C glycoprotein, in the developing rat kidney

2010 ◽  
Vol 299 (1) ◽  
pp. F187-F198 ◽  
Author(s):  
Ki-Hwan Han ◽  
Su-Youn Lee ◽  
Wan-Young Kim ◽  
Jung-A Shin ◽  
Jin Kim ◽  
...  
Keyword(s):  
Kidney Development ◽  
Collecting Duct ◽  
Family Members ◽  
Ammonia Excretion ◽  
Intercalated Cells ◽  
Double Labeling ◽  
Ammonia Metabolism ◽  
Intercalated Cell ◽  
Transporter Family ◽  
In Cells

Ammonia metabolism is a primary component of acid-base homeostasis but is incompletely developed at time of birth. Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg) are recently recognized ammonia transporter family members expressed in the mammalian kidney. This study's purpose was to establish the expression and localization of Rhbg and Rhcg during kidney development. We examined kidneys from fetal days 16 ( E16), 18 ( E18), and 20 ( E20), and from the first 21 days of postnatal development. Rhbg was expressed initially at E18, with expression only in the connecting tubule (CNT); at E20, Rhbg was expressed in both the CNT and the medullary collecting duct (MCD). In contrast, Rhcg was first expressed at E16 with basal expression in the ureteric bud; at E18, it was expressed in a subset of CNT cells with an apical pattern, followed by apical and basolateral expression in the MCD at E20. In the cortex, Rhbg and Rhcg expression increased in the CNT before expression in the cortical collecting duct during fetal development. In the MCD, both Rhbg and Rhcg expression was initially in cells in the papillary tip, with gradual removal from the tip during the late fetal period and transition during the early neonatal period to an adult pattern with predominant expression in the outer MCD and only rare expression in cells in the initial inner MCD. Double-labeling with intercalated cell-specific markers identified that Rhbg and Rhcg were expressed initially in CNT cells, CNT A-type intercalated cells and non-A, non-B intercalated cells, and in MCD A-type intercalated cells. We conclude that expression of Rhbg and Rhcg parallels intercalated cell development and that immature Rhbg and Rhcg expression at birth contributes to incomplete ammonia excretion capacity.

scholarly journals Sex Differences in Renal Ammonia Metabolism

2020 ◽  
Author(s):  
Autumn N. Harris ◽  
I. David Weiner
Keyword(s):  
Proximal Tubule ◽  
Structural Changes ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Acid Base ◽  
Ammonia Metabolism ◽  
Transport Studies ◽  
Renal Structure ◽  
Optimal Health ◽  
Acid Load

Sexual dimorphic variations are present in many aspects of biology and involve the structure and/or function of nearly every organ system. Acid-base homeostasis is critical for optimal health, and renal ammonia metabolism has a major role in the maintenance of acid-base homeostasis. Recent studies have shown sex-dependent differences in renal ammonia metabolism with regards to both basal ammonia excretion and the response to an exogenous acid load. These sexual dimorphisms are associated with structural changes in the proximal tubule and the collecting duct and variations in the expression of multiple proteins involved in ammonia metabolism and transport. Studies using orchiectomy (ORCH)-induced testosterone deficiency and physiological testosterone replacement show testosterone underlies much of the sex-dependent differences in the proximal tubule. This parallels the finding that the canonical testosterone target receptor, androgen receptor (AR), is present exclusively in the proximal tubule. Thus, testosterone, possibly acting through AR activation, regulates multiple coponents of renal structure and ammonia metabolism. The lack of detectable AR in the remainder of the nephron and the collecting duct suggests that some dimorphisms in renal structure and ammonia transporter expression are mediated through mechanisms other than direct testosterone-dependent AR activation. A better understanding of the mechanism and biological implications of sex's effect on renal structure and ammonia metabolism is critical for optimizing our ability to care for both men and women with acid-base disturbances.

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 Intercalated cell-specific Rh B glycoprotein deletion diminishes renal ammonia excretion response to hypokalemia

2013 ◽  
Vol 304 (4) ◽  
pp. F422-F431 ◽  
Author(s):  
Jesse M. Bishop ◽  
Hyun-Wook Lee ◽  
Mary E. Handlogten ◽  
Ki-Hwan Han ◽  
Jill W. Verlander ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Ammonia Concentration ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Intercalated Cell ◽  
Transporter Family ◽  
Total Ammonia ◽  
Normal Increase

The ammonia transporter family member, Rh B Glycoprotein (Rhbg), is an ammonia-specific transporter heavily expressed in the kidney and is necessary for the normal increase in ammonia excretion in response to metabolic acidosis. Hypokalemia is a common clinical condition in which there is increased renal ammonia excretion despite the absence of metabolic acidosis. The purpose of this study was to examine Rhbg's role in this response through the use of mice with intercalated cell-specific Rhbg deletion (IC-Rhbg-KO). Hypokalemia induced by feeding a K+-free diet increased urinary ammonia excretion significantly. In mice with intact Rhbg expression, hypokalemia increased Rhbg protein expression in intercalated cells in the cortical collecting duct (CCD) and in the outer medullary collecting duct (OMCD). Deletion of Rhbg from intercalated cells inhibited hypokalemia-induced changes in urinary total ammonia excretion significantly and completely prevented hypokalemia-induced increases in urinary ammonia concentration, but did not alter urinary pH. We conclude that hypokalemia increases Rhbg expression in intercalated cells in the cortex and outer medulla and that intercalated cell Rhbg expression is necessary for the normal increase in renal ammonia excretion in response to hypokalemia.

Acid-Base Effects of Combined Renal Deletion of NBCe1-A and NBCe1-B

2022 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Jill W. Verlander ◽  
Gary E Shull ◽  
Autumn N. Harris ◽  
I. David Weiner
Keyword(s):  
Proximal Tubule ◽  
Splice Variant ◽  
Molecular Mechanisms ◽  
Ammonia Excretion ◽  
Basal Diet ◽  
Acid Base ◽  
Outer Medulla ◽  
Ammonia Metabolism ◽  
Induced Changes ◽  
Acid Loading

The molecular mechanisms regulating ammonia metabolism are fundamental to acid-base homeostasis. Deleting the A splice variant of the Na⁺-bicarbonate cotransporter, electrogenic, isoform 1 (NBCe1-A) partially blocks the effect of acidosis to increase urinary ammonia excretion, and this appears to involve the dysregulated expression of ammoniagenic enzymes in the proximal tubule (PT) in the cortex, but not in the outer medulla (OM). A second NBCe1 splice variant, NBCe1-B, is present throughout the PT, including the OM, where NBCe1-A is not present. The current studies determined the effects of combined renal deletion of NBCe1-A and NBCe1-B on systemic and proximal tubule ammonia metabolism. We generated NBCe1-A/B deletion using Cre-loxP techniques and used Cre-negative mice as controls. Since renal NBCe1-A and NBCe1-B expression is limited to the proximal tubule, Cre-positive mice had proximal tubule NBCe1-A/B deletion (PT-NBCe1-A/B KO). While on basal diet, PT-NBCe1-A/B KO mice had severe metabolic acidosis, yet urinary ammonia excretion was not changed significantly. PT-NBCe1-A/B KO decreased expression of phosphate-dependent glutaminase (PDG) and phospho­enol­pyruvate carboxy­kinase (PEPCK) and increased expression of glutamine synthetase (GS), an ammonia recycling enzyme, in PT in both the cortex and OM. Exogenous acid-loading increased ammonia excretion in control mice, but PT-NBCe1-A/B KO prevented any increase. PT-NBCe1-A/B KO significantly blunted acid loading-induced changes in PDG, PEPCK, and GS expression in the proximal tubule in both the cortex and OM. We conclude that NBCe1-B, at least in the presence of NBCe1-A deletion, contributes to proximal tubule ammonia metabolism in the OM and thereby to systemic acid-base regulation.

scholarly journals Proximal tubule-specific glutamine synthetase deletion alters basal and acidosis-stimulated ammonia metabolism

2016 ◽  
Vol 310 (11) ◽  
pp. F1229-F1242 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Gunars Osis ◽  
Mary E. Handlogten ◽  
Wouter H. Lamers ◽  
Farrukh A. Chaudhry ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Glutamine Synthetase ◽  
Proximal Tubule ◽  
Ammonia Excretion ◽  
Renal Proximal Tubule ◽  
Acid Excretion ◽  
Ammonia Metabolism ◽  
Adaptive Changes ◽  
Multiple Components

Glutamine synthetase (GS) catalyzes the recycling of NH4+ with glutamate to form glutamine. GS is highly expressed in the renal proximal tubule (PT), suggesting ammonia recycling via GS could decrease net ammoniagenesis and thereby limit ammonia available for net acid excretion. The purpose of the present study was to determine the role of PT GS in ammonia metabolism under basal conditions and during metabolic acidosis. We generated mice with PT-specific GS deletion (PT-GS-KO) using Cre-loxP techniques. Under basal conditions, PT-GS-KO increased urinary ammonia excretion significantly. Increased ammonia excretion occurred despite decreased expression of key proteins involved in renal ammonia generation. After the induction of metabolic acidosis, the ability to increase ammonia excretion was impaired significantly by PT-GS-KO. The blunted increase in ammonia excretion occurred despite greater expression of multiple components of ammonia generation, including SN1 (Slc38a3), phosphate-dependent glutaminase, phospho enolpyruvate carboxykinase, and Na+-coupled electrogenic bicarbonate cotransporter. We conclude that 1) GS-mediated ammonia recycling in the PT contributes to both basal and acidosis-stimulated ammonia metabolism and 2) adaptive changes in other proteins involved in ammonia metabolism occur in response to PT-GS-KO and cause an underestimation of the role of PT GS expression.

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 Renal ammonia excretion in response to hypokalemia: effect of collecting duct-specific Rh C glycoprotein deletion

2013 ◽  
Vol 304 (4) ◽  
pp. F410-F421 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Jill W. Verlander ◽  
Jesse M. Bishop ◽  
Mary E. Handlogten ◽  
Ki-Hwan Han ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Metabolic Alkalosis ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Immunogold Electron Microscopy ◽  
Acid Base ◽  
Outer Medulla ◽  
Rhesus Factor ◽  
Base Disorder ◽  
Urine Alkalinization

The Rhesus factor protein, Rh C glycoprotein (Rhcg), is an ammonia transporter whose expression in the collecting duct is necessary for normal ammonia excretion both in basal conditions and in response to metabolic acidosis. Hypokalemia is a common clinical condition associated with increased renal ammonia excretion. In contrast to basal conditions and metabolic acidosis, increased ammonia excretion during hypokalemia can lead to an acid-base disorder, metabolic alkalosis, rather than maintenance of acid-base homeostasis. The purpose of the current studies was to determine Rhcg's role in hypokalemia-stimulated renal ammonia excretion through the use of mice with collecting duct-specific Rhcg deletion (CD-Rhcg-KO). In mice with intact Rhcg expression, a K+-free diet increased urinary ammonia excretion and urine alkalinization and concurrently increased Rhcg expression in the collecting duct in the outer medulla. Immunohistochemistry and immunogold electron microscopy showed hypokalemia increased both apical and basolateral Rhcg expression. In CD-Rhcg-KO, a K+-free diet increased urinary ammonia excretion and caused urine alkalinization, and the magnitude of these changes did not differ from mice with intact Rhcg expression. In mice on a K+-free diet, CD-Rhcg-KO increased phosphate-dependent glutaminase (PDG) expression in the outer medulla. We conclude that hypokalemia increases collecting duct Rhcg expression, that this likely contributes to the hypokalemia-stimulated increase in urinary ammonia excretion, and that adaptive increases in PDG expression can compensate for the absence of collecting duct Rhcg.

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