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 NBCe1-A Regulates Proximal Tubule Ammonia Metabolism under Basal Conditions and in Response to Metabolic Acidosis

2018 ◽  
Vol 29 (4) ◽  
pp. 1182-1197 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Gunars Osis ◽  
Autumn N. Harris ◽  
Lijuan Fang ◽  
Michael F. Romero ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Proximal Tubule ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Molecular Mechanisms ◽  
Collecting Duct ◽  
Critical Role ◽  
Ammonia Excretion ◽  
Urine Ph ◽  
Ammonia Metabolism ◽  
Acid Loading

Renal ammonia metabolism is the primary mechanism through which the kidneys maintain acid-base homeostasis, but the molecular mechanisms regulating renal ammonia generation are unclear. In these studies, we evaluated the role of the proximal tubule basolateral plasma membrane electrogenic sodium bicarbonate cotransporter 1 variant A (NBCe1-A) in this process. Deletion of the NBCe1-A gene caused severe spontaneous metabolic acidosis in mice. Despite this metabolic acidosis, which normally causes a dramatic increase in ammonia excretion, absolute urinary ammonia concentration was unaltered. Additionally, NBCe1-A deletion almost completely blocked the ability to increase ammonia excretion after exogenous acid loading. Under basal conditions and during acid loading, urine pH was more acidic in mice with NBCe1-A deletion than in wild-type controls, indicating that the abnormal ammonia excretion was not caused by a primary failure of urine acidification. Instead, NBCe1-A deletion altered the expression levels of multiple enzymes involved in proximal tubule ammonia generation, including phosphate-dependent glutaminase, phosphoenolpyruvate carboxykinase, and glutamine synthetase, under basal conditions and after exogenous acid loading. Deletion of NBCe1-A did not impair expression of key proteins involved in collecting duct ammonia secretion. These studies demonstrate that the integral membrane protein NBCe1-A has a critical role in basal and acidosis-stimulated ammonia metabolism through the regulation of proximal tubule ammonia-metabolizing enzymes.

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 Role of the Renal Androgen Receptor in Ammonia Metabolism

2021 ◽  
Author(s):  
Autumn N. Harris ◽  
Rebeca A Castro ◽  
Hyun-Wook Lee ◽  
Jill W. Verlander ◽  
I. David Weiner
Keyword(s):  
Sex Differences ◽  
Androgen Receptor ◽  
Proximal Tubule ◽  
Ammonia Excretion ◽  
Volume Density ◽  
Plasma Testosterone ◽  
Kidney Size ◽  
Ammonia Metabolism ◽  
Female Mice

Background: There are sex differences in renal ammonia metabolism and structure, many of which are mediated by testosterone. This study's goal was to determine the role of renal expression of testosterone's canonical receptor, androgen receptor (AR), in these sexual dimorphisms. Methods: We studied mice with kidney-specific AR deletion (KS-AR-KO) generated using Cre/loxP techniques; control mice were Cre-negative littermates (WT). Results: In male, but not female, mice, KS-AR-KO increased ammonia excretion, which eliminated sex differences. Although renal structural size typically parallel ammonia excretion, KS-AR-KO decreased kidney size, cortical proximal tubule volume density and cortical proximal tubule cell height in males; neither were altered in females and collecting duct volume density was unaltered in both sexes. Analysis of key protein involved in ammonia handling showed in male mice that KS-AR-KO increased both PEPCK and NKCC2 expression, and decreased NHE3 and NBCe1-A expression. In female mice, KS-AR-KO did not alter these parameters. These effects occurred even though KS-AR-KO did not alter plasma testosterone, food intake or serum Na+, K+, or HCO3- significantly in either sex. Conclusions: AR-dependent signaling pathways in male, but not female, kidney regulate PEPCK and NKCC2 expression and lead to the sexual differences in ammonia excretion. Opposing effects on NHE-3 and NBCe1-A expression likely limit the magnitude of ammonia excretion changes. Since AR is not present in the TAL, the effect of KS-AR-KO on NKCC2 expression is indirect. Finally, AR mediates the greater kidney size and PT volume density in male than in female mice.

scholarly journals Differences in renal ammonia metabolism in male and female kidney

2018 ◽  
Vol 315 (2) ◽  
pp. F211-F222 ◽  
Author(s):  
Autumn N. Harris ◽  
Hyun-Wook Lee ◽  
Gunars Osis ◽  
Lijuan Fang ◽  
Kierstin L. Webster ◽  
...  
Keyword(s):  
Sex Differences ◽  
Ammonia Excretion ◽  
Normal Diet ◽  
Lower Percentage ◽  
Male Mice ◽  
Ammonia Metabolism ◽  
Female Mice ◽  
Collecting Ducts ◽  
Structural Differences ◽  
Primary Determinant

Renal ammonia metabolism has a major role in the maintenance of acid-base homeostasis. Sex differences are well recognized as an important biological variable in many aspects of renal function, including fluid and electrolyte metabolism. However, sex differences in renal ammonia metabolism have not been previously reported. Therefore, the purpose of the current study was to investigate sex differences in renal ammonia metabolism. We studied 4-mo-old wild-type C57BL/6 mice fed a normal diet. Despite similar levels of food intake, and, thus, protein intake, which is the primary determinant of endogenous acid production, female mice excreted greater amounts of ammonia, but not titratable acids, than did male mice. This difference in ammonia metabolism was associated with fundamental structural differences between the female and male kidney. In the female mouse kidney, proximal tubules account for a lower percentage of the renal cortical parenchyma compared with the male kidney, whereas collecting ducts account for a greater percentage of the renal parenchyma than in male kidneys. To further investigate the mechanism(s) behind the greater ammonia excretion in female mice, we examined differences in the expression of proteins involved in renal ammonia metabolism and transport. Greater basal ammonia excretion in females was associated with greater expression of PEPCK, glutamine synthetase, NKCC2, Rhbg, and Rhcg than was observed in male mice. We conclude that there are sex differences in basal ammonia metabolism that involve both renal structural differences and differences in expression of proteins involved in ammonia metabolism.

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.

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 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 Sex differences in renal and metabolic responses to a high-fructose diet in mice

2015 ◽  
Vol 308 (5) ◽  
pp. F400-F410 ◽  
Author(s):  
Nikhil Sharma ◽  
Lijun Li ◽  
C. M. Ecelbarger
Keyword(s):  
Sex Differences ◽  
Glucose Transporter ◽  
Collecting Duct ◽  
Urine Volume ◽  
Thick Ascending Limb ◽  
Male Mice ◽  
Male And Female ◽  
Female Mice ◽  
High Fructose Diet ◽  
High Fructose

High fructose intake has been associated with increased incidences of renal disease and hypertension, among other pathologies. Most fructose is cleared by the portal system and metabolized in the liver; however, systemic levels of fructose can rise with increased consumption. We tested whether there were sex differences in the renal responses to a high-fructose diet in mice. Two-month-old male and female C57BL6/129/SV mice ( n = 6 mice per sex per treatment) were randomized to receive control or high-fructose (65% by weight) diets as pelleted chow ad libitum for 3 mo. Fructose feeding did not significantly affect body weight but led to a 19% and 10% increase in kidney weight in male and female mice, respectively. In male mice, fructose increased the expression (∼50%) of renal cortical proteins involved in metabolism, including glucose transporter 5 (facilitative fructose transporter), ketohexokinase, and the insulin receptor (β-subunit). Female mice had lower basal levels of glucose transporter 5, which were unresponsive to fructose. However, female mice had increased urine volume and plasma K+ and decreased plasma Na+ with fructose, whereas male mice were less affected. Likewise, female mice showed a two- to threefold reduction in the expression Na+-K+-2Cl− cotransporter 2 in the thick ascending limb and aquaporin-2 in the collecting duct with fructose relative to female control mice, whereas male mice had no change. Overall, our results support greater proximal metabolism of fructose in male animals and greater distal tubule/collecting duct (electrolyte homeostasis) alterations in female animals. These sex differences may be important determinants of the specific nature of pathologies that develop in association with high fructose consumption.

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 Effect of intercalated cell-specific Rh C glycoprotein deletion on basal and metabolic acidosis-stimulated renal ammonia excretion

2010 ◽  
Vol 299 (2) ◽  
pp. F369-F379 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Jill W. Verlander ◽  
Jesse M. Bishop ◽  
Raoul D. Nelson ◽  
Mary E. Handlogten ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Principal Cell ◽  
Intercalated Cells ◽  
Outer Medulla ◽  
Ammonia Content ◽  
Principal Cells ◽  
Intercalated Cell ◽  
Acid Loading

Rh C glycoprotein (Rhcg) is an NH3-specific transporter expressed in both intercalated cells (IC) and principal cells (PC) in the renal collecting duct. Recent studies show that deletion of Rhcg from both intercalated and principal cells inhibits both basal and acidosis-stimulated renal ammonia excretion. The purpose of the current studies was to better understand the specific role of Rhcg expression in intercalated cells in basal and metabolic acidosis-stimulated renal ammonia excretion. We generated mice with intercalated cell-specific Rhcg deletion (IC-Rhcg-KO) using Cre-loxP techniques; control (C) mice were floxed Rhcg but Cre negative. Under basal conditions, IC-Rhcg-KO and C mice excreted urine with similar ammonia content and pH. Mice were then acid loaded by adding HCl to their diet. Ammonia excretion after acid loading increased similarly in IC-Rhcg-KO and C mice during the first 2 days of acid loading but on day 3 was significantly less in IC-Rhcg-KO than in C mice. During the first 2 days of acid loading, urine was significantly more acidic in IC-Rhcg-KO mice than in C mice; there was no difference on day 3. In IC-Rhcg-KO mice, acid loading increased principal cell Rhcg expression in both the cortex and outer medulla as well as expression of another ammonia transporter, Rh glycoprotein B (Rhbg), in principal cells in the outer medulla. We conclude that 1) Rhcg expression in intercalated cells is necessary for the normal renal response to metabolic acidosis; 2) principal cell Rhcg contributes to both basal and acidosis-stimulated ammonia excretion; and 3) adaptations in Rhbg expression occur in response to acid-loading.

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