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 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 Testosterone modulates renal ammonia metabolism

2020 ◽  
Vol 318 (4) ◽  
pp. F922-F935 ◽  
Author(s):  
Autumn N. Harris ◽  
Hyun-Wook Lee ◽  
Jill W. Verlander ◽  
I. David Weiner
Keyword(s):  
Proximal Tubule ◽  
Ammonia Excretion ◽  
Primary Component ◽  
Testosterone Replacement ◽  
Thick Ascending Limb ◽  
Ammonia Metabolism ◽  
Cellular Expression ◽  
Renal Structure ◽  
Bilateral Orchiectomy

There are substantial sex differences in renal structure and ammonia metabolism that correlate with differences in expression of proteins involved in ammonia generation and transport. This study determined the role of testis-derived testosterone in these differences. We studied 4-mo-old male C57BL/6 mice 4 and 8 wk after either bilateral orchiectomy (ORCH) or sham-operated control surgery and determined the effect of testosterone replacement to reverse the effects of ORCH. Finally, we determined the cellular expression of androgen receptor (AR), testosterone’s canonical target receptor. ORCH decreased kidney and proximal tubule size, and testosterone replacement reversed this effect. ORCH increased ammonia excretion in a testosterone-dependent fashion; this occurred despite similar food intake, which is the primary component of endogenous acid production. ORCH increased expression of both phospho enolpyruvate, a major ammonia-generating protein, and Na+-K+-2Cl− cotransporter, which mediates thick ascending limb ammonia reabsorption; these changes were reversed with testosterone replacement. Orchiectomy also decreased expression of Na+/H+ exchanger isoform 3, which mediates proximal tubule ammonia secretion, in a testosterone-dependent pattern. Finally, ARs are expressed throughout the proximal tubule in both the male and female kidney. Testosterone, possibly acting through ARs, has dramatic effects on kidney and proximal tubule size and decreases ammonia excretion through its effects on several key proteins involved in ammonia metabolism.

scholarly journals NBCe1-A is required for the renal ammonia and K+ response to hypokalemia

2020 ◽  
Vol 318 (2) ◽  
pp. F402-F421 ◽  
Author(s):  
Hyun-Wook Lee ◽  
Autumn N. Harris ◽  
Michael F. Romero ◽  
Paul A. Welling ◽  
Charles S. Wingo ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Proximal Tubule ◽  
Splice Variant ◽  
Ammonia Excretion ◽  
Wild Type ◽  
Outer Medulla ◽  
Ammonia Metabolism ◽  
Tissue Sections ◽  
K Response

Hypokalemia increases ammonia excretion and decreases K+ excretion. The present study examined the role of the proximal tubule protein NBCe1-A in these responses. We studied mice with Na+-bicarbonate cotransporter electrogenic, isoform 1, splice variant A (NBCe1-A) deletion [knockout (KO) mice] and their wild-type (WT) littermates were provided either K+ control or K+-free diet. We also used tissue sections to determine the effect of extracellular ammonia on NaCl cotransporter (NCC) phosphorylation. The K+-free diet significantly increased proximal tubule NBCe1-A and ammonia excretion in WT mice, and NBCe1-A deletion blunted the ammonia excretion response. NBCe1-A deletion inhibited the ammoniagenic/ammonia recycling enzyme response in the cortical proximal tubule (PT), where NBCe1-A is present in WT mice. In the outer medulla, where NBCe1-A is not present, the PT ammonia metabolism response was accentuated by NBCe1-A deletion. KO mice developed more severe hypokalemia and had greater urinary K+ excretion during the K+-free diet than did WT mice. This was associated with blunting of the hypokalemia-induced change in NCC phosphorylation. NBCe1-A KO mice have systemic metabolic acidosis, but experimentally induced metabolic acidosis did not alter NCC phosphorylation. Although KO mice have impaired ammonia metabolism, experiments in tissue sections showed that lack of ammonia does impair NCC phosphorylation. Finally, urinary aldosterone was greater in KO mice than in WT mice, but neither expression of epithelial Na+ channel α-, β-, and γ-subunits nor of H+-K+-ATPase α1- or α2-subunits correlated with changes in urinary K+. We conclude that NBCe1-A is critical for the effect of diet-induced hypokalemia to increase cortical proximal tubule ammonia generation and for the expected decrease in urinary K+ excretion.

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 NBCe1 expression is required for normal renal ammonia metabolism

2015 ◽  
Vol 309 (7) ◽  
pp. F658-F666 ◽  
Author(s):  
Mary E. Handlogten ◽  
Gunars Osis ◽  
Hyun-Wook Lee ◽  
Michael F. Romero ◽  
Jill W. Verlander ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Gene Deletion ◽  
Ammonia Excretion ◽  
Ammonia Metabolism ◽  
Gene Dose ◽  
Ammonia Transport ◽  
Microscopy Examination ◽  
Lower Urinary

The mechanisms regulating proximal tubule ammonia metabolism are incompletely understood. The present study addressed the role of the proximal tubule basolateral electrogenic Na+-coupled bicarbonate cotransporter (NBCe1; Slc4a4) in renal ammonia metabolism. We used mice with heterozygous and homozygous NBCe1 gene deletion and compared these mice with their wild-type littermates. Because homozygous NBCe1 gene deletion causes 100% mortality before day 25, we studied mice at day 8 (±1 day). Both heterozygous and homozygous gene deletion caused a gene dose-related decrease in serum bicarbonate. The ability to lower urinary pH was intact, and even accentuated, with NBCe1 deletion. However, in contrast to the well-known effect of metabolic acidosis to increase urinary ammonia excretion, NBCe1 deletion caused a gene dose-related decrease in ammonia excretion. There was no identifiable change in proximal tubule structure by light microscopy. Examination of proteins involved in renal ammonia metabolism showed decreased expression of phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase, key enzymes in proximal tubule ammonia generation, and increased expression of glutamine synthetase, which recycles intrarenal ammonia and regenerates glutamine. Expression of key proteins involved in ammonia transport outside of the proximal tubule (rhesus B glycoprotein and rhesus C glycoprotein) was not significantly changed by NBCe1 deletion. We conclude from these findings that NBCe1 expression is necessary for normal proximal tubule ammonia metabolism.

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.

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 Sex differences in Alzheimer’s-related Tau biomarkers and a mediating effect of testosterone

2020 ◽  
Author(s):  
Erin Sundermann ◽  
Matthew S. Panizzon ◽  
Xu Chen ◽  
Murray Andrews ◽  
Douglas Galasko ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Sex Differences ◽  
Sex Difference ◽  
Mediating Effect ◽  
Interactive Effects ◽  
Plasma Testosterone ◽  
Testosterone Levels ◽  
Before And After

Abstract Women show greater pathological Tau biomarkers than men along the Alzheimer’s disease (AD) continuum, particularly among apolipoprotein ε-E4 (APOE4) carriers; however, the reason for this sex difference in unknown. Sex differences often indicate an underlying role of sex hormones. We examined whether testosterone levels might influence this sex difference and the modifying role of APOE4 status. Analyses included 172 participants (25 cognitively normal, 97 mild cognitive impairment, 50 AD participants) from the Alzheimer’s Disease Neuroimaging Initiative (34% female, 54% APOE4+, aged 55–90). We examined the separate and interactive effects of plasma testosterone levels and APOE4 on cerebrospinal fluid phosphorylated-tau181 (p-Tau) levels in the overall sample, and the sex difference in p-Tau levels before and after adjusting for testosterone. A significant APOE4-by-testosterone interaction revealed that lower testosterone levels related to higher p-Tau levels among APOE4 carriers regardless of sex. As expected, women had higher p-Tau levels than men among APOE4 carriers only, yet this difference was eliminated upon adjustment for testosterone. Results suggest that testosterone is protective against p-Tau particularly among APOE4 carriers. The lower testosterone levels that typically characterize women may predispose them to pathological Tau, particularly among female APOE4 carriers.

scholarly journals Sex differences in adaptive downregulation of pre-macula densa sodium transporters with ANG II infusion in mice

2010 ◽  
Vol 298 (1) ◽  
pp. F187-F195 ◽  
Author(s):  
Swasti Tiwari ◽  
Lijun Li ◽  
Shahla Riazi ◽  
Veerendra K. Madala Halagappa ◽  
Carolyn M. Ecelbarger
Keyword(s):  
Sex Differences ◽  
Plasma Testosterone ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Ang Ii ◽  
Male Mice ◽  
Male And Female ◽  
Female Mice ◽  
Sodium Transporters ◽  
Pressure Natriuresis

An increase in blood pressure (BP) due to angiotensin II (ANG II) infusion or other means is associated with adaptive pressure natriuresis due to reduced sodium reabsorption primarily in proximal tubule (PT) and thick ascending limb (TAL). We tested the hypothesis that male and female mice would show differential response to ANG II infusion with regard to the regulation of the protein abundance of sodium transporters in the PT and TAL and that these responses would be modulated by aging. Young (∼3 mo) and old (∼21 mo) male and female mice were infused with ANG II at 800 ng·kg body wt−1·min−1 by osmotic minipump for 7 days or received a sham operation. ANG II increased mean arterial pressure (MAP), measured by radiotelemetry, significantly more in male mice of both ages (increased ∼30–40 mmHg), compared with females (increased ∼15–25 mmHg). On day 1, MAP was also significantly increased in old mice, relative to young ( P = 0.01). ANG II infusion was associated with a significant decline in plasma testosterone (to <30% of control male) in male mice and rise in young female mice (to 478% of control female). No sex differences were found in the upregulation of the sodium hydrogen exchanger abundance on Western blots observed with ANG II infusion or the downregulation of the sodium phosphate cotransporter; however, aging did impact on some of these changes. Male mice (especially young) also had significantly reduced levels of the TAL bumetanide-sensitive Na-K-2Cl cotransporter (to 60% of male control), while young females showed an increase (to 126% of female control) with ANG II infusion. These sex differences do not support impaired pressure natriuresis in male mice, but might reflect a greater need and attempt to mount an appropriately BP-metered natriuretic response by additional downregulation of TAL sodium reabsorption.

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