scholarly journals Compensatory increase in AQP2, p-AQP2, and AQP3 expression in rats with diabetes mellitus

2001 ◽  
Vol 280 (4) ◽  
pp. F715-F726 ◽  
Author(s):  
Lene N. Nejsum ◽  
Tae-Hwan Kwon ◽  
David Marples ◽  
Allan Flyvbjerg ◽  
Mark A. Knepper ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Plasma Membrane ◽  
Sodium Excretion ◽  
Collecting Duct ◽  
Distal Tubule ◽  
Urinary Sodium Excretion ◽  
Apical Plasma Membrane ◽  
Compensatory Increase ◽  
Intracellular Vesicles

Diabetes mellitus (DM) is associated with osmotic diuresis and natriuresis. At day 15, rats with DM induced by streptozotocin ( n = 13) had severe hyperglycemia (27.1 ± 0.4 vs. 4.7 ± 0.1 mM in controls) and had a fivefold increase in water intake (123 ± 5 vs. 25 ± 2 ml/day) and urine output. Semiquantitative immunoblotting revealed a significant increase in inner medullary AQP2 (201 ± 12% of control rats, P < 0.05) and phosphorylated (Ser256) AQP2 (p-AQP2) abundance (299 ± 32%) in DM rats. Also, the abundance of inner medullary AQP3 was markedly increased to 171 ± 19% of control levels (100 ± 4%, n = 7, P < 0.05). In contrast, the abundance of whole kidney AQP1 (90 ± 3%) and inner medullary AQP4 (121 ± 16%) was unchanged in rats with DM. Immunoelectron microscopy further revealed an increased labeling of AQP2 in the apical plasma membrane of collecting duct principal cells (with less labeling in the intracellular vesicles) of DM rats, indicating enhanced trafficking of AQP2 to the apical plasma membrane. There was a marked increase in urinary sodium excretion in DM. Only Na+/H+ exchanger NHE3 was downregulated (67 ± 10 vs. 100 ± 11%) whereas there were no significant changes in abundance of type 2 Na-phosphate cotransporter (128 ± 6 vs. 100 ± 10%); the Na-K-2Cl cotransporter (125 ± 19 vs. 100 ± 10%); the thiazide-sensitive Na-Cl cotransporter (121 ± 9 vs. 100 ± 10%); the α1-subunit of the Na-K-ATPase (106 ± 7 vs. 100 ± 5%); and the proximal tubule Na-HCO3 cotransporter (98 ± 16 vs. 100 ± 7%). In conclusion, DM rats had an increased AQP2, p-AQP2, and AQP3 abundance as well as high AQP2 labeling of the apical plasma membrane, which is likely to represent a vasopressin-mediated compensatory increase in response to the severe polyuria. In contrast, there were no major changes in the abundance of AQP1, AQP4, and several major proximal and distal tubule Na+ transporters except NHE3 downregulation, which may participate in the increased sodium excretion.

H(+)V-ATPase-dependent luminal acidification in the kidney collecting duct and the epididymis/vas deferens: vesicle recycling and transcytotic pathways

2000 ◽  
Vol 203 (1) ◽  
pp. 137-145 ◽  
Author(s):  
D. Brown ◽  
S. Breton
Keyword(s):  
Plasma Membrane ◽  
B Cells ◽  
Vas Deferens ◽  
Collecting Duct ◽  
Kidney Cortex ◽  
Apical Plasma Membrane ◽  
Intercalated Cells ◽  
A Cells ◽  
Basolateral Plasma Membrane ◽  
Intracellular Vesicles

Many vertebrate transporting epithelia contain characteristic ‘mitochondria-rich’ cells that express high levels of a vacuolar proton-pumping ATPase (H(+)V-ATPase) on their plasma membrane and on intracellular vesicles. In the kidney cortex, A-cells and B-cells are involved in proton secretion and bicarbonate secretion, respectively, in the distal nephron and collecting duct. A-cells have an H(+)V-ATPase on their apical plasma membrane and on intracellular vesicles, whereas the cellular location of the H(+)V-ATPase can be apical, basolateral, bipolar or diffuse in B-cells. The rat epididymis and vas deferens also contain a distinct population of H(+)V-ATPase-rich epithelial cells. These cells are involved in generating a low luminal pH, which is involved in sperm maturation and in maintaining sperm in an immotile state during their passage through the epididymis and vas deferens. In both kidney and reproductive tract, H(+)V-ATPase-rich cells have a high rate of apical membrane recycling. H(+)V-ATPase molecules are transported between the cell surface and the cytoplasm in vesicles that have a well-defined ‘coat’ structure formed of the peripheral V(1) subunits of the H(+)V-ATPase. In addition, we propose that B-type intercalated cells have a transcytotic pathway that enables them to shuttle H(+)V-ATPase molecules from apical to basolateral plasma membrane domains. This hypothesis is supported by data showing that A-cells and B-cells have different intracellular trafficking pathways for LGP120, a lysosomal glycoprotein. LGP120 was found both on the basolateral plasma membrane and in lysosomes in B-cells, whereas no LGP120 was detectable in the plasma membrane of A-cells. We propose that the ‘polarity reversal’ of the H(+)V-ATPase in B-intercalated cells is mediated by a physiologically regulated transcytotic pathway that may be similar to that existing in some other cell types.

Increased apical targeting of renal ENaC subunits and decreased expression of 11βHSD2 in HgCl2-induced nephrotic syndrome in rats

2006 ◽  
Vol 290 (3) ◽  
pp. F674-F687 ◽  
Author(s):  
Soo Wan Kim ◽  
Sophie de Seigneux ◽  
Martin C. Sassen ◽  
JongUn Lee ◽  
Jin Kim ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Sodium Excretion ◽  
Collecting Duct ◽  
Urinary Sodium Excretion ◽  
Brown Norway ◽  
Apical Plasma Membrane ◽  
Control Group ◽  
Sodium Retention ◽  
Outer Medulla ◽  
Outer Stripe

Nephrotic syndrome is often accompanied by sodium retention and generalized edema. We hypothesize that dysregulation of the epithelial sodium channel (ENaC) and/or of sodium (co)transporters may be responsible for the increased sodium retention associated with HgCl2-induced nephropathy. In addition, we examined the hypothesis that the expression of type 2 11β-hydroxysteroid dehydrogenase (11βHSD2) is reduced, contributing to the enhanced mineralocorticoid activity. Membranous nephropathy was induced in Brown Norway rats by repeated injections of HgCl2 (1 mg/kg sc), whereas the control group received only vehicle. After 13 days of treatment, the abundance of ENaC subunits, sodium (co)transporters, and 11βHSD2 in the kidney was examined by immunoblotting and immunohistochemistry. HgCl2 treatment induced marked proteinuria, hypoalbuminemia, decreased urinary sodium excretion, and ascites. The protein abundance of α-ENaC was increased in the cortex/outer stripe of outer medulla (OSOM) and inner stripe of the outer medulla (ISOM). The protein abundances of β-ENaC and γ-ENaC were decreased in the cortex/OSOM while increased in the ISOM. Immunoperoxidase microscopy demonstrated increased targeting of ENaC subunits to the apical plasma membrane in the distal convoluted tubule, connecting tubule, and cortical and medullary collecting duct segments. Moreover, 11βHSD2 abundance was decreased in cortex/OSOM and ISOM. The protein abundances of type 3 Na/H exchanger (NHE3), Na-K-2Cl cotransporter (NKCC2), and thiazide-sensitive Na-Cl cotransporter (NCC) were decreased. Moreover, the abundance of the α-1 subunit of the Na-K-ATPase was decreased in the cortex/OSOM and ISOM but remained unchanged in the inner medulla. These results suggest that increased apical targeting of ENaC subunits combined with diminished abundance of 11βHSD2 may contribute to sodium retention associated with HgCl2-induced nephrotic syndrome. The decreased abundance of NHE3, NKCC2, NCC, and Na-K-ATPase may play a compensatory role in promoting sodium excretion.

Localization and regulation of PKA-phosphorylated AQP2 in response to V2-receptor agonist/antagonist treatment

2000 ◽  
Vol 278 (1) ◽  
pp. F29-F42 ◽  
Author(s):  
Birgitte Mønster Christensen ◽  
Marina Zelenina ◽  
Anita Aperia ◽  
Søren Nielsen
Keyword(s):  
Plasma Membrane ◽  
Immunoelectron Microscopy ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Fold Increase ◽  
Apical Plasma Membrane ◽  
Complete Disappearance ◽  
Vasopressin Secretion ◽  
V2 Receptor ◽  
Intracellular Vesicles

Phosphorylation of Ser256, in a PKA consensus site, in AQP2 (p-AQP2) appears to be critically involved in the vasopressin-induced trafficking of AQP2. In the present study, affinity-purified antibodies that selectively recognize AQP2 phosphorylated at Ser256 were developed. These antibodies were used to determine 1) the subcellular localization of p-AQP2 in rat kidney and 2) changes in distribution and/or levels of p-AQP2 in response to [desamino-Cys1,d-Arg8]vasopressin (DDAVP) treatment or V2-receptor blockade. Immunoelectron microscopy revealed that p-AQP2 was localized in both the apical plasma membrane and in intracellular vesicles of collecting duct principal cells. Treatment of rats with V2-receptor antagonist for 30 min resulted in almost complete disappearance of p-AQP2 labeling of the apical plasma membrane with only marginal labeling of intracellular vesicles remaining. Immunoblotting confirmed a marked decrease in p-AQP2 levels. In control Brattleboro rats (BB), lacking vasopressin secretion, p-AQP2 labeling was almost exclusively present in intracellular vesicles. Treatment of BB rats with DDAVP for 2 h induced a 10-fold increase in p-AQP2 labeling of the apical plasma membrane. The overall abundance of p-AQP2, however, was not increased, as determined both by immunoelectron microscopy and immunoblotting. Consistent with this, 2 h of DDAVP treatment of normal rats also resulted in unchanged p-AQP2 levels. Thus the results demonstrate that AQP2 phosphorylated in Ser256 is present in the apical plasma membrane and in intracellular vesicles and that both the intracellular distribution/trafficking, as well as the abundance of p-AQP2, are regulated via V2 receptors by altering phosphorylation and/or dephosphorylation of Ser256in AQP2.

Immunocytochemical localization of pendrin in intercalated cell subtypes in rat and mouse kidney

2002 ◽  
Vol 283 (4) ◽  
pp. F744-F754 ◽  
Author(s):  
Young-Hee Kim ◽  
Tae-Hwan Kwon ◽  
Sebastian Frische ◽  
Jin Kim ◽  
C. Craig Tisher ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Immunoelectron Microscopy ◽  
Collecting Duct ◽  
Mouse Kidney ◽  
Laser Scanning Microscopy ◽  
Apical Plasma Membrane ◽  
Intercalated Cells ◽  
Type B ◽  
Connecting Tubule ◽  
Intracellular Vesicles

Recent studies have demonstrated that a novel anion exchanger, pendrin, is expressed in the apical domain of type B intercalated cells in the mammalian collecting duct. The purpose of this study was 1) to determine the expression and distribution of pendrin along the collecting duct and connecting tubule of mouse and rat kidney and establish whether pendrin is expressed in the non-A-non-B intercalated cells and 2) to determine the intracellular localization of pendrin in the different populations of intercalated cells by immunoelectron microscopy. A peptide-derived affinity-purified antibody was generated that specifically recognized pendrin in immunoblots of rat and mouse kidney. Immunohistochemistry and confocal laser scanning microscopy demonstrated the presence of pendrin in apical domains of all type B intercalated cells in mouse and rat connecting tubule and collecting duct. In addition, strong pendrin immunostaining was observed in non-A-non-B intercalated cells. There was no labeling of type A intercalated cells. Immunoelectron microscopy demonstrated that pendrin was located in the apical plasma membrane and intracellular vesicles of both type B intercalated cells and non-A-non-B cells; the latter was identified by the presence of H+-ATPase in the apical plasma membrane. The results of this study demonstrate that both pendrin and H+-ATPase are expressed in the apical plasma membrane of non-A-non-B intercalated cells, suggesting that these cells are capable of both HCO[Formula: see text] and proton secretion. Furthermore, the presence of pendrin in both the apical plasma membrane and the apical intracellular vesicles of type B and non-A-non-B intercalated cells suggests that HCO[Formula: see text] secretion may be regulated by trafficking of pendrin between the two membrane compartments.

Increased expression and apical targeting of renal ENaC subunits in puromycin aminonucleoside-induced nephrotic syndrome in rats

2004 ◽  
Vol 286 (5) ◽  
pp. F922-F935 ◽  
Author(s):  
Soo Wan Kim ◽  
Weidong Wang ◽  
Jakob Nielsen ◽  
Jeppe Praetorius ◽  
Tae-Hwan Kwon ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Plasma Membrane ◽  
Sodium Excretion ◽  
Collecting Duct ◽  
Apical Plasma Membrane ◽  
Control Group ◽  
Na Channel ◽  
Sodium Retention ◽  
Puromycin Aminonucleoside ◽  
Connecting Tubule

Nephrotic syndrome is often accompanied by sodium retention and generalized edema. However, the molecular basis for the decreased renal sodium excretion remains undefined. We hypothesized that epithelial Na channel (ENaC) subunit dysregulation may be responsible for the increased sodium retention. An experimental group of rats was treated with puromycin aminonucleoside (PAN; 180 mg/kg iv), whereas the control group received only vehicle. After 7 days, PAN treatment induced significant proteinuria, hypoalbuminemia, decreased urinary sodium excretion, and extensive ascites. The protein abundance of α-ENaC and β-ENaC was increased in the inner stripe of the outer medulla (ISOM) and in the inner medulla (IM) but was not altered in the cortex. γ-ENaC abundance was increased in the cortex, ISOM, and IM. Immunoperoxidase brightfield- and laser-scanning confocal fluorescence microscopy demonstrated increased targeting of α-ENaC, β-ENaC, and γ-ENaC subunits to the apical plasma membrane in the distal convoluted tubule (DCT2), connecting tubule, and cortical and medullary collecting duct segments. Immunoelectron microscopy further revealed an increased labeling of α-ENaC in the apical plasma membrane of cortical collecting duct principal cells of PAN-treated rats, indicating enhanced apical targeting of α-ENaC subunits. In contrast, the protein abundances of Na+/H+ exchanger type 3 (NHE3), Na+-K+-2Cl- cotransporter (BSC-1), and thiazide-sensitive Na+-Cl- cotransporter (TSC) were decreased. Moreover, the abundance of the α1-subunit of the Na-K-ATPase was decreased in the cortex and ISOM, but it remained unchanged in the IM. In conclusion, the increased or sustained expression of ENaC subunits combined with increased apical targeting in the DCT2, connecting tubule, and collecting duct are likely to play a role in the sodium retention associated with PAN-induced nephrotic syndrome. The decreased abundance of NHE3, BSC-1, TSC, and Na-K-ATPase may play a compensatory role to promote sodium excretion.

Redistribution of aquaporin-2 water channels induced by vasopressin in rat kidney inner medullary collecting duct

1995 ◽  
Vol 269 (3) ◽  
pp. C655-C664 ◽  
Author(s):  
D. Marples ◽  
M. A. Knepper ◽  
E. I. Christensen ◽  
S. Nielsen
Keyword(s):  
Plasma Membrane ◽  
Immunoelectron Microscopy ◽  
Collecting Duct ◽  
Water Channel ◽  
Fold Increase ◽  
Apical Plasma Membrane ◽  
Water Loading ◽  
Aquaporin 2 ◽  
Intracellular Vesicle ◽  
Intracellular Vesicles

Aquaporin-2 (AQP2) is the predominant vasopressin-regulated water channel of the renal collecting duct. We tested whether vasopressin induces translocation of AQP2 from intracellular vesicles into the apical plasma membrane. AQP2 was quantitated in plasma membrane and intracellular vesicle fractions prepared from the inner medulla of one kidney from each rat before or 20 min after intravenous 1-desamino-8-D-arginine vasopressin (DDAVP) treatment, using immunoblotting and densitometry. Contralateral kidneys were prepared for immunofluorescence and immunoelectron microscopy. Immunoblotting revealed that, compared with untreated controls, DDAVP treatment significantly increased the fraction of AQP2 protein associated with the plasma membrane fraction relative to intracellular vesicles. This increase averaged 2.0-fold in untreated rats and 2.9-fold in rats water loaded for 12 h. Water loading, presumably by suppressing circulating vasopressin levels, decreased the fraction of AQP2 associated with the plasma membrane by 55%, suggesting retrieval of AQP2 from the plasma membrane. In rats sequentially thirsted for 48 h to increase expression and then water loaded for 72 h to minimize plasma membrane labeling, DDAVP caused a 12-fold increase in the plasma membrane to intracellular vesicle labeling ratio. The accentuation of the DDAVP response seen after water loading is consistent with the observed increase in the fraction of AQP2 in the intracellular pool available for insertion. Immunofluorescence confirmed a marked DDAVP-induced redistribution of AQP2 from intracellular to plasma membrane domains. Furthermore, quantitative immunoelectron microscopy demonstrated a 3.4-fold increase in apical plasma membrane to intracellular vesicle labeling ratio. These results provide a direct in vivo demonstration of vasopressin-induced translocation of AQP2 into the apical plasma membrane.

Vasopressin regulates apical targeting of aquaporin-2 but not of UT1 urea transporter in renal collecting duct

1999 ◽  
Vol 276 (4) ◽  
pp. F559-F566 ◽  
Author(s):  
Takeaki Inoue ◽  
James Terris ◽  
Carolyn A. Ecelbarger ◽  
Chung-Lin Chou ◽  
Soren Nielsen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Membrane Fraction ◽  
Collecting Duct ◽  
Apical Plasma Membrane ◽  
Low Density ◽  
Brattleboro Rats ◽  
Urea Transporter ◽  
Short Term ◽  
Intracellular Vesicles

In the renal inner medullary collecting duct (IMCD), vasopressin regulates two key transporters, namely aquaporin-2 (AQP2) and the vasopressin-regulated urea transporter (VRUT). Both are present in intracellular vesicles as well as the apical plasma membrane. Short-term regulation of AQP2 has been demonstrated to occur by vasopressin-induced trafficking of AQP2-containing vesicles to the apical plasma membrane. Here, we have carried out studies to determine whether short-term regulation of VRUT occurs by a similar process. Cell surface labeling with NHS-LC-biotin in rat IMCD suspensions revealed that vasopressin causes a dose-dependent increase in the amount of AQP2 labeled at the cell surface, whereas VRUT labeled at the cell surface did not increase in response to vasopressin. Immunoperoxidase labeling of inner medullary thin sections from Brattleboro rats treated with 1-desamino-8-d-arginine vasopressin (DDAVP) for 20 min revealed dramatic translocation of AQP2 to the apical region of the cell, with no change in the cellular distribution of VRUT. In addition, differential centrifugation of inner medullary homogenates from Brattleboro rats treated with DDAVP for 60 min revealed a marked depletion of AQP2 from the low-density membrane fraction (enriched in intracellular vesicles) but did not alter the quantity of VRUT in this fraction. Finally, AQP2-containing vesicles immunoisolated from a low-density membrane fraction from renal inner medulla did not contain immunoreactive VRUT. Thus vasopressin-mediated regulation of AQP2, but not of VRUT, depends on regulated vesicular trafficking to the plasma membrane.

scholarly journals Association of Urinary Sodium Excretion and Left Ventricular Hypertrophy in People With Type 2 Diabetes Mellitus: A Cross-Sectional Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Jianfang Liu ◽  
Xiaoyu Yang ◽  
Peizhen Zhang ◽  
Dan Guo ◽  
Bingyan Xu ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Risk Factors ◽  
Sodium Excretion ◽  
Ventricular Hypertrophy ◽  
Sodium Intake ◽  
Urinary Sodium Excretion ◽  
Left Ventricular ◽  
Urinary Sodium ◽  
Cross Sectional

BackgroundIt has been well documented that left ventricular hypertrophy (LVH) is highly associated with the incidence of cardiovascular disease (CVD). Evidence indicated that high sodium intake was closely related with LVH in general population. However, information is not available regarding the association between urinary sodium excretion and LVH in patients with type 2 diabetes mellitus (T2DM). This study aimed to explore the association between urinary sodium excretion and LVH in patients with T2DM.MethodsThis cross-sectional analysis included baseline data from 1,556 individuals with T2DM enrolled in the NanFang Prospective Diabetes Study (NFPDS). Urinary sodium excretion levels were measured from 24-hour urine samples of inpatients and morning fasting urine samples of outpatients. Left ventricular dimensions were assessed by echocardiography. The associations between urinary sodium excretion and the risks of cardiovascular events, LVH and left ventricular mass index (LVMI) were examined using linear regression analysis, logistic regression and restricted cubic splines (RCS).ResultsUrinary sodium excretion levels were positively associated with cardiometabolic risk factors, including systolic blood pressure, body mass index, waist circumference and LVMI (All P&lt;0.001). Odds ratios of the highest quartile of urinary sodium excretion compared with the lowest quartile were 1.80 (95% CI, 1.28-2.54; P=0.001) for LVH and 1.77 (95% CI, 1.06-2.94; P=0.028) for CVD, after adjusted for demographics, lifestyle risk factors and cardiovascular risk factors. Multivariable-adjusted RCS analysis of the association between urinary sodium excretion and LVMI showed a significant association (P=0.001) and lacked evidence of a nonlinear association (P=0.406).ConclusionThis study indicated that high urinary sodium excretion was independently associated with increased risk of LVH and CVD in patients with T2DM, suggesting that control of sodium intake may be valuable for the prevention of diabetic cardiovascular complications.

Aquaporins in the Kidney: From Molecules to Medicine

2002 ◽  
Vol 82 (1) ◽  
pp. 205-244 ◽  
Author(s):  
Søren Nielsen ◽  
Jørgen Frøkiær ◽  
David Marples ◽  
Tae-Hwan Kwon ◽  
Peter Agre ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Water Balance ◽  
Diabetes Insipidus ◽  
Proximal Tubule ◽  
Water Retention ◽  
Collecting Duct ◽  
Apical Plasma Membrane ◽  
Urinary Concentration ◽  
Principal Cells ◽  
Intracellular Vesicles

The discovery of aquaporin-1 (AQP1) answered the long-standing biophysical question of how water specifically crosses biological membranes. In the kidney, at least seven aquaporins are expressed at distinct sites. AQP1 is extremely abundant in the proximal tubule and descending thin limb and is essential for urinary concentration. AQP2 is exclusively expressed in the principal cells of the connecting tubule and collecting duct and is the predominant vasopressin-regulated water channel. AQP3 and AQP4 are both present in the basolateral plasma membrane of collecting duct principal cells and represent exit pathways for water reabsorbed apically via AQP2. Studies in patients and transgenic mice have demonstrated that both AQP2 and AQP3 are essential for urinary concentration. Three additional aquaporins are present in the kidney. AQP6 is present in intracellular vesicles in collecting duct intercalated cells, and AQP8 is present intracellularly at low abundance in proximal tubules and collecting duct principal cells, but the physiological function of these two channels remains undefined. AQP7 is abundant in the brush border of proximal tubule cells and is likely to be involved in proximal tubule water reabsorption. Body water balance is tightly regulated by vasopressin, and multiple studies now have underscored the essential roles of AQP2 in this. Vasopressin regulates acutely the water permeability of the kidney collecting duct by trafficking of AQP2 from intracellular vesicles to the apical plasma membrane. The long-term adaptational changes in body water balance are controlled in part by regulated changes in AQP2 and AQP3 expression levels. Lack of functional AQP2 is seen in primary forms of diabetes insipidus, and reduced expression and targeting are seen in several diseases associated with urinary concentrating defects such as acquired nephrogenic diabetes insipidus, postobstructive polyuria, as well as acute and chronic renal failure. In contrast, in conditions with water retention such as severe congestive heart failure, pregnancy, and syndrome of inappropriate antidiuretic hormone secretion, both AQP2 expression levels and apical plasma membrane targetting are increased, suggesting a role for AQP2 in the development of water retention. Continued analysis of the aquaporins is providing detailed molecular insight into the fundamental physiology and pathophysiology of water balance and water balance disorders.

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