Development of urinary concentrating capacity: role of aquaporin-2

1996 ◽  
Vol 271 (2) ◽  
pp. F461-F468 ◽  
Author(s):  
M. Yasui ◽  
D. Marples ◽  
R. Belusa ◽  
A. C. Eklof ◽  
G. Celsi ◽  
...  
Keyword(s):  
Single Injection ◽  
Collecting Duct ◽  
Water Channel ◽  
Urine Osmolality ◽  
Postnatal Life ◽  
Mrna Levels ◽  
Adult Rats ◽  
Protein Levels ◽  
Aquaporin 2 ◽  
Low Expression

The capacity to concentrate urine develops progressively during postnatal life in most mammalian species. Here we have examined whether low expression of the arginine vasopressin (AVP)-activated water channel aquaporin-2 (AQP-2) may be a limiting factor for the concentrating capacity in the infant rats. Urine osmolality in response to 24-h dehydration increased significantly from 10 to 40 days of age. The most rapid increase occurred during the weaning period, i.e., days 15-20. A similar developmental pattern was observed for AQP-2 mRNA levels in the renal medulla. AQP-2 protein levels also increased markedly from day 10 to 40. Immunohistochemistry revealed that AQP-2 was exclusively located in collecting duct principal cells both in infant and adult rats but that the signal was much weaker in infants. To further examine the relationship between urinary concentrating capacity and AQP-2 expression, we treated rats with a single injection of betamethasone, which is known to accelerate maturation in several organs. Twenty-four hours after treatment, there was an increase in urine osmolality, renal medullary AQP-2 mRNA, and AQP-2 protein levels in infant but not in adult rats. A single injection of a specific V2 agonist caused within 6 h significant increase of AQP-2 mRNA in both infant and adult. The expression of the mRNA of three other transporters involved in the concentrating process, medullary Na(+)-K(+)-ATPase alpha-subunit, Na-K-2Cl cotransporter, and epithelial chloride channel also increased during the weaning period and were upregulated by glucocorticoids. We conclude that there is a well-synchronized development of the many of the components that determine the concentrating capacity and that the low expression of AQP-2 is one of the limiting factors for low concentrating capacity in infants.

scholarly journals Aquaporin-2 in the immature rat: expression, regulation, and trafficking.

1997 ◽  
Vol 8 (10) ◽  
pp. 1502-1509 ◽  
Author(s):  
M Bonilla-Felix ◽  
W Jiang
Keyword(s):  
Water Channel ◽  
Urine Osmolality ◽  
Developmental Expression ◽  
Postnatal Life ◽  
Adult Rats ◽  
Immature Rat ◽  
Aquaporin 2 ◽  
Proportional Increase ◽  
Intracellular Vesicles ◽  
Ad Libitum Intake

The immature kidney is resistant to arginine vasopressin. To define the role of aquaporin-2 (AQP-2), the developmental expression of this water channel was studied in rats. AQP-2 levels were lower during early postnatal life, reaching maximal expression at 10 wk of age. Concurrently, urine osmolality increased from 242 +/- 60 to 1267 +/- 311 mosmol/kg. To study the regulation of AQP-2, immature and adult rats were kept on ad libitum intake or were water-deprived. Under normal conditions, AQP-2 levels in the immature rat were significantly lower (52.3 +/- 5.8%, P < 0.001) than in the adult. However, after dehydration the expression increased to adult levels. Interestingly, the increase in AQP-2 observed in the immature kidney was not accompanied by a proportional increase in urine osmolality. To rule out a potential alteration in AQP-2 trafficking, the transport of this water channel was investigated in a group of rats subjected to dehydration, treated with desmopressin acetate (dDAVP), or water loaded. Dehydration and dDAVP stimulated translocation of AQP-2 from intracellular vesicles to the plasma membrane, whereas water loading caused a shift of AQP-2 channels back to intracellular vesicles in both adult and immature animals. In summary, AQP-2 expression and trafficking in the immature kidney is appropriately stimulated by water deprivation and dDAVP. However, urine osmolality remained significantly decreased. From this study, it is concluded that although AQP-2 expression may play a role in the development of urine concentrating abilities, there still is a significant defect, yet to be defined, distal to AQP-2.

Downregulation of renal vasopressin V2 receptor and aquaporin-2 expression parallels age-associated defects in urine concentration

2004 ◽  
Vol 287 (4) ◽  
pp. F797-F805 ◽  
Author(s):  
Ying Tian ◽  
Ryota Serino ◽  
Joseph G. Verbalis
Keyword(s):  
Collecting Duct ◽  
Water Channel ◽  
Age Groups ◽  
Urine Osmolality ◽  
Brown Norway ◽  
Water Restriction ◽  
Water Excretion ◽  
F1 Hybrid ◽  
Young Rats ◽  
Aquaporin 2

Renal concentrating ability is known to be impaired with aging. The antidiuretic hormone AVP plays an important role in renal water excretion by regulating the membrane insertion and abundance of the water channel aquaporin-2 (AQP2); this effect is primarily mediated via the V2 subtype of the AVP receptor (V2R). This study evaluated the hypothesis that decreased renal sensitivity to AVP, with subsequent altered renal AQP2 expression, contributes to the reduced urinary concentrating ability with aging. Our results show that under baseline conditions, urine osmolality is significantly lower in aged Fischer 344 and Brown-Norway F1 hybrid (F344BN) rats despite equivalent plasma AVP concentrations as in young rats. Levels of kidney V2R mRNA expression and AQP2 abundances were also significantly decreased in aged F344BN rats, as was AQP2 immunostaining in collecting duct cells. In response to moderate water restriction, urine osmolality increased by significantly lesser amounts in aged F344BN rats compared with young rats despite similar increases in plasma AVP levels. Moderate water restriction induced equivalent relative increases in renal AQP2 abundances in all age groups but resulted in significantly lower abundances in total kidney AQP2 protein in aged compared with young F344BN rats. These results therefore demonstrate a functional impairment of renal concentrating ability in aged F344BN rats that is not due to impaired secretion of AVP but rather appears to be related to impaired responsiveness of the kidney to AVP that is secondary, at least in part, to a downregulation of renal V2R expression and AQP2 abundance.

scholarly journals Nephrogenic diabetes insipidus in mice caused by deleting COOH-terminal tail of aquaporin-2

2007 ◽  
Vol 292 (5) ◽  
pp. F1334-F1344 ◽  
Author(s):  
Peijun P. Shi ◽  
Xiao R. Cao ◽  
Jing Qu ◽  
Ken A. Volk ◽  
Patricia Kirby ◽  
...  
Keyword(s):  
Diabetes Insipidus ◽  
Hormonal Regulation ◽  
Nephrogenic Diabetes Insipidus ◽  
Mdck Cells ◽  
Collecting Duct ◽  
Phosphorylation Site ◽  
Water Channel ◽  
Urine Osmolality ◽  
Functional Expression ◽  
Aquaporin 2

In mammals, the hormonal regulation of water homeostasis is mediated by the aquaporin-2 water channel (Aqp2) of the collecting duct (CD). Vasopressin induces redistribution of Aqp2 from intracellular vesicles to the apical membrane of CD principal cells, accompanied by increased water permeability. Mutations of AQP2 gene in humans cause both recessive and dominant nephrogenic diabetes insipidus (NDI), a disease in which the kidney is unable to concentrate urine in response to vasopressin. In this study, we generated a line of mice with the distal COOH-terminal tail of the Aqp2 deleted ( Aqp2Δ 230), including the protein kinase A phosphorylation site (S256), but still retaining the putative apical localization signal (221–229) at the COOH-terminal. Mice heterozygous for the truncation appear normal. Homozygotes are viable to adulthood, with reduced urine concentrating capacity, increased urine output, decreased urine osmolality, and increased daily water consumption. Desmopressin increased urine osmolality in wild-type mice but had no effect on Aqp2Δ 230/Δ 230 mice. Kidneys from affected mice showed CD and pelvis dilatation and papillary atrophy. By immunohistochemical and immunoblot analyses using antibody against the NH2-terminal region of the protein Aqp2Δ 230/Δ 230 mice had a markedly reduced protein abundance. Expression of the truncated protein in MDCK cells was consistent with a small amount of functional expression but no stimulation. Thus we have generated a mouse model of NDI that may be useful in studying the physiology and potential therapy of this disease.

scholarly journals Aquaporin-2 downregulation in kidney medulla of aging rats is posttranscriptional and is abolished by water deprivation

2008 ◽  
Vol 294 (6) ◽  
pp. F1408-F1414 ◽  
Author(s):  
S. Combet ◽  
S. Gouraud ◽  
R. Gobin ◽  
V. Berthonaud ◽  
G. Geelen ◽  
...  
Keyword(s):  
Protein Expression ◽  
Water Deprivation ◽  
Collecting Duct ◽  
Mrna Level ◽  
Water Channel ◽  
Urine Osmolality ◽  
Osmotic Gradient ◽  
Kidney Medulla ◽  
Aquaporin 2 ◽  
Age Related

Aging kidney is associated in humans and rodents with polyuria and reduced urine concentrating ability. In senescent female WAG/Rij rats, this defect is independent of arginine-vasopressin (AVP)/V2 receptor/cAMP pathway. It has been attributed to underexpression and mistargeting of aquaporin-2 (AQP2) water channel in the inner medullary collecting duct (IMCD). We showed previously that dDAVP administration could partially correct this defect. Since AQP2 can also be regulated by AVP-independent pathways in water deprivation (WD), we investigated AQP2 and phosphorylated AQP2 (p-AQP2) regulation in thirsted adult (10 mo old) and senescent (30 mo old) female WAG/Rij rats. Following 2-day WD, urine flow rate decreased and urine osmolality increased in both groups. However, in agreement with significantly lower cortico-papillary osmotic gradient with aging, urine osmolality remained lower in senescent animals. WD induced sixfold increase of plasma AVP in all animals which, interestingly, did not result in higher papillary cAMP level. Following WD, AQP2 and p-AQP2 expression increased hugely in 10- and 30-mo-old rats and their mistargeting in old animals was corrected. Moreover, the age-related difference in AQP2 regulation was abolished after WD. To further investigate the mechanism of AQP2 underexpression with aging, AQP2 mRNA was quantified by real-time RT-PCR. In the outer medulla, preservation of AQP2 protein expression was achieved through increased AQP2 mRNA level in senescent rats. In the IMCD, no change in AQP2 mRNA was detected with aging but AQP2 protein expression was markedly lower in 30-mo-old animals. In conclusion, there is a posttranscriptional downregulation of AQP2 with aging, which is abolished by WD.

scholarly journals Decreased aquaporin-2 expression and apical plasma membrane delivery in kidney collecting ducts of polyuric hypercalcemic rats.

1998 ◽  
Vol 9 (12) ◽  
pp. 2181-2193 ◽  
Author(s):  
J H Earm ◽  
B M Christensen ◽  
J Frøkiaer ◽  
D Marples ◽  
J S Han ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Molecular Mechanisms ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Water Channel ◽  
Urine Osmolality ◽  
Apical Plasma Membrane ◽  
Similar Reduction ◽  
Aquaporin 2 ◽  
Urine Production

Hypercalcemia is frequently associated with a urinary concentrating defect and overt polyuria. The molecular mechanisms underlying this defect are poorly understood. Dysregulation of aquaporin-2 (AQP2), the predominant vasopressin-regulated water channel, is known to be associated with a range of congenital and acquired water balance disorders including nephrogenic diabetes insipidus and states of water retention. This study examines the effect of hypercalcemia on the expression of AQP2 in rat kidney. Rats were treated orally for 7 d with dihydrotachysterol, which produced significant hypercalcemia with a 15 +/- 2% increase in plasma calcium concentration. Immunoblotting and densitometry of membrane fractions revealed a significant decrease in AQP2 expression in kidney inner medulla of hypercalcemic rats to 45.7 +/- 6.8% (n = 11) of control levels (100 +/- 12%, n = 9). A similar reduction in AQP2 expression was seen in cortex (36.9 +/- 4.2% of control levels, n = 6). Urine production increased in parallel, from 11.3 +/- 1.4 to a maximum of 25.3 +/- 1.9 ml/d (P < 0.01), whereas urine osmolality decreased from 2007 +/- 186 mosmol/kg x H2O to 925 +/- 103 mosmol/kg x H2O (P < 0.01). Immunocytochemistry confirmed a decrease in total AQP2 labeling of collecting duct principal cells from kidneys of hypercalcemic rats, and reduced apical labeling. Immunoelectron microscopy demonstrated a significant reduction in AQP2 labeling of the apical plasma membrane, consistent with the development of polyuria. In summary, the results strongly suggest that AQP2 downregulation and reduced apical plasma membrane delivery of AQP2 play important roles in the development of polyuria in association with hypercalcemia.

Importance of aquaporin-2 expression levels in genotype -phenotype studies in nephrogenic diabetes insipidus

2000 ◽  
Vol 279 (4) ◽  
pp. F778-F784 ◽  
Author(s):  
E. J. Kamsteeg ◽  
P. M. T. Deen
Keyword(s):  
Diabetes Insipidus ◽  
Nephrogenic Diabetes Insipidus ◽  
Competitive Inhibition ◽  
Water Channel ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Expression Levels ◽  
Protein Levels ◽  
Aquaporin 2 ◽  
Low Expression

Aquaporin-2 (AQP2) water channel mutations cause autosomal recessive and dominant nephrogenic diabetes insipidus. Expressed in oocytes, a mutant in dominant (AQP2-E258K), but not in recessive (AQP2-R187C), NDI conferred a specific dominant-negative effect (DNE) on wild-type (WT) AQP2 water permeability ( P f) but only at low expression levels. Here, we determined the cell biological basis for this requirement. Injection of different amounts of WT-AQP2 cRNAs revealed that a correlation between AQP2 protein levels and P f is only obtained with low expression levels. In coexpression studies of WT- and mutant AQP2 proteins, higher expression levels of AQP2-R187C also exerted a DNE on the P f of WT-AQP2. Immunoblot and immunoprecipitation analysis revealed that this DNE was caused by competitive inhibition of WT-AQP2 expression and escape of AQP2-R187C from the endoplasmic reticulum, resulting in oligomerization with WT-AQP2. Because many disease-related mutants of multimeric renal membrane transporters and channels are likely to be identified, our data provide important information for studying the effects of such mutants on the activity of WT transporters and channels in oocytes.

Fasting downregulates renal water channel AQP2 and causes polyuria

2001 ◽  
Vol 280 (3) ◽  
pp. F513-F523 ◽  
Author(s):  
Hassane Amlal ◽  
Qian Chen ◽  
Khalid Habo ◽  
Zhaohui Wang ◽  
Manoocher Soleimani
Keyword(s):  
Collecting Duct ◽  
Water Channel ◽  
Urine Volume ◽  
Urine Osmolality ◽  
Immunoblot Analysis ◽  
Recovery Phase ◽  
Northern Hybridization ◽  
Mrna Levels ◽  
Medullary Collecting Duct ◽  
Urinary Concentrating Ability

Starvation causes impairment in the urinary concentrating ability. The mechanism of this defect, however, remains unknown. We tested the possibility that food deprivation might affect the expression and activity of aquaporins (AQP1, 2), thereby impairing renal water reabsorption in the kidney. Rats fasted for 24 h exhibited severe polyuria (urine volume increased from 11 before fasting to 29 ml/24 h after fasting, P < 0.0001) along with failure to concentrate their urine (urine osmolality decreased from 1,485 before fasting to 495 mosmol/kgH2O after fasting, P < 0.0001). Refeeding for 24 h returned the urinary concentrating ability back to normal. Northern hybridization and immunoblot analysis demonstrated that fasting was associated with a decrease in AQP2 protein (−80%, P ≤ 0.002) and mRNA levels (−69%, P ≤ 0.003) in the outer medulla. In the cortex, fasting decreased AQP2 protein abundance by 60% ( P ≤ 0.004) but did not alter its mRNA expression. During the recovery phase, AQP2 expression returned to normal level in both tissues. In the inner medulla, the expression of AQP2 was not altered in fasting, but was increased significantly at both protein ( ± 92%) and mRNA ( ± 43%) levels during the recovery from fasting. The proximal nephron water channel (AQP1) was not affected in response to fasting or recovery from fasting. We conclude that 1) fasting impairs the urinary concentrating ability in rats, and 2) the renal water-handling defect in fasting results specifically from the downregulation of AQP2 in the cortical and outer medullary collecting duct.

Functional and molecular characterization of NHE3 expression during ontogeny in rat jejunal epithelium

1997 ◽  
Vol 273 (6) ◽  
pp. C1937-C1946 ◽  
Author(s):  
James F. Collins ◽  
Hua Xu ◽  
Pawel R. Kiela ◽  
Jiamin Zeng ◽  
Fayez K. Ghishan
Keyword(s):  
Northern Blot ◽  
Polyclonal Antibodies ◽  
Membrane Vesicle ◽  
Age Groups ◽  
Fold Increase ◽  
Jejunal Mucosa ◽  
Mrna Levels ◽  
Adult Rats ◽  
Intestinal Brush Border Membrane ◽  
Protein Levels

Ontogenic changes occur in intestinal brush-border membrane vesicle (BBMV) Na+/H+exchange activity. The present studies were designed to investigate ontogenic changes in Na+/H+exchanger (NHE) isoform 3 in rat jejunum. pH-dependent Na+ uptake was assayed in four age groups of rats in the presence of 0, 50, or 800 μM HOE-694, a specific NHE inhibitor with differential sensitivities for NHE2 [inhibition constant ( K i) = 5 μM in PS120 fibroblasts] and NHE3 ( K i = 650 μM). Results showed that NHE2 and NHE3 contribute to basal BBMV uptake at all ages. Uptake levels were highest in 6-wk-old rats, lower in adult rats, and lowest in 2-wk-old (suckling) and 3-wk-old (weanling) rats. NHE3 contribution ranged from 92% at 6 wk of age to 59% at 2 and 3 wk of age. NHE3 inhibition by 800 μM HOE-694 was 38–45%. Statistical analysis showed that HOE-694 had a significant effect at both concentrations at all ages and that differences were present between all ages except 2- and 3-wk rats (at all HOE-694 concentrations). Northern blot analyses of jejunal mucosa showed lowest NHE3 mRNA levels in 2-wk animals and higher levels in all other age groups. Polyclonal antibodies were developed against an NHE3 COOH-terminal fusion protein, and antiserum was characterized with NHE3-transfected PS120 cells and by immunohistochemistry. Western blot analyses showed lowest protein levels in 2-wk animals and higher levels in the other ages. Suckling rats were subcutaneously injected with methylprednisone (MP) for 2 days and killed 1 day later. Northern blot analyses showed a twofold increase in NHE3 mRNA expression with MP treatment. Immunoblot analyses showed a 2.5-fold increase in NHE3 immunoreactive protein levels with MP injection. Overall, these data suggest that NHE3 is regulated during ontogeny and that ontogenic changes are most apparent around the time of weaning. Furthermore, the data suggest that NHE3 is regulated at transcriptional and posttranscriptional levels during mammalian intestinal development.

Downregulation of aquaporin-2 and -3 in aging kidney is independent of V2 vasopressin receptor

2000 ◽  
Vol 279 (1) ◽  
pp. F144-F152 ◽  
Author(s):  
L. Preisser ◽  
L. Teillet ◽  
S. Aliotti ◽  
R. Gobin ◽  
V. Berthonaud ◽  
...  
Keyword(s):  
Binding Sites ◽  
Collecting Duct ◽  
Urinary Volume ◽  
Adult Rats ◽  
Camp Content ◽  
Aquaporin 2 ◽  
Age Related ◽  
Medullary Collecting Duct ◽  
V2 Vasopressin Receptor ◽  
Aging Kidney

The mechanisms underlying age-related polyuria were investigated in 10- and 30-mo-old female WAG/Rij rats. Urinary volume and osmolality were 3.9 ± 0.3 ml/24 h and 2,511 ± 54 mosmol/kgH2O in adult rats and 12.8 ± 0.8 ml/24 h and 1,042 ± 44 mosmol/kgH2O in senescent animals. Vasopressin V2 receptor mRNA did not significantly differ between 10 and 30 mo, and [3H]vasopressin binding sites in membrane papilla were reduced by 30%. The cAMP content of the papilla was unchanged with age, whereas papillary osmolality was significantly lowered in senescent animals. The expression of aquaporin-1 (AQP1) and -4 was mostly unaltered from 10 to 30 mo. In contrast, aquaporin-2 (AQP2) and -3 (AQP3) expression was downregulated by 80 and 50%, respectively, and AQP2 was markedly redistributed into the intracellular compartment, in inner medulla of senescent animals, but not in renal cortex. These results indicate that age-related polyuria is associated with a downregulation of AQP2 and AQP3 expression in the medullary collecting duct, which is independent of vasopressin-mediated cAMP accumulation.

scholarly journals Lixivaptan, a New Generation Diuretic, Counteracts Vasopressin-Induced Aquaporin-2 Trafficking and Function in Renal Collecting Duct Cells

2019 ◽  
Vol 21 (1) ◽  
pp. 183
Author(s):  
Annarita Di Mise ◽  
Maria Venneri ◽  
Marianna Ranieri ◽  
Mariangela Centrone ◽  
Lorenzo Pellegrini ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Water Channel ◽  
Plasma Osmolality ◽  
Kinetic Measurements ◽  
Aquaporin 2 ◽  
Plasma Vasopressin ◽  
Duct Cells ◽  
Collecting Duct Cells ◽  
Renal Collecting Duct ◽  
New Generation

Vasopressin V2 receptor (V2R) antagonists (vaptans) are a new generation of diuretics. Compared with classical diuretics, vaptans promote the excretion of retained body water in disorders in which plasma vasopressin concentrations are inappropriately high for any given plasma osmolality. Under these conditions, an aquaretic drug would be preferable over a conventional diuretic. The clinical efficacy of vaptans is in principle due to impaired vasopressin-regulated water reabsorption via the water channel aquaporin-2 (AQP2). Here, the effect of lixivaptan—a novel selective V2R antagonist—on the vasopressin-cAMP/PKA signaling cascade was investigated in mouse renal collecting duct cells expressing AQP2 (MCD4) and the human V2R. Compared to tolvaptan—a selective V2R antagonist indicated for the treatment of clinically significant hypervolemic and euvolemic hyponatremia—lixivaptan has been predicted to be less likely to cause liver injury. In MCD4 cells, clinically relevant concentrations of lixivaptan (100 nM for 1 h) prevented dDAVP-induced increase of cytosolic cAMP levels and AQP2 phosphorylation at ser-256. Consistent with this finding, real-time fluorescence kinetic measurements demonstrated that lixivaptan prevented dDAVP-induced increase in osmotic water permeability. These data represent the first detailed demonstration of the central role of AQP2 blockade in the aquaretic effect of lixivaptan and suggest that lixivaptan has the potential to become a safe and effective therapy for the treatment of disorders characterized by high plasma vasopressin concentrations and water retention.

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