Urinary excretion of aquaporin-2 water channel protein in human and rat.

Previous studies by the authors demonstrated that the response of urinary aquaporin-2 (AQP2) excretion to dDAVP (deamino-8-D-arginine vasopressin) infusion is an index of vasopressin action on the kidney (N Engl J Med 332: 1540-1545, 1995). In the study presented here, the characteristics of urinary excretion of AQP2 were examined further. An RIA suitable for AQP2 in the urine was established. Relatively high concentrations of detergent and bovine serum albumin in the RIA buffer allowed analysis of urine samples with a wide range of concentrations and increased the sensitivity of the assay. AQP2 in the urine existed as a high molecular weight form of approximately 190 kD by HPLC analysis. The mean urinary AQP2 concentration corrected for creatinine in spot urine samples of healthy subjects who voided in the morning was 1081 +/- 699 fmol/mg creatinine (mean +/- SD, n = 208). The amount of daily excretion of AQP2 in the urine was the same in men and women. Urinary AQP2 content was not affected by age of the subjects and showed a positive correlation with urine osmolality. Finally, the fraction of AQP2 excreted in the urine compared with whole kidney content was determined in the rat. Approximately 3% of AQP2 in the kidney was excreted daily, and this fraction did not change when rats were dehydrated for 3 d. These data demonstrate the necessity of establishing well-designed protocols to use urinary AQP2 as a marker of AVP action.

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Urinary Excretion of Hydroxyproline after Fractures

Clinical Chemistry ◽

10.1093/clinchem/16.10.853 ◽

1970 ◽

Vol 16 (10) ◽

pp. 853-855

Author(s):

Mala Herzberg ◽

Z Oberman ◽

O Khermosh ◽

S L Weissman

Keyword(s):

Low Back Pain ◽

Back Pain ◽

Urinary Excretion ◽

Collagen Metabolism ◽

Bone Collagen ◽

Control Group ◽

Low Back ◽

Multiple Fractures ◽

Daily Excretion ◽

The Mean

Abstract Urinary excretion of hydroxyproline was measured in 12 cases of multiple fractures as an index of bone collagen metabolism. Measurements were made for 10 consecutive days after injury; 10 patients with low back pain served as the control group. With three exceptions, the mean daily excretion of hydroxyproline and the day-to-day variations were within the same range in the group with multiple fractures as in the control group.

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

AJP Renal Physiology ◽

10.1152/ajprenal.00403.2003 ◽

2004 ◽

Vol 287 (4) ◽

pp. F797-F805 ◽

Cited By ~ 37

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.

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Urinary excretion of the water channel aquaporin 2 correlated with the pharmacological effect of tolvaptan in cirrhotic patients with ascites

Journal of Gastroenterology ◽

10.1007/s00535-015-1143-3 ◽

2015 ◽

Vol 51 (6) ◽

pp. 620-627 ◽

Cited By ~ 21

Author(s):

Hiroyuki Nakanishi ◽

Masayuki Kurosaki ◽

Takanori Hosokawa ◽

Yuka Takahashi ◽

Jun Itakura ◽

...

Keyword(s):

Urinary Excretion ◽

Water Channel ◽

Pharmacological Effect ◽

Aquaporin 2 ◽

Cirrhotic Patients

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Purine derivatives in spot urine samples and plasma of sheep: a possible index of microbial protein supply

Proceedings of the British Society of Animal Production (1972) ◽

10.1017/s0308229600023369 ◽

1993 ◽

Vol 1993 ◽

pp. 5-5 ◽

Cited By ~ 1

Author(s):

X. B. Chen ◽

Adriana T. Mejia ◽

D. J. Kyle ◽

E. R. Ørskov

Keyword(s):

Urinary Excretion ◽

Feed Intake ◽

Urine Samples ◽

Plasma Samples ◽

Microbial Protein ◽

Purine Derivatives ◽

Feeding Regime ◽

Spot Urine ◽

Alternative Index ◽

Protein Supply

In ruminants, daily urinary excretion of purine derivatives (PD) reflects the absorption of microbial purines and can be used as an index of microbial protein supply (Chen, Ørskov and Hovell, 1991). The application could be extended to farm conditions if measurements based on spot urine samples or plasma could serve as an alternative index. The objective of this study was to examine whether PD concentrations in spot urine or plasma samples vary diurnally during a given feeding regime and if they reflect differences in daily PD excretion induced by varying feed intake.

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Urinary Aquaporin 2 and Calciuria Correlate with the Severity of Enuresis in Children

Journal of the American Society of Nephrology ◽

10.1681/asn.v11101873 ◽

2000 ◽

Vol 11 (10) ◽

pp. 1873-1881

Author(s):

GIOVANNA VALENTI ◽

ANTONIA LAERA ◽

GIUSEPPE PACE ◽

GABRIELLA ACETO ◽

MARIA L. LOSPALLUTI ◽

...

Keyword(s):

Urinary Excretion ◽

Urine Sample ◽

Western Blotting ◽

Nocturnal Enuresis ◽

Urine Samples ◽

Healthy Children ◽

Nocturnal Polyuria ◽

Aquaporin 2 ◽

Threefold Increase ◽

Absorptive Hypercalciuria

Abstract. This study examined the hypothesis that nocturnal enuresis might be paralleled by aquaporin 2 (AQP2) urinary excretion. Eighty children who experienced nocturnal enuresis were studied and compared with 9 healthy children. The 24-h urine samples were divided into two portions: night collections and day collections. Creatinine equivalents of urine samples from each patient were analyzed by Western blotting. AQP2 levels were semiquantified by densitometric scanning and reported as a ratio between the intensity of the signal in the day urine sample versus the night urine sample (D/N AQP2 ratio). The D/N AQP2 ratio was 0.59 ± 0.11 (n = 9) in healthy children and increased to 1.27 ± 0.24 (n = 10) in a subpopulation of enuretic children who had low nocturnal vasopressin levels. In enuretic children who displayed hypercalciuria and had normal vasopressin levels, the D/N AQP2 ratio was 1.05 ± 0.27 (n = 8). These data indicate that reduced secretion of vasopressin and absorptive hypercalciuria are independently associated with an approximately twofold increase in the urinary D/N AQP2 ratio. When low nocturnal vasopressin levels were associated with hypercalciuria, a nearly threefold increase in the D/N AQP2 ratio was observed (1.67 ± 0.41, n = 11). In addition, in all enuretic patients tested, the urinary D/N AQP2 ratio correlates perfectly with the severity of the disorder (nocturnal polyuria). The findings reported in this article indicate that urinary AQP2 correlates with the severity of enuresis in children.

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Urinary aquaporin-2 excretion in nocturnal enuresis

Acta Endocrinologica ◽

10.1530/eje.0.1450435 ◽

2001 ◽

pp. 435-438 ◽

Cited By ~ 12

Author(s):

G Radetti ◽

C Paganini ◽

F Rigon ◽

L Gentili ◽

U Gebert ◽

...

Keyword(s):

Urinary Excretion ◽

Nocturnal Enuresis ◽

Plasma Osmolality ◽

Urine Osmolality ◽

Posterior Lobe ◽

Healthy Children ◽

Serum Concentrations ◽

Aquaporin 2 ◽

Magnetic Resonance Imaging Mri ◽

Study Participants

OBJECTIVE: To evaluate the role of the arginine vasopressin (AVP)-aquaporin-2 (AQP-2) axis in the pathogenesis of nocturnal enuresis. STUDY PARTICIPANTS: Twelve children (seven male and five female), aged 11.6+/-4.3 (6.7-15.6) years, suffering from primary monosymptomatic nocturnal enuresis and 12 healthy children, matched for sex and age. Enuretic children were further subdivided into responders and non-responders to treatment with 1-desamino-8-d-AVP (DDAVP). METHODS: Serum concentrations of AVP, and plasma and urine osmolality were measured at night (0100, 0400 and 0700 h), together with nocturnal urinary excretion of AQP-2 (2000-0800 h). Magnetic resonance imaging (MRI) of the pituitary gland was carried out to evaluate the amount of AVP stored in the posthypophysis. RESULTS: Mean AVP serum concentrations were similar in patients and controls. Urinary AQP-2 was also similar in patients and controls, but responders had a significantly lower level of AQP-2 than non-responders (P<0.005). Plasma osmolality was greater in patients than in controls (P<0.001), whereas urinary osmolality was similar in both groups. No difference in the ratio of the signal intensity of the posterior lobe of the hypophysis to that of the pons (AVP content) was found between patients and controls or between responders and non-responders. CONCLUSION: A decreased urinary excretion of AQP-2 is associated with, and seems to have a role in, nocturnal enuresis, at least in some children, and this could also explain why only some of them respond to DDAVP treatment.

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Urinary excretion of aquaporin-2 in humans: a potential marker of collecting duct responsiveness to vasopressin.

Journal of the American Society of Nephrology ◽

10.1681/asn.v73403 ◽

1996 ◽

Vol 7 (3) ◽

pp. 403-409 ◽

Cited By ~ 1

Author(s):

S Elliot ◽

P Goldsmith ◽

M Knepper ◽

M Haughey ◽

B Olson

Keyword(s):

Urinary Excretion ◽

Collecting Duct ◽

Water Channel ◽

Apical Plasma Membrane ◽

Hydration Status ◽

Standard Curve ◽

Western Analysis ◽

Aquaporin 2 ◽

Potential Marker ◽

Collecting Ducts

The vasopressin-sensitive water channel (aquaporin 2; AQP-2) mediates water transport across the apical plasma membrane of the renal collecting ducts and is excreted in human urine. This study presents the hypothesis that measurements of the AQP-2 excretion rate might be used as a marker of collecting-duct responsiveness to vasopressin, and therefore could be useful in the clinical evaluation of various water-balance disorders. This study presents information about the development of an antibody to human AQP-2, and measures the urinary excretion of AQP-2 by quantitative Western analysis. A standard curve of band densities was generated by using known quantities of the modified immunizing peptide to derive the amount of AQP-2 contained in aliquots of urine. AQP-2 urinary excretion changed with short-term alterations in hydration status produced either by water loading (76% decrease, P < 0.01) or by 3% sodium chloride (760% increase, P < 0.01). Steady-state 24-h urinary excretion of AQP-2 was 43 +/- 10 nmol/24 h (or 28.5 +/- 6.9 pmol/mg creatinine), and 20 +/- 6 nmol/24 h (or 18.3 +/- 7.9 pmol/mg creatinine) in men and women, respectively. Therefore, urinary AQP-2 excretion can be quantified by using Western analysis, and may serve as a marker of collecting-duct responsiveness to vasopressin in different physiologic settings.

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Development of urinary concentrating capacity: role of aquaporin-2

AJP Renal Physiology ◽

10.1152/ajprenal.1996.271.2.f461 ◽

1996 ◽

Vol 271 (2) ◽

pp. F461-F468 ◽

Cited By ~ 19

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.

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Concanavalin-A-mediated thymocyte agglutination: a model for a quantitative study of cell adhesion

Journal of Cell Science ◽

10.1242/jcs.56.1.21 ◽

1982 ◽

Vol 56 (1) ◽

pp. 21-48

Author(s):

C. Capo ◽

F. Garrouste ◽

A.M. Benoliel ◽

P. Bongrand ◽

A. Ryter ◽

...

Keyword(s):

Cell Adhesion ◽

Quantitative Study ◽

Concanavalin A ◽

Cell Metabolism ◽

Quantitative Model ◽

Experimental Conditions ◽

Wide Range ◽

Binding Probability ◽

The Mean ◽

High Concentrations

This report describes a quantitative study of the agglutination of rat thymocytes with concanavalin A (ConA). The probability that two ConA-coated cells remain bound after centrifugation was determined over a wide range of lectin concentrations. The minimal force required to separate agglutinated cells and the number of ConA molecules bound per cell were measured in similar experimental conditions. Agglutinated cells were examined by electron microscopy to estimate the area of membrane involved in adhesion. The dependence of agglutination on cell metabolism was studied: cold (4 degrees C), sodium azide (15 mM) and cytochalasin B (10 micrograms/ml) inhibited thymocyte adhesion. The importance of lateral movements of ConA molecules was assayed by measuring the adhesion of ConA-coated glutaraldehyde-fixed thymocytes to untreated cells: substantial binding occurred, but at a reduced level relative to untreated cells. A mathematical analysis of experimental data allowed the following conclusions. (1) At least 10(3) ConA bonds were involved in cross-linking two bound cells, which required the lectin molecules to be concentrated in the binding area, at least when low ConA concentrations (0.5 microgram/ml or less) were used. (2) The dependence of the binding probability on lectin concentration was fairly linear when the latter was small, which implied that the limiting step in cell-cell adhesion was the formation of a bond between a single ConA molecule and a ligand on the other cell. (3) The mean intercellular-contact time for the formation of this first bond was about 10 S for high concentrations of ligand (8 micrograms/ml). It was possible to fit the above data into a physically consistent quantitative model of cell adhesion.

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