Increased expression but not targeting of ENaC in adrenalectomized rats with PAN-induced nephrotic syndrome

2006 ◽  
Vol 291 (1) ◽  
pp. F208-F217 ◽  
Author(s):  
Sophie de Seigneux ◽  
Soo Wan Kim ◽  
Sophie C. Hemmingsen ◽  
Jørgen Frøkiær ◽  
Søren Nielsen
Keyword(s):  
Nephrotic Syndrome ◽  
Subcellular Distribution ◽  
Sodium Retention ◽  
Puromycin Aminonucleoside ◽  
Sodium Transporters ◽  
Aquaporin 2 ◽  
Adrenalectomized Rats

Sodium retention is a hallmark of nephrotic syndrome (NS). Puromycin aminonucleoside (PAN)-induced NS is associated with high aldosterone levels and increased ENaC expression and apical targeting. However, the mechanisms associated with increased apical targeting of ENaC in NS remain undefined, and it is unclear whether this is secondary to high aldosterone levels and whether aldosterone and/or apical ENaC targeting are important for the development of sodium retention. This study aimed at uncovering 1) whether aldosterone is essential for sodium retention in PAN-induced NS, 2) whether ENaC expression or apical targeting is secondary to high aldosterone levels, and 3) the role of aldosterone in the dysregulation of sodium transporters in NS. Puromycin treatment of adrenalectomized (ADX) rats supplemented with dexamethasone induced sodium retention despite the absence of aldosterone. Immunocytochemical analyses revealed an absence of enhanced apical targeting of ENaC subunits in PAN-treated ADX (ADX-PAN) rats, with distribution of labeling similar to adrenalectomized dexamethasone-treated control rats (ADX). Moreover, ENaC subunit abundance was increased in ADX-PAN rats. The abundance of aquaporin-2 was unchanged, whereas apical targeting was enhanced. Key sodium transporters were downregulated as previously observed in nonadrenalectomized puromycin-treated rats (Kim SW, Wang W, Nielsen J, Praetorius J, Kwon TH, Knepper MA, Frøkiær J, and Nielsen S. Am J Physiol Renal Physiol 286: F922–F935, 2004), whereas the global expression of the α1-subunit of the Na-K-ATPase was unchanged. In conclusion, PAN treatment in the absence of aldosterone induced sodium retention, increased ENaC expression, but did not change the subcellular distribution of ENaC. This indicates that the previously observed enhanced apical targeting of ENaC in PAN-induced NS (Kim SW, Wang W, Nielsen J, Praetorius J, Kwon TH, Knepper MA, Frøkiær J, and Nielsen S. Am J Physiol Renal Physiol 286: F922–F935, 2004) is caused by aldosterone and that development of sodium retention can occur in the absence of aldosterone in NS.

Collecting Duct Na+/K+-ATPase Activity Is Correlated with Urinary Sodium Excretion in Rat Nephrotic Syndromes

2000 ◽  
Vol 11 (4) ◽  
pp. 604-615 ◽  
Author(s):  
GEORGES DESCHÊNES ◽  
ALAIN DOUCET
Keyword(s):  
Nephrotic Syndrome ◽  
Atpase Activity ◽  
Sodium Excretion ◽  
Collecting Duct ◽  
Urinary Sodium ◽  
Sodium Balance ◽  
Brattleboro Rats ◽  
Sodium Retention ◽  
Puromycin Aminonucleoside ◽  
Stimulation Of

Abstract. In puromycin aminonucleoside (PAN)-treated nephrotic rats, sodium retention is associated with increased Na+/K+-ATPase activity in the cortical collecting ducts (CCD). This study was undertaken to determine whether stimulation of Na+/K+-ATPase in the CCD is a feature of other experimental nephrotic syndromes, whether it might be responsible for renal sodium retention, and whether it is mediated by increased plasma vasopressin levels or activation of calcineurin. For this purpose, the time courses of urinary excretion of sodium and protein, sodium balance, ascites, and Na+/K+-ATPase activities in microdissected CCD were studied in rats with PAN or adriamycin nephrosis or HgCl2nephropathy. The role of vasopressin and calcineurin in PAN nephrosis were evaluated by measuring these parameters in Brattleboro rats and in rats treated with cyclosporin or tacrolimus. Despite different patterns of changes in urinary sodium and protein excretion in the three nephrotic syndrome models, there was a linear relationship between CCD Na+/K+-ATPase activities and sodium excretion in all three cases. The results also indicated that there was no correlation between proteinuria and sodium retention, but ascites was present only when proteinuria was associated with marked reduction of sodium excretion. Finally, the lack of vasopressin in Brattleboro rats or the inhibition of calcineurin by administration of either cyclosporin or tacrolimus did not prevent development of the nephrotic syndrome in PAN-treated rats or stimulation of CCD Na+/K+-ATPase. It is concluded that stimulation of Na+/K+-ATPase in the CCD of nephrotic rats might be responsible for sodium retention and that this phenomenon is independent of proteinuria and vasopressin and calcineurin activities.

Role of renal nerves in renal sodium retention of nephrotic syndrome

1989 ◽  
Vol 256 (5) ◽  
pp. F823-F829 ◽  
Author(s):  
P. J. Herman ◽  
L. L. Sawin ◽  
G. F. DiBona
Keyword(s):  
Nephrotic Syndrome ◽  
Renal Denervation ◽  
Sodium Content ◽  
Vehicle Control ◽  
Dietary Sodium ◽  
Sodium Balance ◽  
Renal Nerves ◽  
Sodium Retention ◽  
Edema Formation

To define the role of the renal nerves in the renal sodium retention of the nephrotic syndrome, experiments were conducted in rats given adriamycin to produce nephrotic syndrome. All rats developed proteinuria and hypoalbuminemia and exhibited edema formation. Adriamycin-injected nephrotic rats were subjected to bilateral renal denervation (ADRIADNX) or sham renal denervation (ADRIASHAM). Rats injected with adriamycin vehicle were subjected to bilateral renal denervation (DNX) or sham renal denervation (SHAM). Metabolic balance studies were carried out in all rats beginning on the 8th day after bilateral or sham renal denervation. Dietary sodium content was 210 meq/kg Na on days 8-12 and days 24-26 and was 10 meq/kg Na on days 13-23. Nephrotic rats demonstrated significantly greater overall (19 days) cumulative sodium balance than vehicle control rats, ADRIASHAM 8.47 +/- 0.81 vs. SHAM 5.74 +/- 0.34 meq Na, P less than 0.01. Bilateral renal denervation did not significantly affect overall cumulative sodium balance in the vehicle control rats, DNX 6.15 +/- 0.71 vs. SHAM 5.74 +/- 0.34 meq Na. However, bilateral renal denervation significantly decreased overall cumulative sodium balance in the nephrotic rats, ADRIADNX 6.59 +/- 0.56 vs. ADRIASHAM 8.47 +/- 0.81 meq Na, P less than 0.01. Results indicated that the increased renal sodium retention characteristic of nephrotic syndrome is dependent, in large part, on increased efferent renal sympathetic nerve activity.

scholarly journals Decreased Excretion of Urinary Exosomal Aquaporin-2 in a Puromycin Aminonucleoside-Induced Nephrotic Syndrome Model

2020 ◽  
Vol 21 (12) ◽  
pp. 4288
Author(s):  
Ahmed Abdeen ◽  
Hiroko Sonoda ◽  
Ayaha Kaito ◽  
Sayaka Oshikawa-Hori ◽  
Naruki Fujimoto ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Water Channel ◽  
Control Group ◽  
Puromycin Aminonucleoside ◽  
Renal Epithelial Cells ◽  
Aquaporin 2 ◽  
Single Intraperitoneal Injection ◽  
Marker Proteins ◽  
Experimental Rat Model ◽  
Renal Expression

Urinary exosomes, small extracellular vesicles present in urine, are secreted from all types of renal epithelial cells. Aquaporin-2 (AQP2), a vasopressin-regulated water channel protein, is known to be selectively excreted into the urine through exosomes (UE-AQP2), and its renal expression is decreased in nephrotic syndrome. However, it is still unclear whether excretion of UE-AQP2 is altered in nephrotic syndrome. In this study, we examined the excretion of UE-AQP2 in an experimental rat model of nephrotic syndrome induced by the administration of puromycin aminonucleoside (PAN). Rats were assigned to two groups: a control group administered saline and a PAN group given a single intraperitoneal injection of PAN (125 mg/kg) at day 0. The experiment was continued for 8 days, and samples of urine, blood, and tissue were collected on days 2, 5, and 8. The blood and urine parameters revealed that PAN induced nephrotic syndrome on days 5 and 8, and decreases in the excretion of UE-AQP2 were detected on days 2 through 8 in the PAN group. Immunohistochemistry showed that the renal expression of AQP2 was decreased on days 5 and 8. The release of exosomal marker proteins into the urine through UEs was decreased on day 5 and increased on day 8. These data suggest that UE-AQP2 is decreased in PAN-induced nephrotic syndrome and that this reflects its renal expression in the marked proteinuria phase after PAN treatment.

scholarly journals MO061PLASMINOGEN DEFIENCY DOES NOT PROTECT MICE FROM SODIUM RETENTION IN EXPERIMENTAL NEPHROTIC SYNDROME

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Mengyun Xiao ◽  
Bernhard Nikolaus Bohnert ◽  
Matthias Woern ◽  
Edward Plow ◽  
Tobias B Huber ◽  
...  
Keyword(s):  
Body Weight ◽  
Nephrotic Syndrome ◽  
Sodium Excretion ◽  
Serine Proteases ◽  
Essential Role ◽  
Urinary Sodium Excretion ◽  
Sodium Retention ◽  
Plasmin Activity ◽  
Edema Formation

Abstract Background and Aims Sodium retention and edema formation are the hallmarks of nephrotic syndrome and thought to be mediated by proteolytic activation of the epithelial sodium channel (ENaC) by aberrantly filtered serine proteases. Plasmin is highly abundant in nephrotic urine and has been proposed to be the principal serine protease responsible for ENaC activation in nephrotic syndrome. However, there is not enough evidence to demonstrate the essential role of plasmin in mediating sodium retention in an experimental nephrotic model. Method We investigated sodium retention and edema formation in a mouse model of nephrotic syndrome based on an inducible podocyte-specific podocin knockout (Bl6-Nphs2tm3.1Antc or Δipod * Tg(Nphs1-rtTA*3G8Jhm)* Tg(tetO-cre) 1Jaw). To generate an inducible podocin knockout with plasminogen deficient model (Nphs2Δipod * Plg-/-, hereafter referred to as Plg-/-), plasminogen deficient mice (Bl6-Plgtm1Jld or -/-) were intercrossed with Nphs2Δipod mice. Nephrotic syndrome was induced after oral doxycycline treatment for 14 days. Body weight, urinary protein, urinary sodium excretion, as well as urinary plasmin activity were daily determined 14 days after end of induction. To determine if sodium retention can be prevented by serine protease inhibitor aprotinin in Plg+/+ and Plg-/- mice after induction of nephrotic syndrome, sustained-release pellets containing aprotinin (2 mg per day) or placebo pellets were implanted to either Plg+/+ or Plg-/- mice (n=4 per group). Results Uninduced Plg+/+ (n=6-13) and Plg-/- mice (n=6-14) had normal kidney function and sodium handling. After end of doxycycline induction, there was no significant differencein proteinuria increase between Plg+/+ (from 2 ± 0 to 161 ± 16 mg/mg creatinine, p<0.05) and Plg-/- mice (from 9 ± 8 to 146 ± 44 mg/mg creatinine, p<0.05) leading to similar hypoalbuminemia. In urine samples from Plg+/+ mice, Western blot revealed urinary excretion of plasminogen/plasmin which was completely absent in Plg-/- mice. Accordingly, urinary plasmin activity was only detectable in Plg+/+ mice using a chromogenic substrate. After onset of proteinuria, amiloride-sensitive natriuresis was increased compared to uninduced mice indicating ENaC activation. While urinary sodium excretion dropped in both genotypes indicating sodium retention (from 193 ± 16 to 16 ± 6 µmol/24h in Plg+/+ mice, p<0.05; from 229 ± 11 to 26 ± 7 µmol/24h in Plg-/-mice, p<0.05). As a consequence, body weight maximum increased in both genotypes 21 ± 1% in Plg+/+ and 17 ± 2% in Plg-/- mice (p=0.616) and was paralleled by development of ascites. Urinary amidolytic activity were completely prevented by the presence of aprotinin, as well as sodium retention and ascites in both Plg+/+and Plg-/- mice. Conclusion This study shows for the first time that mice lacking urinary plasmin are not protected from ENaC-mediated sodium retention in experimental nephrotic syndrome, however it can be prevented by aprotinin. These findings point to an essential role of other hitherto unknown serine proteases excreted in nephrotic urine.

Role of Aldosterone in the Sodium Retention of Patients with Nephrotic Syndrome

1990 ◽  
Vol 10 (1) ◽  
pp. 44-48 ◽  
Author(s):  
Michael D. Shapiro ◽  
James Hasbargen ◽  
Johannes Hensen ◽  
Robert W. Schrier
Keyword(s):  
Nephrotic Syndrome ◽  
Sodium Retention

Epithelial sodium channel (ENaC) subunit mRNA and protein expression in rats with puromycin aminonucleoside-induced nephrotic syndrome

2003 ◽  
Vol 104 (4) ◽  
pp. 389-395 ◽  
Author(s):  
A. AUDIGÉ ◽  
Z.R. YU ◽  
B.M. FREY ◽  
D.E. UEHLINGER ◽  
F.J. FREY ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Sodium Channel ◽  
Mrna Expression ◽  
Sodium Excretion ◽  
Early Phase ◽  
Urinary Sodium Excretion ◽  
Urinary Sodium ◽  
Sodium Retention ◽  
Puromycin Aminonucleoside ◽  
Epithelial Sodium Channel Enac

In experimental nephrotic syndrome, urinary sodium excretion is decreased during the early phase of the disease. The molecular mechanism(s) leading to salt retention has not been completely elucidated. The rate-limiting constituent of collecting duct sodium transport is the epithelial sodium channel (ENaC). We examined the abundance of ENaC subunit mRNAs and proteins in puromycin aminonucleoside (PAN)-induced nephrotic syndrome. The time courses of urinary sodium excretion, plasma aldosterone concentration and proteinuria were studied in male Sprague–Dawley rats treated with a single dose of either PAN or vehicle. The relative amounts of αENaC, βENaC and γENaC mRNAs were determined in kidneys from these rats by real-time quantitative TaqMan PCR, and the amounts of proteins by Western blot. The kinetics of urinary sodium excretion and the appearance of proteinuria were comparable with those reported previously. Sodium retention occurred on days 2, 3 and 6 after PAN injection. A significant up-regulation of αENaC and βENaC mRNA abundance on days 1 and 2 preceded sodium retention on days 2 and 3. Conversely, down-regulation of αENaC, βENaC and γENaC mRNA expression on day 3 occurred in the presence of high aldosterone concentrations, and was followed by a return of sodium excretion to control values. The amounts of αENaC, βENaC and γENaC proteins were not increased during PAN-induced sodium retention. In conclusion, ENaC mRNA expression, especially αENaC, is increased in the very early phase of the experimental model of PAN-induced nephrotic syndrome in rats, but appears to escape from the regulation by aldosterone after day 3.

Role of aldosterone in sodium retention of pregnancy in the rat

1981 ◽  
Vol 240 (3) ◽  
pp. R175-R181 ◽  
Author(s):  
S. Churchill ◽  
H. H. Bengele ◽  
J. C. Melby ◽  
E. A. Alexander
Keyword(s):  
Critical Role ◽  
Plasma Aldosterone ◽  
Sodium Retention ◽  
Control Groups ◽  
Pregnant Rats ◽  
Plasma Aldosterone Concentration ◽  
Water Drinking ◽  
Serial Measurements ◽  
Adrenalectomized Rats

The purpose of this study was to test whether the absence or inhibition of aldosterone would alter the Na retention of pregnancy in the rat. We performed metabolic balance studies during the last 2 wk of the 3-wk rat pregnancy in the following four groups of saline-drinking rats: nonpregnant, sham adrenalectomized; pregnant, sham adrenalectomized; nonpregnant, adrenalectomized; and pregnant, adrenalectomized. Significant net Na retention was not found during the 2nd wk in any of the groups. During the final week, however, both pregnant groups retained between 8 and 11 meq Na more than their respective control groups. In addition, we measured plasma aldosterone concentration in these rats at term. The mineralocorticoid was not detectable in the nonpregnant adrenalectomized rats but was present in the pregnant adrenalectomized rats at a concentration of about 50% of that found in the pregnant sham-adrenalectomized rats. Serial measurements revealed that aldosterone was measurable by day 18 and nondetectable by 2 days postpartum in these pregnant adrenalectomized rats. Comparable balance studies were also performed in three groups of water-drinking rats: nonpregnant, pregnant, and pregnant rats that received large daily doses of spironolactone. During the 3rd wk both pregnant groups were in significant positive Na balance. Net Na retention for untreated pregnant rats was 8.4 meq and for the spironolactone treated, 6.9 meq, values that were not significantly different. We conclude that is is unlikely that aldosterone plays a critical role in the Na retention found during rat pregnancy.

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.

Sign in / Sign up

Export Citation Format

Share Document