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Objective: The aim of the work described here was to determine the feasibility of using a novel biopsy needle detection technique that achieves high sensitivity and specificity in a trade-off of resolution, detectability and depth of imaging., Methods: The proposed needle detection method consists of a model-based image analysis, temporal needle projection and needle library matching: (i) Image analysis was formulated under the signal decomposition framework; (ii) temporal projection converted the time-resolved needle dynamics into a single image of the desired needle; and (iii) the enhanced needle structure was spatially refined by matching a long, straight linear object in the needle library. The efficacy was examined with respect to different needle visibility., Results: Our method effectively eliminated confounding effects of the background tissue artifacts more robustly than conventional methods, thus improving needle visibility even with the low contrast between the needle and tissue. The improvement in needle structure further resulted in an improvement in estimation performance for the trajectory angle and tip position., Conclusion: Our three-step needle detection method can reliably detect needle position without the need for external devices, increasing the needle conspicuity and reducing motion sensitivity., Competing Interests: Conflict of interest The authors declare no competing interests., (Copyright © 2023 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

The prevalence of kidney diseases has been increasing worldwide due to the aging population and has results in an increased socioeconomic burden as well as increased morbidity and mortality. A deep understanding of the mechanisms underlying the physiological regulation of the kidney and the pathogenesis of related diseases can help identify potential therapeutic targets. The farnesoid X receptor (FXR, NR1H4) is a primary nuclear bile acid receptor that transcriptionally regulates bile acid homeostasis as well as glucose and lipid metabolism in multiple tissues. The roles of FXR in tissues other than hepatic and intestinal tissues are poorly understood. In studies over the past decade, FXR has been demonstrated to have a protective effect against kidney diseases through its anti-inflammatory and antifibrotic effects; it also plays roles in glucose and lipid metabolism in the kidney. In this review, we discuss the physiological role of FXR in the kidney and its pathophysiological roles in various kidney diseases, including acute kidney injury and chronic kidney diseases, diabetic nephropathy, and kidney fibrosis. Therefore, the regulatory mechanisms involving nuclear receptors, such as FXR, in the physiology and pathophysiology of the kidney and the development of agonists and antagonists for modulating FXR expression and activation should be elucidated to identify therapeutic targets for the treatment of kidney diseases., (© 2023. The Author(s).)

Background: Although anastomosing hemangiomas are very rare and benign vascular neoplasms, these tumors are more common among patients with end-stage kidney disease. Incidental finding of these tumors in the kidney or adrenal gland has been reported. Herein, we describe a case in which an anastomosing hemangioma was misdiagnosed as a renal cell carcinoma before kidney transplant., Case Presentation: A 35-year-old woman with lupus nephritis was admitted to our emergency department for suspected uremic symptoms of nausea and general weakness. She had received hemodialysis due to end-stage kidney disease, and a living-donor kidney transplantation from her father was planned. On pre-operative contrast-enhanced computed tomography and magnetic resonance imaging, a 1.7 cm renal cell carcinoma was observed in the right kidney. On staining after radical nephrectomy, irregularly shaped vascular spaces of various sizes were observed, with these spaces having an anastomosing pattern. As the findings of the anastomosing hemangioma are similar to those of a renal cell carcinoma on imaging, histology examination was necessary to confirm the diagnosis of anastomosing hemangioma and to prevent delay in listing for kidney transplantation. Good kidney function was achieved after transplantation, with no tumor recurrence., Conclusion: Our case underlines the importance for prompt surgical resection of an enhancing renal mass to confirm diagnosis in patients scheduled for kidney transplantation to avoid any delay., (© 2021. The Author(s).)

In the decades since the discovery of angiotensin-converting enzyme 2 (ACE2), its protective role in terms of antagonizing activation of the classical renin-angiotensin system (RAS) axis has been recognized in clinical and experimental studies on kidney and cardiovascular diseases. The effects of ACE inhibitor/angiotensin type 1 receptor blockers (ACEi/ARBs) on ACE2-angiotensin-(1-7) (Ang- (1-7))-Mas receptor (MasR) axis activation has encouraged the use of such blockers in patients with kidney and cardiovascular diseases, until the emergence of coronavirus disease 2019 (COVID-19). The previously unchallenged functions of the ACE2-Ang-(1-7)-MasR axis and ACEi/ARBs are being re-evaluated in the era of COVID-19; the hypothesis is that ACEi/ARBs may increase the risk of severe acute respiratory syndrome coronavirus 2 infection by upregulating the human ACE2 receptor expression level. In this review, we examine ACE2 molecular structure, function (as an enzyme of the RAS), and distribution. We explore the roles played by ACE2 in kidney, cardiovascular, and pulmonary diseases, highlighting studies that defined the benefits imparted when ACEi/ARBs activated the local ACE2- Ang-(1-7)-MasR axis. Finally, the question of whether ACEi/ARBs therapies should be stopped in COVID-19-infected patients will be reviewed by reference to the available evidence.

In this study, we propose the use of glycol chitosan for the targeted delivery of hydrophobic drugs such as tacrolimus (TAC) towards the kidney. We synthesized a hydrophobically modified glycol chitosan (HGC) polymeric nanomicelle followed by loading TAC resulting in TAC loaded HGC nanomicelles (HGC-TAC). The HGC-TAC nanomicelles displayed spherical morphology with superior drug loading content and encapsulation efficiency. in vitro and in vivo evaluations demonstrated that HGC-TAC nanomicelles are non toxic and delivered TAC preferentially to kidney while lowering the plasma concentrations. The therapeutic effects of HGC-TAC and unencapsulated ("bare") TAC on the kidneys showed that a single intravenous administration of HGC-TAC achieved a therapeutic efficacy comparable to that obtained from daily intraperitoneal injections of TAC for 14 days without any systemic side effects. Thus, HGC-TAC nanomicelles could be effectively used for delivery of TAC towards the kidney, highlighting its potential as a safe modality for renal-targeted delivery of therapeutics., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Renal fibrosis is the common pathway of chronic kidney disease progression. The nuclear receptor farnesoid X receptor [FXR, NR1H4 (nuclear receptor subfamily 1 group member 4)], a multifunctional transcription factor, plays a pivotal role in protecting against fibrosis. However, the mechanisms underlying these antifibrotic actions of FXR in kidney disease are largely unknown. Here, we show that agonist GW4064-mediated FXR activation inhibits the activity of the nonreceptor tyrosine kinase Src (proto-oncogene tyrosine-protein kinase), which is critical for regulation of yes-associated protein (YAP) phosphorylation and nuclear localization in renal fibrosis. Activation of FXR suppressed renal fibrosis and Tyr416-Src phosphorylation in TGF-β-treated human renal proximal tubule epithelial (HK2) cells. Moreover, GW4064 treatment in HK2 cells increased Ser127 phosphorylation, cytosolic accumulation of YAP, and interaction of the hippo core kinases (Ste20-like kinase 1, large tumor suppressor kinase 1, and salvador homolog 1). Inhibition of Src using PP2 (Src kinase inhibitor) prevented renal fibrosis and increased Ser127 phosphorylation and cytosolic accumulation of YAP. The expression of fibrosis markers, inflammatory genes, and YAP target genes was increased in the kidneys of FXR knockout mice compared with those of wild-type mice. In addition, GW4064 or WAY-362450 (turofexorate isopropyl) treatment protected against unilateral ureteral obstruction-induced renal fibrosis. Collectively, our data support the novel conclusion that Src-mediated crosstalk between FXR and YAP protects against renal fibrosis, making this pathway a possible therapeutic target for chronic kidney disease.-Kim, D.-H., Choi, H.-I., Park, J. S., Kim, C. S., Bae, E. H., Ma, S. K., Kim, S. W. Src-mediated crosstalk between FXR and YAP protects against renal fibrosis.

Renal fibrosis is a common final pathway of end-stage kidney disease which is induced by aberrant accumulation of myofibroblasts. This process is triggered by reactive oxygen species (ROS) and proinflammatory cytokines generated by various source of injured kidney cells. Peroxiredoxin 5 (Prdx5) is a thiol-dependent peroxidase that reduces oxidative stress by catalyzing intramolecular disulfide bonds. Along with its antioxidant effects, expression level of Prdx5 also was involved in inflammatory regulation by immune stimuli. However, the physiological effects and the underlying mechanisms of Prdx5 in renal fibrosis have not been fully characterized. Sprague-Dawley rats were subjected to unilateral ureteral obstruction (UUO) for 1 or 7 days. For the in vitro model, NRK49F cells, a rat kidney interstitial fibroblast cell lines, were treated with transforming growth factor β (TGF-β) for 0, 1, 3, or 5 days. To access the involvement of its peroxidase activity in TGF-β induced renal fibrosis, wild type Prdx5 (WT) and double mutant Prdx5 (DM), converted two active site cysteines at Cys 48 and Cys 152 residue to serine, were transiently expressed in NRK49F cells. The protein expression of Prdx5 was reduced in UUO kidneys. Upregulation of fibrotic markers, such as fibronectin and alpha-smooth muscle actin (α-SMA), declined at 5 days in time point of higher Prdx5 expression in TGF-β treated NRK49F cells. The overexpression of wild type Prdx5 by transient transfection in NRK49F cells attenuated the TGF-β induced upregulation of fibronectin and α-SMA. On the other hand, the transient transfection of double mutant Prdx5 did not prevent the activation of fibrotic markers. Overexpression of Prdx5 also suppressed the TGF-β induced upregulation of Stat3 phosphorylation, while phosphorylation of Smad 2/3 was unchanged. In conclusion, Prdx5 protects TGF-β induced fibrosis in NRK49F cells by modulating Stat3 activation in a peroxidase activity dependent manner.

Background: Angiotensin-(1-7) [Ang-(1-7)] counteracts many actions of the renin-angiotensin-aldosterone system. Despite its renoprotective effects, extensive controversy exists regarding the role of Ang-(1-7) in obstructive nephropathy, which is characterized by renal tubulointerstitial fibrosis and apoptosis., Methods: To examine the effects of Ang-(1-7) in unilateral ureteral obstruction (UUO), male Sprague-Dawley rats were divided into three groups: control, UUO, and Ang-(1-7)-treated UUO rats. Ang-(1-7) was continuously infused (24 μg/[kg·h]) using osmotic pumps. We also treated NRK-52E cells in vitro with Ang II (1 μM) in the presence or absence of Ang-(1-7) (1 μM), Mas receptor antagonist A779 (1 μM), and Mas receptor siRNA (50 nM) to examine the effects of Ang-(1-7) treatment on Ang II-stimulated renal injury via Mas receptor., Results: Angiotensin II (Ang II) and angiotensin type 1 receptor (AT1R) protein expression was higher in UUO kidneys than in controls. Ang-(1-7) treatment also decreased proapoptotic protein expression in UUO kidneys. Ang-(1-7) also significantly ameliorated TUNEL positive cells in UUO kidneys. Additionally, Ang-(1-7) reduced profibrotic protein expression and decreased the increased tumor growth factor (TGF)-β1/Smad signaling present in UUO kidneys. In NRK-52E cells, Ang II induced the expression of TGF-β1/Smad signaling effectors and proapoptotic and fibrotic proteins, as well as cell cycle arrest, which were attenuated by Ang-(1-7) pretreatment. However, treatment with A779 and Mas receptor siRNA enhanced Ang II-induced apoptosis and fibrosis. Moreover, Ang II increased tumor necrosis factor-α converting enzyme (TACE) and decreased angiotensin-converting enzyme 2 (ACE2) expression in NRK-52E cells, while pretreatment with Ang-(1-7) or A779 significantly inhibited or enhanced these effects, respectively., Conclusion: Ang-(1-7) prevents obstructive nephropathy by suppressing renal apoptosis and fibrosis, possibly by regulating TGF-β1/Smad signaling and cell cycle arrest via suppression of AT1R expression. In addition, Ang-(1-7) increased and decreased ACE2 and TACE expression, respectively, which could potentially mediate a positive feedback mechanism via the Mas receptor.

A 31-year-old woman with no significant past medical or family history was admitted with complaints of general weakness. Laboratory tests revealed: serum potassium 3.0 mEq/L, arterial blood pH 7.28, serum bicarbonate 17.8 mEq/L and urinary pH 7.0. Double-labeling confocal fluorescence microscopy using H(+)-ATPase and pendrin antibodies demonstrated a decreased expression of these proteins in the patient's renal collecting duct compared to normal controls. Anti-Sjögren's-syndrome-related antigen A (Anti-Ro/SS-A) and anti-Sjögren's syndrome type B (anti-La/SS-B) antibodies were strongly positive with very high titers, consistent with Sjögren's syndrome. We present a case of distal renal tubular acidosis-associated Sjögren's syndrome with a defect in H(+)-ATPase and pendrin in the renal collecting duct.

Background: This study aimed to compare the changes in kidney function and the association of tumor size and renal outcomes between patients with renal cell carcinoma (RCC) who underwent radical nephrectomy (RN) and those who underwent partial nephrectomy (PN)., Methods: A retrospective cohort study was conducted for 557 patients with an RCC of ≤7 cm in diameter and normal contralateral kidney function who underwent PN or RN. PN was performed for 218 (39%) patients. Renal outcomes included the incidence of acute kidney injury (AKI), new-onset chronic kidney disease (CKD), and a ≥25% decline in eGFR 1 year after surgery., Results: Serial changes in eGFR were compared during the 3 years of follow-up. Postoperative eGFR was significantly lower in patients undergoing RN than in those undergoing PN. The incidence of AKI and new-onset CKD was significantly higher in patients after RN (70.1% vs. 24.3%, respectively; P<0.001) than after PN (55.7% vs. 6.2%, respectively; P<0.001). According to the multivariable logistic regression analysis, RN was an independent risk factor for a ≥25% decline in kidney function after 1 year regardless of the tumor size, even after adjusting for various covariates., Conclusions: Compared to PN, RN for even a moderate sized RCC leads to an increased incidence of AKI and new-onset CKD, and is a significant risk factor for kidney function decline. Therefore, PN should be considered as the choice of surgical treatment for RCCs that are ≤7 cm in diameter in order to preserve renal function postoperatively.

Chronic kidney disease (CKD) has been recognized as a significant global health problem because of the increased risk of total and cardiovascular morbidity and mortality. Vitamin D deficiency or insufficiency is common in patients with CKD, and serum levels of vitamin D appear to have an inverse correlation with kidney function. Growing evidence has indicated that vitamin D deficiency may contribute to deteriorating renal function, as well as increased morbidity and mortality in patients with CKD. Recent studies have suggested that treatment with active vitamin D or its analogues can ameliorate renal injury by reducing fibrosis, apoptosis, and inflammation in animal models; this treatment also decreases proteinuria and mortality in patients with CKD. These renoprotective effects of vitamin D treatment are far beyond its classical role in the maintenance of bone and mineral metabolism, in addition to its pleiotropic effects on extra-mineral metabolism. In this review, we discuss the altered metabolism of vitamin D in kidney disease, and the potential renoprotective mechanisms of vitamin D in experimental and clinical studies. In addition, issues regarding the effects of vitamin D treatment on clinical outcomes are discussed.

Purpose: The present study aimed to investigate the impact of high-sensitivity C-reactive protein (hs-CRP) and renal dysfunction on clinical outcomes in acute myocardial infarction (AMI) patients., Materials and Methods: The study involved a retrospective cohort of 8332 patients admitted with AMI. The participants were divided into 4 groups according to the levels of estimated glomerular filtration rate (eGFR) and hs-CRP: group I, no renal dysfunction (eGFR ≥60 mL·min(-1)·1.73 m(-2)) with low hs-CRP (≤2.0 mg/dL); group II, no renal dysfunction with high hs-CRP; group III, renal dysfunction with low hs-CRP; and group IV, renal dysfunction with high hs-CRP. We compared major adverse cardiac events (MACE) over a 1-year follow-up period., Results: The 4 groups demonstrated a graded association with increased MACE rates (group I, 8.8%; group II, 13.8%; group III, 18.6%; group IV, 30.1%; p<0.001). In a Cox proportional hazards model, mortality at 12 months increased in groups II, III, and IV compared with group I [hazard ratio (HR) 2.038, 95% confidence interval (CI) 1.450-2.863, p<0.001; HR 3.003, 95% CI 2.269-3.974, p<0.001; HR 5.087, 95% CI 3.755-6.891, p<0.001]., Conclusion: High hs-CRP, especially in association with renal dysfunction, is related to the occurrence of composite MACE, and indicates poor prognosis in AMI patients.

Background: A limited number of studies have investigated the impact of gender on renal function and clinical outcomes after ST-segment elevated myocardial infarction (STEMI), and these studies have provided discrepant results., Methods and Results: This study was based on a retrospective cohort, the Korean Acute Myocardial Infarction Registry (KAMIR). Patients (n = 7,679) with a discharge diagnosis of STEMI were analyzed to investigate association of gender with renal function and clinical outcomes. Compared to men, women were older and exhibited more comorbidity, including impaired renal function. Women showed higher mortality compared to men (1-month mortality,5.6% in men vs. 12.6% in women, p < 0.001; 1-year mortality, 6.8% in men vs. 14.4% in women, p < 0.001). The risk of death proportionally increased as estimated glomerular filtration rate (eGFR) decreased in both genders. After adjusting for potential confounders, hazard ratios for women did not significantly differ from those for men at each eGFR level.The interaction test showed no significant interaction between gender and eGFR in 1-month mortality and 1-year mortality., Conclusions: Impaired renal function was an independent prognostic factor after STEMI in both genders, and the impact of impaired renal function on prognosis after STEMI did not significantly differ between genders.

Background/aims: Sildenafil, the first selective phosphodiesterase-5 (PDE5) inhibitor to be widely used for treating erectile dysfunction, has been investigated with regard to its cardioand renoprotective effects in animal models. This study further investigated the renoprotective effects of sildenafil and their molecular mechanisms in deoxycorticosterone acetate (DOCA)-salt hypertensive (DSH) rats., Methods: DOCA strips (200 mg/kg) were implanted in rats 1 week after unilateral nephrectomy. These rats were fed on a control diet, with or without sildenafil (50 mg·kg(-1)day(-1)), for 2 weeks. Systolic blood pressure (SBP) was measured by the tail cuff method, and the urinary albumin-to-creatinine ratio (ACR) was calculated. The extent of glomerulosclerosis and tubulointerstitial fibrosis was determined by Masson's trichrome stain. Renal expression of ED-1, transforming growth factor-β1 (TGF-β1), Bax, and Bcl-2 were determined by semiquantitative immunoblotting, polymerase chain reaction (PCR), and immunohistochemistry. TUNEL staining was used for detecting apoptotic cells., Results: The increased SBP in DSH rats was not attenuated by sildenafil treatment. The decreased creatinine clearance and increased ACR in DSH rats, compared with control animals, were attenuated by sildenafil treatment. Further, sildenafil treatment attenuated glomerulosclerosis and tubulointerstitial fibrosis in DSH rats and counteracted the increased expression of ED-1, TGF-β1, and Bax and the decreased expression of Bcl-2 in the kidneys of these rats. The increase in the number of apoptotic cells in DSH rats was attenuated by sildenafil treatment., Conclusion: Sildenafil effectively prevented the progression of renal injury in DSH rats via its anti-inflammatory, antifibrotic, and antiapoptotic effects., (Copyright © 2012 S. Karger AG, Basel.)

The present study was aimed to determine whether there is an altered role of local nitric oxide (NO) and atrial natriuretic peptide (ANP) systems in the kidney in association with the angiotensin (Ang) II-induced hypertension. Male Sprague-Dawley rats were used. Ang II (100 ng·min⁻¹·kg⁻¹) was infused through entire time course. Thirteenth day after beginning the regimen, kidneys were taken. The protein expression of NO synthase (NOS) and nitrotyrosine was determined by semiquantitative immunoblotting. The mRNA expression of components of ANP system was determined by real-time polymerase chain reaction. The activities of soluble and particulate guanylyl cyclases were determined by the amount of cGMP generated in responses to sodium nitroprusside and ANP, respectively. There developed hypertension and decreased creatinine clearance in the experimental group. The protein expression of eNOS, nNOS and nitrotyrosine was increased in the cortex, while that of iNOS remained unaltered. The urinary excretion of NO increased in Ang II-induced hypertensive rats. The catalytic activity of soluble guanylyl cyclase was blunted in the glomerulus in Ang II-induced hypertensive rats. The mRNA expression of ANP was increased in Ang II-induced hypertensive rats. Neither the expression of NPR-A nor that of NPR-C was changed. The protein expression of neutral endopeptidase was decreased and the activity of particulate guanylyl cyclase was blunted in the glomerulus and papilla in Ang II-induced hypertensive rats. In conclusion, the synthesis of NO and ANP was increased in the kidney of Ang II-induced hypertension, while stimulated cGMP response was blunted. These results suggest desensitization of guanylyl cyclase in the kidney of Ang II-induced hypertensive rats, which may contribute to the associated renal vasoconstriction and hypertension., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Previously we demonstrated that ANG II receptor (AT1R) blockade attenuates V2 receptor (V2R), AQP2, and pS256-AQP2 downregulation in the postobstructed kidney and partially reverses obstruction-induced inhibition of cAMP generation and cyclooxygenase 2 (COX-2) induction. Therefore, we speculated whether the effects of AT1R blockade on V2R and the vasopressin-regulated pathway are attributable to attenuated COX-2 induction. To examine this, rats were subjected to 24-h bilateral ureteral obstruction (BUO) followed by 48-h release and treated with the COX-2 inhibitor parecoxib or saline. Control rats were sham-operated. Parecoxib treatment significantly reduced urine output 24 h after release of BUO whereas urine osmolality and solute-free water reabsorption was comparable between saline- and parecoxib-treated BUO rats. Immunoblotting revealed a significant decrease in AQP2 and pS256-AQP2 abundance to 20 and 23% of sham levels in parecoxib-treated BUO rats compared with 40 and 55% of sham levels in saline-treated BUO rats. Immunohistochemistry confirmed the exacerbated AQP2 and pS256-AQP2 downregulation in parecoxib-treated BUO rats. Finally, parecoxib treatment had no effect on V2R downregulation and the inhibited, vasopressin-stimulated cAMP generation in inner medullary membrane fractions from the postobstructed kidney. In conclusion, COX-2 inhibition exacerbates AQP2 and pS256-AQP2 downregulation 48 h after release of 24-h BUO independently of V2R abundance and vasopressin-stimulated cAMP generation. The results indicate that COX-2 inhibition does not mimic AT1R blockade-mediated effects and that AT1R-mediated AQP2 regulation in the postobstructed kidney collecting duct is independent of COX-2 induction.

Purpose: Unilateral ureteral obstruction is a common clinical problem that is often associated with a urinary acidification defect caused by decreased net H(+) secretion and/or HCO(3)(-) reabsorption. To clarify the molecular mechanisms of these defects we examined expression levels of key acid-base transporters along the renal nephron segments and collecting duct., Materials and Methods: Wistar rats (Møllegard Breeding Centre, Eiby, Denmark) underwent 24-hour unilateral ureteral obstruction, unilateral ureteral obstruction release followed for 4 days or unilateral ureteral obstruction release followed for 4 days plus experimental acidosis induced by NH(4)Cl oral administration. After sacrifice kidneys were processed for immunoblotting and immunohistochemistry., Results: Semiquantitative immunoblotting revealed that unilateral ureteral obstruction caused significant mean +/- SE down-regulation of type 3 Na(+)/H(+) exchanger to 53% +/- 9%, electrogenic Na(+)/HCO(3)(-) cotransporter to 60% +/- 9%, type 1 bumetanide sensitive Na(+)-K(+)(NH(4)(+)) -2Cl(-) cotransporter to 64% +/- 7%, electroneutral Na(+)/HCO(3)(-) cotransporter to 43% +/- 4% and anion exchanger (pendrin) to 53% +/- 10% in the obstructed kidney, which was confirmed by immunohistochemistry. After release of unilateral ureteral obstruction down-regulation of these transporters persisted together with marked down-regulation of H(+)-adenosine triphosphatase in the obstructed kidney. In rats with unilateral ureteral obstruction release followed for 4 days with experimental acidosis induced by NH(4)Cl oral administration plasma pH and HCO(3)(-) were dramatically decreased in response to NH(4)Cl for 2 days compared with those in sham operated rats with acid loading, indicating a defect in H(+) excretion and HCO(3)(-) reabsorption after obstruction release. Expression of these transporters did not change in the contralateral nonobstructed kidney of rats with unilateral ureteral obstruction and unilateral ureteral obstruction release followed for 4 days., Conclusions: The expression of renal acid-base transporters is markedly decreased in the obstructed kidney, which may be responsible for the contribution of impaired renal H(+) excretion and HCO(3)(-) reabsorption to the urinary acidification defect in response to unilateral ureteral obstruction.

Heart failure (HF) was induced by ligation of the left anterior descending artery (LAD). Left ventricular end-diastolic pressure (LVEDP) >25 mmHg (at day 23 after LAD ligation) was the inclusion criterion. The rats were divided into three groups: sham-operated (Sham, n = 23, LVEDP: 5.6 +/- 0.6 mmHg), HF (n = 14, LVEDP: 29.4 +/- 1.4 mmHg), and candesartan (1 mg.kg(-1).day(-1) sc)-treated HF (HF + Can, n = 9, LVEDP: 29.2 +/- 1.2 mmHg). After 7 days (i.e., 29 days after LAD ligation) semiquantitative immunoblotting revealed increased abundance of inner medulla aquaporin-2 (AQP2) and AQP2 phosphorylated at Ser(256) (p-AQP2) in HF. There was also markedly enhanced apical targeting of AQP2 and p-AQP2 in inner medullary collecting duct (IMCD) in HF compared with Sham rats, shown by immunocytochemistry. Candesartan treatment significantly reversed the increases in both AQP2 and p-AQP2 expression and targeting. In contrast, there were only modest changes in other collecting duct segments. Semiquantitative immunoblots revealed increased expression of type 3 Na(+)/H(+) exchanger (NHE3) and Na(+)-K(+)-2Cl(-) cotransporter (NKCC2) in kidneys from HF compared with Sham rats: both effects were reversed or prevented by candesartan treatment. The protein abundance of alpha-epithelial sodium channel (alpha-ENaC) was increased while beta-ENaC and gamma-ENaC expression was decreased in the cortex and outer stripe of the outer medulla in HF compared with Sham rats, which was partially reversed by candesartan treatment. These findings strongly support an important role of angiotensin II in the pathophysiology of renal water and sodium retention associated with HF.

Background: Cisplatin-induced nephropathy has been related to increased lipid peroxide formation and decreased activity of antioxidant enzymes in the kidney. The present study aimed to examine whether treatment with alpha-lipoic acid (alpha-LA) prevents the cisplatin-induced nephrotoxicity., Methods: Two groups of rats were treated with cisplatin, one of which being cotreated with alpha-LA. The control group was treated with vehicle only. Four days later, the expression of aquaporins and sodium transporters was determined in the kidney by immunoblotting and immunohistochemistry. The arginine vasopressin-stimulated generation of cAMP was measured by radioimmunoassay. The expression of nitric oxide synthases (NOS) was determined by immunoblotting. The mRNA expression of endothelin-1 (ET-1) and tumour necrosis factor (TNF)-alpha was measured by real-time PCR. Apoptosis was examined by TUNEL staining., Results: Following the treatment with cisplatin, urinary volume and fractional excretion of sodium increased. Accordingly, the expression of aquaporins 1-3, Na,K-ATPase, NHE3 and NKCC2 was decreased. The expression of adenylyl cyclase VI and vasopressin-stimulated cAMP generation was decreased. The expression of inducible NOS was increased, while that of endothelial NOS decreased. The ET-1 expression was increased. TUNEL-positive cells were increased, in association with an increased expression of TNF-alpha. alpha-LA treatment prevented dysregulation of these parameters and resumed the renal function., Conclusion: alpha-LA may prevent the cisplatin-induced nephrotoxicity, possibly through preserving the activities of NO and ET systems and inhibiting the development of apoptosis.

The present study aimed to examine whether there is an altered regulation of local hormonal systems in the kidney following the treatment of glycyrrhizic acid (GA), the active ingredient in licorice. Male Sprague-Dawley rats were treated with GA for 3 weeks. The expression of mineralocorticoid receptor (MR) was determined in the kidney by immunoblotting and real-time polymerase chain reaction (PCR). The protein expression of endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) was determined. The expression of atrial natriuretic peptide (ANP), natriuretic peptide receptor (NPR)-A and NPR-C was determined by real-time PCR. The activity of guanylyl cyclase was determined by the amount of cGMP generated in responses to sodium nitroprusside (SNP) or ANP. Following the GA treatment, systolic blood pressure was increased. The mRNA and protein expressions of MR were increased in the kidney. The protein expression of eNOS and iNOS was also increased. The expression of ANP mRNA was increased although that of NPR-A and NPR-C mRNA was not changed. The cGMP production provoked by either SNP or ANP was not changed. The increased expression of MR may contribute to GA-induced hypertension. The enhanced expression of NOS and ANP may play a compensatory role in GA-induced hypertension., (Copyright (c) 2008 John Wiley & Sons, Ltd.)

Aims: To determine whether the renal regulation of aquaporin (AQP) water channels and sodium transporters are altered in 2-kidney, 1-clip (2K1C) hypertension., Methods: Male Sprague-Dawley rats were used. They were made 2K1C hypertensive for 1 week. The renal expression of AQPs and sodium transporters was determined by semiquantitative immunoblotting and immunohistochemistry. The activity of adenylyl cyclase was measured by stimulated generation of cAMP., Results: Systolic blood pressure was increased in 2K1C rats. Experimental rats revealed impaired urinary concentration in association with increased urine volume. Urinary sodium excretion also increased. The expression of AQP1-3 was decreased in the clipped kidney compared with the control kidney, whereas it was unchanged in the non-clipped kidney. The adenylyl cyclase activity provoked by arginine vasopressin, sodium fluoride or forskolin was blunted in the clipped kidney, but remained unaltered in the contralateral kidney. The expressions of the Na,K-ATPase alpha1-subunit, type 3 Na(+)/H(+) exchanger, Na-K-2Cl cotransporter and epithelial sodium channels were decreased in the clipped kidney, while remaining unchanged in the non-clipped kidney., Conclusion: The downregulation of AQPs and major sodium transporters/channels in the clipped kidney may play a role in the urinary concentration defect and impaired sodium reabsorption in 2K1C hypertension., (Copyright 2009 S. Karger AG, Basel.)

Urinary tract obstruction impairs renal function and is often associated with a urinary acidification defect caused by diminished net H+ secretion and/or HCO3- reabsorption. To identify the molecular mechanisms of these defects, protein expression of key acid-base transporters were examined along the renal nephron and collecting duct of kidneys from rats subjected to 24-h bilateral ureteral obstruction (BUO), 4 days after release of BUO (BUO-R), or BUO-R rats with experimentally induced metabolic acidosis (BUO-A). Semiquantitative immunoblotting revealed that BUO caused a significant reduction in the expression of the type 3 Na+/H+ exchanger (NHE3) in the cortex (21 +/- 4%), electrogenic Na+/HCO3- cotransporter (NBC1; 71 +/- 5%), type 1 bumetanide-sensitive Na+-K+-2Cl- cotransporter (NKCC2; 3 +/- 1%), electroneutral Na+/HCO3- cotransporter (NBCn1; 46 +/- 7%), and anion exchanger (pendrin; 87 +/- 2%). The expression of H+-ATPase increased in the inner medullary collecting duct (152 +/- 13%). These changes were confirmed by immunocytochemistry. In BUO-R rats, there was a persistent downregulation of all the acid-base transporters including H+-ATPase. Two days of NH4Cl loading reduced plasma pH and HCO3- levels in BUO-A rats. The results demonstrate that the expression of multiple renal acid-base transporters are markedly altered in response to BUO, which may be responsible for development of metabolic acidosis and contribute to the urinary acidification defect after release of the obstruction.

1. The effects of volume depletion and NaHCO(3) loading on the expression of Na(+)/H(+) exchanger isoform 3 (NHE3), Na(+) : HCO(3)(-) cotransporter type 1 (NBC1) and neuronal (n) and inducible (i) isoforms of nitric oxide synthase (NOS) were determined in rat kidney. 2. Adult male Sprague-Dawley rats were used. Rats were divided into four groups: (i) euvolaemic (EC); (ii) hypovolaemic (HC); (iii) euvolaemia with NaHCO(3) loading (EB); and (iv) hypovolaemia with NaHCO(3) loading (HB). The expression of NHE3, NBC1, nNOS and iNOS proteins was determined in the cortex of the kidney by immunoblotting and immunohistochemistry. Tissue content of nitric oxide (NO) metabolites (NO(x)) were also determined in the cortex using a colourimetric assay. 3. Compared with the EC group, the expression of NHE3 and NBC1 was increased in the HC group and decreased in the EB group. Comparing the EB and HB groups, the expression of NHE3 and NBC1 was higher in the latter group. The expression of NHE3 was decreased and that of NBC1 was increased in the HB group compared with the HC group. The NO(x) content and nNOS expression were decreased in the hypovolaemic (HC) and NaHCO(3)-loaded (EB and HB) rats. Moreover, the expression of iNOS was decreased in the HB group compared with the other groups. 4. An altered volume status and NaHCO(3) loading may affect the regulation of NHE3 and NBC1 in the kidney and the endogenous NO system may play a role in the observed effects.

We investigated whether alpha-lipoic acid (alpha-LA), an antioxidant, attenuates the ischemia-reperfusion (I/R)-induced dysregulation of these transporters. Both renal pedicles of male Sprague-Dawley rats were clamped for 40 min. alpha-LA (80 mg/kg) was administered intraperitoneally before and immediately after induction of ischemia. After 2 days, the expression of aquaporins (AQPs), sodium transporters, and nitric oxide synthases (NOS) was determined in the kidney by immunoblotting and immunohistochemistry. The expression of endothelin-1 (ET-1) mRNA was determined by real-time PCR. Activities of adenylyl cyclase and guanylyl cyclase were measured by stimulated generation of cAMP and cGMP, respectively. The expression of AQP1-3 as well as that of the alpha(1)-subunit of Na-K-ATPase, type 3 Na/H exchanger, Na-K-2Cl cotransporter, and Na-Cl cotransporter was markedly decreased in response to I/R. The expression of type VI adenylyl cyclase was decreased in I/R-injured rats, which was counteracted by the treatment of alpha-LA. AVP-stimulated cAMP generation was blunted in I/R rats and was then ameliorated by alpha-LA treatment. alpha-LA treatment attenuated the downregulation of AQPs and sodium transporters. The expression of endothelial NOS was decreased in I/R rats, which was prevented by alpha-LA. The cGMP generation in response to sodium nitroprusside was blunted in I/R rats, which was also significantly prevented by alpha-LA. The mRNA expression of ET-1 was increased, which was recovered to the control level by alpha-LA treatment. In conclusion, alpha-LA treatment prevents I/R-induced dysregulation of AQPs and sodium transporters in the kidney, possibly through preserving normal activities of local AVP/cAMP, nitric oxide/cGMP, and ET systems.

Background: The present study was designed to investigate the role of the local renin-angiotensin-aldosterone system (RAAS), endothelin (ET) and the natriuretic peptide system (NPS) for the development of renal fibrosis and progressive renal disease in experimental unilateral ureteral obstructed (UUO) rats., Methods: Male Sprague-Dawley rats (180-200 g) were unilaterally obstructed by ligation of the proximal ureters for 14 days. Control rats were treated in the same way, except that no ligature was made. The mRNA expressions of local renin-angiotensin system, aldosterone synthase (CYP11B2), ET-1 and NPS was determined in the cortex by real-time polymerase chain reaction., Results: Following the unilateral ureteral obstruction, the mRNA expressions of angiotensin-converting enzyme 1, ET-1 and transforming growth factor-beta1 (TGF-beta1) were increased, while angiotensin-converting enzyme 2 was decreased in the obstructed kidney compared with the controls. Angiotensin II type 1 receptor was decreased and TGF-beta1 was not changed in contralateral kidney compared with the controls. Atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide expressions were increased in UUO kidneys compared with the controls, while natriuretic peptide receptor-A was decreased in UUO kidneys., Conclusion: The local RAAS and ET-1 was upregulated which may play a role in the progressive renal fibrosis in obstructed kidneys in rats with UUO. The enhanced activity of NPS in UUO kidney may play a role to compensate against progressive renal fibrosis in chronic obstructive uropathy., (2007 S. Karger AG, Basel)

Aims: To investigate whether the regulation of aquaporin (AQP) channels is altered by inhibition of type 2 11beta-hydroxysteroid dehydrogenase (11betaHSD2)., Methods: Male Sprague-Dawley rats were treated with glycyrrhizic acid (GA, 2 g/l drinking water) for 7 days. The expression of AQP2 and AQP3 was determined in the kidney by immunoblotting and immunohistochemistry. The expression of Gsalpha and type VI adenylyl cyclase, and the activity of adenylyl cyclase were also determined., Results: Following the GA treatment, the expression of 11betaHSD2 was significantly decreased in the kidney. The expression of AQP3 was increased, while that of AQP2 remained unchanged. Plasma renin activity and serum aldosterone levels were decreased. Plasma arginine vasopressin (AVP) levels were comparable between the groups. Neither the forskolin-stimulated cAMP generation nor the expression of Gsalpha and type VI adenylyl cyclase was altered significantly., Conclusion: A decreased expression of 11betaHSD2 may result in an upregulation of AQP3, in which AVP/cAMP-dependent mechanisms are unlikely to be involved., (Copyright 2007 S. Karger AG, Basel.)

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, Frøkiaer J, and Nielsen S. Am J Physiol Renal Physiol 286: F922-F935, 2004), whereas the global expression of the alpha1-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, Frøkiaer 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.

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 HgCl(2)-induced nephropathy. In addition, we examined the hypothesis that the expression of type 2 11beta-hydroxysteroid dehydrogenase (11betaHSD2) is reduced, contributing to the enhanced mineralocorticoid activity. Membranous nephropathy was induced in Brown Norway rats by repeated injections of HgCl(2) (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 11betaHSD2 in the kidney was examined by immunoblotting and immunohistochemistry. HgCl(2) treatment induced marked proteinuria, hypoalbuminemia, decreased urinary sodium excretion, and ascites. The protein abundance of alpha-ENaC was increased in the cortex/outer stripe of outer medulla (OSOM) and inner stripe of the outer medulla (ISOM). The protein abundances of beta-ENaC and gamma-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, 11betaHSD2 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 alpha-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 11betaHSD2 may contribute to sodium retention associated with HgCl(2)-induced nephrotic syndrome. The decreased abundance of NHE3, NKCC2, NCC, and Na-K-ATPase may play a compensatory role in promoting sodium excretion.

Atrial natriuretic peptide (ANP) acutely promotes water and sodium excretion, whereas subchronic effects involve water retention. Renal hemodynamics, water and sodium excretion, and aquaporin-2 (AQP2) and epithelial Na channel (ENaC) subcellular trafficking were determined in response to continuous ANP infusion in conscious rats, where body sodium and fluid balance was constantly maintained. ANP (0.5 microg x kg(-1) x min(-1)) evoked a transient (peak at 10 min) fivefold diuresis followed by reduced urine production to control levels (30- to 90-min period). The fractional distal water excretion was significantly increased initially and then decreased in response to ANP. There was no change in the subcellular localization of AQP2 and AQP2 phosphorylated in PKA consensus site S256 (p-AQP2) 10 min after ANP infusion. In contrast, after 90 min a marked increase in apical labeling of AQP2 and p-AQP2 was observed in the inner and outer medullary collecting ducts but not in cortical collecting ducts. In support of this, ANP induced plasma membrane targeting of AQP2 in transiently AQP2-transfected cells. ANP infusion evoked an instant increase in renal sodium excretion, which persisted for 90 min. Ten minutes of ANP infusion induced no changes in the subcellular localization of ENaC subunits, whereas a marked increase in apical targeting of alpha- and gamma-subunits was observed after 90 min. In conclusion, 1) ANP infusion induced a sustained natriuresis and transient diuresis; 2) there were no changes in the subcellular localization of AQP2 and ENaC subunits after 10 min of ANP infusion; and 3) there was a marked increase in apical targeting of AQP2, p-AQP2, and alpha- and gamma-ENaC after 90 min of ANP infusion. The increased targeting of ENaC and AQP2 likely represents direct or compensatory effects to increase sodium and water reabsorption and to prevent volume depletion in response to prolonged ANP infusion.

Aims: A neural mechanism regulating aquaporin (AQP) water channels in the kidney was investigated., Methods: Male Sprague-Dawley rats were used. Renal denervation was induced by painting the renal vessels with 10% phenol. The expression of AQP1-4 proteins was determined in the denervated and contralateral kidneys. The expression was also examined in rats which were renally denervated and subjected to water restriction or deoxycorticosterone acetate (DOCA)-salt treatment., Results: Following the unilateral denervation, tissue contents of norepinephrine were significantly decreased in the denervated kidney, while increased in the contralateral kidney. Accordingly, the expression of AQP1-4 proteins was decreased by 15-40% in the denervated kidney, and increased by 30-50% in the contralateral kidney. Immunohistochemistry of AQP2 confirmed its decreases in the denervated kidney and increases in the contralateral kidney. In bilaterally denervated rats, the urine flow increased along with decreased osmolarity. The water restriction increased the expression of AQP channels, however, the magnitude of which was lower in the denervated than in the contralateral kidney. Renal denervation decreased the degree of DOCA-salt hypertension, along with lower expression of AQP channels., Conclusion: It is suggested that the sympathetic nerve should play a specific excitatory role in the regulation of AQP channels in the kidney., (Copyright 2006 S. Karger AG, Basel)

It was hypothesized that dysregulation of renal epithelial sodium channel (ENaC) subunits and/or 11beta-hydroxysteroid dehydrogenase (11betaHSD2) may play a role in the increased sodium retention in liver cirrhosis (LC). Experimental LC was induced in rats by CCl(4) (1 ml/kg, intraperitoneally, twice a week) for 12 wk (protocol 1) or for 11 wk (protocol 2). In both protocols, one group of rats with cirrhosis showed significantly decreased urinary sodium excretion and urinary Na/K ratio (group A), whereas a second group exhibited normal urinary sodium excretion (group B) compared with controls, even though extensive ascites was seen in both groups of rats with cirrhosis. In group A, protein abundance of alpha-ENaC was unchanged, whereas beta-ENaC abundance was decreased in the cortex/outer stripe of outer medulla compared with controls. The gamma-ENaC underwent a complex change associated with increased abundance of the 70-kD band with a concomitant decrease in the main 85-kD band, corresponding to an aldosterone effect. In contrast, no changes in the abundance of ENaC subunit were observed in group B. Immunoperoxidase microscopy revealed an increased apical targeting of alpha-, beta-, and gamma-ENaC subunits in distal convoluted tubule (DCT2), connecting tubule (CNT), and cortical and medullary collecting duct segments in group A but not in group B. Immunolabeling intensity of 11betaHSD2 in the DCT2, CNT, and cortical collecting duct was significantly reduced in group A but not in group B, and this was confirmed by immunoblotting. In conclusion, increased apical targeting of ENaC subunits combined with diminished abundance of 11betaHSD2 in the DCT2, CNT, and cortical collecting duct is likely to play a role in the sodium retaining stage of liver cirrhosis.

In models of genetic hypertension, renal tubular dysfunction could be involved in the increased sodium and water reabsorption. However, the molecular basis for the increased renal sodium and water retention remains largely undefined in spontaneously hypertensive rats (SHR). We hypothesized that dysregulation of renal epithelial sodium channels (ENaC), sodium (co)transporters, or aquaporin-2 (AQP2) could be involved in the pathogenesis of hypertension in SHR. Six-week-old or twelve-week-old SHR and corresponding age-matched Wistar-Kyoto control rats (WKY) were studied. In both SHR groups, systolic blood pressure was markedly increased, whereas urine output, creatinine clearance, and urinary sodium excretion were decreased compared with corresponding WKY. Moreover, urine osmolality and urine-to-plasma osmolality ratio were increased compared with WKY. Semiquantitative immunoblotting demonstrated that the protein abundance of beta- and gamma-subunits of ENaC was increased in the cortex and outer stripe of the outer medulla and inner stripe of the outer medulla (ISOM) in SHR, whereas alpha-ENaC abundance was increased in ISOM. Immunoperoxidase microscopy confirmed the increased labeling of beta-ENaC and gamma-ENaC subunits in the late distal convoluted tubule, connecting tubule, and cortical and outer medullary collecting duct segments. In contrast, subcellular localization of alpha-ENaC, beta-ENaC, and gamma-ENaC was not changed. Expression of sodium/hydrogen exchanger type 3, bumetanide-sensitive Na-K-2Cl cotransporter, and thiazide-sensitive Na-Cl cotransporter was not altered in SHR. AQP2 levels were increased in the ISOM in SHR, and immunoperoxidase microscopy demonstrated an increased apical labeling of AQP2 in the inner medullary collecting duct in SHR. These results suggest that the increased protein abundance of ENaC subunits as well as the increased apical targeting of AQP2 may contribute to renal sodium and water retention observed during the development of hypertension in SHR.

The effect of nonsteroidal antiinflammatory drugs on the regulation of aquaporin-2 (AQP2) water channels in the kidney was determined. Male Sprague-Dawley rats were injected with indomethacin (5 mg/kg twice a day intraperitoneally) for 2 d. The control group was injected with vehicle. The expression of AQP2 proteins was determined in the kidney by immunoblotting and immunohistochemistry. The expression of G(salpha) and type VI adenylyl cyclase was determined by immunoblotting. The activity of adenylyl cyclase complexes was determined by stimulated accumulation of cAMP. Immunoblotting revealed that indomethacin markedly decreased the expression of AQP2. Accordingly, however, the ratio of AQP2 expression in the membrane fraction versus that in the cytoplasmic fraction was increased. The urinary excretion of AQP2 proteins also increased. Immunohistochemistry demonstrated almost exclusive apical labeling of AQP2 with scanty cytoplasmic localization along the collecting duct. The expression of G(salpha) and adenylyl cyclase VI proteins was decreased. The generation of cAMP provoked by arginine vasopressin, sodium fluoride, or forskolin was blunted. These results suggest that indomethacin increases the shuttling of AQP2 while it decreases its abundance in the collecting duct.

1. Effects of non-steroidal anti-inflammatory drugs on the local atrial natriuretic peptide (ANP) and nitric oxide (NO) systems in the kidney were investigated. 2. Male Sprague-Dawley rats were treated with indomethacin (5 mg/kg, every 12 h, i.p.) for 2 days. The expression of ANP and natriuretic peptide receptor-A (NPR-A) mRNA was determined in the kidney, as was that of endothelial NO synthase (NOS) proteins. Particulate and soluble guanylyl cyclase activities were determined separately. 3. Following treatment with indomethacin, urinary sodium excretion decreased significantly. Although the renal expression of ANP was not changed significantly, that of NPR-A decreased significantly. The expression of NOS increased significantly. Particulate guanylyl cyclase activity was decreased, whereas the activity of soluble guanylyl cyclase was increased. The catalytic activity of Na(+)/K(+)-ATPase was increased, with no significant changes in its expression. The expression of the type 3 Na/H exchanger and Na-K-2CL cotransporters increased significantly. 4. The indomethacin-induced decrease in urinary sodium excretion may be attributed, at least in part, to decreased activity of the local ANP/cGMP system. The increased activity of the NO/cGMP system may be a compensatory response to the diminished activity of the prostaglandin system.

Background/aims: Whether the postobstructive natriuresis and diuresis is related with an altered regulation of sodium transporters in the kidney was examined., Methods: Male Sprague-Dawley rats underwent either bilateral (BUO) or unilateral obstruction (UUO) of the proximal ureters for 24 h. The expression of Na,K-ATPase, type-3 sodium-hydrogen exchanger (NHE3), type-1 bumetanide-sensitive sodium cotransporter (BSC1), and thiazide-sensitive sodium cotransporter (TSC) proteins was determined in the obstructed kidney by Western blot analysis and immunohistochemistry. Catalytic activity of Na,K-ATPase was also determined., Results: The expression of alpha1 and beta1 subunit proteins and the catalytic activity of Na,K-ATPase were significantly decreased in the obstructed kidney in BUO. The expressions of NHE3, BSC1 and TSC proteins were also significantly decreased. Immunohistochemistry confirmed the downregulation of these sodium transporters in the obstructed kidney. In UUO, the expression of sodium transporters was similarly decreased in the obstructed kidney., Conclusion: The postobstructive natriuresis and diuresis may in part be accounted for by a reduced abundance of sodium transporters in the kidney., (Copyright 2004 S. Karger AG, Basel)

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease. There are some reports in the literature concerning unilateral ADPKD. However, in adults, only a few cases of unilateral ADPKD with agenesis of contralateral kidney have been reported. We present a case of unilateral ADPKD with agenesis of contralateral kidney in a 66-yr-old man. Radiographic images showed the enlarged right kidney with multiple variable-sized cysts and the absence of the left kidney. The diagnosis of ADPKD was confirmed by the family screening. The patient received maintenance hemodialysis for endstage renal disease. We report a case of unilateral ADPKD associated with contralateral renal agenesis in a 66-yr-old male patient with a literature review.

Objective: We investigated whether regulation of aquaporin (AQP) water channels is altered in the ureteral-obstructed kidney., Material and Methods: Male Sprague-Dawley rats were unilaterally obstructed of their left proximal ureters for 48 h. The protein expression of AQP1-3 channels was determined in the kidney by Western blot analysis. The expression of AQP2 was also determined by immunohistochemistry. In order to specifically determine primary impairment of the pathway leading to an altered regulation of AQP channels stimulated by the arginine vasopressin (AVP)/cyclic adenosine monophosphate (cAMP) pathway, the catalytic activity and protein expression of different parts of the adenylyl cyclase complex were separately determined., Results: In the previously obstructed kidney, urinary osmolality and free water reabsorption were greatly decreased. The expression of AQP2 proteins was decreased in the cortex, outer medulla and inner medulla. Immunohistochemistry also showed a marked decrease in AQP2 expression. The expression of AQP1 and AQP3 was decreased in the outer medulla and inner medulla. cAMP generation in response to AVP, sodium fluoride or forskolin was greatly decreased. The expression of Gsalpha and adenylyl cyclase VI proteins was decreased. The contralateral kidney showed minimal or no changes in these parameters., Conclusions: The reduced abundance of AQP water channels may at least partly account for the urinary concentration defect in the ureteral-obstructed kidney. The primary point of impairment of AQP channels regulated by the AVP/cAMP pathway may lie at the level of the catalytic unit of adenylyl cyclase.

Gitelman's syndrome is a variant of Bartter's syndrome characterized by hypocalciuria and hypomagnesemia. The administration of thiazide diuretics may induce a subnormal increase of urinary Na+ and Cl- excretion in patients with Gitelman's syndrome, consistent with the hypothesis that less Na+ and Cl- than normal is reabsorbed by the thiazide-inhibitable transporter in Gitelman's syndrome. Specific mutations of NaCl cotransporter, coupled with mutant NaCl cotransporter expression studies clearly demonstrated that many of the characteristics of individuals with Gitelman's syndrome are explained by lack of function of NaCl cotransporter. We recently diagnosed a patient with Gitelman's syndrome by performing the thiazide and furosemide tests, and it is suggested that the clearance studies by diuretic administration may be of diagnostic help in Gitelman's syndrome.

The present study was aimed to determine the molecular mechanisms underlying the water retention associated with hypothyroidism. Male Sprague-Dawley rats (200-220g) were experimentally induced of hypothyroidism by treatment with methimazole in drinking water (0.04%) for 8 weeks. In the experimental group, serum concentrations of thyroxine and triiodothyronine were significantly decreased. The expression of aquaporin 2 (AQP2) was significantly increased in the cortex, outer medulla, and inner medulla of the kidney. The expression of AQP1 as well as that of AQP3 was significantly increased in the cortex, though not in the medulla. The adenylyl cyclase activity provoked by arginine vasopressin (AVP), sodium fluoride, or forskolin was blunted in the hypothyroid kidney, while plasma levels of AVP were not significantly changed. The increased expression of AQP1-3 channels may in part account for the water retention in hypothyroidism.

1. The aim of the present study was to explore the mechanisms underlying the renal effects of caffeine. 2. Male Sprague-Dawley rats were treated with caffeine, consisting of a single oral bolus (0.2%, 20 mL/kg) followed by supplementation in drinking water (0.2%) for 1 day. Rats treated the same but given water without caffeine served as controls. 3. The expression of alpha1- and beta1-subunits of Na+/K+-ATPase, the type 3 Na+/H+ exchanger (NHE3) and aquaporin-1 was determined in the kidney by western blot analysis. 4. To explore possible involvement of local humoral mediators, the tissue expression of nitric oxide synthase (NOS) proteins was determined by western blot analysis and the expression of atrial natriuretic peptide (ANP) mRNA was determined by semiquantitative reverse transcription-polymerase chain reaction. 5. Following treatment with caffeine, the expression of alpha1- and beta1-subunits of Na+/K+-ATPase, as well as that of NHE3, was decreased. Accordingly, the catalytic activity of Na+/K+-ATPase was decreased. In contrast, the expression of aquaporin-1 was not altered significantly. 6. The expression of the endothelial isoform of NOS was increased, along with tissue nitrite/nitrate levels. The expression of ANP mRNA was increased. 7. It is suggested that caffeine decreases Na+/K+-ATPase and NHE3 activities and increases nitric oxide and ANP activities in the kidney.

The present study was aimed at investigating whether the regulation of the local natriuretic peptide system is altered in the kidney and the vasculature in obstructive uropathy. Male Sprague-Dawley rats were bilaterally obstructed by ligation of the proximal ureters for 48 h. Control rats were treated in the same way, except that no ligature was made. The mRNA expression of the various isoforms of atrial, brain, and C-type natriuretic peptide (ANP, BNP, CNP) and different subtypes of natriuretic peptide receptor-A, -B, and -C (NPR-A, NPR-B, NPR-C) was determined in the kidney and the thoracic aorta by reverse transcription-polymerase chain reaction. The basal and stimulated activities of particulate guanylyl cyclase were also examined. Following the bilateral ureteral obstruction, the expression of ANP, BNP, and CNP was increased in the aorta as well as in the kidney. Contrary to this, the expression of NPR-A, NPR-B, and NPR-C was decreased both in the kidney and the aorta. Accordingly, the guanylyl cyclase activity was significantly decreased in response to natriuretic peptides. ANP relaxed phenylephrine-precontracted aortic rings in a dose-dependent manner, the degree of which was significantly diminished. Our results suggest that the local synthesis of natriuretic peptides is increased in the kidney and in the vasculature in obstructive uropathy.

Whether postobstructive diuresis could be related to altered regulation of aquaporin (AQP) water channels in the kidney was investigated. Male Sprague-Dawley rats underwent bilateral obstruction of the proximal ureters for 48 h. The renal expression of AQP1 to AQP4 proteins was then determined by Western blot and immunohistochemical analyses. For elucidation of the primary impairment in the upstream pathway leading to the expression of cAMP-mediated AQP channels, the expression of G(salpha) and that of adenylyl cyclase were also determined. For some rats, the obstruction was released for collection of urine samples. After the ureteral obstruction, the urinary flow rate was increased and free water reabsorption was decreased. In the obstructed kidneys, the expression of AQP1 to AQP3 was decreased in the cortex, outer medulla, and inner medulla, whereas that of AQP4 was decreased in the inner medulla. Immunoreactivities for AQP1 to AQP4 were also decreased in the obstructed kidneys. The protein expression of G(salpha) was decreased in the cortex, outer medulla, and inner medulla, whereas that of adenylyl cyclase VI was decreased in the outer and inner medullae. cAMP generation stimulated by arginine vasopressin was decreased in the cortex, outer medulla, and inner medulla. cAMP generation in response to forskolin was decreased in the outer and inner medullae, whereas that in response to sodium fluoride was decreased in the cortex, outer medulla, and inner medulla. These results suggest that a reduced abundance of AQP water channels in the kidney accounts in part for postobstructive diuresis. The primary impairment of AQP channels that are regulated via the arginine vasopressin/cAMP pathway may lie at the level of G proteins and adenylyl cyclase itself.

The present study examined whether the cisplatin induced urinary concentration defect can be related to an altered regulation of aquaporin (AQP) water channels in the kidney. Cisplatin (8 mg/kg) was injected intraperitoneally into male Sprague-Dawley rats. The control group was without cisplatin treatment. Four d later, the expression of AQP1, AQP2, and AQP3 proteins was determined in the kidney. To specify further the primary point of derangement in the pathway that activates the arginine vasopressin-mediated AQP channels, different components of adenylyl cyclase complex were examined separately. The cisplatin treatment caused a polyuric renal failure in association with decreases of free water reabsorption. The expression of AQP1 and AQP2 was decreased in the cortex, the outer medulla, and the inner medulla, whereas that of AQP3 was decreased in the outer medulla and the inner medulla. The expression of AQP2 proteins in the apical membrane-enriched fraction decreased in parallel with that in the subapical vesicle-enriched fraction, indicating a preserved targeting. Immunohistochemistry of the outer medulla also revealed that cisplatin decreased immunoreactivity for AQP1, AQP2, and AQP3. The arginine vasopressin-evoked generation of cyclic adenosine monophosphate was attenuated by cisplatin, being most prominent in the outer medulla. However, the cyclic adenosine monophosphate generation in response to forskolin was not affected, whereas that to sodium fluoride was diminished significantly. Cisplatin also decreased the expression of Gsalpha proteins in the outer medulla and the inner medulla. These results suggest that a reduced expression of AQP water channels accounts at least in part for the cisplatin-induced urinary concentration defect.

Background information: Tubulointerstitial fibrosis is the end‐point of chronic kidney diseases. Tamoxifen, a selective oestrogen receptor (ER) modulator, attenuates renal fibrosis, by regulating the transforming growth factor (TGF)‐β/Smad signalling. Src and phosphoinositide 3‐kinase (PI3K)/Akt pathways play critical roles in the pathogenesis of renal fibrosis. However, the activation of the non‐canonical TGF‐β signalling in renal fibrosis after treatment with tamoxifen remains unclear. Renal fibrosis was induced by unilateral ureteral obstruction (UUO) in rats. Tamoxifen was orally administered after UUO. Additionally, HK‐2 cells were treated with tamoxifen in the presence or absence of TGF‐β1. The selective ER down‐regulator ICI and ER‐α silencing were used to confirm the involvement of ER‐α on the effect of tamoxifen on TGF‐β1‐stimulated fibrosis in HK‐2 cells. Results: Tamoxifen treatment ameliorated UUO‐induced renal fibrosis as shown by decreased expression of α‐smooth muscle actin (SMA), fibronectin and connective tissue growth factor (CTGF). The phosphorylation of Src, PI3K, Akt, mammalian target of rapamycin (mTOR) and p70S6K significantly decreased in UUO kidneys from tamoxifen‐treated animals. Tamoxifen dose‐dependently suppressed the TGF‐β1‐induced expression of α‐SMA and CTGF, and phosphorylation of Src, PI3K, Akt, mTOR and p70S6K in HK‐2 cells. These anti‐fibrotic effects were reversed by treatment with ICI and silencing of ER‐α. Moreover, inhibition of the PI3K/Akt and mTOR/p70S6K pathways was observed in HK‐2 cells co‐treated with PP1 (a Src kinase inhibitor) and tamoxifen. Conclusions: The anti‐fibrotic effects of tamoxifen are associated with the suppression of Src kinase function via ER‐α, followed by inhibition of the PI3K/Akt and mTOR/p70S6K signalling pathways. Significance: Our findings suggest that tamoxifen is a novel therapeutic option for the prevention and treatment of renal fibrosis. Research Article: Our results demonstrated that phosphorylation of Src kinase in the obstructive kidney medicates renal fibrosis by activation of PI3K/Akt and mTOR/p70S6K signalling pathway, and treatment of tamoxifen has anti‐fibrotic effect on renal fibrosis by suppressing these pathways. In addition, our in vitro results suggested that anti‐fibrotic effect and its downstream signalling pathway were attenuated by tamoxifen in an ER‐α‐dependent manner. However, at present, it remains difficult to determine whether tamoxifen acts as anti‐oestrogenic or oestrogenic effect in our study. [ABSTRACT FROM AUTHOR]