Distal Tubule Research Articles

Renal Mechanisms of Diuretic Resistance in Congestive Heart Failure

This study reviews the renal aspects of diuretic resistance occurring in diuretic treatment, mostly with loop diuretics of congestive heart failure. A short discussion on the different classes of diuretics, including the recently introduced sodium-glucose transporter 2 inhibitors, and their mechanism of action in the nephron is provided, followed by a summary of recent data discussing the different causes and pathophysiological mechanisms of diuretic resistance. The major cause of diuretic resistance appears to be localized within the distal tubule. Traditionally, the concept of compensatory post-diuretic sodium reabsorption (CPDSR) was considered the major cause of diuretic resistance; however, recent studies have disputed this traditional concept and demonstrated that patients with congestive heart failure are in constant sodium-avid state. Finally, the different options of therapeutic strategies, combining different classes of diuretics are summarized.

PL-4: INSIGHTS INTO MOLECULAR MECHANISMS OF HYPERTENSION FROM HUMAN GENETICS

Identification and investigation of rare patients with extreme forms of high and low blood pressure has led to the identification of specific genes whose mutation results in these outlier phenotypes. These rare mutations converge on genes that mediate or regulate the renal reabsorption of Na-Cl. Mutations that increase or decrease renal salt reabsorption respectively increase or decrease blood pressure. Mutations that cause hypertension include gain of function mutations in subunits of the epithelial Na+ channel (ENaC) and in any of eight genes that cause constitutive activity of ENaC by its stimulation via its major regulator, the mineralocorticoid receptor, the target of aldosterone signaling; these increase salt reabsorption in the distal nephron. Conversely, mutations that cause hypotension include loss of function mutations in ENaC subunits, but also mutations the thiazide-sensitive Na-Cl cotransporter (NCC) or a K+ channel required for cotransporter function that act in the distal convoluted tubule (DCT), or mutations in the Na-K-2Cl cotransporter as well as K+ and Cl- channels expressed in the thick ascending limb of Henle that are required for normal Na-Cl reabsorption in this nephron segment. ENaC, the Na-Cl cotransporter and the Na-K-2Cl cotransporter, as well as the mineralocorticoid receptor are all commonly used targets for treatment of hypertension and/or diuresis. In addition to these genes, genetic studies also identified a previously unrecognized pathway that regulates the balance between renal salt reabsorption and K+ secretion. Mutations in the kinases WNK1 or WNK4, or genes that mediate their degradation via ubiquitylation, CUL3 and KLHL3 cause hypertension with hyperkalemia. Activity of WNK1 and WNK4 stimulates activation of NCC promoting Na-Cl reabsorption in the DCT, reducing Na-Cl- delivery distally, thereby limiting ENaC activity and limiting K+ secretion in the distal nephron. Conversely, hyperkalemia inhibits WNK activity, promoting distal Na-Cl delivery and maximizing K+ secretion. Angiotensin II signaling promotes WNK activity, increasing Na-Cl reabsorption in the DCT and inhibiting K+ secretion, while hyperkalemia appears to inhibit WNK activity, providing distal Na+ delivery that is used to drive K+ secretion. The importance of this pathway is that it can explain the mechanism by which increased dietary K+ lowers blood pressure. Both reduced dietary salt intake and increased dietary K+ can reduce blood pressure in controlled settings, and recent large population studies have shown that increased dietary K+ and reduced Na-Cl intake not only lower blood pressure but reduce the incidence of cardiovascular disease and death.

Control of sodium and potassium homeostasis by renal distal convoluted tubules.

Distal convoluted tubules (DCT), which contain the Na-Cl cotransporter (NCC) inhibited by thiazide diuretics, undergo complex modulation to preserve Na+ and K+ homeostasis. The lysine kinases 1 and 4 (WNK1 and WNK4), identified as hyperactive in the hereditary disease pseudohypoaldosteronism type 2, are responsible for activation of NCC and consequent hypokalemia and hypertension. WNK4, highly expressed in DCT, activates the SPAK/OSR1 kinases, which phosphorylate NCC and other regulatory proteins and transporters in the distal nephron. WNK4 works as a chloride sensor through a Cl- binding site, which acts as an on/off switch at this kinase in response to changes of basolateral membrane electrical potential, the driving force of cellular Cl- efflux. High intracellular Cl- in hyperkalemia decreases NCC phosphorylation and low intracellular Cl- in hypokalemia increases NCC phosphorylation and activity, which makes plasma K+ concentration a central modulator of NCC and of K+ secretion. The WNK4 phosphorylation by cSrc or SGK1, activated by angiotensin II or aldosterone, respectively, is another relevant mechanism of NCC, ENaC, and ROMK modulation in states such as volume reduction, hyperkalemia, and hypokalemia. Loss of NCC function induces upregulation of electroneutral NaCl reabsorption by type B intercalated cells through the combined activity of pendrin and NDCBE, as demonstrated in double knockout mice (KO) animal models, Ncc/pendrin or Ncc/NDCBE. The analysis of ks-Nedd-4-2 KO animal models introduced the modulation of NEDD4-2 by intracellular Mg2+ activity as an important regulator of NCC, explaining the thiazide-induced persistent hypokalemia.

S-27-6: ADAPTIVE IMMUNITY REGULATES RENAL SALT-RETENTION AND BLOOD PRESSURE

Hypertension is a major public health problem, which contributes to a plethora of other cardiovascular diseases. A long-time postulate is that a defect in the kidney plays a key role in the development of hypertension. Years of intense research have confirmed that distal nephron plays important role in excessive salt retention, which contributes to the pathogenesis of hypertension. Yet the precise identity of this kidney defect and the downstream signaling mechanisms that impair sodium handling remain unclear. In the past decade, T cells, in particular CD8+ T cells (CD8Ts), have garnered attention as an important contributor to hypertension. T cells infiltrate into the kidneys of hypertensive animals, possibly driven by elevated perfusion pressure. Subsequently elevation of blood pressure and salt content stimulate T cell-activation and cytokine production. We recently reported a new mechanism by which renal infiltrated CD8Ts contribute to salt retention and hypertension: CD8Ts upregulate the sodium-chloride cotransporter (NCC) in the renal distal tubules, resulting in excessive salt retention via direct interactions between CD8Ts and renal distal convoluted tubule cells (DCTs) (Image in enclosed figure). This finding raises the exciting prospect that kidney-accumulation of CD8Ts and their interactions with DCTs represent one kidney defect in the pathogenesis of salt-sensitive hypertension. Although blocking NCC using thiazide temporarily lowered blood pressure in hypertensive animals, it failed to diminish T cell-homing to the kidneys, and hypertension returned after withdrawal of thiazide. Thus, in order to design effective therapeutics for salt-sensitive hypertension which interrupt the initial stimuli that trigger renal sodium retention, it is critical for us to define mechanisms of T cell-homing to the kidney and identify the key molecules mediating the CD8T-DCT interaction. Here, we further identified critical molecular players and demonstrated their roles in augmenting the CD8T-DCT interaction leading to salt-sensitive hypertension. We found that activated CD8Ts exhibit enhanced interaction with DCTs via IFNγ-induced upregulation of MHC-I and PDL1 in DCTs, thereby stimulating higher expression of NCC in DCTs to cause excessive salt retention and progressive elevation of blood pressure. Eliminating IFNγ or renal tubule-specific knockdown of PDL1 prevented T cell homing into the kidney, thereby attenuating hypertension in two different mouse models. These findings provide a new mechanism for T cell involvement in the pathogenesis of hypertension and reveal novel therapeutic targets.

Hipokalemija - rani marker autozomno recesivne tubulopatije (Gitelmanov sindrom) - prikaz slučaja

Hypokalemia is the most common feature of Gitelman syndrome, which is a rare, inherited, autosomal recessive kidney disease associated with tubule disease. In addition to hypokalemia, it is also characterized by hypomagnesemia, metabolic alkalosis, hyperrenemic hyperaldosteronism, normal or lower blood pressure, while the presence of arterial hypertension does not exclude the diagnosis. It affects men and women equally, with a prevalence of 1 to 10 cases per 40,000 inhabitants. The most common cause are mutations in the SLC12A3 gene, which encodes the thiazidesensitive sodium chloride cotransporter (NCCT) in the renal distal tubules, and the TRPM6 (cation channel subfamily 6 protein claudin 16) gene, which controls distal tubular magnesium transport. The aim of the paper is to present an adult patient with pronounced hypokalemia as part of Gitelman's syndrome. Case report: We present a 21-year-old man with severe hypokalemia as part of Gitelman's syndrome. The disease manifested itself in non-specific complaints, and laboratory findings showed hypokalemia of 2.0 mmol/L, which was the reason for urgent hospitalization. Further examinations of the patient verified the following: hypomagnesemia, hypocalciuria, metabolic alkalosis, preserved kidney function and arterial hypotension. Other potential causes of hypokalemia were excluded by differential diagnosis. He was treated with potassium and magnesium replacement therapy, after which the symptoms of hypokalemia disappeared, and the electrolyte values were closer to the reference values. The diagnosis of Gitelman's syndrome was made based on clinical and laboratory findings. A geneticist was also consulted. Hypokalemia as part of Gitelman's syndrome is rarely encountered in clinical practice, and it is rarely thought of. Severe forms of hypokalemia should arouse suspicion of its existence and lead to a final diagnosis, for which rich clinical experience and teamwork are necessary. The patients with symptoms should be treated symptomatically, and those without symptoms should be monitored 1-2 times a year.

In vitro methods to assess 11β-hydroxysteroid dehydrogenase type 2 activity.

11β-Hydroxysteroid dehydrogenase type 2 (11β-HSD2) converts active 11β-hydroxyglucocorticoids to their inactive 11-keto forms, fine-tuning the activation of mineralocorticoid and glucocorticoid receptors. 11β-HSD2 is expressed in mineralocorticoid target tissues such as renal distal tubules and cortical collecting ducts, and distal colon, but also in placenta where it acts as a barrier to reduce the amount of maternal glucocorticoids that reach the fetus. Disruption of 11β-HSD2 activity by genetic defects or inhibitors causes the syndrome of apparent mineralocorticoid excess (AME), characterized by hypernatremia, hypokalemia and hypertension. Secondary hypertension due to 11β-HSD2 inhibition has been observed upon consumption of excessive amounts of licorice and in patients treated with the azole fungicides posaconazole and itraconazole. Furthermore, inhibition of 11β-HSD2 during pregnancy with elevated exposure of the fetus to cortisol can cause neurological complications with a lower intelligence quotient, higher odds of attention deficit and hyperactivity disorder as well as metabolic reprogramming with an increased risk of cardio-metabolic disease in adulthood. This chapter describes in vitro methods for the determination of 11β-HSD2 activity that can be applied to identify inhibitors that may cause secondary hypertension and characterize the enzyme's activity in disease models. The included decision tree and the list of methods with their advantages and disadvantages aim to enable the reader to select and apply an in vitro method suitable for the scientific question and the equipment available in the respective laboratory.

PS-C37-5: NEW THERAPEUTIC PERSPECTIVES FOR BLOOD PRESSURE CONTROL: DEXFADROSTAT PHOSPHATE, A NOVEL ALDOSTERONE SYNTHASE INHIBITOR, IN PATIENTS WITH PRIMARY ALDOSTERONISM

Objective: Aldosterone, the primary mineralocorticoid produced by the adrenal gland, regulates fluid homeostasis by stimulating sodium reabsorption in exchange for potassium in the distal tubules and collecting duct of the kidney. Aldosterone synthase (CYP11B2) is the rate-limiting enzyme for aldosterone biosynthesis. Patients with primary aldosteronism (PA) are characterized by an uncontrolled, excess production of aldosterone and are at higher risk of stroke, atrial fibrillation, and heart failure compared to patients with essential hypertension. Furthermore, PA increases the risk of death even after initiation of medical treatment to control blood pressure. Therefore, PA is the compelling indication to demonstrate the value for an aldosterone synthase inhibitor (ASI) as targeted treatment. Previous attempts to eliminate the excessive spontaneous aldosterone synthesis defining PA have been unsuccessful, particularly due to the unintended inhibition of other steroid hormones. Dexfadrostat phosphate is a novel ASI that acts directly on CYP11B2, targeting the root cause of primary aldosteronism. Design and method: Dexfadrostat phosphate was first investigated in patients with PA diagnosed within 1 year of study entry according to medical guidelines including a suppression test to demonstrate autonomous aldosterone production. Eligibility was verified and approved by a Central Review panel. Following a 2-week placebo-controlled run-in period, enrolled patients were randomized to one of three doses of dexfadrostat taken orally, once daily. After 8 weeks of treatment, patients were switched to placebo and followed for an additional 2 weeks. Blood samples were taken at 2-week intervals and evaluated in a central laboratory for steroid and peptide hormone as well as electrolyte levels. Blood pressure was measured in the office during each clinic visit. Ambulatory systolic blood pressure (aSBP) was monitored over 24-hours at baseline and after 8 weeks of dexfadrostat treatment. Results: All endpoints of the study were met with high significance. Dexfadrostat phosphate treatment was safe and well tolerated. We present the effects on the aldosterone-to-renin ratio (ARR) and subsequent blood pressure reduction, the correction of hypokalemia, and the persistence and reversal of therapeutic effects upon drug withdrawal. Conclusions: The phase 2 study in patients evaluated the ability of dexfadrostat phosphate to deliver both biochemical (ARR, potassium) and subsequent clinical (aSBP) correction of the consequences of uncontrolled aldosterone production. By demonstrating its clinical utility in a rarely diagnosed indication of extreme aldosterone dysregulation, the potential of dexfadrostat phosphate may well expand to address essential hypertension, chronic kidney disease, hypokalemia, volume expansion and organ remodeling.

PS-B01-11: GENERATION OF TRANSGENIC MICE WITH PROXIMAL TUBULE-SPECIFIC OVEREXPRESSION OF ATRAP AND ANALYSIS OF PROXIMAL TUBULE ATRAP IN BLOOD PRESSURE REGULATION

Objective: Proximal tubule angiotensin II type 1 receptor (AT1R) is involved in blood pressure (BP) regulation (Li XC, et al. Hypertension, 77:1285-1298, 2021). AT1 receptor-associated protein (ATRAP) interacts with AT1R and promotes constitutive internalization of AT1R, to inhibit pathological activation of its downstream signaling (Tamura K, et al. Hypertens Res, 45:32–39, 2022). Endogenous ATRAP is abundantly expressed along kidney tubules in the kidney, and our previous investigations using systemic ATRAP knockout and distal tubule-dominant ATRAP transgenic mice revealed that ATRAP suppressed Ang II-induced hypertension mainly through a distal tubule-mediated mechanism (Wakui H, et al. Hypertension, 61:1203–10, 2013; Ohsawa M, et al. Kidney Int, 86:570–81, 2014). On the other hand, proximal tubule-specific ATRAP knockout mice exhibited similar baseline BP and pressor response to Ang II compared with wild-type mice (Kinguchi S, et al. J Am Heart Assoc, 8(8):e012395, 2019). The present study was performed to investigate the effects of enhancement of proximal tubule ATRAP on Ang II-mediated hypertension, using proximal tubule-specific ATRAP transgenic mice. Design and method: [Experiment 1] Using mouse ATRAP cDNA linked to the type II sodium-dependent phosphate cotransporters (NPT2) promoter, we generated transgenic mice (NPT2-Tg mice) with proximal tubule-specific overexpression of ATRAP. ATRAP mRNA expression in the proximal tubule was quantified by a laser capture microdissection and quantitative reverse transcription-polymerase chain reaction analysis. [Experiment 2] Male NPT2-Tg and wild-type littermate control (LC) mice were divided into Ang II (1000 ng/kg/min) and vehicle groups. BP was measured using a tail-cuff method before and 14 days after treatment, and then mice were sacrificed and their organs were collected. Results: [Experiment 1] 5 of 12 lines of ATRAP Tg mice exhibited kidney overexpression of the ATRAP-transgene in comparison with LC mice. Kidney ATRAP expression at the protein level revealed the highest expression level of ATRAP in lines 23, approximately 10-fold higher compared to LC mice. Therefore, we chose line 23 (NPT2-Tg23) for further analysis. ATRAP mRNA expression was increased approximately 9-fold in the proximal tubules of NPT2-Tg23 mice compared with LC mice. On the other hand, ATRAP mRNA expression in the distal tubules was comparable between NPT2-Tg23 and LC mice. [Experiment 2] We are currently conducting the experiments and will present our findings at this conference. Conclusions: We succeeded in generating transgenic mice with proximal tubule-specific overexpression of ATRAP. We plan to present the results of the impact of enhancement of proximal tubular ATRAP on Ang II-dependent hypertension at this conference.

Morphological and histometric features of the caudal kidney in piranha Pygocentrus nattereri (Characiformes: Serrasalmidae)

Abstract Pygocentrus nattereri is a widely distributed species in the Neotropical region and a potential bio-indicator. Kidneys have functions in fish physiology, allowing them to live in different environments. We aimed to compare the histological characteristics of caudal kidneys between males and females, associating them with the renosomatic index (RSI). For this purpose, 15 males and 14 females were used for biometric and histological analyses. Structural volumetric density (SVD), renal corpuscle histometric measures, and hemosiderin and lipofuscin deposit frequency in macrophages melanogenic (MMs) were assessed. No biometric differences were observed between the sexes, but body weight and standard length were correlated with RSI. The SVD showed difference in hematopoietic tissue between female and males, whereas the density of the other structures was not different. The RSI was positively associated with hematopoietic tissue and proximal tubule density in contrast to distal tubules, blood vessels, collecting ducts and MMs. Females exhibited a higher renal corpuscle area, glomerulus area, distal tubule diameter, collecting tubule area, and collecting tubule lumen area. These differences may be due to metabolic differences between males and females. Sex effect in P. nattereri may define punctual differences in future studies on the metabolism and immunity of this species.

Comparison of acute kidney injury following brain death between male and female rats

BackgroundClinical reports associate kidneys from female donors with worse prognostic in male recipients. Brain Death (BD) produces immunological and hemodynamic disorders that affect organ viability. Following BD, female rats are associated with increased renal inflammation interrelated with female sex hormone reduction. Here, the aim was to investigate the effects of sex on BD-induced Acute Kidney Injury (AKI) using an Isolated Perfused rat Kidney (IPK) model. MethodsWistar rats, females, and males (8 weeks old), were maintained for 4h after BD. A left nephrectomy was performed and the kidney was preserved in a cold saline solution (30 min). IPK was performed under normothermic temperature (37°C) for 90 min using WME as perfusion solution. AKI was assessed by morphological analyses, staining of complement system components and inflammatory cell markers, perfusion flow, and creatinine clearance. ResultsBD-male kidneys had decreased perfusion flow on IPK, a phenomenon that was not observed in the kidneys of BD-females (p < 0.0001). BD-male kidneys presented greater proximal (p = 0.0311) and distal tubule (p = 0.0029) necrosis. However, BD-female kidneys presented higher expression of eNOS (p = 0.0060) and greater upregulation of inflammatory mediators, iNOS (p = 0.0051), and Caspase-3 (p = 0.0099). In addition, both sexes had increased complement system formation (C5b-9) (p=0.0005), glomerular edema (p = 0.0003), and nNOS (p = 0.0051). ConclusionThe present data revealed an important sex difference in renal perfusion in the IPK model, evidenced by a pronounced reduction in perfusate flow and low eNOS expression in the BD-male group. Nonetheless, the upregulation of genes related to the proinflammatory cascade suggests a progressive inflammatory process in BD-female kidneys.

Aldosterone Antagonist Dosing and the Risk of Hyponatremia in Patients With Cirrhosis and Ascites.

Ascites is a common decompensating event in cirrhosis.1 For initial treatment, major liver societies recommend spironolactone 100 mg daily with or without furosemide 40 mg daily.2 Although supporting data are lacking, the generally accepted dosing ratio of spironolactone to furosemide is 5:2 so as to maintain potassium equilibrium.2 However, aldosterone antagonists are a common cause of hyponatremia because they induce natriuresis at the distal tubule and collecting ducts, leaving scant opportunity for sodium reabsorption.

Diagnosis and Treatment of Monogenic Hypertension in Children.

Although the majority of individuals with hypertension (HTN) have primary and polygenic HTN, monogenic HTN is a secondary type that is widely thought to play a key role in pediatric HTN, which has the characteristics of early onset, refractory HTN with a positive family history, and electrolyte disorders. Monogenic HTN results from single genetic mutations that contribute to the dysregulation of blood pressure (BP) in the kidneys and adrenal glands. It is pathophysiologically associated with increased sodium reabsorption in the distal tubule, intravascular volume expansion, and HTN, as well as low renin and varying aldosterone levels. Simultaneously increased or decreased potassium levels also provide clues for the diagnosis of monogenic HTN. Discovering the genetic factors that cause an increase in BP has been shown to be related to the choice of and responses to antihypertensive medications. Therefore, early and precise diagnosis with genetic sequencing and effective treatment with accurate antihypertensive agents are critical in the management of monogenic HTN. In addition, understanding the genetic architecture of BP, causative molecular pathways perturbing BP regulation, and pharmacogenomics can help with the selection of precision and personalized medicine, as well as improve morbidity and mortality in adulthood.

PS-B08-8: THERAPEUTIC STRATEGIES TARGETING RAGE IMPROVES RENAL OUTCOME IN LUPUS NEPHRITIS

Introduction: Lupus nephritis (LN) is present in 60% of patients with systemic lupus erythematosus (SLE). Despite of current development of immunosuppressant agents, LN still impairs the survival and quality of life in SLE patients. Receptor for advanced glycation endproducts (RAGE) is a multi-ligand receptor that belongs to the immunoglobulin superfamily, which is strongly associated with innate immune system. In the present study, we examined whether RAGE is involved in the development of LN. Further, we explored the therapeutic impact of DNA-aptamer directed against RAGE on lupus-related kidney injury. Methods: [Protocol 1] RAGE expression in kidneys and urinary RAGE excretion (uRAGE) were determined at 8, 12, 16, 18, 20-week-old by real-time PCR and ELISA, respectively in MRL/lpr, SLE-prone mice. [Protocol 2] LN was induced by peritoneally injecting pristane in wild type and RAGE globally knockout mice. [Protocol 3] MRL/lpr mice were subcutaneously administrated with DNA-aptamer raised against RAGE (RAGE-apt) or Control-aptamer (Ctrl-apt) for 10weeks. Results: [Protocol 1] uRAGE levels, but not urinary protein excretion, were significantly increased in 8-week-old MRL/lpr mice when compared to those in control MRL/MPJ mice, suggesting that uRAGE could be an early marker of LN.. Immunofluorescence staining demonstrated that RAGE was upregulated in distal tubules but not in glomerulus in 8-week-old mice. Glomerular RAGE expression was increased from 12-week-old with mesangial matrix expansion and formation of cellular crescents. RAGE expression was also found in endothelium and infiltrated macrophages in glomerulus while RAGE was merged with cathepsine D, a lysosomal aspartyl protease, and Rab7, a marker of late endocytosis in tubular epithelial cells. [Protocol 2] Pristane-induced increase in systolic blood pressure was reduced with improvement of renal dysfunction in RAGE knockouts. RAGE knockouts also showed less fibrosis with decrease in macrophage infiltration when compared to wild type mice in pristane-induced lupus nephritis. [Protocol 3] Administration of RAGE-apt ameliorated mesangial expansion, crescent formation, and macrophage infiltration into glomerulus in MRL/lpr mice. RAGE-apt, but not Ctrl-apt, reduced the level of pro-inflammatory cytokines gene expression including IL-6, TNF-α, and MCP-1 in renal cortex of MRL/lpr mice. Conclusion: RAGE could be involved in the pathogenesis of LN, and RAGE-DNA aptamer might be one of the promising therapeutic strategies for preventing the development of LN.

Efficacy of orally administered montmorillonite in myoglobinuric acute renal failure model in male rats.

Acute kidney injury can be associated with serious consequences and therefore early treatment is critical to decreasing mortality and morbidity rate. We evaluated the effect of montmorillonite, the clay with strong cation exchange capacity, on the AKI model in rats. Glycerol (50% solution, 10 ml/kg) was injected in the rat hind limbs to induce AKI. 24 hr after induction of acute kidney injury, the rats received oral doses of montmorillonite (0.5 g/kg or 1 g/kg), or sodium polystyrene sulfonate (1 g/kg) for three consecutive days. Glycine induced acute kidney injury in rats with high levels of urea (336.60± 28.19 mg/dl), creatinine (4.10± 0.21 mg/dl), potassium (6.15 ± 0.28 mEq/L), and calcium (11.52 ± 0.19 mg/dl). Both doses of montmorillonite (0.5 and 1 g/kg) improved the serum urea (222.66± 10.02 and 170.20±8.06, P<0.05), creatinine (1.86±0.1, 2.05± 0.11, P<0.05), potassium (4.68 ± 0.4, 4.73 ± 0.34, P<0.001) and calcium (11.15 ± 0.17, 10.75 ± 0.25, P<0.01) levels. Treatment with montmorillonite especially at a high dose reduced the kidney pathological findings including, tubular necrosis, amorphous protein aggregation, and cell shedding into the distal and proximal tubule lumen. However, administration of SPS could not significantly decrease the severity of damages. According to the results of this study, as well as the physicochemical properties of montmorillonite, such as high ion exchange capacity and low side effects, montmorillonite can be a low-cost and effective treatment option to reduce and improve the complications of acute kidney injury. However, the efficacy of this compound in human and clinical studies needs to be investigated.

Distal renal tubular system-on-a-chip for studying the pathogenesis of influenza A virus-induced kidney injury.

Influenza A viruses typically cause acute respiratory infections in humans. However, virus-induced acute kidney injury (AKI) has dramatically increased mortality. The pathogenesis remains poorly understood due to limited disease models. Here, a distal renal tubular system-on-a-chip (dRTSC) was constructed to explore the pathogenesis. The renal tubule-vascular reabsorption interface was recapitulated by co-culturing the distal renal tubule and peritubular vessel with a collagen-coated porous membrane. To study the pathways of influenza virus entry into the kidney, dynamic tracking of fluorescence-labeled virus-infected blood vessels was performed. For the first time, the virus was shown to enter the kidney rapidly by cell-free transmission without disrupting the vascular barrier. Direct virus infection of renal tubules in dRTSC reveals disruption of tight junctions, microvilli formation, polar distribution of ion transporters, and sodium reabsorption function. This robust platform allows for a straightforward investigation of virus-induced AKI pathogenesis. The combination with single-virus tracking technology provides new insights into understanding influenza virus-induced extra-respiratory disease.

Rats kidney morphological particularities and functions post-treatment with vernonia amygdalina extract and low-dose lead acetate

This study was conducted to evaluate the effect of Vernonia amygdalina extract on Pb-induced kidney toxicity in Wistar rats. This investigation was carried out using 25 Wistar rat of both sexes, and the animals were divided into five groups: 5 rats per group. Group A served as the negative control group and was orally gavaged with 5mg/ kg body weight of normal saline daily. Group B served as the positive control and was treated with daily intraperitoneal (IP) injection of 8 mg/kg body weight of Pb acetate (Pb). Group C was treated with daily intraperitoneal (IP) injection of 8 mg/kg body weight of Pb along with 20 mg/kg body weight of Vernonia amygdalina extract orally. Group D was treated with daily intraperitoneal (IP) injection of 8 mg/kg body weight of Pb along with 40 mg/kg body weight of Vernonia amygdalina extract orally. Group 5 was treated with daily intraperitoneal (IP) injection of 8 mg/kg body weight of Pb along with 60 mg/kg body weight of Vernonia amygdalina extract orally. All treatments were done for a period of 28 days. The animals were sacrificed on the 29th day by cervical dislocation, then blood was collected by cardiac puncture, and kidneys were collected for histological profile. Lipid peroxidation (MDA), creatinine and urea level were all determined. There was marked elevation in MDA level with a concomitant depletion in urea and creatinine content in the group treated with only Pb when compared with the negative control group. There was a significant increase in proximal tubular area, distal tubular area, glomerular membrane thickness, area, perimeter and feret’s diameter and a significant decrease in proximal tubule, distal tubule ratio and cellularity in this group of rats when compared to the negative control. Oxidation and histological changes in the kidneys were successfully prevented by the pre- administration of Vernonia amygdalina as evidenced by creatinine and urea and MDA level. These were made evident as the morphological scores across all experimental groups were significantly different from those of the positive control (group 2). Based on the current findings, it can be concluded that Vernonia amygdalina successfully minimizes the deleterious effects in kidney function and histological coherence associated with nephrotoxicity by strengthening the antioxidant defense system, suppressing oxidative stress, and mitigating apoptosis.

Load Tests of the Renal form of Primary Hyperparathyroidism in Children

After the introduction of calcium chloride (12.4 mg/kg) examined the levels in the blood at 20 and 120 minutes. The calcium content in a comparison group of children after 120 minutes returned to the baseline, in patients with a renal form of primary hyperparathyroidism its level was greater than 1.3 times. The test was sensitive and provided an opportunity to reveal hypercalcemia in 39 children who had been the normo[1]and hypocalcemia. The impaired renal function had no effect on the significance of the test. Osmotic hypertension develops under the influence of hypertonic sodium chloride. In osmotic diuresis, the excretions of calcium and sodium cations are interdependent. Increasing sodium in the loops of Henle and distal renal tubules stimulates sodium excretion, decreased reabsorption, which leads to increased levels of calcium in the daily urine in children with primary hyperparathyroidism. Test with sodium chloride made it possible to detect hypercalciuria in 12 (21.43%) children who have had normal levels of calcium in urine.

Lectin Histochemistry of the Normal Feline Kidney.

Lectins have a strict binding specificity to carbohydrate moieties of cellular components, and can thus indicate changes in the glycosylation of cells in diseases. However, lectin-binding patterns in nephron segments of feline kidneys have not been fully surveyed. The present study reported lectin-binding patterns in normal feline kidneys by histochemical investigations of eight commercially available lectin detection kits. Kidneys from four normal cats (intact males, 23-27 months old) were fixed in 4% paraformaldehyde, and embedded in paraffin; lectin histochemistry was performed for WGA, s-WGA, RCA-I, ConA, PNA, SBA, DBA, and UEA-I lectins. WGA, RCA, and ConA binding was observed from Bowman's capsule to the collecting ducts, while only WGA was detected in the glomerular capillary. s-WGA was observed from the proximal tubules to the collecting ducts, showing discriminative heterogeneous binding. PNA and SBA were detected in the distal nephrons, such as the thin limbs of the loops of Henle, distal tubules, and collecting ducts. UEA-I binding was observed in the thick ascending limbs of the loops of Henle, especially in the macula densa regions. DBA lectin showed no positive labeling in nephrons. The observed binding patterns may prove beneficial for the analysis of changes in glycosylation in feline kidney diseases.

About combination of positive and negative outcomes of a subchronic exposure of rats to selenium oxide nanoparticles

Introduction. Occupational contact with selenium and its compounds, including nanoscale forms, occurs in the glass production, rubber industry, metallurgy (metallurgical processes of copper sludge processing, copper pyrite roasting, manganese, selenium and tellurium production). There are scarce data on the toxicity of selenium nanoparticles. Material and methods. Stable suspensions of nanoparticles or deionized water (control group) were administered to male rats 3 times a week for 6 weeks. A single dose of selenium oxide nanoparticles was 0.2 or 1 or 2 mg/kg of body weight). The condition of the animal organism was assessed with a number of indicators of toxic action at the end of the experiment. The statistical significance of intergroup differences was assessed by Student's t-test. Results. Activity of succinate dehydrogenase in blood lymphocytes reflecting the intensity of energy processes in the organism was decreased. The number of eosinophils in smears-imprints of parenchymal organs and mesenteric lymph nodes increased, indicating the ability of selenium nanooxide to trigger signaling cascades in immunocompetent cells. The number of degenerated cells in the proximal and distal tubules in smears of the kidneys was increased. A tendency to a decrease in all hemodynamics parameters was found. A change in the QT duration, together with an increase in the amplitude of the T wave, probably indicates a violation of the processes of myocardial repolarization. The coefficient of fragmentation of genomic DNA in nucleated blood cells decreased. Limitations. The research was limited to the study of indicators of toxic action in only one study using a limited dose range. Conclusion. An ambiguous effect of selenium oxide nanoparticles on rats was found. Along with negative impact of nanoparticles we have demonstrated, for the first time, some beneficial outcomes, in particular, genome -protective action which is in a striking contrast with the genotoxicity of all elemental and element-oxide nanoparticles previously studied in our laboratory.

Immunohistochemical Localization of Alogliptin, a DPP-4 Inhibitor, in Tissues of Normal and Type 2 Diabetes Model Rat.

We investigated the pharmacokinetics of alogliptin (AG) at the cell and tissue level in healthy Wistar rats and a type 2 diabetic Goto-Kakizaki (GK) rat model. Immunohistochemistry of the renal tissue in these rats, post 1 hr of AG administration, showed that the signal was observed in the glomeruli, proximal tubule S3 segments, distal tubules, collecting ducts, and only in the brush border of the epithelial cells of the proximal tubule S1, S2 segments. After 6 hr of AG administration, the staining intensity of the regions other than the S3 segments was considerably reduced in Wistar rats, with no change observed in GK rats. At 24 hr, the staining intensity was considerably reduced, even in GK rats; however, the staining of the S3 segment remained unaltered in both. Hepatocytes in zone III of the hepatic lobule were more intensely stained than those in zone I in Wistar rats at 1 hr. However, almost no staining was observed in the hepatocytes of GK rats at 1 hr. Complete loss of signal was observed in the hepatocytes of the Wistar rats after 6 hr. This study revealed that the pharmacokinetics of AG in GK rats are different from those in Wistar rats.