Sodium Overload Research Articles

Inhibition of microRNA-429 in the renal medulla increased salt sensitivity of blood pressure in Sprague Dawley rats.

We have previously shown that high salt intake suppresses the expression of prolyl hydroxylase domain-containing protein 2 (PHD2), an enzyme promoting the degradation of hypoxia-inducible factor (HIF)-1α, and increases HIF-1α along with its target genes in the renal medulla, which promotes sodium excretion and regulates salt sensitivity of blood pressure. However, it remains unknown how high salt inhibits the expression of PHD2. The current study first revealed that high-salt-induced PHD2 inhibition was due to the enhanced decay of mRNA. We then found that high salt significantly increased the expression of miR-429, which was subsequently proven to target the 3'-untranslated region of PHD2 and reduce PHD2 levels, in the renal medulla. To define the functional role of renal medullary miR-429 in the regulation of PHD2/HIF-1α-mediated renal adaptation to high salt intake and salt sensitivity of blood pressure, we locally inhibited miR-429 in the renal medulla by locked nucleic acid anti-miR-429 in uninephrectomized rats. Our results demonstrated that inhibition of miR-429 remarkably increased the levels of PHD2, which disrupted PHD2-associated adaptive activation of HIF-1α-mediated gene expression in response to high salt in the renal medulla and consequently inhibited urinary sodium excretion, enhanced sodium retention in response to chronic sodium overloading, and as a result, produced a salt-sensitive hypertension. It is concluded that miR-429 is an important upstream mediator in PHD2/HIF-1α-associated renal adaptation to high salt intake and that deficiency in miR-429-mediated PHD2 inhibition in response to high salt in the renal medulla may represent a pathogenic mechanism for salt-sensitive hypertension.

Differential calcium sensitivity in NaV 1.5 mixed syndrome mutants.

SCN5a mutations may express gain-of-function (Long QT Syndrome-3), loss-of-function (Brugada Syndrome 1) or both (mixed syndromes), depending on the mutation and environmental triggers. One such trigger may be an increase in cytosolic calcium, accompanying exercise. Many mixed syndromes mutants, including ∆KPQ, E1784K, 1795insD and Q1909R, are found in calcium-sensitive regions. Elevated cytosolic calcium attenuates gain-of-function properties in ∆KPQ, 1795insD and Q1909R, but not in E1784K. By contrast, elevated cytosolic calcium further exacerbates gain-of-function in E1784K by destabilizing slow inactivation. Action potential modelling, using a modified O'Hara Rudy model, suggests that elevated heart rate rescues action potential duration in ∆KPQ, 1795insD and Q1909R, but not in E1784K. Action potential simulations suggest that E1784K carriers have an increased intracellular sodium-to-calcium ratio under bradycardia and tachycardia conditions. Elevated cytosolic calcium, which is common during high heart rates, ameliorates or exacerbates the mixed syndrome phenotype depending on the genetic signature. Inherited arrhythmias may arise from mutations in the gene for SCN5a, which encodes the cardiac voltage-gated sodium channel, NaV 1.5. Mutants in NaV 1.5 result in Brugada Syndrome (BrS1), Long-QT Syndrome (LQT3) or mixed syndromes (an overlap of BrS1/LQT3). Exercise is a potential arrhythmogenic trigger in mixed syndromes. We aimed to determine the effects of elevated cytosolic calcium, which is common during exercise, in mixed syndrome NaV 1.5 mutants. We used whole-cell patch clamp to assess the biophysical properties of NaV 1.5 wild-type (WT), ∆KPQ, E1784K, 1795insD and Q1909R mutants in human embryonic kidney 293 cells transiently transfected with the NaV 1.5 α subunit (WT or mutants), β1 subunit and enhanced green fluorescent protein. Voltage-dependence and kinetics were measured at cytosolic calcium levels of approximately 0, 500and 2500nm. In silico, action potential (AP) model simulations were performed using a modified O'Hara Rudy model. Elevated cytosolic calcium attenuates the late sodium current in ∆KPQ, 1795insD and Q1909R, but not in E1784K. Elevated cytosolic calcium restores steady-state slow inactivation (SSSI) to the WT-form in Q1909R, but depolarized SSSI in E1784K. Our AP simulations showed a frequency-dependent reduction of AP duration in ∆KPQ, 1795insD and Q1909R carriers. In E1784K, AP duration is relatively prolonged at both low and high heart rates, resulting in a sodium overload. Cellular perturbations during exercise may affect BrS1/LQT3 patients differently depending on their individual genetic signature. Thus, exercise may be therapeutic or may be an arrhythmogenic trigger in some SCN5a patients.

Oral rehydration of malnourished children with diarrhoea and dehydration: A systematic review

Background: Diarrhoea complicates over half of admissions to hospital with severe acute malnutrition (SAM). World Health Organization (WHO) guidelines for the management of dehydration recommend the use of oral rehydration with ReSoMal (an oral rehydration solution (ORS) for SAM), which has lower sodium (45mmols/l) and higher potassium (20mmols/l) content than standard ORS. The composition of ReSoMal was designed specifically to address theoretical risks of sodium overload and potential under-treatment of severe hypokalaemia with rehydration using standard ORS. In African children, severe hyponatraemia at admission is a major risk factor for poor outcome in children with SAM complicated by diarrhoea. We therefore reviewed the evidence for oral rehydration therapy in children with SAM. Methods: We conducted a systematic review of randomised controlled trials (RCTs) on 18th July 2017 comparing different oral rehydration solutions in severely malnourished children with diarrhoea and dehydration, using standard search terms. The author assessed papers for inclusion. The primary endpoint was frequency of hyponatraemia during rehydration. Results: Six RCTs were identified, all published in English and conducted in low resource settings in Asia. A range of ORS were evaluated in these studies, including standard ORS, hypo-osmolar ORS and ReSoMal. Hyponatraemia was observed in two trials evaluating ReSoMal, three children developed severe hyponatraemia with one experiencing convulsions. Hypo-osmolar ORS was found to have benefits in time to rehydration, reduction of stool output and duration of diarrhoea. No trials reported over-hydration or fatalities. Conclusions: Current WHO guidelines strongly recommend the use of ReSoMal based on low quality of evidence. Studies indicate a significant risk of hyponatraemia on ReSoMal in Asian children, none have been conducted in Africa, where SAM mortality remains high. Further research should be conducted in Africa to evaluate optimal ORS for children with SAM and to generate evidence based, practical guidelines.

Na+-H+ exchanger and proton channel in heart failure associated with Becker and Duchenne muscular dystrophies.

Cardiomyopathy is found in patients with Duchenne (DMD) and Becker (BMD) muscular dystrophies, which are linked muscle diseases caused by mutations in the dystrophin gene. Dystrophin defects are not limited to DMD but are also present in mild BMD. The hereditary cardiomyopathic hamster of the UM-X7.1 strain is a particular experimental model of heart failure (HF) leading to early death in muscular dystrophy (dystrophin deficiency and sarcoglycan mutation) and heart disease (δ-sarcoglycan deficiency and dystrophin mutation) in human DMD. Using this model, our previous work showed a defect in intracellular sodium homeostasis before the appearance of any apparent biochemical and histological defects. This was attributed to the continual presence of the fetal slow sodium channel, which was also found to be active in human DMD. Due to muscular intracellular acidosis, the intracellular sodium overload in DMD and BMD was also due to sodium influx through the sodium-hydrogen exchanger NHE-1. Lifetime treatment with an NHE-1 inhibitor prevented intracellular Na+ overload and early death due to HF. Our previous work also showed that another proton transporter, the voltage-gated proton channel (Hv1), exists in many cell types including heart cells and skeletal muscle fibers. The Hv1 could be indirectly implicated in the beneficial effect of blocking NHE-1.

Effect of isotonic versus hypotonic maintenance fluid therapy on urine output, fluid balance, and electrolyte homeostasis: a crossover study in fasting adult volunteers

BackgroundDaily and globally, millions of adult hospitalized patients are exposed to maintenance i.v. fluid solutions supported by limited scientific evidence. In particular, it remains unclear whether fluid tonicity contributes to the recently established detrimental effects of fluid, sodium, and chloride overload. MethodsThis crossover study consisted of two 48 h study periods, during which 12 fasting healthy adults were treated with a frequently prescribed solution (NaCl 0.9% in glucose 5% supplemented by 40 mmol litre−1 of potassium chloride) and a premixed hypotonic fluid (NaCl 0.32% in glucose 5% containing 26 mmol litre−1 of potassium) at a daily rate of 25 ml kg−1 of body weight. The primary end point was cumulative urine volume; fluid balance was thus calculated. We also explored the physiological mechanisms behind our findings and assessed electrolyte concentrations. ResultsAfter 48 h, 595 ml (95% CI: 454–735) less urine was voided with isotonic fluids than hypotonic fluids (P<0.001), or 803 ml (95% CI: 692–915) after excluding an outlier with ‘exaggerated natriuresis of hypertension’. The isotonic treatment was characterized by a significant decrease in aldosterone (P<0.001). Sodium concentrations were higher in the isotonic arm (P<0.001), but all measurements remained within the normal range. Potassium concentrations did not differ between the two solutions (P=0.45). Chloride concentrations were higher with the isotonic treatment (P<0.001), even causing hyperchloraemia. ConclusionsEven at maintenance rate, isotonic solutions caused lower urine output, characterized by decreased aldosterone concentrations indicating (unintentional) volume expansion, than hypotonic solutions and were associated with hyperchloraemia. Despite their lower sodium and potassium content, hypotonic fluids were not associated with hyponatraemia or hypokalaemia. Clinical trial registrationClinicalTrials.gov (NCT02822898) and EudraCT (2016-001846-24).

Contemporary Approaches to Perioperative IV Fluid Therapy.

Intravenous fluid therapy is required for most surgical patients, but inappropriate regimens are commonly prescribed. The aim of this narrative review was to provide evidence-based guidance on appropriate perioperative fluid management. We did a systematic literature search of the literature to identify relevant studies and meta-analyses to develop recommendations. Of 275 retrieved articles, we identified 25 articles to inform this review. "Normal" saline (0.9% sodium chloride) is not physiological and can result in sodium overload and hyperchloremic acidosis. Starch colloid solutions are not recommended in surgical patients at-risk of sepsis or renal failure. Most surgical patients can have clear fluids and/or administration of carbohydrate-rich drinks up to 2h before surgery. An intraoperative goal-directed fluid strategy may reduce postoperative complications and reduce hospital length of stay. Regular postoperative assessment of the patient's fluid status and requirements should include looking for physical signs of dehydration or hypovolemia, or fluid overload. Both hypovolemia and salt and water overload lead to adverse events, complications and prolonged hospital stay. Urine output can be an unreliable indicator of hydration status in the postoperative surgical patient. Excess fluid administration has been linked to acute kidney injury, gastrointestinal dysfunction, and cardiac and pulmonary complications. There is good evidence supporting the avoidance of unnecessary fasting and the value of an individualized perioperative IV fluid regimen, with transition to oral fluids as soon as possible, to help patients recover from major surgery.

The Natriuretic and Diuretic Response to Uroguanylin is Blunted in Dahl‐Salt Sensitive Rats

Uroguanylin (UGN) is a 17 aminoacids long peptide with diuretic and natriuretic activity. UGN, an intestinal natriuretic peptide, is delivered to the kidney as an unprocessed propeptide, prouroguanylin (pro‐UGN). Circulating pro‐UGN is processed to its active natriuretic form exclusively within the renal tubules. The circulating levels of pro‐UGN and the urinary levels of UGN are increased during sodium overload and this natriuretic peptide and the kidney response to UGN is increased in rats maintained in a high salt intake. We hypothesized that the diuretic and natriuretic response to UGN are altered in Dahl‐salt sensitive rats (DS) as compared to Wistar (WR) rats. Dahl‐salt sensitive (DS) rats (n=5/group) received water with 1% NaCl during 15 days and the tail systolic blood pressure (mmHg) increased from 108.0±2.0 to 145.9±2.6 while no remarkable changes were observed in Wistar rats. After the end of this period, rats were anesthetized and prepared for classical renal clearance and hemodynamics studies. After a 1‐hour control period, UGN was intravenously infused at 100nmoles/kg/min rate during 1‐hour period and heart rate (HR), mean arterial pressure (MAP), renal vascular resistance (RVR), glomerular filtration rate (GFR), renal blood flow (RBF), urine output (V′), UNaV and fractional sodium excretion (FENa+) were evaluated during infusion and for an additional 1‐hour post‐infusion period. No significant changes were observed for HR, MAP, RVR or RBF in any group or period during the whole experimental period. UGN did not change GFR (ml/g/min) in WR rats but increased it from 1.7±0.8 to 4.4±1.1 in DS rats. In addition, UGN infusion induced a significant diuresis that was stable during the infusion and post‐infusion period. The urinary output (μL/g of kidney/min) increased from 6.7±1.1 to 21.6±5.4 (p&lt;0.001) during the infusion with UGN in WR and from 5.7±2.6 to 11.5±3.6 in DS. Strikingly, the basal levels of UnaV (μEq/g of kidney/min) in DS are significantly lower than the levels observed for WR (0.04±0.01‐DS vs. 0.23±0.07‐p&lt;0.001). The infusion of UGN increases UNaV from 0.23±0.07 to 0.48±0.01 (p&lt;0.01) in WR and from 0.04±0.01 to 0.27±0.08 (P&lt;0.001). Similarly, the basal FENa+ is remarkably lower in DS when compared to WR. DS rats excrete 10 times less sodium than WR. The infusion of UGN does not increase FENa+ (%) in DS but induced a 60% increase in in WR from 1.5±0.12 to 2.5±0.16 at the end of the infusion period. The diuretic and natriuretic effects of UGN are blunted in DS rats. The defect of this counter regulatory mechanism may have a role in the genesis and maintenance of hypertension in this strain of rats.Support or Funding InformationCNPq, FUNCAP and CAPES

Sodium-glucose co-transporter type 2 inhibitors reduce evening home blood pressure in type 2 diabetes with nephropathy.

The effects of sodium-glucose co-transporter type 2 inhibitors on home blood pressure were examined in type 2 diabetes with nephropathy. The patients with diabetic nephropathy were screened from medical records in our hospitals. Among them, 52 patients who measured home blood pressure and started to take sodium-glucose co-transporter type 2 inhibitors were selected. Clinical parameters including estimated glomerular filtration rate, albuminuria and home blood pressure for 6 months were analysed. Sodium-glucose co-transporter type 2 inhibitors (luseogliflozin 5 mg/day or canagliflozin 100 mg/day) reduced body weight, HbA1c, albuminuria, estimated glomerular filtration rate and office blood pressure. Although sodium-glucose co-transporter type 2 inhibitors did not alter morning blood pressure, it reduced evening systolic blood pressure. Regression analyses revealed that decreases in evening blood pressure predicted decrements in albuminuria. The present data suggest that sodium-glucose co-transporter type 2 inhibitors suppress sodium overload during daytime to reduce evening blood pressure and albuminuria.

Adverse effects of tempol on hidrosaline balance in rats with acute sodium overload

We studied the effects of tempol, an oxygen radical scavenger, on hydrosaline balance in rats with acute sodium overload. Male rats with free access to water were injected with isotonic (control group) or hypertonic saline solution (0.80 mol/l NaCl) either alone (Na group) or with tempol (Na-T group). Hydrosaline balance was determined during a 90 min experimental period. Protein expressions of aquaporin 1 (AQP1), aquaporin 2 (AQP2), angiotensin II (Ang II) and endothelial nitric oxide synthase (eNOS) were measured in renal tissue. Water intake, creatinine clearance, diuresis and natriuresis increased in the Na group. Under conditions of sodium overload, tempol increased plasma sodium and protein levels and increased diuresis, natriuresis and sodium excretion. Tempol also decreased water intake without affecting creatinine clearance. AQP1 and eNOS were increased and Ang II decreased in the renal cortex of the Na group, whereas AQP2 was increased in the renal medulla. Nonglycosylated AQP1 and eNOS were increased further in the renal cortex of the Na-T group, whereas AQP2 was decreased in the renal medulla and was localized mainly in the cell membrane. Moreover, p47-phox immunostaining was increased in the hypothalamus of Na group, and this increase was prevented by tempol. Our findings suggest that tempol causes hypernatremia after acute sodium overload by inhibiting the thirst mechanism and facilitating diuresis, despite increasing renal eNOS expression and natriuresis.

Mid-regional pro-adrenomedullin (MR-proADM), a marker of positive fluid balance in critically ill patients: results of the ENVOL study.

BackgroundThe optimal control of blood volume without fluid overload is a main challenge in the daily care of intensive care unit (ICU) patients. Accordingly this study focused on the identification of biomarkers to help characterize fluid overload status.MethodsSixty-seven patients were studied from ICU admission to day 7 (D7). Blood and urine samples were taken daily and sodium and water balance strictly calculated resulting in a total cumulative assessment of ∆Na+ and ∆H2O. Furthermore, plasmatic biomarkers (cortisol, epinephrine, norepinephrine, renin, angiotensin II, aldosterone, pro-endothelin, copeptine, atrial natriuretic peptide, erythropoietin, mid-regional pro-adrenomedullin (MR-proADM)) and Sequential Organ Failure Assessment (SOFA) scores were measured at D2, D5 and D7. Blood volumes were measured with 51Cr fixed on red blood cells at D2 and D7.ResultsThe ∆Na+ or ∆H2O were increased in all patients but never related to blood volumes at D2 nor D7. Total blood volumes were at normal values with constantly low red blood cell volumes and normal or decreased plasmatic volume. Weight, plasmatic proteins, and hemoglobin were weakly related to ∆Na+ or ∆H2O. Amongst all tested biomarkers, only MR-proADM was related to sodium and fluid overload. This biomarker was also a predictor of SOFA scores.ConclusionsPlasmatic concentration in MR-proADM seems to be a good surrogate for evaluation of ∆Na+ or ∆H2O and predicts sodium and extracellular fluid overload.Trial registrationClinicalTrials.gov: NCT01858675 in May 13, 2013.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1540-x) contains supplementary material, which is available to authorized users.

Why Is Your Patient Still Short of Breath? Understanding the Complex Pathophysiology of Dyspnea in Chronic Kidney Disease.

Dyspnea is one of the most common symptoms associated with CKD. It has a profound influence on the quality of life of CKD patients, and its underlying causes are often associated with a negative prognosis. However, its pathophysiology is poorly understood. While hemodialysis may address fluid overload, it often does not significantly improve breathlessness, suggesting multiple and co-existing alternative issues exist. The aim of this article is to discuss the main pathophysiologic mechanisms and the most important putative etiologies underlying dyspnea in CKD patients. Congestive heart failure, unrecognized chronic lung disease, pulmonary hypertension, lung fibrosis, air microembolism, dialyzer bio-incompatibility, anemia, sodium, and fluid overload are potential frequent causes of breathing disorders in this population. However, the relative contributions in any one given patient are poorly understood. Systemic inflammation is a common theme and contributes to the development of endothelial dysfunction, lung fibrosis, anemia, malnutrition, and muscle wasting. The introduction of novel multimodal imaging techniques, including pulmonary functional magnetic resonance imaging with inhaled contrast agents, could provide new insights into the pathophysiology of dyspnea in CKD patients and ultimately contribute to improving our clinical management of this symptom.

Reduction of eNOS in Vascular Smooth Muscle by Salt Independently of Hypertension.

Endothelial nitric oxide synthase (eNOS) is known to be expressed in endothelium and smooth muscle cells of arteries. The aim of this study was to investigate the expression of eNOS in intimal and medial layer of aorta from rats fed with a high salt diet and its modulation by losartan and tempol. Rats were fed during three weeks with: normal salt diet (NS, 0.4% NaCl); high salt diet (HS, 8% NaCl); NS plus tempol 1 mM (NS-T); HS plus tempol (HS-T); NS plus losartan 40mg.kg-1 (NS-L) and HS plus losartan (HS-L). Systolic blood pressure was recorded by the tail cuff method. Rats were then anaesthetized and the thoracic aorta and small arteries (bronchial branches of aorta) were processed to evaluate the expression of eNOS and aquaporin-1 (AQP-1) by immunohistochemistry. HS group showed increased systolic blood pressure, increased eNOS and AQP-1 immunoexpression in the aorta intimal layer, and decreased eNOS immunoexpression in the aorta medial layer, respect to NS group. Losartan and tempol prevented hypertension and changes in the expression of eNOS and AQP-1 of the intimal layer. However, only tempol increased the expression of eNOS elicited by sodium overload in the medial layer of the aorta and small arteries respect to HS group. A high salt diet decreases eNOS expression in vascular smooth muscle layers of aorta and small arteries, which is reversed by tempol. These results suggest an adverse effect of oxidative stress on vascular eNOS in rats fed a high salt diet independently of hypertension.

MPS 07-05 ROLE OF THE NATRIURETIC PEPTIDE-A RECEPTOR ON PODOCYTES IN ALDOSTERONE-INDUCED GLOMERULAR INJURY

Objective: Aldosterone is a key molecule in glomerular injury and tubulointerstitial fibrosis. Natriuretic peptide receptor/guanylyl cyclase-A (GC-A) signaling exerts renoprotective effects by eliciting natriuresis, reducing blood pressure, and inhibiting fibrosis. We demonstrated that uninephrectomized GC-A knockout (KO) mice with aldosterone and sodium overload exhibited accelerated hypertension with massive proteinuria. In this model, inhibition of p38 MAP kinase (MAPK) ameliorated renal injury. However, local effect of natriuretic peptide receptor/GC-A signaling in podocyte is not fully elucidated. Design and Method: To explore the role of GC-A signaling in podocyte, we generated podocytes-specific GC-A KO mice (pod-GC-A cKO). Pod-GC-A cKO mice or wild-type mice were uninephrectomized and then treated with high salt orally and aldosterone subcutaneously using an osmotic minipump for 4 weeks. Results: Although systolic blood pressure was not different between control and pod-GC-A cKO mice, pod-GC-A cKO mice showed significantly increased urinary albumin excretion by 13-fold (n = 7, p < 0.01). Glomerular hypertrophy, mesangial expansion and apoptosis determined by TUNEL assay were increased in pod-GC-A cKO mice. Urinary potassium excretion was not affected between two groups. Administration of aldosterone increased phosphorylation of p38 MAPK mainly in podocytes. In vitro study, overexpression of MKK3 in cultured human podocytes upregulated the phosphorylation of p38 MAPK and BAX mRNA expression. Such induction was significantly inhibited by the administration of ANP. Conclusions: These results suggest that endogenous natriuretic peptide/GC-A system on podocytes acts renoprotective and anti-apoptotic roles in aldosterone-induced renal injury by inhibiting phosphorylation of p38 MAPK.

Do the carotid body chemoreceptors mediate cardiovascular and sympathetic adjustments induced by sodium overload in rats?

Acute plasma hypernatremia induces several cardiovascular and sympathetic responses. It is conceivable that these responses contribute to rapid sodium excretion and restoration of normal conditions. Afferent pathways mediating these responses are not entirely understood. The present study analyses the effects of acute carotid chemoreceptor inactivation on cardiovascular and sympathetic responses induced by infusion of hypertonic saline (HS). All experiments were performed on anesthetized male Wistar rats instrumented for recording of arterial blood pressure (ABP), renal blood flow (RBF) and renal sympathetic nerve activity (RSNA). Animals were subjected to sham surgery or carotid chemoreceptor inactivation by bilateral ligation of the carotid body artery (CBA). In sham rats (n=8), intravenous infusion of HS (3 M NaCl, 1.8 ml/kg b.wt.) elicited a transient increase (9±2mmHg) in ABP, and long lasting (30 min) increases in RBF (138±5%) and renal vascular conductance (RVC) (128±5%) with concurrent decrease in RSNA (-19±4%). In rats submitted to CBA ligation (n=8), the pressor response to HS was higher (24±2mmHg; p<0.05). However, RBF and RVC responses to HS infusion were significantly reduced (113±5% and 93±4%, respectively) while RSNA was increased (13±2%). When HS (3M NaCl, 200μl) was administrated into internal carotid artery (ICA), distinct sympathetic and cardiovascular responses were observed. In sham-group, HS infusion (3M NaCl, 200μl) into ICA promoted an increase in ABP (26±8mmHg) and RSNA (29±13%). In CBA rats, ABP (-3±5.6mmHg) remained unaltered despite sympathoinhibition (-37.6±5.4%). These results demonstrate that carotid body chemoreceptors play a role in the development of hemodynamic and sympathetic responses to acute HS infusion.

Blood pressure, arterial stiffness and endogenous lithium clearance in relation to AGTR1 A1166C and AGTR2 G1675A gene polymorphisms

Introduction:Although recently a matter of epidemiologic controversy, sodium overload and its interaction with genetic factors predispose to hypertension and related target organ complications.Methods:In 131 (66 male) treated hypertensives, we measured peripheral and central arterial pressures and pulse wave augmentation indexes (AIxP, AIxC1, AIxC2), pulse wave velocity (PWV), daily urinary sodium excretion and did genetic studies of AGTR1 A1166C and AGTR2 G1675A polymorphisms. Proximal (FELi) and distal (FDRNa) sodium reabsorption measurements were performed using endogenous lithium clearance.Results:In men, we found interaction between FDRNa and AGTR2 G1675A polymorphism with respect to AIxC1 (pINT=0.01), AIxC2 (pINT=0.05) and AIxP (pINT=0.006). Arterial stiffness increased with higher sodium reabsorption in the distal tubule, in the presence of AGTR2 G allele with the opposite tendency in A allele carriers. In the subgroup with FDRNa below median, as compared to those with FDRNa above median, the AIxC1 (139.6±3.8 vs 159.1±5.7%; p=0.009), AIxC2 (26.3±1.8 vs 33.3±1.7%; p=0.016) and AIxP (83.4±2.5 vs 96.5±2.6%; p<0.0001) were lower, in the G allele carrying men and GG homozygous women.Conclusions:The relation between sodium reabsorption in the distal tubule and the development of arterial stiffness depends on the AGTR2 G1675A polymorphism in blood pressure independent fashion.

Sodium Overload Induces Remodeling of Aorta and Cardiac Arteries Without Blood Pressure Changes in Mice

Sodium intake is considered an important mechanism of cardiovascular stress, and can lead to the development of pathologies as hypertension. Hypertension is a well‐known determinant of structural and functional changes of arteries. It is unclear if the effect of salt overload is related to the described hypertension or if there are other mechanisms involved.The objective of this study was to evaluate the effect of sodium overload upon wall structure of elastic and muscular arteries in normotensive male and female mice. For this, 4 weeks age male and female C57Bl/6 mice were divided into 3 groups (n=8 to 10 for each group): control, drinking normal water (cont), treated with 1% NaCl solution for 2 weeks (salt‐2) or 12 weeks (salt‐12). Body weight was measured at weeks 4, 6, 8, 10 and 12, and at the end of the study were also measured pulse blood pressure (BP) and heart rate (HR) by tail plethysmography. Before tissue collection, water ingestion, urine volume and sodium excretion were measured by using metabolic cages. Then, aorta and heart were collected, prepared for histological analysis, and sections (5μm) were stained by Verhoeff‐Van Gieson for analysis of arterial thickening, by picrosirius for analysis of perivascular collagen deposition, and by Weigert for elastic lamellae analysis. The results were compared by ANOVA, using p≤0.05 as significant.At the end of the experiment, we did not observe differences between groups when we compare body weight, BP and HR. Water ingestion (salt‐2M:+95; salt‐12M:+100%), urine volume (salt‐2M:+107; salt‐12M:+114%), and sodium excretion (salt‐2M:+281; salt‐12M:+164%) increased in salt treated mice, particularly in males. Elastic lamellae in aorta increased in females after salt overload (salt‐2F:+20%; salt‐12F:+40%). Interestingly, perivascular collagen deposition in cardiac arteries reduced in salt‐treated males (salt‐2M:−50%; salt‐12M:−55%). On the other hand, aorta collagen deposition increased, both in males (salt‐2M:+26%; salt‐12M:+40%), and females (salt‐2F:+20%; salt‐12F:+80%).The lack of changes in BP and HR suggest that the structural changes observed are not directly related to hemodynamic mechanisms. Morphometric results suggest that sodium overload induces adaptive responses in different fashion in male and female mice, indicating a possible artery thickening in female as consequence of salt chronic ingestion.Support or Funding InformationFAPESP, CAPES and CNPq

Addition of indapamide to frusemide increases natriuresis and creatinine clearance, but not diuresis, in fluid overloaded ICU patients

BackgroundFluid and sodium overload are a common problem in critically ill patients. Frusemide may result in diuresis in excess of natriuresis. The addition of indapamide may achieve a greater natriuresis, and also circumvent some of the problems associated with frusemide. The objective of this study was to examine the effect of adding indapamide to frusemide on diuresis, natriuresis, creatinine clearance and serum electrolytes. MethodsFluid overloaded ICU patients were randomised to either intravenous frusemide (Group F) or intravenous frusemide and enteral indapamide (Group F + I). Comprehensive exclusion criteria were applied to address confounders. 24 hour urine was analysed for electrolytes and creatinine. Serum electrolytes were measured before and 24 hours after administration of diuretics. ResultsForty patients (20 in each group) were included in the study. The groups were similar in their baseline characteristics. Over the 24 h study period, patients in Group F + I, had a larger natriuresis (P = 0.01), chloride loss (P = 0.01) and kaliuresis (P = 0.047). Patients in Group F + I also had a greater 24 hour urinary creatinine clearance (P = 0.01). The 24 hour urine volume and fluid balance was similar between the groups. Patients in Group F had an increase in serum sodium (P = 0.04), while patients in Group F + I had a decrease in both serum chloride (P = 0.01) and peripheral oedema (P < 0.001) during the study duration. ConclusionIn fluid overloaded ICU patients, addition of indapamide to frusemide led to a greater natriuresis and creatinine clearance. Such a strategy might be utilised in optimising sodium balance in ICU patients.

The Development of Intensive Care Unit Acquired Hypernatremia Is Not Explained by Sodium Overload or Water Deficit: A Retrospective Cohort Study on Water Balance and Sodium Handling.

Background. ICU acquired hypernatremia (IAH, serum sodium concentration (sNa) ≥ 143 mmol/L) is mainly considered iatrogenic, induced by sodium overload and water deficit. Main goal of the current paper was to answer the following questions: Can the development of IAH indeed be explained by sodium intake and water balance? Or can it be explained by renal cation excretion? Methods. Two retrospective studies were conducted: a balance study in 97 ICU patients with and without IAH and a survey on renal cation excretion in 115 patients with IAH. Results. Sodium intake within the first 48 hours of ICU admission was 12.5 [9.3–17.5] g in patients without IAH (n = 50) and 15.8 [9–21.9] g in patients with IAH (n = 47), p = 0.13. Fluid balance was 2.3 [1–3.7] L and 2.5 [0.8–4.2] L, respectively, p = 0.77. Urine cation excretion (urine Na + K) was < sNa in 99 out of 115 patients with IAH. Severity of illness was the only independent variable predicting development of IAH and low cation excretion, respectively. Conclusion. IAH is not explained by sodium intake or fluid balance. Patients with IAH are characterized by low urine cation excretion, despite positive fluid balances. The current paradigm does not seem to explain IAH to the full extent and warrants further studies on sodium handling in ICU patients.

Contribution of the late sodium current to intracellular sodium and calcium overload in rabbit ventricular myocytes treated by anemone toxin.

Pathological enhancement of late Na(+) current (INa) can potentially modify intracellular ion homeostasis and contribute to cardiac dysfunction. We tested the hypothesis that modulation of late INa can be a source of intracellular Na(+) ([Na(+)]i) overload. Late INa was enhanced by exposing rabbit ventricular myocytes to Anemonia sulcata toxin II (ATX-II) and measured using whole cell patch-clamp technique. [Na(+)]i was determined with fluorescent dye Asante NaTRIUM Green-2 AM. Pacing-induced changes in the dye fluorescence measured at 37°C were more pronounced in ATX-II-treated cells than in control (dye washout prevented calibration). At 22-24°C, resting [Na(+)]i was 6.6 ± 0.8 mM. Treatment with 5 nM ATX-II increased late INa 8.7-fold. [Na(+)]i measured after 2 min of electrical stimulation (1 Hz) was 10.8 ± 1.5 mM and 22.1 ± 1.6 mM (P < 0.001) in the absence and presence of 5 nM ATX-II, respectively. Inhibition of late INa with GS-967 (1 μM) prevented Na(+) i accumulation. A strong positive correlation was observed between the late INa and the pacing-induced increase of [Na(+)]i (R(2) = 0.88) and between the rise in [Na(+)]i and the increases in cytosolic Ca(2+) (R(2) = 0.96). ATX-II, tetrodotoxin, or GS-967 did not affect [Na(+)]i in quiescent myocytes suggesting that late INa was solely responsible for triggering the ATX-II effect on [Na(+)]i. Experiments with pinacidil and E4031 indicate that prolongation of the action potential contributes to as much as 50% of the [Na(+)]i overload associated with the increase in late INa caused by ATX-II. Enhancement of late INa can cause intracellular Na(+) overload in ventricular myocytes.

The relation between ACE D/I and CYP11B2 C-344T polymorphisms and parameters of arterial stiffness in the context of renal sodium handling

Background. Sodium overload is related to the development of primary hypertension and its complications. Methods. In 131 (65 female) treated hypertensives (average blood pressure 144/82 mmHg and duration of hypertension 11.7 years), we measured peripheral and central arterial pressures, peripheral (AIxP) and central (AIxC1, AIxC2) augmentation indices, pulse-wave velocity (PWV) and daily urinary sodium excretion, and conducted genetic studies of ACE D/I and CYP11B2 C-344T polymorphisms. Proximal (FELi) and distal (FDRNa) sodium reabsorption measurements were performed using endogenous lithium clearance. Results. We found statistically significant interactions between FELi and ACE D/I polymorphism with respect to AIxC2 (PINT = 0.05) and between FELi and CYP11B2 C-344T polymorphism with respect to AIxC1 (PINT = 0.01), AIxC2 (PINT = 0.04) and AIxP (PINT = 0.01). In the group of ACE I allele carriers compared with DD homozygotes, the AIxC1 (154.1 vs 140.6%; p = 0.02), AIxC2 (33.3 vs 26.9%; p = 0.02) and AIxP (94.6 vs 85.2%; p = 0.01) were higher in the subgroup with FELi below the median value (FELi1), but not in the subgroup with FELi above the median value (FELi2). In the group of CYP11B2 TT homozygotes compared with C allele carriers, we observed higher values of AIxC1 (158.5 vs 146.4%; p = 0.03), AIxC2 (36.0 vs 29.4%; p = 0.01) and AIxP (99.0 vs 88.7%; p = 0.005) in the FELi1 but not the FELi2 subgroup. Conclusions. In the population with assumed high dietary sodium intake and long-standing history of hypertension, the relation between proximal sodium reabsorption and the development of arterial stiffness depends on the genetic context of the selected genetic polymorphisms of the renin—angiotensin—aldosterone system, independent of blood pressure.