Diuretics

A pharmacovigilance study on clinical factors of active vitamin D3 analog-related acute kidney injury using the Japanese Adverse Drug Event Report Database

Acute kidney injury (AKI) due to vitamin D therapy for osteoporosis is encountered in clinical practice, but epidemiological studies are scarce. We aimed to determine the association between AKI and vitamin D therapy and to identify risk factors for AKI using the Japanese Adverse Drug Event Report database. We used reporting odds ratios (RORs) to detect signals and evaluate risk factors using multiple logistic regression analysis. Among 298,891 reports from April 2004 to September 2023, 1071 implicated active vitamin D3 analogs as suspect drugs for adverse events. There was a significant association between AKI and active vitamin D3 analogs (ROR [95% confidence interval {CI}], eldecalcitol: 16.75 [14.23-19.72], P < 0.001; alfacalcidol: 5.29 [4.07-6.87], P < 0.001; calcitriol: 4.46 [1.88-10.59], P < 0.001). The median duration of administration before AKI onset was 15.4 weeks. Multiple logistic regression analysis showed a significant association between AKI and age ≥ 70 years (odds ratio [95% CI], 1.47 [1.04-2.07]; P = 0.028), weight < 50 kg (1.55 [1.12-2.13]; P = 0.007), hypertension (1.90 [1.42-2.54]; P < 0.001), and concomitant use of nonsteroidal anti-inflammatory drugs (1.58 [1.10-2.25], P = 0.012) and magnesium oxide (1.96 [1.38-2.78]; P < 0.001). Our results suggest that active vitamin D3 analogs are associated with AKI development. Physicians prescribing these medications to patients with risk factors should consider the possibility of AKI, especially during the first 6 months.

Utility of fractional excretion of urea in acute kidney injury with comparison to fractional excretion of sodium: A systematic review and meta-analysis

BACKGROUND

Differentiating between intrinsic and prerenal acute kidney injury (AKI) presents a challenge. Here, we assessed the performance of the fractional excretion of urea (FEUrea) and compared it to the fractional excretion of sodium (FENa) in distinguishing intrinsic from prerenal AKI.

METHODS

A thorough search was conducted in several databases until January 16, 2024. We included studies evaluating FEUrea, with or without FENa, for differentiating AKI etiologies in adults. We assessed the methodological quality using the QUADAS-2 and QUADAS-C tools. We performed a meta-analysis using the bivariate random effects model, with subgroup analyses to explore the impact of diuretic therapy on FEUrea, and direct statistical comparisons between FEUrea and FENa involving the subgroups with and without diuretics.

RESULTS

We included 11 studies with 1108 hospitalized patients. Among eight studies (915 patients) evaluating FEUrea >35% for distinguishing intrinsic from prerenal AKI, the pooled sensitivity and specificity were 66% (95% CI, 49%-79%) and 75% (95% CI, 60%-85%), respectively. In a subset of six studies (302 patients) comparing FEUrea at 35% to FENa at 1% in patients not receiving diuretics, there were no significant differences in sensitivity (77% versus 89%, P = 0.410) or specificity (80% versus 79%, P = 0.956). In four studies, 244 patients on diuretics, FEUrea demonstrated lower sensitivity (52% versus 92%, P < 0.001) but higher specificity (82% versus 44%, P < 0.001) compared to FENa for the diagnosis of intrinsic AKI.

CONCLUSIONS

FEUrea has limited utility in differentiating intrinsic from prerenal AKI. FEUrea does not provide a superior alternative to FENa, even in patients receiving diuretics.

Effects of esaxerenone on blood pressure, urinary albumin excretion, serum levels of NT-proBNP, and quality of life in patients with primary aldosteronism

Primary aldosteronism (PA) is typically managed with mineralocorticoid receptor antagonists (MRAs) barring adrenalectomy. The efficacy of esaxerenone, a nonsteroidal MRA, were explored in patients with PA. Various parameters such as the urinary albumin to creatinine ratio (UACR) and serum levels of N-terminal prohormone of brain natriuretic peptide (NT-proBNP) were evaluated in 25 PA patients before and 3 and 6 months after esaxerenone treatment. Systolic and diastolic blood pressure (BP), and the estimated glomerular filtration rate decreased after treatment, while serum levels of potassium and active renin increased. Significant reductions were observed in UACR 3 and 6 months after treatment. A significant decrease in NT-proBNP was evident at 6 months but not 3 months after treatment. Correlation analysis indicated that the reductions in BP and UACR at 3 months were independent of estimated daily salt intake. Furthermore, the effect of esaxerenone treatment on lowering UACR and NT-proBNP levels was independent of BP reduction. Responders whose systolic BP decreased 6 months after esaxerenone treatment by more than 10 mmHg compared to pretreatment had higher pretreatment NT-proBNP and similar UACR before and after treatment when compared with nonresponders. Esaxerenone improved mental, physical, and social quality of life (QOL) 6 months after treatment compared to healthy controls and increased over time. No patients discontinued treatment due to severe hyperkalemia or renal dysfunction. In conclusion, esaxerenone is a safe and effective MRA for PA treatment, offering significant benefits in terms of hypertension, albuminuria, NT-proBNP levels, and QOL improvement. Esaxerenone effectively lowers BP, UACR, and serum levels of NT-proBNP independent of dietary salt intake in mild PA patients. ARC active renin concentration, DBP diastolic blood pressure, MR mineralocorticoid receptor, MRA mineralocorticoid receptor antagonist, NT-proBNP N-terminal pro-brain natriuretic peptide, PA primary aldosteronism, QOL quality of life, SBP systolic blood pressure, SF-36 Medical Outcomes Study 36-Item Short-Form Health Survey, UACR urinary albumin to creatinine ratio.

Canagliflozin independently reduced plasma volume from conventional diuretics in patients with type 2 diabetes and chronic heart failure: a subanalysis of the CANDLE trial

Sodium-glucose cotransporter 2 inhibitors (SGLT2is) reduce the risk of heart failure progression and mortality rates. Moreover, osmotic diuresis induced by SGLT2 inhibition may result in an improved heart failure prognosis. Independent of conventional diuretics in patients with type 2 diabetes (T2D) and chronic heart failure, especially in patients with heart failure with preserved ejection fraction (HFpEF), it is unclear whether SGLT2i chronically reduces estimated plasma volume (ePV). As a subanalysis of the CANDLE trial, which assessed the effect of canagliflozin on N-terminal pro-brain natriuretic peptide (NT-proBNP), we examined the change (%) in ePV over 24 weeks of treatment based on the baseline level associated with diuretic usage. In the CANDLE trial, nearly all patients were clinically stable (NYHA class I-II), with approximately 70% of participants presenting a baseline phenotype of HFpEF. A total of 99 (42.5%) patients were taking diuretics (mostly furosemide) at baseline, while 134 (57.5%) were not. Relative to glimepiride, canagliflozin significantly reduced ePV without worsening renal function in patients in both groups: -4.00% vs. 1.46% (p = 0.020) for the diuretic group and -6.14% vs. 1.28% (p < 0.001) for the nondiuretic group. Furthermore, canagliflozin significantly reduced serum uric acid without causing major electrolyte abnormalities in patients in both subgroups. The long-term beneficial effect of SGLT2i on intravascular congestion could be independent of conventional diuretic therapy without worsening renal function in patients with T2D and HF (HFpEF predominantly). In addition, the beneficial effects of canagliflozin are accompanied by improved hyperuricemia without causing major electrolyte abnormalities.

Importance of dietary salt restriction for patients with primary aldosteronism during treatment with mineralocorticoid receptor antagonists: The potential importance of post-treatment plasma renin levels

We measured dietary salt intake in 26 patients with primary aldosteronism treated with mineralocorticoid receptor antagonists and evaluated whether plasma renin levels were affected by dietary salt intake pre-treatment and post 6 months of mineralocorticoid receptor antagonist treatment. The dietary salt intake level was calculated using spot urine sodium and creatinine concentrations, body weight, height, and age. The clinical parameters pre- and post- treatment were compared. The systolic and diastolic blood pressure levels decreased, and the serum potassium and active renin concentration increased significantly. Although the dietary salt intake did not change after treatment, the differences in dietary salt intake and active renin concentration pre- and post- treatment were inversely correlated (r = -0.418, p = 0.03). The 26 patients were divided into two groups with active renin concentration levels ≥5 pg/mL (Group 1) and <5 pg/mL (Group 2) after treatment. The Group parameters did not differ pre- and post- treatment. Group 1 evidenced improvements in systolic and diastolic blood pressures, and the potassium level and active renin concentration over time; Group 2 did not. Group 1 evidenced no significant correlation between the differences in dietary salt intake and active renin concentration levels (r = -0.481, p = 0.11) but Group 2 showed a strong inverse correlation (r = -0.7599, p = 0.01). In conclusion, we found that an active renin concentration level <5 pg/mL post-mineralocorticoid receptor antagonist treatment may indicate that salt sensitivity has not adequately improved, emphasizing the importance of measuring plasma renin levels after such treatment.

Use of Thiazides to Treat Hypertension and Advanced CKD

PURPOSE OF REVIEW

Hypertension is often difficult to control in patients with CKD as manifested by suboptimal control rates in this population. Use of thiazides in CKD patients has been limited as these agents are thought to be ineffective in reducing blood pressure in people with advanced CKD. This review summarizes recent studies impacting indications and safety of use of thiazide in patients with CKD and discusses the mechanism of how thiazides reduce blood pressure.

RECENT FINDINGS

Chlorthalidone reduces blood pressure compared to placebo in patients with advanced CKD, challenging the belief that thiazide diuretics lose efficacy at lower levels of GFR. Recent clinical trial data indicate that thiazides are effective in patients with advanced kidney disease for blood pressure lowering. However, monitoring of electrolytes and kidney function is important to ensure patient safety when prescribing these agents in patients with CKD.

The effect of trichlormethiazide in autosomal dominant polycystic kidney disease patients receiving tolvaptan: a randomized crossover controlled trial

The vasopressin V2 receptor antagonist tolvaptan delays the progression of autosomal dominant polycystic kidney disease (ADPKD). However, some patients discontinue tolvaptan because of severe adverse aquaretic events. This open-label, randomized, controlled, counterbalanced, crossover trial investigated the effects of trichlormethiazide, a thiazide diuretic, in patients with ADPKD receiving tolvaptan (n = 10) who randomly received antihypertensive therapy with or without trichlormethiazide for 12 weeks. The primary and secondary outcomes included amount and osmolarity of 24-h urine and health-related quality-of-life (HRQOL) parameters assessed by the Kidney Disease Quality of Life-Short Form questionnaire, renal function slope, and plasma/urinary biomarkers associated with disease progression. There was a significant reduction in urine volume (3348 ± 584 vs. 4255 ± 739 mL; P < 0.001) and a significant increase in urinary osmolarity (182.5 ± 38.1 vs. 141.5 ± 38.1 mOsm; P = 0.001) in patients treated with trichlormethiazide. Moreover, trichlormethiazide improved the following HRQOL subscales: effects of kidney disease, sleep, emotional role functioning, social functioning, and role/social component summary. No significant differences were noted in renal function slope or plasma/urinary biomarkers between patients treated with and without trichlormethiazide. In patients with ADPKD treated with tolvaptan, trichlormethiazide may improve tolvaptan tolerability and HRQOL parameters.

A rare case of persistent hyperkalaemia

Hyperkalaemia is a common biochemical finding that can allude to preanalytical or truly pathological causes. Here, we present a case of a 41-year-old female patient who has regularly presented with incidences of isolated hyperkalaemia since 2012, with otherwise normal renal function and no other associated symptoms. Investigations into the patient's family history revealed similar biochemical findings in her brother and eldest son. Familial causes of hyperkalaemia were investigated and an eventual diagnosis of pseudo-hypoaldosteronism type 2C was established. This is a rare congenital renal tubular disorder - also known as Gordon syndrome - that can cause a characteristic triad of symptoms that include hyperkalaemia, metabolic acidosis and hypertension. The presence and severity of each of these symptoms is dependent upon the disease-causing mutation that occurs in WNK4, WNK1, CUL3 or KLHL3 genes. These mutations alter the regulation of sodium/chloride co-transporter (NCC) expression on the luminal membrane of the principal cells of the distal convoluted tubule, disrupting normal homeostatic regulation of electrolyte reabsorption and excretion. The resolution for treating this condition is the administration of a thiazide diuretic, which directly counteracts the effects of NCC co-transporter overexpression and consequently aims to resolve the symptoms that arise as a result of this aberrant signalling. The case described here uniquely presents an extremely rare pathogenic variant in the conserved acidic motif of WNK1 resulting in a clear electrolyte phenotype with no hypertension.

Efficacy of furosemide-albumin compared with furosemide in critically ill hypoalbuminemia patients admitted to intensive care unit: a prospective randomized clinical trial

BACKGROUND

Some physicians co-administer albumin with loop diuretics to overcome diuretic resistance in critically ill hypoalbuminemia patients, though previous studies have reported conflicting results on this matter.

OBJECTIVE

The effects of adding albumin to furosemide to enhance its efficacy in critically ill hypoalbuminemia patients are evaluated.

METHODS

This was a non-blinded randomized trial. 49 adult critically ill patients with hypoalbuminemia and generalized edema who received randomly furosemide and furosemide/albumin complex were enrolled. The patients' urine was collected at intervals of 2, 4, 6 and 8 h after initiation of the furosemide treatment, and the urine output and urinary excretion of furosemide and sodium were measured. The urinary excretion of furosemide was considered an indicator of drug efficacy.

RESULTS

The amount of sodium and furosemide excreted in urine showed no significant differences between the two groups; however, the mean of the urinary excretion of furosemide in the first 2 h after drug infusion was significantly higher (p = 0.03) in the furosemide/albumin group. No significant correlation between APACHE II scores and serum albumin levels and the urinary excretion of furosemide was seen.

CONCLUSION

The results indicated that there is not statistically significant differences between groups with furosemide alone and combined with albumin in urinary furosemide excretion. It seems that adding albumin for furosemide pharmacotherapy regime is not recommended as an intervention to increase furosemide efficacy in critically ill hypoalbuminemia patients.

TRIAL REGISTRATION

IRCT with the registration number IRCT201412132582N12 in 23 February 2015; https://en.irct.ir/trial/2356 Graphical abstract.

Evaluation of Diuretic and Antioxidant Properties in Aqueous Bark and Fruit Extracts of Pine

OBJECTIVE

The present study has been carried out to evaluate the diuretic and antioxidant properties of pine herb in an animal model.

MATERIALS AND METHODS

45 adult male rats were randomly divided into nine groups including: groups I (the negative control), groups II (positive control, furosemide 10 mg/kg), groups III to VIII (treatment groups received 100, 200, 400 mg/kg of the aqueous extracts of bark and fruit) and group IX received the combination of aqueous extract of bark (100 mg/kg) and the fruit (100 mg/kg). The urine output, glomerular filtration rate (GFR), electrolytes, urea, and creatinine levels were evaluated. Furthermore, the phenolic content and antioxidant activity of both extracts were also assessed using 2, 2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and Folin-Ciocalteu methods.

RESULTS

The aqueous extracts of the pine bark and fruit increased the urinary output in a dosedependent manner. The combination of the two extracts compared to the other extracts alone significantly increased the serum potassium level. This study also showed each extract increase creatinine clearance in a dose-dependent manner (p<0.01 and p<0.05). The increase of GFR in the combination group was not significant. The current data showed a significant increase in the total phenolic content in pine bark extract in compared with the fruit extract.

CONCLUSION

The pine bark and fruit can be useful in the prevention and treatment of kidney stones due to the high diuretic properties and antioxidant activity.

Effects of hydrochlorothiazide on drainage volume and seroma formation in deep inferior epigastric perforator flap breast reconstruction: Randomized controlled trial

BACKGROUND

Seroma is a recognized complication encountered at the reconstructed breast and donor site after abdominal-based breast reconstruction. Seroma is caused by lymphatic channel disruption and the formation of a large space between the deep fascia during flap elevation. Surgical techniques to preserve the lymphatics and secure the closure of the donor site can reduce seroma formation. This study investigated the safety and effectiveness of the diuretic hydrochlorothiazide at reducing interstitial fluid accumulation and seroma formation during deep inferior epigastric perforator (DIEP) flap breast reconstruction.

METHODS

Sixty patients with breast cancer who underwent skin- or nipple-sparing mastectomy and DIEP flap reconstruction were enrolled between August 2016 and June 2017. The patients were randomly assigned to receive either 25 mg per day of hydrochlorothiazide from the second to the twentieth day after surgery (treatment) or no diuretic (control). The clinicopathological characteristics, drainage time, and drainage volume were statistically compared between the two groups.

RESULTS

The average total drainage volume at the donor site was 291 mL in the treatment group and 434 mL in the control group (p = 0.003). The differences in body mass index and flap weight between the two groups were not statistically significant (p = 0.879 and p = 0.963, respectively). No hypotension or electrolyte imbalance was noted during the follow-up.

CONCLUSIONS

Intake of 25 mg per day of hydrochlorothiazide tablets effectively reduced the total abdominal drainage volume and removal time of indwelling drains. However, the adverse effects should be further investigated in a large population and multiracial cohort before using hydrochlorothiazide for seroma prevention.

Micronutrients in Liver Disease: Roles, Risk Factors for Deficiency, and Recommendations for Supplementation

Micronutrients are essential components of the diet and are required to maintain fundamental bodily functions. Liver disease has a profound effect on nutrient intake, metabolism of nutrients, and nutrition status, often resulting in some degree of malnutrition, including micronutrient deficiency. Vitamin and mineral deficiencies can impair metabolic processes at the cellular and biochemical level even before clinical and physical alterations are seen. It is essential that micronutrient status is evaluated as part of a comprehensive nutrition assessment for all patients with chronic or advanced liver disease. Early intervention to correct suspected or confirmed deficiencies may minimize symptoms and improve clinical outcomes and quality of life. In this narrative review, different types of liver disease and associated micronutrient abnormalities are outlined, and methods of micronutrient assessment and supplementation are discussed.

Hypercalcemia and acute kidney injury induced by eldecalcitol in patients with osteoporosis: a case series of 32 patients at a single facility

BACKGROUND

Eldecalcitol (ELD) is an active vitamin D3 analog that is widely used in Japan for the treatment of osteoporosis. The most common adverse drug reaction of ELD is hypercalcemia. However, few reports have focused on acute kidney injury (AKI) associated with ELD-induced hypercalcemia.

MATERIALS AND METHODS

We retrospectively reviewed the medical records at our hospital for cases of hypercalcemia-induced AKI between April 2013 and February 2018. Among them, we focused on patients who developed AKI secondary to ELD-induced hypercalcemia.

RESULTS

Among 69 patients who developed hypercalcemia-induced AKI, 32 patients (46.4%) developed AKI associated with ELD-induced hypercalcemia. Their mean age was 82 ± 5 years, 97% of them were female, mean corrected serum calcium level was 12.2 ± 1.5 mg/dL, serum creatinine level was 2.5 ± 2.2 mg/dL, and estimated glomerular filtration rate was 23.9 ± 14.4 ml/min/1.73 m2 on admission. ELD administration was discontinued in all patients and some of them were treated with hydration with or without calcitonin, which was followed by a normalization of serum calcium level. Corrected serum calcium level on admission was significantly higher (p < .05) in patients treated with magnesium oxide. Although there were no significant differences, serum calcium and creatine levels on admission tended to be higher in patients who were treated with other drugs that affect renal hemodynamics and renal calcium metabolism than those not taking these drugs.

CONCLUSIONS

Prescribers of ELD should regularly monitor serum calcium levels and kidney function to prevent hypercalcemia and AKI associated with ELD and pay more attention to concomitant drugs especially magnesium oxide.

Utility of the Cardiovascular Physical Examination and Impact of Spironolactone in Heart Failure With Preserved Ejection Fraction

BACKGROUND

The prognostic value of physical examination, its relation to quality of life, and influence of therapy in heart failure with preserved ejection fraction is not well known.

METHODS AND RESULTS

We studied participants from the Americas with available physical examination (jugular venous distention, rales, and edema) at baseline in the TOPCAT trial (Treatment of Preserved Cardiac Function Heart Failure with an Aldosterone Antagonist). The association of the number of signs of congestion with the primary outcome (cardiovascular death or heart failure hospitalization), its individual components, and all-cause mortality was assessed using time-updated, multivariable-adjusted Cox regression analyses. We evaluated whether spironolactone improved congestion at 4 months and whether improvement in congestion was related to quality of life as assessed by Kansas City Cardiomyopathy Questionnaire overall summary scores and to outcomes. Among 1644 participants, 22%, 54%, 20%, and 4% had 0, 1, 2, and 3 signs of congestion, respectively, at baseline. After multivariable adjustment, each additional increase in sign of congestion was associated with a 30% to 60% increased risk of each outcome ( P<0.001). Spironolactone reduced the total number of signs of congestion by -0.10 ( P=0.005) signs, jugular venous distention (odds ratio, 0.60; P=0.01), and edema (odds ratio, 0.74; P=0.006) at 4 months compared with placebo. Each reduction in sign of congestion was independently associated with a 4.0 (95% CI, 2.4-5.6) point improvement in Kansas City Cardiomyopathy Questionnaire overall summary score. When assessed simultaneously, time-updated, but not baseline congestion, predicted outcomes.

CONCLUSIONS

In heart failure with preserved ejection fraction, the physical exam provides independent prognostic value for adverse outcomes. Spironolactone improved congestion compared with placebo. Reducing congestion was independently associated with improved quality of life and outcomes and is a modifiable risk factor.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT00094302.

Gallic acid, a phenolic compound isolated from Mimosa bimucronata (DC.) Kuntze leaves, induces diuresis and saluresis in rats

Although present in the leaves of Mimosa bimucronata (DC.) and many other medicinal plants commonly used to augment urinary volume excretion, the effects of gallic acid as a diuretic agent remain to be studied. Wistar rats were orally treated with vehicle, hydrochlorothiazide, or gallic acid. The effects of gallic acid in the presence of hydrochlorothiazide, furosemide, amiloride, L-NAME, atropine, and indomethacin were also investigated. Diuretic index, pH, conductivity, and electrolyte excretion were evaluated at the end of the experiment (after 8 or 24 h). Gallic acid induced diuretic and saluretic (Na⁺ and Cl^-) effects, without interfering with K⁺ excretion, when orally given to female and male rats at a dose of 3 mg/kg. These effects were associated with increased creatinine and conductivity values while pH was unaffected by any of the treatments. Plasma Na⁺, K⁺, and Cl^- levels were not affected by any of the acute treatments. The combination with hydrochlorothiazide or furosemide was unable to intensify the effects of gallic acid when compared with the response obtained with each drug alone. On the other hand, the treatment with amiloride plus gallic acid amplified both diuresis and saluresis, besides to a marked potassium-sparing effect. Its diuretic action was significantly prevented in the presence of indomethacin, a cyclooxygenase inhibitor, but not with the pretreatments with L-NAME or atropine. Although several biological activities have already been described for gallic acid, this is the first study demonstrating its potential as a diuretic agent.

The non-immunosuppressive management of childhood nephrotic syndrome

Idiopathic nephrotic syndrome (INS) is one of the most common renal diseases found in the paediatric population and is associated with significant complications, including infection and thrombosis. A high proportion of children enter sustained remission before adulthood, and therapy must therefore mitigate the childhood complications, while minimising the long-term risk to health. Here we address the main complications of INS and summarise the available evidence and guidance to aid the clinician in determining the appropriate treatment for children with INS under their care. Additionally, we highlight areas where no consensus regarding appropriate management has been reached. In this review, we detail the reasons why routine prophylactic antimicrobial and antithrombotic therapy are not warranted in INS and emphasise the conservative management of oedema. When pharmacological intervention is required for the treatment of oedema, we provide guidance to aid the clinician in determining the appropriate therapy. Additionally, we discuss obesity and growth, fracture risk, dyslipidaemia and thyroid dysfunction associated with INS. Where appropriate, we describe how recent developments in research have identified potential novel therapeutic targets.

Volume Overload in Heart Failure: An Evidence-Based Review of Strategies for Treatment and Prevention

Acute decompensated heart failure is the leading cause of hospital admission in the United States, with a high risk of readmission within 30 days. Most acute decompensated heart failure admissions are driven by congestive signs and symptoms resulting from fluid and sodium overload. We reviewed the evidence base addressing the management and prevention of fluid overload in heart failure, focusing on recent clinical trials. All the references in this review were obtained through PubMed and had at least 1 of the following key words: heart failure and volume overload, congestion, loop diuretics, thiazide diuretics, aldosterone antagonists, dopamine, cardiorenal syndrome, nesiritide, vasopressin antagonists, ultrafiltration, sodium restriction, fluid restriction, telemonitoring, and invasive hemodynamic monitoring. We also reviewed relevant references cited in the obtained articles, especially articles addressing methods of treating or preventing volume overload in patients with heart failure.

Diuretic and Anti-Inflammatory Activities of the Microencapsulated Acrocomia aculeata (Arecaceae) Oil on Wistar Rats

Acrocomia aculeata, popularly known as "bocaiuva," is widely acknowledged in culinary and traditional medicines to treat cardiovascular diseases, a combined effect with diuretics that are also used for hypertension. However, there are no scientific data published to support its use as functional food and its ethnopharmacological use. This study intended to determine the composition of fatty acids of the pulp oil and evaluate the diuretic action and anti-inflammatory activity of the in natura and microencapsulated oil orally administrated on rats. The obtained results confirm the prevalence of monounsaturated fatty acids (68.51%), especially oleic acid (65.68%±1.05%), in the oil from the bocaiuva pulp. The in natura A. aculeata oil has diuretic (P<.01) and anti-inflammatory potential, which promoted a marked inhibition on the hind paw edema induced by carrageenan (67%±7% after 2 h) (P<.01). In addition, results show that the oral administration of the bocaiuva oil at 300 (P<.05) and 700 (P<.05) mg/kg doses significantly inhibited the leukocyte migration induced by carrageenan to the pleural cavity in rats. The inhibitions equaled 91%±3% and 81%±16%, respectively. The microencapsulated oil also showed antiedematogenic (P<.01) as well as diuretic activities (P<.01). The microencapsulation by complex coacervation was shown to be a technique that favors the bioavailability and preservation of bioactive components of the bocaiuva oil.

Molecular pathophysiology of Bartter's and Gitelman's syndromes

BACKGROUND

In the last two decades, progress in cytogenetic and genome research has enabled investigators to unravel the underlying molecular mechanisms of inherited tubulopathies such as Bartter's and Gitelman's syndromes and helped physicians to better understand not only these two pathologic entities but also renal pathophysiology and salt sensitive hypertension.

DATA SOURCES

Articles collected from PubMed and open access journals included original articles, research articles, and comprehensive reviews. They were evaluated by the authors with an special emphasis on originality and up to date information about molecular pathophysiology.

RESULTS

Bartter's and Gitelman's syndromes are two different inherited salt loosing tubulopathies. They are characterized by various inability of distal nephron to reabsorb sodium chloride with resultant extarcellular volume contraction and increased activity of the renin angiotensin aldosterone system. Hypokalemic metabolic alkalosis is a common feature of these two forms of tubulopathies. Hypercalciuria characterizes the majority of Bartter's syndrome, and hypomagnesemia with hypocalciuria characterizes Gitelman's syndrome. Low blood pressure is a common feature among patients who suffered from these tubulopathies. Bartter's syndromes encompass a heterogeneous group of ion channels defects localized at the thick ascending limp of Henle's loop with resultant loss of function of sodium-potassium-2 chloride cotransporter. These defects result in the impairment of the countercurrent multiplication system of the kidney as well as calcium, potassium and acid base disturbances which in the majority of cases are proved lethal especially in the antenatal and/or immediate postnatal life period. The underlying pathology in Gitelman's syndrome is defined to the distal convoluted tubule and is related to loss of function of the sodium-chloride cotransporter. The results of this defect encompass the inability of extracellular volume homeostasis, magnesium and potassium conservation, and acid base disturbances which are generally mild and in the majority of cases are not life-threatening.

CONCLUSIONS

Recent advances in molecular pathophysiology of Bartter's and Gitelman's syndromes have helped physicians to better understand the underlying mechanisms of these pathologic entities which remain obscure. Data collected from experiments among genetically manipulated animals enable us to better understand the pathophysiology of mammalian kidney and the underlying mechanisms of salt sensitive hypertension and to lay a foundation for the future development of new drugs, especially diuretics and antihypertensive drugs.

Association between loop diuretic use and fracture risk

SUMMARY

Loop diuretic use has been shown to be associated with an increased fracture risk, but the findings have been inconsistent. The present meta-analysis suggests that loop diuretics show a significant positive association with the overall risk of total fractures and, specifically, hip fractures.

INTRODUCTION

Despite being widely used, there is limited, prospective randomized trial evidence regarding the skeletal effects of loop diuretics. Previous observational studies have reported conflicting findings regarding the association between loop diuretic use and the risk of fractures.

METHODS

This meta-analysis of observational studies assessed the association between loop diuretic use and the risk of fractures. The PubMed, EMBASE, and OVID databases were searched for prospective cohort and case-control studies. Relative risks (RR) with 95% confidence intervals (CI) were derived using random-effects models throughout the analysis.

RESULTS

Thirteen studies (4 cohort studies and 9 case-control studies) were included, involving 842,644 participants and 108,247 fracture cases. Compared with non-users, people who had taken loop diuretics had an approximately 15% higher risk of total fractures (95% CI, 1.04-1.26; p<0.01), with high heterogeneity between studies (I2=80.5%; p<0.01). The RR was 1.14 (95% CI, 1.08-1.19) for hip fractures and 0.99 (95% CI, 0.93-1.05) for lower arm or wrist fractures. The RR was 1.05 (95% CI, 1.00-1.11) in prospective cohort studies and 1.22 (95% CI, 1.00-1.44) in case-control studies. There was no evidence of publication bias.

CONCLUSION

The results suggest that loop diuretics show a significant positive association with the overall risk of total fractures and hip fractures.

Adverse skeletal effects of drugs - beyond Glucocorticoids

Osteoporotic fractures are an important public health problem with significant individual and societal costs. In addition to the major risk factors for osteoporotic fracture, low bone mineral density (BMD), age, low body weight and history of fracture or falls, some drugs are now considered to be important secondary risk factor for bone loss and fracture, particularly amongst predisposed individuals. Currently available data are often generated from small observational clinical studies, making risk assessment and development of management guidelines difficult. In many cases, the exposed population has a low baseline risk for fracture and additional assessment and treatment may not be necessary. In this review, we focus on drugs other than glucocorticoids identified as potentially causing adverse skeletal effects, summarizing the existing evidence from preclinical and clinical studies, and suggest recommendations for patient management.

Diuretic and antilithiasic activities of ethanolic extract from Piper amalago (Piperaceae)

OBJECTIVE

Piper amalago is used in Brazilian folk medicine as diuretic and for the treatment of urinary calculus disease, although no scientific data have been described to support these effects. Thus, this study aims to evaluate the diuretic effects and antilithiatic activity of the ethanolic extract of P. amalago (EEPam).

MATERIALS AND METHODS

Ethanolic extracts of P. amalago (125, 250 and 500mg/kg) were orally administered in male Wistar rats (n=5) and urinary excretion was measured at intervals of up to 24h after administration. The antilithiasic effect of EEPam on calcium oxalate urolithiasis crystallization was examined in a turbidimetric model.

RESULTS

The oral administration of all doses of EEPam significantly increased urine output after 24h when compared to control group. Moreover, the application of EEPam, induced an inhibitory effect on calcium oxalate crystallization.

CONCLUSIONS

According to results, P. amalago extracts showed diuretic and natriuretic activity and antilithiasic effects.

Heterozygous disruption of renal outer medullary potassium channel in rats is associated with reduced blood pressure

The renal outer medullary potassium channel (ROMK, KCNJ1) mediates potassium recycling and facilitates sodium reabsorption through the Na(+)/K(+)/2Cl(-) cotransporter in the loop of Henle and potassium secretion at the cortical collecting duct. Human genetic studies indicate that ROMK homozygous loss-of-function mutations cause type II Bartter syndrome, featuring polyuria, renal salt wasting, and hypotension; humans heterozygous for ROMK mutations identified in the Framingham Heart Study have reduced blood pressure. ROMK null mice recapitulate many of the features of type II Bartter syndrome. We have generated an ROMK knockout rat model in Dahl salt-sensitive background by using zinc finger nuclease technology and investigated the effects of knocking out ROMK on systemic and renal hemodynamics and kidney histology in the Dahl salt-sensitive rats. The ROMK(-/-) pups recapitulated features identified in the ROMK null mice. The ROMK(+/-) rats, when challenged with a 4% salt diet, exhibited a reduced blood pressure compared with their ROMK(+/+) littermates. More importantly, when challenged with an 8% salt diet, the Dahl salt-sensitive rats with 50% less ROMK expression showed increased protection from salt-induced blood pressure elevation and signs of protection from renal injury. Our findings in ROMK knockout Dahl salt-sensitive rats, together with the previous reports in humans and mice, underscore a critical role of ROMK in blood pressure regulation.

Prevalence and prognostic role of resistant hypertension in chronic kidney disease patients

OBJECTIVES

This study sought to evaluate in chronic kidney disease (CKD) prevalence and prognosis of true resistant hypertension (RH) (i.e., confirmed by ambulatory blood pressure [ABP] monitoring).

BACKGROUND

In CKD, uncontrolled hypertension is a major risk factor, but no study has properly investigated the role of RH.

METHODS

We prospectively studied 436 hypertensive CKD patients under nephrology care. Four groups were constituted by combining 24-h ABP with diagnosis of RH (office blood pressure ≥130/80 mm Hg, despite adherence to ≥3 full-dose antihypertensive drugs including a diuretic agent or ≥4 drugs): control (ABP <125/75 mm Hg without RH); pseudoresistance (ABP <125/75 mm Hg with RH); sustained hypertension (ABP ≥125/75 mm Hg without RH); and true resistance (ABP ≥125/75 mm Hg with RH). Endpoints of survival analysis were renal (end-stage renal disease or death) and cardiovascular events (fatal and nonfatal cardiovascular event).

RESULTS

Age was 65 ± 14 years, men 58%, diabetes 36%, cardiovascular disease 30%, median proteinuria 0.24 (interquartile range 0.09 to 0.83) g/day, estimated glomerular filtration rate 43 ± 20 ml/min/1.73 m(2), office blood pressure 146 ± 19/82 ± 12 mm Hg, and 24-h ABP 129 ± 17/72 ± 10 mm Hg. True resistant patients were 22.9%, and pseudoresistant patients were 7.1%, whereas patients with sustained hypertension were 42.9%, and control subjects were 27.1%. Over 57 months of follow-up, 109 cardiovascular events and 165 renal events occurred. Cardiovascular risk (hazard ratio [95% confidence interval]) was 1.24 (0.55 to 2.78) in pseudoresistance, 1.11 (0.67 to 1.84) in sustained hypertension, and 1.98 (1.14 to 3.43) in true resistance, compared with control subjects. Corresponding hazards for renal events were 1.18 (0.45 to 3.13), 2.14 (1.35 to 3.40), and 2.66 (1.62 to 4.37).

CONCLUSIONS

In CKD, pseudoresistance is not associated with an increased cardio-renal risk, and sustained hypertension predicts only renal outcome. True resistance is prevalent and identifies patients carrying the highest cardiovascular risk.

Resistant hypertension in nondialysis chronic kidney disease

Resistant hypertension (RH) is defined as blood pressure (BP) that remains above the target of less than 140/90 mmHg in the general population and 130/80 mmHg in people with diabetes mellitus or chronic kidney disease (CKD) in spite of the use of at least three full-dose antihypertensive drugs including a diuretic or as BP that reaches the target by means of four or more drugs. In CKD, RH is a common condition due to a combination of factors including sodium retention, increased activity of the renin-angiotensin system, and enhanced activity of the sympathetic nervous system. Before defining the hypertensive patient as resistant it is mandatory to exclude the so-called “pseudoresistance.” This condition, which refers to the apparent failure to reach BP target in spite of an appropriate antihypertensive treatment, is mainly caused by white coat hypertension that is prevalent (30%) in CKD patients. Recently we have demonstrated that “true” RH represents an independent risk factor for renal and cardiovascular outcomes in CKD patients.

Increased expression of renal TRPM6 compensates for Mg(2+) wasting during furosemide treatment

Background

Furosemide is a loop diuretic, which blocks the Na⁺, K⁺, 2Cl⁻ cotransporter (NKCC2) in the thick ascending limb of Henle (TAL). By diminishing sodium (Na⁺) reabsorption, loop diuretics reduce the lumen-positive transepithelial voltage and consequently diminish paracellular transport of magnesium (Mg²⁺) and calcium (Ca²⁺) in TAL. Indeed, furosemide promotes urinary Mg²⁺ excretion; however, it is unclear whether this leads, especially during prolonged treatment, to hypomagnesaemia. The aim of the present study was, therefore, to determine the effect of chronic furosemide application on renal Mg²⁺ handling in mice.

Methods

Two groups of 10 mice received an osmotic minipump subcutaneously for 7 days with vehicle or 30 mg/kg/day furosemide. Serum and urine electrolyte concentrations were determined. Next, renal mRNA levels of the epithelial Mg²⁺ channel (TRPM6), the Na⁺, Cl⁻ cotransporter (NCC), the epithelial Ca²⁺ channel (TRPV5), the cytosolic Ca²⁺-binding protein calbindin-D_28K, as well parvalbumin (PV), claudin-7 (CLDN7) and claudin-8 (CLDN8), the epithelial Na⁺ channel (ENaC) and the Na⁺–H⁺ exchanger 3 (NHE3) were determined by real-time quantitative polymerase chain reaction. Renal protein levels of NCC, TRPV5, calbindin-D_28K and ENaC were also measured using semi-quantitative immunohistochemistry and immunoblotting.

Results

The mice chronically treated with 30 mg/kg/day furosemide displayed a significant polyuria (2.1 ± 0.3 and 1.3 ± 0.2 mL/24 h, furosemide versus control respectively, P < 0.05). Furosemide treatment resulted in increased serum concentrations of Na⁺ [158 ± 3 (treated) and 147 ± 1 mmol/L (control), P < 0.01], whereas serum K⁺, Ca²⁺ and Mg²⁺ values were not significantly altered in mice treated with furosemide. Urinary excretion of Na⁺, K⁺, Ca²⁺ and Mg²⁺ was not affected by chronic furosemide treatment. The present study shows specific renal upregulation of TRPM6, NCC, TRPV5 and calbindin-D_28K.

Conclusions

During chronic furosemide treatment, enhanced active reabsorption of Mg²⁺ via the epithelial channel TRPM6 in DCT compensates for the reduced reabsorption of Mg²⁺ in TAL.

The added-up albumin enhances the diuretic effect of furosemide in patients with hypoalbuminemic chronic kidney disease: a randomized controlled study

Background

Chronic kidney disease (CKD) with edema is a common clinical problem resulting from defects in water and solute excretion. Furosemide is the drug of choice for treatment. In theory, good perfusion and albumin are required for the furosemide to be secreted at the tubular lumen. Thus, in the situation of low glomerular filtration rate (GFR) and hypoalbuminemia, the efficacy of furosemide alone might be limited. There has been no study to validate the effectiveness of the combination of furosemide and albumin in this condition.

Methods

We conducted a randomized controlled crossover study to compare the efficacy of diuretics between furosemide alone and the combination of furosemide plus albumin in stable hypoalbuminemic CKD patients by measuring urine output and sodium. The baseline urine output/sodium at 6 and 24 hours were recorded. The increment of urine output/sodium after treatment at 6 and 24 hours were calculated by using post-treatment minus baseline urine output/sodium at the corresponding period.

Results

Twenty-four CKD patients (GFR = 31.0 ± 13.8 mL/min) with hypoalbuminemia (2.98 ± 0.30 g/dL) were enrolled. At 6 hours, there were significant differences in the increment of urine volume (0.47 ± 0.40 vs 0.67 ± 0.31 L, P < 0.02) and urine sodium (37.5 ± 29.3 vs 55.0 ± 26.7 mEq, P < 0.01) between treatment with furosemide alone and with furosemide plus albumin. However, at 24 hours, there were no significant differences in the increment of urine volume (0.49 ± 0.47 vs 0.59 ± 0.50 L, P = 0.46) and urine sodium (65.3 ± 47.5 vs 76.1 ± 50.1 mEq, P = 0.32) between the two groups.

Conclusion

The combination of furosemide and albumin has a superior short-term efficacy over furosemide alone in enhancing water and sodium diuresis in hypoalbuminemic CKD patients.

Trial registration

The Australian New Zealand Clinical Trials Registration (ANZCTR12611000480987)

Advances in WNK signaling of salt and potassium metabolism: clinical implications

Recent evidence due to the discovery of a family of kinases implicated in arterial hypertension now points to the underlying molecular mechanisms that dictate Na(+), K(+) and water handling in the nephron. These new key players need to be understood in order to fully comprehend the pathophysiology, manifestations, and treatment of common clinical entities such as hypovolemic shock, congestive heart failure, primary hyperaldosteronism, nephrotic syndrome and hypertension. It is through the analysis of the volume status and electrolyte abnormalities that commonly present with these diseases that we can begin to create a link between the abstract concept of a kinase regulation and how a patient will respond to a particular treatment. This review is an attempt to bridge that gap.

Management of loop diuretic resistance in the intensive care unit

PURPOSE

The management of loop diuretic resistance in the intensive care unit (ICU) is reviewed.

SUMMARY

Volume overload, a common complication of fluid resuscitation, is frequently encountered in the ICU and is associated with numerous adverse effects, including pulmonary and peripheral edema, acute lung injury, and pleural effusions. Loop diuretics are used to treat volume overload and acute renal failure and to ameliorate their associated complications. When administered intravenously, these drugs induce vigorous and prompt diuresis, which may result in negative fluid balance. This may also result in significant adverse effects, including electrolyte imbalance, ototoxicity, and volume contraction. Prolonged use of loop diuretics may lead to loop diuretic resistance, a frequent observation in the ICU. Three general mechanisms are used to explain loop diuretic resistance: rebound sodium retention, postdiuretic effect, and diuretic braking. While very few agents have joined the armamentarium and no new strategies have been developed to deal with this phenomenon, several options are available to clinicians for managing loop diuretic resistance, including salt restriction, administration of i.v. loop diuretics, continuous infusion of loop diuretics, and combination therapy using loop diuretics and thiazides.

CONCLUSION

Loop diuretic resistance presents a challenge for clinicians in the ICU setting. Strategies to improve patients' responsiveness to these agents include fluid and salt restriction, switching from oral to i.v. loop diuretics, increasing diuretic dose, continuous infusion, and combination therapy with thiazides. Several of these strategies may be used concurrently to combat diuretic resistance and promote symptomatic relief of edema in the critically ill patient.

Use of diuretics and risk of implant failure after primary total hip arthroplasty: a nationwide population-based study

INTRODUCTION

Thiazid and loop diuretics have been associated with changes in bone mineral density and fracture risk. However, data on survival of prosthesis implants are lacking. We evaluated the association between diuretic use and the risk of revision after primary total hip arthroplasty (THA).

MATERIALS AND METHODS

We conducted a nationwide population-based case-control study using medical databases in Denmark. In the Danish Hip Arthroplasty Registry, we identified 2491 cases that were revised after primary THA in the period 1995-2005 and who could be matched on age, gender and year of primary operation with 4943 non-revised THA controls. By means of conditional logistic regression, we estimated the relative risk (RR) of revision due to all causes and due to specific causes according to postoperative use of thiazid and loop diuretic, respectively.

RESULTS

The 10-year cumulated implant revision rate in the underlying cohort of 57,575 THA procedures from the Danish Hip Arthroplasty Registry was 8.9% (95% CI: 8.4-9.4). Postoperative thiazid diuretic use was not associated with neither the overall risk of revision nor revision due to specific causes compared to non-use. Postoperative loop diuretic use was associated with an adjusted RR of revision of 1.14 (95% CI; 0.98-1.32) compared with non-use. The adjusted RR of revision due to deep infection and periprosthetic fracture in loop diuretic users was 1.71 (1.15-2.55) and 6.39 (1.84-22.21), respectively. Loop diuretic use was not associated with risk of revision due to aseptic loosening, dislocation or miscellaneous causes.

DISCUSSION

Loop diuretics but not thiazides may be associated with an increased risk of revision following primary THA. Further studies are warranted in order to confirm this finding and clarify the nature of the association.

Loop diuretic use and rates of hip bone loss and risk of falls and fractures in older women

OBJECTIVES

To determine whether loop diuretic use is associated with hip bone loss and greater risk of falls and fractures in older women.

DESIGN

Prospective cohort study from August 1992 to April 2004.

SETTING

Four regions in the United States from the Study of Osteoporotic Fractures (SOF).

PARTICIPANTS

Women aged 65 and older (N=8,127) with medication use data who participated in the fourth SOF examination, from which three study cohorts were derived.

MEASUREMENTS

Bone mineral density (BMD) of the total hip assessed using dual-energy X-ray absorptiometry at the fourth and sixth examinations (n=2,980); recurrent (> or =2) falls in the year after the fourth examination (n=6,244); and incident fracture, including nonspine (n=6,778) and hip fracture (n=7,272).

RESULTS

After multivariable adjustment, loop diuretic users had greater loss of total hip BMD than nonusers (mean annualized % BMD -0.87 vs -0.71, P=.03) after a mean of 4.4+/-0.6 years. The risks of recurrent falls (odds ratio=0.99, 95% confidence interval (CI)=0.71-1.39), nonspine (relative risk (RR)=1.04, 95% CI=0.90-1.21), and hip fracture (RR=1.03, 95% CI=0.81-1.31) were not greater in loop diuretic users than in nonusers.

CONCLUSION

In this cohort of older women, loop diuretic use was associated with a small but significantly higher rate of hip bone loss than nonuse after a mean duration of 4.4 years, although the risk of falls or fracture did not differ between the two groups.

A review of drug-induced hypocalcemia

Hypocalcemia (defined as total serum calcium lower than 8.5 mg/dl or as ionized serum calcium lower than 4.7 mg/dl) is a relatively common metabolic abnormality observed in hospitalized patients. Although it is associated with certain pharmacological agents such as bisphosphonates and cisplatin, hypocalcemia may occasionally develop in the course of treatment with drugs used in everyday clinical practice, including antiepileptics, aminoglycosides, and proton pump inhibitors. Hypocalcemia associated with drug treatment can be easily missed as a consequence of coexistence of multiple factors contributing to low serum calcium levels. Drug-related hypocalcemia is usually mild and asymptomatic but may be severe as well. Effective clinical management can be handled through awareness of this adverse effect induced by certain pharmaceutical compounds on serum calcium concentrations. Herein, we review pertinent clinical information on the incidence of hypocalcemia associated with specific drug treatment and discuss the underlying pathophysiological mechanisms.

Acute diuretic effect of continuous intravenous infusion of an aqueous extract of Coriandrum sativum L. in anesthetized rats

AIM OF THE STUDY

The present investigation was carried out to evaluate the acute diuretic activity of continuous intravenous infusion of an aqueous extract of the seed of Coriandrum sativum L. Apiaceae (coriander) in rats.

MATERIALS AND METHODS

The aqueous extract of coriander seed was administered by continuous intravenous infusion (120 min) at two doses (40 and 100mg/kg) to anesthetized Wistar rats. Furosemide (10mg/kg), a standard diuretic was used as the reference drug. Excretion of water and electrolytes (sodium, potassium and chloride) in urine was measured, and glomerular filtration rate (equal to creatinine clearance) was determined.

RESULTS

The crude aqueous extract of coriander seeds increased diuresis, excretion of electrolytes, and glomerular filtration rate in a dose-dependent way; furosemide was more potent as a diuretic and saluretic. The mechanism of action of the plant extract appears to be similar to that of furosemide.

CONCLUSIONS

The aqueous extract of coriander seed possesses diuretic and saluretic activity, thus, validating the use of coriander as a diuretic plant in Moroccan pharmacopoeia.

Cardiorenal syndrome at different stages of chronic kidney disease

The central concept of the cardiorenal syndrome (CRS) is that the heart and the kidney should be regarded not solely as individual organs but rather as a dipole with multiple interconnections. The interplay between the heart and the kidney seems complex and multifactorial: cardiac output, regulation of extracellular volume, blood pressure and renal sodium handling are the major parameters that determine the crosstalk between the 2 organs. These basic parameters are controlled through mediators (renin-angiotensin system, endothelin) and the relevant antagonists (natriuretic peptides). Recently, it has been shown that the nitric oxide / reactive oxygen species balance, sympathetic nervous system activation and the presence of systemic inflammation aggravate atherosclerosis, promote structural alterations in left ventricular geometry and favor progression of renal disease. Although the prevalence of the CRS is high, major clinical trials for heart failure have only partially addressed this issue. The present review tries to dissect the role of various components of the CRS in a way that could potentially facilitate the implementation of specific therapeutic strategies. The multiple factors that participate in the pathogenesis of this syndrome are studied in detail in an effort to better understand this syndrome and address effectively its various components, since a holistic approach could (ideally) alter the syndrome's course and hence ameliorate the prognosis of the CRS.

Effects of furosemide on renal calcium handling

Furosemide is a loop diuretic agent that has been used to treat hypercalcemia because it increases renal calcium excretion. The effect of furosemide on calcium transport molecules in distal tubules has yet to be investigated. We conducted studies to examine the effects of furosemide on renal calcium excretion and expression of calcium transport molecules in mice. Mice were administered with a single dose of furosemide (15 mg/kg) and examined 4 h later or were given twice-daily furosemide injections for 3 days. To evaluate the effects of volume depletion, drinking water was supplemented with salt. Our results showed that, in acute experiments, furosemide enhanced urinary calcium excretion, which was associated with a significant increase in mRNA levels of TRPV5, TRPV6, and calbindin-D28k but not calbindin-D9k as measured by real-time PCR (TRPV5 and TRPV6 are transient receptor potential vanilloid 5 and 6). Chronic furosemide administration induced three- to fourfold increases in urinary calcium excretion and elevated mRNA levels of TRPV5, TRPV6, calbindin-D28k, and calbindin-D9k without or with salt supplement. Similar upregulation of calcium transport molecules was observed in mice with gentamicin-induced hypercalciuria. Coadministration of chlorothiazide decreased furosemide-induced calciuria, either acutely or chronically, although still accompanied by upregulation of these transport molecules. Immunofluorescent staining studies revealed comparably increased protein abundance in TRPV5 and calbindin-D28k. We conclude that furosemide treatment enhances urinary calcium excretion. Increased abundance of calcium transport molecules in the distal convoluted tubule represents a solute load-dependent effect in response to increased calcium delivery and serves as a compensatory adaptation in the downstream segment.

Salt intake and depletion increase circulating levels of endogenous ouabain in normal men

High-salt diets elevate circulating Na+ pump inhibitors, vascular resistance, and blood pressure. Ouabain induces a form of hypertension mediated via the alpha2-Na+ pump isoform and the calcium influx mode of the vascular sodium calcium exchanger (NCX). Whereas elevated levels of an endogenous ouabain (EO) and NCX have been implicated in salt-sensitive hypertension, acute changes in sodium balance do not affect plasma EO. This study investigated the impact of longer-term alterations in sodium balance on the circulating levels and renal clearance of EO in normal humans. Thirteen normal men consumed a normal diet, high-salt diet, and hydrochlorothiazide (HCTZ), each for 5-day periods to alter sodium balance. EO and other humoral and urinary variables were determined daily. On a normal diet, urinary sodium excretion (140 +/- 16 meq/day), plasma EO (0.43 +/- 0.08 nmol/l) and urinary EO excretion (1.04 +/- 0.13 nmol/day) were at steady state. On the 3rd day of a high-salt diet, urine sodium excretion (315 +/- 28 meq/day), plasma EO (5.8 +/- 2.2 nmol/l), and the urinary EO excretion (1.69 +/- 0.27 nmol/day) were significantly increased, while plasma renin activity and aldosterone levels were suppressed. The salt-evoked increase in plasma EO was greater in older individuals, in subjects whose baseline circulating EO was higher, and in those with low renal clearance. During HCTZ, body weight decreased and plasma renin activity, aldosterone, and EO (1.71 +/- 0.77 nmol/l) rose, while urinary EO excretion remained within the normal range (1.44 +/- 0.31 nmol/day). Blood pressure fell in one subject during HCTZ. HPLC of the plasma extracts showed one primary peak of EO immunoreactivity with a retention time equivalent to ouabain. High-salt diets and HCTZ raise plasma EO by stimulating EO secretion, and a J-shaped curve relates sodium balance and EO in healthy men. Under normal dietary conditions, approximately 98% of the filtered load of EO is reabsorbed by the kidney, and differences in the circulating levels of EO are strongly influenced by secretion and urinary excretion of EO. The dramatic impact of high-salt diets on plasma EO is consistent with its proposed role as a humoral vasoconstrictor that links salt intake with vascular function in hypertension.

Molecular Physiology and Pathophysiology of Electroneutral Cation-Chloride Cotransporters

Electroneutral cation-Cl−cotransporters compose a family of solute carriers in which cation (Na+or K+) movement through the plasma membrane is always accompanied by Cl−in a 1:1 stoichiometry. Seven well-characterized members include one gene encoding the thiazide-sensitive Na+−Cl−cotransporter, two genes encoding loop diuretic-sensitive Na+−K+−2Cl−cotransporters, and four genes encoding K+−Cl−cotransporters. These membrane proteins are involved in several physiological activities including transepithelial ion absorption and secretion, cell volume regulation, and setting intracellular Cl−concentration below or above its electrochemical potential equilibrium. In addition, members of this family play an important role in cardiovascular and neuronal pharmacology and pathophysiology. Some of these cotransporters serve as targets for loop diuretics and thiazide-type diuretics, which are among the most commonly prescribed drugs in the world, and inactivating mutations of three members of the family cause inherited diseases such as Bartter's, Gitelman's, and Anderman's diseases. Major advances have been made in the past decade as consequences of molecular identification of all members in this family. This work is a comprehensive review of the knowledge that has evolved in this area and includes molecular biology of each gene, functional properties of identified cotransporters, structure-function relationships, and physiological and pathophysiological roles of each cotransporter.

Achievement of target blood pressure levels in chronic kidney disease: a salty question?

A large body of evidence supports the validity of lowering blood pressure (BP) to prevent cardiovascular (CV) disease in the general population. This issue becomes even more critical in renal patients because they carry a greater CV risk across the entire spectrum of chronic kidney disease (CKD). In these patients, achievement of lower BP levels also is fundamental to limit the progression of renal damage, especially in the presence of significant proteinuria. Although expert panels have strongly recommended to intensively decrease BP in patients with CKD, management of hypertension in these patients remains inadequate. Armed with the knowledge of the extreme salt-sensitivity of BP in patients with CKD, it is reasonable to hypothesize that more aggressive treatment of volume expansion can be helpful. Nevertheless, although abundant literature has evidenced that dietary sodium restriction decreases BP levels in patients with essential hypertension, no large and prospective study has been conducted to date on this issue in patients with CKD. A potential reason is the low compliance of patients with CKD to dietary prescriptions; however, this problem can be overcome by specific counseling. Alternatively, loop diuretics administered at a high dose should represent the cornerstone of therapy, but, again, well-designed studies verifying the effectiveness of these agents in a large CKD population are still awaited. Nephrologists seem to be reluctant to adequately administer diuretics because of the fear of adverse events. Conversely, the major detrimental effect, that is, excessive hypovolemia, can be prevented if daily body weight loss is limited to 0.3 to 0.5 kg during the initial period of treatment.