Chronic Furosemide Research Articles

Urine chloride trajectory and relationship with diuretic response in acute heart failure.

Sodium excretion is a well-defined marker used to assess diuretic response in acute heart failure (AHF). Despite a strong pathophysiological background, the role of urine chloride excretion has not been described and established yet. We aimed to evaluate chloride trajectory during intensive diuretic treatment in AHF patients and examine its potential role in predicting poor diuretic response. The study was conducted on 50 AHF patients. Participants were included within the first 36h of hospitalization. They received furosemide dose adjusted for body weight (half in bolus, half in 2h infusion). Post-diuretic hourly urine collection with biochemical analysis was performed. In general, the concentrations of urine chloride (uCl-) and sodium (uNa+) at the baseline samples exhibited a comparable level (71±39 vs. 70±44mmol/L, respectively; P=0.99), but across all post-furosemide study timepoints, uCl- remained significantly higher than uNa+ since 1 to 6h of the study. In this course, both ions (uCl- and uNa+) reached peak values in 2h (114±28 vs. 97±34mmol/L, respectively; P<0.01). The pattern of uCl- dominance over uNa+ concentration was also observed in separate analyses of patients naïve to furosemide and those chronically exposed to furosemide. Regardless of these patterns, naïve to furosemide individuals excreted more ions (both uCl- and uNa+) than chronically exposed patients at all timepoints. Additionally, a strong, linear correlation between uCl- and uNa+ was observed in each post-furosemide timepoint (the strongest in 1h r=0.87; P<0.001). Both interdependent ions concentration was almost parallel when analysed in chronic furosemide users and those naïve to furosemide separately [uCl-=0.85*uNa++28.82, P<0.001, R2=0.83 for chronic furosemide users, and uCl-=0.72*uNa++41.55, P<0.001, R2=0.65 for naïves to furosemide (linear regression model)]. Moreover, uCl- (with cutoff point: 72mmol/L) was a satisfactory predictive factor for poor diuretic response (<100mL/h in 6h since the beginning of furosemide infusion) [odds ratio (OR) 95% confidence interval (CI): 39.0 (3.8-405.00)]. It presented those properties also after adjusting for urine creatinine [cutoff point: 0.296mmol/mg-OR (95% CI): 81.0 (8.0-816.0)]. Urine chloride and sodium are highly interrelated during decongestion of AHF patients. The uCl- (cutoff 72mmol/L) exhibits better prognostic abilities to identify poor diuretic response than uNa+.

High-resolution plasma metabolomics and thiamine status in critically Ill adult patients

IntroductionThiamine (Vitamin B1) is an essential micronutrient and is classically considered a co-factor in energy metabolism. The association between thiamine status and whole-body metabolism in critical illness has not been studied.ObjectivesTo determine association between whole blood thiamine pyrophosphate (TPP) concentrations and plasma metabolites and connected metabolic pathways using high resolution metabolomics (HRM) in critically ill patients.MethodsCross-sectional study performed at Erciyes University Hospital, Kayseri, Turkey and Emory University, Atlanta, GA, USA. Participants were critically ill adults with an expected length of intensive care unit stay longer than 48 h and receiving chronic furosemide therapy. A total of 76 participants were included. Mean age was 69 years (range 33–92 years); 65% were female. Blood for TPP and metabolomics was obtained on the day of ICU admission. Whole blood TPP was measured by HPLC and plasma HRM was performed using liquid chromatography/mass spectrometry. Data was analyzed using regression analysis of TPP levels against all plasma metabolomic features in metabolome-wide association studies (MWAS). MWAS using the highest and lowest TPP concentration tertiles was performed as a secondary analysis.ResultsSpecific metabolic pathways associated with whole blood TPP levels in regression and tertile analysis included pentose phosphate, fructose and mannose, branched chain amino acid, arginine and proline, linoleate, and butanoate pathways.ConclusionsPlasma HRM revealed that thiamine status, determined by whole blood TPP concentrations, was significantly associated with metabolites and metabolic pathways related to metabolism of energy, carbohydrates, amino acids, lipids, and the gut microbiome in adult critically ill patients.

Spot urine sodium as a marker of urine dilution and decongestive abilities in acute heart failure

The decongestion ability in response to diuretic treatment plays a crucial role in the treatment of acute heart failure. This effectiveness is evaluated through the assessment of sodium concentration and urine volume, which are also treatment goals themselves. However, the bidirectional interconnection between these factors remains not fully understood. The objective of this study is to provide mechanistic insights into the correlation between spot urine sodium concentrations (UNa+) and urine dilution. This aims to better understand of the decongestive abilities in acute heart failure (AHF). The study was single-center, prospective, conducted on a group of 50 AHF patients. Each participant received a standardized furosemide dose of 1 mg per kg of body weight. Hourly diuresis was measured in the first 6 h of the study, and urine composition was assessed at predefined timepoints. The study group presented the exponential (rather than linear) pattern of relationship between UNa+ and 6-h urine volume, whereas relationship between eGFR and 6-h urine volume was linear (r = 0.61, p < 0.001). The relationship between UNa+ and all other analyzed indices of urine dilution, including the change from baseline in urine creatinine concentration, urine osmolarity, and urine osmolarity corrected for urine sodium, also exhibited an exponential relationship. Patients who were chronically exposed to furosemide demonstrated a significantly lower urine dilution (1.78 [1.18–3.54] vs 11.58 [3.9–17.88]; p < 0.001) in comparison to naïve individuals. In conclusion, it should be noted that in AHF higher UNa+ is associated with disproportionally higher urine dilution, and patients naïve to furosemide have significantly greater ability to dilute urine when compare to chronic furosemide users.

How Much Furosemide Should be Administered to Prevent Transfusion-Associated Circulatory Overload? Results of a Dose-Finding Study

BACKGROUND: Transfusion-associated circulatory overload (TACO) is a common but under-reported complication of transfusion therapy, and results in significant morbidity and mortality. Pre-transfusion furosemide has been proposed as a mitigating strategy but has not received widespread endorsement, in part due to uncertainty regarding safe and effective dosing. An observational study was therefore conducted with the goal of creating a reliable dose-response curve in patients at high risk of TACO, using the statistical technique of Multiple Comparisons Procedure with Modelling (MCP-MOD). METHODS: Eligible patients were identified by screening bolus intravenous (IV) furosemide orders at two large academic hospitals. Eligibility criteria were selected to mimic those of a planned randomized controlled trial (RCT) of pre-transfusion furosemide for the prevention of TACO. Inclusion criteria were inpatients 50 years of age or older. Exclusion criteria were active bleeding, hemodynamic instability, glomerular filtration rate (GFR) &amp;lt; 30mL/min or need for dialysis, diuretic therapy (other than furosemide) administered less than 24 hours, furosemide (either IV or PO) administered less than 12 hours, or exogenous albumin administered less than 8 hours prior to index furosemide therapy. The primary outcome measure was the total volume of urine output in the six hours following IV furosemide administration. MCP-MOD analysis was performed after every 50 patients and continued until a weight-adjusted dose-response curve could be established with 100 mL precision, using the following covariates: age, sex, mean arterial pressure (MAP), serum albumin, GFR and history of chronic furosemide use. RESULTS: A total of 149 participants (53 female and 96 male) were enrolled over 2 years. As too few patients received doses exceeding 0.6 mg/kg to allow for a precise dose-response curve, only 132 patients receiving weight-adjusted doses ranging from 0.1 to 0.6 mg/kg were included in the MCP-MOD analysis. The characteristics of these patients are shown in Table 1. The dose-response curve formula that was derived from these patients was: Urine Output at 6 hours (mL) = 717.21 + 191.33 ln(dose (mg)/weight (kg)) + 0.73 × Age (years) + 103.37 × Sex (M=1/F=0) + 1.63 × GFR (ml/min) + 5.45 × MAP (mmHg) - 9.56 × albumin (g/L) - 62.31 × chronic diuretic use (Y=1/N-0) The curve with accompanying 95% confidence intervals is shown in Figure 1 This formula suggests that in an 80 kg patient with a GFR of 75 mL/min, a MAP of 85 mmHg, albumin of 40 g/L and no history of chronic diuretic use, 10 mg of IV furosemide should produce a diuresis of approximately 600 mL, sufficient to prevent circulatory overload from the transfusion of 1 unit of RBCs. A dose of 20 mg would be required to achieve a similar diuresis in patients with either a MAP &amp;lt; 60 mmHg, or a combination of both a GFR &amp;lt; 45 mL/min and a history of chronic diuretic use. CONCLUSIONS: A statistically precise dose-response curve for IV furosemide is possible with the inclusion of relevant clinical covariates, and can be used to guide dosing decisions in patients at risk of transfusion-associated circulatory overload. This formula derived from this study will inform the dosing recommendations of a planned RCT: Transfusion-Associated Circulatory Overload: Best Eliminated by Lasix® (TACO-BEL).

The B1 H + -ATPase ( Atp6v1b1 ) Subunit in Non-Type A Intercalated Cells is Required for Driving Pendrin Activity and the Renal Defense Against Alkalosis.

In the kidney, the B1 H + -ATPase subunit is mostly expressed in intercalated cells (IC). Its importance in acid-secreting type A ICs is evident in patients with inborn distal renal tubular acidosis and ATP6V1B1 mutations. However, the protein is also highly expressed in alkali-secreting non-type A ICs where its function is incompletely understood. We demonstrate in Atp6v1b1 knock out mice that the B1 subunit is critical for the renal response to defend against alkalosis during an alkali load or chronic furosemide treatment. These findings highlight the importance of non-type A ICs in maintaining acid-base balance in response to metabolic challenges or commonly used diuretics. Non-type A ICs in the collecting duct system express the luminal Cl - /HCO 3- exchanger pendrin and apical and/or basolateral H + -ATPases containing the B1 subunit isoform. Non-type A ICs excrete bicarbonate during metabolic alkalosis. Mutations in the B1 subunit (ATP6V1B1) cause distal renal tubular acidosis due to its role in acid secretory type A ICs. The function of B1 in non-type A ICs has remained elusive. We examined the responses of Atp6v1b1-/- and Atp6v1b1+/+ mice to an alkali load and to chronic treatment with furosemide. An alkali load or 1 week of furosemide resulted in a more pronounced hypokalemic alkalosis in male ATP6v1b1-/- versus Atp6v1b1+/+ mice that could not be compensated by respiration. Total pendrin expression and activity in non-type A ICs of ex vivo microperfused cortical collecting ducts were reduced, and β2 -adrenergic stimulation of pendrin activity was blunted in ATP6v1b1-/- mice. Basolateral H + -ATPase activity was strongly reduced, although the basolateral expression of the B2 isoform was increased. Ligation assays for H + -ATPase subunits indicated impaired assembly of V 0 and V 1 H + -ATPase domains. During chronic furosemide treatment, ATP6v1b1-/- mice also showed polyuria and hyperchloremia versus Atp6v1b1+/+ . The expression of pendrin, the water channel AQP2, and subunits of the epithelial sodium channel ENaC were reduced. Our data demonstrate a critical role of H + -ATPases in non-type A ICs function protecting against alkalosis and reveal a hitherto unrecognized need of basolateral B1 isoform for a proper H + -ATPase complexes assembly and ability to be stimulated.

The blunted loop diuretic response in acute heart failure is driven by reduced tubular responsiveness rather than insufficient tubular delivery. The role of furosemide urine excretion on diuretic and natriuretic response in acute heart failure.

Diuretic response in heart failure is blunted when compared to healthy individuals, but the pathophysiology underlying this phenomenon is unclear. We aimed to investigate whether the diuretic resistance mechanism is related to insufficient furosemide tubular delivery or low tubular responsiveness. We conducted a prospective, observational study of 50 patients with acute heart failure patients divided into two groups based on previous furosemide use (furosemide naïve: n = 28 [56%] and chronic furosemide users: n = 22 [44%]). Each patient received a protocol-derived, standardized furosemide dose based on body weight. We measured diuretic response and urine furosemide concentrations. The furosemide naïve group had significantly higher urine volumes and natriuresis when compared to chronic users at all timepoints (all p < 0.05). Urine furosemide delivery was similar in furosemide naïve versus chronic users after accounting for differences in estimated glomerular filtration rate (28.02 [21.03-35.89] vs. 29.70 [18.19-34.71] mg, p = 0.87). However, the tubular response to delivered diuretic was dramatically higher in naïve versus chronic users, that is the urine volume per 1 μg/ml of urine furosemide at 2 h was 148.6 ± 136.1 versus 50.6 ± 56.1 ml (p = 0.005). Patients naïve to furosemide have significantly better diuresis and natriuresis when compared to chronic furosemide users. The blunted diuretic response in patients with chronic loop diuretic exposure is driven by decreased tubular responsiveness rather than insufficient furosemide tubular delivery.

Serum chloride and serum sodium derangements in children on prolonged furosemide therapy and their effect on diuretic response

BackgroundElectrolyte disturbances are not uncommon in patients on chronic furosemide therapy. We hypothesized that serum chloride (Cl) and serum sodium (Na) abnormalities may occur in children on prolonged furosemide therapy affecting the diuretic response in these children.MethodsThe study included 45 children, with congenital left to right shunts causing chronic congestive state which necessitated chronic furosemide therapy. Patients in need to an increase of their furosemide dose were recruited in the study. We assessed serum Cl and serum Na as well as parameters of diuretic responsiveness; net fluid output and change in body weight/40 mg furosemide, and change in urinary Na/K ratio. These parameters were assessed initially and at day 3 after increasing furosemide dose.ResultsAccording to serum levels of Cl and Na, patients were divided into four groups: isolated hyponatremia (15 patients, 33.3%), isolated hypochloremia (9 patients, 20%), combined hypochloremia and hyponatremia (12 patients, 26.7%), and normal serum electrolytes (9 patients, 20%). Patients with combined hyponatremia and hypochloremia and those with isolated hypochloremia showed minimal clinical and radiological signs of decongestion as well as lowest changes in urinary Na/K ratio, fluid output and weight change/40 mg furosemide on augmenting the diuretic dose, unlike the hyponatremic patients who had near normal parameters with no evidence of diuretic resistance.ConclusionBoth hypochloremia and hyponatremia are common in patients on prolonged furosemide therapy. Hypochloremia is associated with a poor diuretic response, unlike isolated hyponatremia which does not seem to affect the diuretic response. Concomitant occurrence of hyponatremia and hypochloremia is associated with poor diuretic response as well which can be worse than that seen in isolated hypochloremia.

NHE3 in the thick ascending limb is required for sustained but not acute furosemide-induced urinary acidification.

Na+/H+ exchanger isoform 3 (NHE3) facilitates Na+ reabsorption and H+ secretion by the kidneys. Despite stronger NHE3 abundance in the thick ascending limb (TAL) compared with the S1 and S2 segments of the proximal tubule, the role of NHE3 in the TAL is poorly understood. To investigate the role of NHE3 in the TAL, we generated and phenotyped TAL-specific NHE3 knockout (NHE3TAL-KO) mice. Compared with control mice, NHE3TAL-KO mice did not show significant differences in body weight, blood pH, or plasma Na+, K+, or Cl- levels. Fluid intake trended to be higher and urine osmolality was significantly lower in NHE3TAL-KO mice. Despite a similar glomerular filtration rate, NHE3TAL-KO mice had a greater urinary K+-to-creatinine ratio. One proposed role of NHE3 relates to furosemide-induced urinary acidification. Acute bolus treatment with furosemide under anesthesia did not result in differences in the dose dependence of urinary flow rate, Cl- excretion, or maximal urinary acidification between genotypes; however, in contrast with control mice, urinary pH returned immediately toward baseline levels in NHE3TAL-KO mice. Chronic furosemide treatment reduced urine osmolality similarly in both genotypes but metabolic alkalosis, hypokalemia, and calciuresis were absent in NHE3TAL-KO mice. Compared with vehicle, chronic furosemide treatment resulted in greater Na+-K+-2Cl- abundance regardless of genotype. Na+-phosphate cotransporter 2a abundance was also greater in furosemide-treated control mice compared with vehicle treatment, an effect that was absent in NHE3TAL-KO mice. In summary, NHE3 in the TAL plays a role in the sustained acidification effect of furosemide. Consistent with this, long-term treatment with furosemide did not result in metabolic alkalosis in NHE3TAL-KO mice.NEW & NOTEWORTHY Na+/H+ exchanger isoform 3 (NHE3) is very abundant in the thick ascending limb (TAL) compared with the proximal tubule. Much has been learned about the role of NHE3 in the proximal tubule; however, the function of NHE3 in the TAL remains elusive. A novel mouse model that lacks NHE3 selectively in the TAL not only shows a phenotype under baseline conditions but also identifies that NHE3 is required for sustained but not acute furosemide-induced urinary acidification.

FC018: The B1 H+-ATPASE (ATP6V1B1) Subunit is Required for Non-Type a Intercalated Cell Function During Alkalosis

Abstract BACKGROUND AND AIMS Non-type A intercalated cells (IC) in the connecting tubule (CNT) and cortical collecting duct (CCD) express the luminal Cl−/HCO3− exchanger pendrin and apical and/or basolateral vacuolar H+-ATPases containing the B1 subunit isoform. One of the main functions of non-type A ICs is the secretion of bicarbonate during metabolic alkalosis. Mutations in the B1 subunit (ATP6V1B1) in man cause distal renal tubular acidosis due to its importance in acid secretion by type A ICs. However, the function of the B1 isoform in non-type A ICs has remained elusive. In this work, we investigated the role of the B1 H+-ATPase subunit in non-type A intercalated in the control of alkalosis. METHOD Acid-base metabolism of Atp6v1b1 mice was studied during an alkali load (0.28 M NaHCO3 in drinking water and 2 mg deoxycorticosterone i.p for 4 days) or during a chronic furosemide treatment (20 mg i.p. injection daily for 9 days). RESULTS Induction of metabolic alkalosis by 0.28 M NaHCO3 resulted in a more pronounced alkalosis in ATP6v1b1−/− mice with increased blood bicarbonate, hypokalaemia and hypochloraemia despite a reduced lung minute volume. Determination of the relative abundance of the different subtypes of cells in the collecting duct system revealed a remodelling of CNT and CCD in the cortex with an increase of type A ICs and a compensatory increase of non-type A ICs in collecting ducts of the outer medullary in ATP6v1b1−/− kidneys. Total pendrin expression in the kidney and activity in non-type A cells of ex vivo microperfused CCD were reduced in ATP6v1b1−/− mice. Moreover, the stimulating effect of Isoproterenol, a β2-adrenergic receptor agonist stimulating cAMP production, on pendrin activity was blunted in non-type A ICs from ATP6v1b1−/− mice. Basolateral H+-ATPase activity in pendrin-expressing cells was strongly reduced, even though the expression of the B2 isoform was increased at their basolateral side. Moreover, the E1 and A H+-ATPase subunits of the V0 domain did only partially colocalize with the a4 H+-ATPase subunit of the V1 domain of H+-ATPases at the basolateral pole of ATP6v1b1−/− non-type A ICs, indicating impaired assembly of V0 and V1 H+-ATPase domains. Finally, when exposed to a chronic furosemide treatment, a treatment associated with a high risk to develop metabolic alkalosis in patients, ATP6v1b1−/− mice developed a more pronounced hypokalaemic hypochloraemic alkalosis with polyuria and loss of urine chloride compared with their wildtype littermates. In ATP6v1b1−/− kidneys, pendrin expression was drastically reduced as well as the water channel AQP2 and the α and γ subunits of the sodium channel ENaC. An increase of BUN and a decrease of kidney klotho expression were also observed in ATP6v1b1−/− mice which might indicate a worsening of their kidney function. CONCLUSION Thus, this study demonstrates for the first time that i) the B1 H+-ATPase subunit is critical for normal non-type A ICs function and protects against alkalosis. ii) Moreover, the B1 subunit is required for the assembly of complete and functional basolateral vacuolar H+-ATPases complexes in intercalated cells.

Physiological clearance of amyloid-beta by the kidney and its therapeutic potential for Alzheimer's disease.

Amyloid-β (Aβ) accumulation in the brain is a pivotal event in the pathogenesis of Alzheimer's disease (AD), and its clearance from the brain is impaired in sporadic AD. Previous studies suggest that approximately half of the Aβ produced in the brain is cleared by transport into the periphery. However, the mechanism and pathophysiological significance of peripheral Aβ clearance remain largely unknown. The kidney is thought to be responsible for Aβ clearance, but direct evidence is lacking. In this study, we investigated the impact of unilateral nephrectomy on the dynamic changes in Aβ in the blood and brain in both humans and animals and on behavioural deficits and AD pathologies in animals. Furthermore, the therapeutic effects of the diuretic furosemide on Aβ clearance via the kidney were assessed. We detected Aβ in the kidneys and urine of both humans and animals and found that the Aβ level in the blood of the renal artery was higher than that in the blood of the renal vein. Unilateral nephrectomy increased brain Aβ deposition; aggravated AD pathologies, including Tau hyperphosphorylation, glial activation, neuroinflammation, and neuronal loss; and aggravated cognitive deficits in APP/PS1 mice. In addition, chronic furosemide treatment reduced blood and brain Aβ levels and attenuated AD pathologies and cognitive deficits in APP/PS1 mice. Our findings demonstrate that the kidney physiologically clears Aβ from the blood, suggesting that facilitation of Aβ clearance via the kidney represents a novel potential therapeutic approach for AD.

Uromodulin is expressed in the distal convoluted tubule, where it is critical for regulation of the sodium chloride cotransporter NCC

Uromodulin, the most abundant protein in normal urine, is essentially produced by the cells lining the thick ascending limb. There it regulates the activity of the cotransporter NKCC2 and is involved in sodium chloride handling and blood pressure regulation. Conflicting reports suggested that uromodulin may also be expressed in the distal convoluted tubule (DCT) where its role remains unknown. Using microdissection studies combined with fluorescent insitu hybridization and co-immunostaining analyses, we found a significant expression of uromodulin in mouse and human DCT at approximately 10% of thick ascending limb expression levels, but restricted to the early part of the DCT (DCT1). Genetic deletion of Umod in mouse was reflected by a major shift in NCC activity from the DCT1 to the downstream DCT2 segment, paralleled by a compensatory expansion of DCT2. By increasing the distal sodium chloride and calcium ion load with chronic furosemide administration, an intrinsic compensatory defect in the DCT from Umod-/- compared to wild type mice was found manifested as sodium wasting and hypercalciuria. In line, co-expression studies in HEK cells suggested a facilitating role for uromodulin in NCC phosphorylation, possibly via SPAK-OSR1 modulation. These experiments demonstrate a significant expression of uromodulin in the early part of mouse and human DCT. Thus, biosynthesis of uromodulin in the DCT1 is critical for its function, structure and plasticity, suggesting novel links between uromodulin, blood pressure control and risk of kidney stones.

Effect of high-dose furosemide on the prognosis of critically ill patients

PurposeDiuretics are used frequently in critically ill patients. We investigated the effects of furosemide on the prognosis. Materials and methodsFollowing a retrospective review of patients admitted to the medical intensive care unit (ICU), we analyzed risk factors with variables including initial furosemide dose for ICU mortality. ResultsA total of 448 patients were included. Total furosemide dose during the first three days of the ICU stay (odds ratio (OR) 2.35, 95% confidence interval (CI) 1.01–5.02) and fluid balance during the same period (OR 3.04, 95% CI 1.46–6.31) were associated with ICU mortality, as were malignancy, chronic furosemide use, and APACHE II score. However, in oliguric patients, positive fluid balance was associated with ICU mortality (OR 22.33, 95% CI 1.82–273.72) but the high-dose furosemide was not. In contrast, in non-oliguric patients, high-dose furosemide was associated with ICU mortality (OR 2.47, 95% CI 1.01–5.68); however, the positive fluid balance showed only a trend for high ICU mortality. ConclusionEarly high-dose furosemide use is associated with ICU mortality, particularly in non-oliguric patients. We suggest that furosemide should be used with caution even in non-oliguric critically ill patients until the safety is confirmed in powered study.

Contributions of Mouse and Human Hematopoietic Cells to Remodeling of the Adult Auditory Nerve After Neuron Loss.

The peripheral auditory nerve (AN) carries sound information from sensory hair cells to the brain. The present study investigated the contribution of mouse and human hematopoietic stem cells (HSCs) to cellular diversity in the AN following the destruction of neuron cell bodies, also known as spiral ganglion neurons (SGNs). Exposure of the adult mouse cochlea to ouabain selectively killed type I SGNs and disrupted the blood-labyrinth barrier. This procedure also resulted in the upregulation of genes associated with hematopoietic cell homing and differentiation, and provided an environment conducive to the tissue engraftment of circulating stem/progenitor cells into the AN. Experiments were performed using both a mouse-mouse bone marrow transplantation model and a severely immune-incompetent mouse model transplanted with human CD34+ cord blood cells. Quantitative immunohistochemical analysis of recipient mice demonstrated that ouabain injury promoted an increase in the number of both HSC-derived macrophages and HSC-derived nonmacrophages in the AN. Although rare, a few HSC-derived cells in the injured AN exhibited glial-like qualities. These results suggest that human hematopoietic cells participate in remodeling of the AN after neuron cell body loss and that hematopoietic cells can be an important resource for promoting AN repair/regeneration in the adult inner ear.

Effect of Chronic Furosemide on Salt and Water Intake of Ponies

Furosemide is used acutely in racehorses and chronically for treatment of edema and congestive heart failure, but the behavioral effects on horses of chronic administration of this drug have not been studied. The objectives of this study were to measure salt and water intake as well as sodium and water losses in ponies treated chronically with furosemide. The salt and water intake of ponies was measured daily for 3 weeks before and 3 weeks during treatment with furosemide at a dose of 0.5 mg/kg/d. Fecal dry matter was measured for 9 days before and during furosemide treatment by collecting a fecal sample from each pony's stall and drying it overnight in a 100°C oven. Urine volume and urine sodium content were measured daily for three consecutive days during pretreatment, treatment, and post-treatment periods so that sodium and water status could be calculated. Sodium chloride intake increased in ponies treated daily with furosemide from 7.9 ± 2.2 (standard error of the mean) to 20.3 ± 2.4 g/d and was significantly higher than control for all weeks of treatment (P < .03). Water intake was also significantly increased from 8.9 ± 1 during the control period to 11 ± 0.7 kg/d during furosemide treatment (P < .001), and the ponies drank more water than they lost. Urine volume and urine sodium concentrations increased significantly during treatment with the diuretic, whereas urinary potassium and calcium concentrations decreased.

Role of IGF1R in Tubular Remodeling of the Mouse Kidney

Loop diuretics, commonly prescribed to treat hypertension and edema, increase sodium excretion by inhibiting the sodium‐potassium 2 chloride cotransporter (NKCC2) in the thick ascending limb. Chronic furosemide use leads to diuretic resistance in humans, but the molecular mechanisms are largely unknown. We developed a mouse model of chronic furosemide use to explore its effects on sodium transport and tubular remodeling. Mice treated with furosemide for seven days had greater sensitivity for thiazide diuretics with significantly increased levels of sodium‐chloride cotransporter (NCC), demonstrating compensatory sodium reabsorption of the distal nephron. Furosemide‐treated mice also exhibited tubular hyperplasia. After 21 days, mice treated with furosemide vs. vehicle, had persistently‐elevated NCC expression increased kidney‐to‐body weight ratio, increased tubular hypertrophy of distal convoluted tubule and connecting tubular segments, and changes in IGF‐1 signaling. There was no increase in IGF‐1 mRNA expression, but specific increases in IGF binding proteins (IGFBPs) which are known to sequester IGF‐1 in kidney cells, and IGF‐1 receptor. To further explore the role of IGF‐1 in tubular remodeling, we developed an inducible, pan‐tubular IGF‐1 receptor knockout mouse. Interestingly, furosemide‐treated IGF‐1 receptor (IGF1R) knockout mice lacked the increased kidney‐to‐body mass increase ratio seen in wild‐type mice, but they developed comparable hypertrophy in distal nephron segments and higher expression of NCC compared with furosemide‐treated wild‐type mice. These results suggest IGF1R signaling is involved in renal tubular remodeling of more proximal nephron segments and distinct factors control the tubular hypertrophy of the distal nephron beyond an increase in NCC expression.Support or Funding InformationNIH/NIDDK

Effects of chronic furosemide on central neural hyperactivity and cochlear thresholds after cochlear trauma in Guinea pig.

Increased neuronal spontaneous firing rates have been observed throughout the central auditory system after trauma to the cochlea and this hyperactivity is believed to be associated with the phantom perception of tinnitus. Previously, we have shown in an animal model of hearing loss, that an acute injection with furosemide can significantly decrease hyperactivity after cochlear trauma and eliminate behavioral evidence of tinnitus of early onset. However, furosemide also has the potential to affect cochlear thresholds. In this paper, we measured the effects of a chronic (daily injections for 7 days) furosemide treatment on the spontaneous firing rate of inferior colliculus neurons and on cochlear thresholds in order to establish whether a beneficial effect on hyperactivity can be obtained without causing additional hearing loss. Guinea pigs were exposed to a 10–kHz, 124 dB, 2 h acoustic trauma, and after 5 days of recovery, were given daily i.p. injections of 80 mg/kg furosemide or an equivalent amount of saline. The activity of single IC neurons was recorded 24 h following the last injection. The furosemide treatment had no effect on cochlear thresholds compared to saline injections but did result in significant reductions in spontaneous firing rates recorded in inferior colliculus. These results that suggest a long-term beneficial effect of furosemide on hyperactivity after cochlear trauma may be achievable without detrimental effects on hearing, which is important when considering therapeutic potential.

Furosemide Administration Affects Mineral Excretion in Exercised Thoroughbreds

IntroductionFurosemide is widely administered to Thoroughbred and Standardbred racehorses to reduce the incidence and severity of EIPH. The magnitude and duration of mineral loss following furosemide administration has not previously been measured in horses.MethodsSix fit Thoroughbreds (age 6.8 ± 1.2 y; bwt 585 ± 19 kg) were used in a 3 x 3 Latin square design trial to measure the effect of furosemide on urinary and fecal mineral excretion for 24 h before (−24 h) and 24 h, 48 h and 72 h after a standardized exercise test (SET) on an inclined (3o) high speed treadmill. The treatment groups consisted of an untreated control (C) and two groups (F and FE) which received furosemide (0.5 mg/kg, IV) 4 h before the SET. C and F were fed 60 g/d NaCl and (FE) was fed 200 g/d of an electrolyte mix (14 g K, 37.7 g Na and 43.3 g Cl) for 21 days before the SET. Following the SET the FE group was supplemented with an additional 10 g/d Ca and 10 g/d Mg.ResultsUrinary Ca, P, Na and Cl excretion increased 24 h post treatment in the F and FE groups (P&lt;0.05). 72 h Ca and Cl balance was decreased in F (P&lt;0.05) and 72 h Mg and Cl balance was decreased in FE (P&lt;0.05). The digestibility of P and Mg was decreased in FE (P&lt;0.05) and Na digestibility was increased in F and FE (P&lt;0.05).ConclusionsA single dose of furosemide negatively affected calcium balance in horses for 72 h post administration. Further research is needed to assess the effect of chronic furosemide use in racehorses on mineral balance and soundness.Ethical Animal ResearchStudy approved by the Kentucky Equine Research Institutional Animal Care and Use Committee. Sources of funding: Kentucky Equine Research. Competing interests: none.

Clinical Pharmacology of Furosemide in Neonates: A Review

Furosemide is the diuretic most used in newborn infants. It blocks the Na+-K+-2Cl− symporter in the thick ascending limb of the loop of Henle increasing urinary excretion of Na+ and Cl−. This article aimed to review the published data on the clinical pharmacology of furosemide in neonates to provide a critical, comprehensive, authoritative and, updated survey on the metabolism, pharmacokinetics, pharmacodynamics and side-effects of furosemide in neonates. The bibliographic search was performed using PubMed and EMBASE databases as search engines; January 2013 was the cutoff point. Furosemide half-life (t1/2) is 6 to 20-fold longer, clearance (Cl) is 1.2 to 14-fold smaller and volume of distribution (Vd) is 1.3 to 6-fold larger than the adult values. t1/2 shortens and Cl increases as the neonatal maturation proceeds. Continuous intravenous infusion of furosemide yields more controlled diuresis than the intermittent intravenous infusion. Furosemide may be administered by inhalation to infants with chronic lung disease to improve pulmonary mechanics. Furosemide stimulates prostaglandin E2 synthesis, a potent dilator of the patent ductus arteriosus, and the administration of furosemide to any preterm infants should be carefully weighed against the risk of precipitation of a symptomatic patent ductus arteriosus. Infants with low birthweight treated with chronic furosemide are at risk for the development of intra-renal calcifications.

Chronic furosemide administration blunts renal BOLD magnetic resonance response to an acute furosemide stimulus in patients being evaluated for renal artery revascularization

Background Blood Oxygen Level Dependent (BOLD) magnetic resonance (MR) is a novel imaging tool that is able to detect tissue oxygenation and has recently been utilized to evaluate renal function in patients with renal artery stenosis (RAS). Renal BOLD imaging is typically performed before and after a furosemide stimulus to assess kidney viability. Furosemide blocks the sodium-potassium2chloride transporter, an oxygen-dependent process, in the ascending loop of Henle located in the renal medulla. Presumably, kidneys that are able to decrease oxygen consumption and increase BOLD (T2*) signal in response to furosemide would be viable and benefit from revascularization procedures. A standard dose of 20mg of intravenous (IV) furosemide is administered to evaluate renal responsiveness (increased T2* signal intensity) and viability. However, little is known about the effect of prior exposure to furosemide on the ability of BOLD MR techniques to evaluate renal function.

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

BackgroundFurosemide 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.MethodsTwo 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-D28K, 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-D28K and ENaC were also measured using semi-quantitative immunohistochemistry and immunoblotting.ResultsThe 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-D28K.ConclusionsDuring chronic furosemide treatment, enhanced active reabsorption of Mg2+ via the epithelial channel TRPM6 in DCT compensates for the reduced reabsorption of Mg2+ in TAL.