RESUMO
PURPOSE OF REVIEW: Postnatal renal tubule development is critical to adult kidney function. Several postnatal changes regulate the differentiation and proliferation of renal tubular cells. Here, we review the literature and our efforts on thick ascending limb (TAL) development in Bartter syndrome (BS). RECENT FINDINGS: Glomerular filtrate quickly increases after birth, imposing fluid shear stress and circumferential stretch on immature renal tubules. Recent studies showed that kidney organoids under flow (superfusion) have better development of tubular structures and the expression of cilia and solute transporters. These effects are likely mediated by mechanosensors, such as cilia and the piezo1 channel. Improved renal oxygenation and sodium pump-dependent active transport can stimulate mitochondrial respiration and biogenesis. The functional coupling between transport and mitochondria ensures ATP supply for energy-demanding reactions in tubular cells, including cell cycle progression and proliferation. We recently discovered that postnatal renal medulla maturation and TAL elongation are impaired in Clc-k2-deficient BS mice. Primary cultured Clc-k2-deficient TAL cells have G1-S transition and proliferation delay. These developmental defects could be part of the early pathogenesis of BS and worsen the phenotype. SUMMARY: Understanding how tubular flow and transepithelial ion fluxes regulate renal tubule development may improve the treatment of congenital renal tubulopathies.
Assuntos
Túbulos Renais , Humanos , Animais , Túbulos Renais/metabolismo , Túbulos Renais/crescimento & desenvolvimento , Síndrome de Bartter/metabolismo , Síndrome de Bartter/fisiopatologia , Síndrome de Bartter/genéticaRESUMO
Abstract Introduction: Bartter's syndrome comprises a heterogeneous group of inherited salt-losing tubulopathies. There are two forms of clinical presentation: classical and neonatal, the most severe type. Types I and II account for most of the neonatal cases. Types III and V are usually less severe. Characteristically Bartter's syndrome type IV is a saltlosing nephropathy with mild to severe neonatal symptoms, with a specific feature - sensorineural deafness. Bartter's syndrome type IV is the least common of all recessive types of the disease. Description: the first reported case of a Portuguese child with neurosensorial deafness, polyuria, polydipsia and failure to thrive, born prematurely due to severe polyhydramnios, with the G47R mutation in the BSND gene that causes Bartter's syndrome type IV. Discussion: there are few published cases of BS type IV due to this mutation and those reported mostly have moderate clinical manifestations which begin later in life. The poor phenotype-genotype relationship combined with the rarity of this syndrome usually precludes an antenatal diagnosis. In the presence of a severe polyhydramnios case, with no fetal malformation detected, normal karyotype and after maternal disease exclusion, autosomal recessive diseases, including tubulopathies, should always be suspected.
Resumo Introdução: a síndrome de Bartter inclui um grupo heterogéneo de tubulopatias hereditárias perdedoras de sal. Existem duas formas de apresentação clínica: clássica e neonatal, a forma mais grave. Os tipo I e II representam a maioria dos casos neonatais. Os tipos III e V são geralmente menos graves. Caracteristicamente, a síndrome de Bartter tipo IV é uma nefropatia perdedora de sal com sintomas neonatais ligeiros a graves, com um aspeto especí- fico - surdez neurossensorial. A síndrome de Bartter tipo IV é o tipo menos comum das formas recessivas da doença. Descrição: relatamos o primeiro caso de uma criança portuguesa, com surdez neurossensorial, poliúria, polidipsia e restrição de crescimento, nascida prematuramente devido a polihidrâmnios grave, homozigótica para a mutação G47R do gene BSND, responsável pela síndrome de Bartter tipo IV. Discussão: são raros os casos publicados sobre síndrome de Bartter tipo IV atribuída a esta mutação, e a maioria referem-se a diagnósticos mais tardios, com manifestações clínicas ligeiras. A fraca correlação fenótipo-genótipo combinada com a raridade desta síndrome tornam o diagnóstico pré-natal desafiante. Perante um caso de polihidrâmnios grave em um feto sem malformações aparentes, cariótipo normal e após exclusão de patologia materna, as doenças autossómicas recessivas, incluindo as tubulopatias, devem ser sempre consideradas.
Assuntos
Humanos , Feminino , Gravidez , Recém-Nascido , Adulto , Diagnóstico Pré-Natal , Síndrome de Bartter/fisiopatologia , Síndrome de Bartter/genética , Poli-Hidrâmnios/diagnóstico , Poli-Hidrâmnios/etiologia , Complicações na Gravidez , Terceiro Trimestre da Gravidez , Perda Auditiva Neurossensorial/genética , Trabalho de Parto PrematuroRESUMO
Bartter-Gitelman syndromes are rare inherited autosomal recessive salt-losing tubulopathies characterized by severe and chronic hypokalemia associated with metabolic alkalosis and secondary hyperaldosteronism. Bartter syndrome results from a furosemide-like defect in sodium reabsorption in the Henle's loop leading to hypercalciuria and defect in urinary concentration capacity. The antenatal Bartter syndrome is defined by polyhydramnios and an infantile polyuria with severe dehydration whereas classic Bartter syndrome appears during childhood or adulthood. Gitelman syndrome is a thiazide-like salt-losing tubulopathy. It is associated with hypomagnesemia, hypocalciuria without defect in urinary concentration capacity. The diagnosis is most often made in adolescents or adults. Clinical symptoms include tetany, delay in the height-weight growth curves, chronic tiredness, muscle weakness, myalgia and vertigo. Nephrocalcinosis in Bartter syndrome could lead to chronic kidney disease. Antenatal Bartter syndrome requires hospitalization in intensive care unit to manage the severe newborn dehydration. Chondrocalcinosis is the major complication in the Gitelman syndrome. The corner stones of treatment is the fluid and electrolyte management Bartter and Gitelman syndromes need lifelong oral supplementations of potassium, salt (Bartter) and magnesium (Gitelman). Indomethacin is efficient to reduce water and electrolyte loss in Bartter. In Gitelman, potassium-sparing diuretics may be helping for severe hypokaliemia but they will reinforce hypovolemia.
Assuntos
Síndrome de Bartter , Síndrome de Gitelman , Síndrome de Bartter/complicações , Síndrome de Bartter/diagnóstico , Síndrome de Bartter/fisiopatologia , Síndrome de Bartter/terapia , Síndrome de Gitelman/complicações , Síndrome de Gitelman/diagnóstico , Síndrome de Gitelman/fisiopatologia , Síndrome de Gitelman/terapia , HumanosRESUMO
BACKGROUND: Renal loss of potassium (K+) and magnesium (Mg2+) in salt losing tubulopathies (SLT) leads to significantly reduced Quality of Life (QoL) and higher risks of cardiac arrhythmia. The normalization of K+ is currently the most widely accepted treatment target, however in even excellently designed RCTs the increase of K+ was only mild and rarely normalized. These findings question the role of K+ as the ideal marker of potassium homeostasis in SLT. Aim of this hypothesis-generating study was to define surrogate endpoints for future treatment trials in SLT in terms of their usefulness to determine QoL and important clinical outcomes. METHODS: Within this prospective cross-sectional study including 11 patients with SLTs we assessed the biochemical, clinical and cardiological parameters and their relationship with QoL (RAND SF-36). The primary hypothesis was that QoL would be more dependent of higher aldosterone concentration, assessed by the transtubular-potassium-gradient (TTKG). Correlations were evaluated using Pearson's correlation coefficient. RESULTS: Included patients were mainly female (82%, mean age 34 ± 12 years). Serum K+ and Mg2+ was 3.3 ± 0.6 mmol/l and 0.7 ± 0.1 mmol/l (mean ± SD). TTKG was 9.5/3.4-20.2 (median/range). While dimensions of mental health mostly correlated with serum Mg2+ (r = 0.68, p = 0.04) and K+ (r = 0.55, p = 0.08), better physical health was associated with lower aldosterone levels (r = -0.61, p = 0.06). TTKG was neither associated with aldosterone levels nor with QoL parameters. No relevant abnormalities were observed in neither 24 h-ECG nor echocardiography. CONCLUSIONS: Hyperaldosteronism, K+ and Mg2+ were the most important parameters of QoL. TTKG was no suitable marker for hyperaldosteronism or QoL. Future confirmatory studies in SLT should assess QoL as well as aldosterone, K+ and Mg2+.
Assuntos
Síndrome de Bartter/fisiopatologia , Síndrome de Gitelman/fisiopatologia , Hiperaldosteronismo/fisiopatologia , Hipopotassemia/fisiopatologia , Magnésio/metabolismo , Qualidade de Vida , Adulto , Aldosterona/metabolismo , Síndrome de Bartter/metabolismo , Síndrome de Bartter/psicologia , Feminino , Síndrome de Gitelman/metabolismo , Síndrome de Gitelman/psicologia , Homeostase , Humanos , Hiperaldosteronismo/metabolismo , Hiperaldosteronismo/psicologia , Hipopotassemia/metabolismo , Hipopotassemia/psicologia , Masculino , Pessoa de Meia-Idade , Potássio/metabolismo , Estudos Prospectivos , Desequilíbrio Hidroeletrolítico/metabolismo , Desequilíbrio Hidroeletrolítico/fisiopatologia , Desequilíbrio Hidroeletrolítico/psicologia , Adulto JovemRESUMO
Bartter's syndrome is a rare disorder usually presenting antenatal or in childhood and is characterized by hypokalemia, metabolic alkalosis, hyperaldosteronism and normal blood pressure. We report a case of adult-onset Bartter's syndrome in a 38 year old male who presented with lower limb weakness.
Assuntos
Síndrome de Bartter/diagnóstico , Hipopotassemia/fisiopatologia , Adulto , Alcalose/fisiopatologia , Síndrome de Bartter/tratamento farmacológico , Síndrome de Bartter/fisiopatologia , Análise Química do Sangue , Pressão Sanguínea , Humanos , Hiperaldosteronismo/fisiopatologia , Hipopotassemia/tratamento farmacológico , Masculino , Potássio/uso terapêuticoAssuntos
Angiotensina I/fisiologia , Síndrome de Bartter/fisiopatologia , Síndrome de Gitelman/fisiopatologia , Lesão Pulmonar/metabolismo , Fragmentos de Peptídeos/fisiologia , Angiotensina I/sangue , Anti-Inflamatórios , Antioxidantes , Humanos , Lesão Pulmonar/sangue , Fragmentos de Peptídeos/sangueRESUMO
INTRODUCTION: Bartter syndrome (BS) is a rare inherited tubulopathy that has two presentation forms, the first one is a severe form of antenatal onset (neonatal Bartter) and the second one is a later on set form during the first years of life (classic Bartter). In the antenatal form, it manifests with fetal polyuria, polyhydramnios of early and severe onset, premature delivery, and intrauterine growth restriction. In the postnatal stage, it presents recurrent episodes of dehydration and electrolyte im balance that can compromise the survival of the patient. OBJECTIVE: To report a clinical case of neo natal BS and a review of the literature. CLINICAL CASE: Premature newborn of 35 weeks of gestation with history of severe polyhydramnios diagnosed at 27 weeks of gestation, without apparent cause. From birth, the patient presented polyuria and hypokalemic metabolic alkalosis making a diagnosis of Neonatal Bartter Syndrome in the first week of life. Laboratory tests confirmed urinary electrolyte losses. The patient was treated with strict water balance and sodium and potassium supplementa tion, achieving weight and electrolyte imbalance stabilization. The patient remains in control in the nephrology unit, with potassium gluconate and sodium chloride supplementation. At the fourth month, ibuprofen was added as part of treatment. At the seventh month of life, renal ultrasound showed nephrocalcinosis. At one year of life, profound sensorineural hearing loss was observed re quiring a cochlear implant. CONCLUSION: The presence of severe polyhydramnios of early onset with no identified cause should lead to suspicion of neonatal BS which even when infrequent determines severe hydroelectrolytic alterations and should be treated early.
Assuntos
Síndrome de Bartter/diagnóstico , Poli-Hidrâmnios/diagnóstico , Adulto , Síndrome de Bartter/fisiopatologia , Síndrome de Bartter/terapia , Feminino , Perda Auditiva Neurossensorial/diagnóstico , Perda Auditiva Neurossensorial/cirurgia , Humanos , Ibuprofeno/administração & dosagem , Lactente , Recém-Nascido , Nefrocalcinose/diagnóstico , Nefrocalcinose/etiologia , Poli-Hidrâmnios/etiologia , GravidezRESUMO
INTRODUCCIÓN: Síndrome de Bartter (SB) es una tubulopatía hereditaria, poco frecuente que tiene dos formas de presentación, forma grave de inicio antenatal (Bartter neonatal) y forma de aparición más tardía (Bartter clásico). En su forma antenatal se manifiesta con poliuria fetal, polihidroamnios de inicio precoz y severo, parto prematuro secundario y restricción de crecimiento intrauterino. La etapa postnatal presenta episodios recurrentes de deshidratación y desbalance electrolítico que pue den comprometer la sobrevida del paciente. OBJETIVO: Comunicar un caso de SB neonatal y presentar una revisión de la literatura en esta patología. CASO CLÍNICO: Prematuro 35 semanas, con antecedente de severo polihidroamnios diagnosticado a las 27 semanas de gestación, sin causa aparente. Desde su nacimiento evolucionó con poliuria y alcalosis metabólica hipokalémica haciendo plantear, en primera semana de vida, diagnóstico de Síndrome de Bartter neonatal. El laboratorio confirmó per didas urinarias de electrólitos. Fue manejado con balance hídrico estricto y suplementación de sodio y potasio, logrando estabilizar peso y desbalance electrolítico. Se mantiene en control nefrológico, con suplementación de gluconato de potasio y cloruro de sodio. Se agregó ibuprofeno al cuarto mes como parte del tratamiento. Al séptimo mes de vida, ecografía renal demostró nefrocalcinosis. Al año de vida se evidenció hipoacusia sensorioneural profunda requiriendo implante coclear. CONCLUSIÓN: Presencia de polihidroamnios severo de aparición temprana sin causa identificada debe hacer sospechar SB, que aun siendo infrecuente determina graves alteraciones hidroelectrolíticas y debe ser iniciado su tratamiento precozmente.
INTRODUCTION: Bartter syndrome (BS) is a rare inherited tubulopathy that has two presentation forms, the first one is a severe form of antenatal onset (neonatal Bartter) and the second one is a later on set form during the first years of life (classic Bartter). In the antenatal form, it manifests with fetal polyuria, polyhydramnios of early and severe onset, premature delivery, and intrauterine growth restriction. In the postnatal stage, it presents recurrent episodes of dehydration and electrolyte im balance that can compromise the survival of the patient. OBJECTIVE: To report a clinical case of neo natal BS and a review of the literature. CLINICAL CASE: Premature newborn of 35 weeks of gestation with history of severe polyhydramnios diagnosed at 27 weeks of gestation, without apparent cause. From birth, the patient presented polyuria and hypokalemic metabolic alkalosis making a diagnosis of Neonatal Bartter Syndrome in the first week of life. Laboratory tests confirmed urinary electrolyte losses. The patient was treated with strict water balance and sodium and potassium supplementa tion, achieving weight and electrolyte imbalance stabilization. The patient remains in control in the nephrology unit, with potassium gluconate and sodium chloride supplementation. At the fourth month, ibuprofen was added as part of treatment. At the seventh month of life, renal ultrasound showed nephrocalcinosis. At one year of life, profound sensorineural hearing loss was observed re quiring a cochlear implant. CONCLUSION: The presence of severe polyhydramnios of early onset with no identified cause should lead to suspicion of neonatal BS which even when infrequent determines severe hydroelectrolytic alterations and should be treated early.
Assuntos
Humanos , Feminino , Gravidez , Recém-Nascido , Lactente , Adulto , Síndrome de Bartter/diagnóstico , Poli-Hidrâmnios/diagnóstico , Síndrome de Bartter/fisiopatologia , Síndrome de Bartter/terapia , Ibuprofeno/administração & dosagem , Poli-Hidrâmnios/etiologia , Perda Auditiva Neurossensorial/cirurgia , Perda Auditiva Neurossensorial/diagnóstico , Nefrocalcinose/diagnóstico , Nefrocalcinose/etiologiaRESUMO
Bartter syndromes (BS) types 1-5 are rare salt-losing tubulopathies presenting with overlapping clinical phenotypes including marked salt wasting and hypokalemia leading to polyuria, polydipsia, volume contraction, muscle weakness and growth retardation. These diseases are due to an impairment of sodium, potassium, chloride reabsorption caused by mutations in genes encoding for ion channel or transporters expressed in specific nephron tubule segments. Particularly, BS type 3 is a clinically heterogeneous form caused by mutations in CLCNKB gene which encodes the ClC-Kb chloride channel involved in NaCl reabsorption in the renal tubule. Specific therapy for BS is lacking and the only pharmacotherapy up today available is purely symptomatic and characterized by limiting side effects. The improvement of our understanding of the phenotype/genotype correlation and of the precise pathogenic mechanisms associated with BS type 3 as well as the pharmacological characterization of ClC-K chloride channels are fundamental to design therapies tailored upon patients' mutation. This mini review focused on recent studies representing relevant forward steps in the field as well as noteworthy examples of how basic and clinical research can cooperate to gain insight into the pathophysiology of this renal channelopathy, paving the way for a personalized therapy.
Assuntos
Síndrome de Bartter/tratamento farmacológico , Doenças Raras/tratamento farmacológico , Síndrome de Bartter/epidemiologia , Síndrome de Bartter/genética , Síndrome de Bartter/fisiopatologia , Canais de Cloreto/deficiência , Canais de Cloreto/genética , Cloretos/metabolismo , Desenho de Fármacos , Genes Recessivos , Estudos de Associação Genética , Humanos , Canais Iônicos/genética , Canais Iônicos/metabolismo , Transporte de Íons , Néfrons/metabolismo , Farmacogenética , Potássio/metabolismo , Medicina de Precisão , Doenças Raras/epidemiologia , Doenças Raras/genética , Sódio/metabolismoAssuntos
Distinções e Prêmios , Síndrome de Bartter/fisiopatologia , Rim/fisiopatologia , Publicações Periódicas como Assunto , Desequilíbrio Hidroeletrolítico , Animais , Síndrome de Bartter/sangue , Modelos Animais de Doenças , Humanos , Rim/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiopatologia , Potássio/sangueRESUMO
Renal tubulopathies provide insights into the inner workings of the kidney, yet also pose therapeutic challenges. Because of the central nature of sodium in tubular transport physiology, disorders of sodium handling may affect virtually all aspects of the homeostatic functions of the kidney. Yet, owing to the rarity of these disorders, little clinical evidence regarding treatment exists. Consequently, treatment can vary widely between individual physicians and centers and is based mainly on understanding of renal physiology, reported clinical observations, and individual experiences. Salt-losing tubulopathies can affect all tubular segments, from the proximal tubule to the collecting duct. But the more frequently observed disorders are Bartter and Gitelman syndrome, which affect salt transport in the thick ascending limb of Henle's loop and/or the distal convoluted tubule, and these disorders generate the greatest controversies regarding management. Here, we review clinical and molecular aspects of salt-losing tubulopathies and discuss novel insights provided mainly by genetic investigations and retrospective clinical reviews. Additionally, we discuss controversial topics in the management of these disorders to highlight areas of importance for future clinical trials. International collaboration will be required to perform clinical studies to inform the treatment of these rare disorders.
Assuntos
Síndrome de Bartter/genética , Síndrome de Fanconi/genética , Síndrome de Gitelman/genética , Túbulos Renais/fisiopatologia , Reabsorção Renal , Proteínas Carreadoras de Solutos/genética , Proteínas Adaptadoras de Transdução de Sinal/genética , Adolescente , Antígenos de Neoplasias/genética , Síndrome de Bartter/fisiopatologia , Criança , Pré-Escolar , Síndrome de Fanconi/fisiopatologia , Síndrome de Gitelman/fisiopatologia , Humanos , Lactente , Recém-Nascido , Reabsorção Renal/genética , Cloreto de Sódio/metabolismoRESUMO
Early diagnosis of Bartter syndrome (BS) in the neonatal period is a clinical challenge, more so in an extremely low birth weight (ELBW) baby because of the inherent renal immaturity and the associated difficulty in fluid management. However, once a diagnosis is made, the disorder is known to respond well to fluid and electrolyte management, prostaglandin inhibitors, and potassium-sparing diuretics. Herein, we report a case of neonatal BS in a very premature ELBW infant.
Assuntos
Síndrome de Bartter/diagnóstico , Lactente Extremamente Prematuro , Recém-Nascido de muito Baixo Peso , Alça do Néfron/fisiopatologia , Desequilíbrio Ácido-Base/etiologia , Desequilíbrio Ácido-Base/fisiopatologia , Síndrome de Bartter/complicações , Síndrome de Bartter/fisiopatologia , Síndrome de Bartter/terapia , Peso ao Nascer , Inibidores de Ciclo-Oxigenase/uso terapêutico , Diurético Poupador de Potássio/uso terapêutico , Feminino , Hidratação , Idade Gestacional , Humanos , Hipopotassemia/etiologia , Hipopotassemia/fisiopatologia , Indometacina/uso terapêutico , Recém-Nascido , Alça do Néfron/efeitos dos fármacos , Poliúria/etiologia , Poliúria/fisiopatologia , Valor Preditivo dos Testes , Espironolactona/uso terapêutico , Resultado do TratamentoRESUMO
PURPOSE OF REVIEW: Antenatal Bartter syndrome (aBS) is a heterogenous disease resulting from defective ion transport in the thick ascending limb of the loop of Henle. Novel insights into the pathophysiology, as well as the recent identification of a novel genetic cause of aBS, merit an update on this topic. RECENT FINDINGS: In aBS, severe salt losing is further aggravated by defective salt sensing in the macula densa, where a reduced tubular salt concentration is perceived and glomerular filtration is increased instead of decreased. As patients with aBS come of age, there is an increased incidence of proteinuria and impaired renal function.Moreover, we recently reported a new form of aBS. Indeed, we described a series of nine families in whom pregnancies with male fetuses where complicated by acute polyhydramnios, preterm delivery and with severe but transient polyuria. We identified mutations in melanoma-associated antigen D2 in all study participants and showed, in vivo and in vitro, reduced expression of the furosemide and thiazide sensitive transporters sodium-potassium-2-chloride cotransporter and sodium chloride cotransporter, respectively. SUMMARY: Genetic studies revealed the complexity of ion transport in the thick ascending limb of the loop of Henle and will help to clarify the pathophysiology, which is essential to design new therapies.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Antígenos de Neoplasias/genética , Síndrome de Bartter/fisiopatologia , Doenças Fetais/fisiopatologia , Síndrome de Bartter/complicações , Síndrome de Bartter/genética , Feminino , Doenças Fetais/genética , Humanos , Masculino , Mutação , Poli-Hidrâmnios/etiologia , Poliúria/etiologia , Gravidez , Nascimento Prematuro/etiologia , Reabsorção Renal , Cloreto de Sódio/metabolismo , Simportadores de Cloreto de Sódio/metabolismo , Simportadores de Cloreto de Sódio-Potássio/metabolismoAssuntos
Amilorida/uso terapêutico , Síndrome de Bartter/tratamento farmacológico , Diurético Poupador de Potássio/uso terapêutico , Homeostase/fisiologia , Apneia/etiologia , Síndrome de Bartter/complicações , Síndrome de Bartter/fisiopatologia , Feminino , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Doenças do Prematuro , Rim/fisiopatologia , Respiração ArtificialRESUMO
The renal outer medullary potassium (ROMK) channel, located at the apical surface of epithelial cells in the thick ascending loop of Henle and cortical collecting duct, contributes to salt reabsorption and potassium secretion, and represents a target for the development of new mechanism of action diuretics. This idea is supported by the phenotype of antenatal Bartter's syndrome type II associated with loss-of-function mutations in the human ROMK channel, as well as, by cardiovascular studies of heterozygous carriers of channel mutations associated with type II Bartter's syndrome. Although the pharmacology of ROMK channels is still being developed, channel inhibitors have been identified and shown to cause natriuresis and diuresis, in the absence of any significant kaliuresis, on acute oral dosing to rats or dogs. Improvements in potency and selectivity have led to the discovery of MK-7145 [5,5'-((1R,1'R)-piperazine-1,4-diylbis(1-hydroxyethane-2,1-diyl))bis(4-methylisobenzofuran-1(3H)-one)], a potential clinical development candidate. In spontaneously hypertensive rats, oral dosing of MK-7145 causes dose-dependent lowering of blood pressure that is maintained during the entire treatment period, and that displays additive/synergistic effects when administered in combination with hydrochlorothiazide or candesartan, respectively. Acute or chronic oral administration of MK-7145 to normotensive dogs led to dose-dependent diuresis and natriuresis, without any significant urinary potassium losses or changes in plasma electrolyte levels. Elevations in bicarbonate and aldosterone were found after 6 days of dosing. These data indicate that pharmacological inhibition of ROMK has potential as a new mechanism for the treatment of hypertension and/or congestive heart failure. In addition, Bartter's syndrome type II features are manifested on exposure to ROMK inhibitors.
Assuntos
Síndrome de Bartter/fisiopatologia , Benzofuranos/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Fenótipo , Piperazinas/farmacologia , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio Corretores do Fluxo de Internalização/antagonistas & inibidores , Animais , Síndrome de Bartter/tratamento farmacológico , Benzimidazóis/farmacologia , Benzofuranos/uso terapêutico , Compostos de Bifenilo , Cães , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Feminino , Células HEK293 , Humanos , Hidroclorotiazida/farmacologia , Masculino , Piperazinas/uso terapêutico , Bloqueadores dos Canais de Potássio/uso terapêutico , Ratos , Tetrazóis/farmacologiaRESUMO
AIM: The basolateral chloride channel ClC-Kb facilitates Cl reabsorption in the distal nephron of the human kidney. Functional mutations in CLCNKB are associated with Bartter's syndrome type 3, a hereditary salt-losing nephropathy. To address the function of ClC-K2 in vivo, we generated ClC-K2-deficient mice. METHODS: ClC-K2-deficient mice were generated using TALEN technology. RESULTS: ClC-K2-deficient mice were viable and born in a Mendelian ratio. ClC-K2-/- mice showed no gross anatomical abnormalities, but they were growth retarded. The 24-h urine volume was increased in ClC-K2-/- mice (4.4 ± 0.6 compared with 0.9 ± 0.2 mL per 24 h in wild-type littermates; P = 0.001). Accordingly, ambient urine osmolarity was markedly reduced (590 ± 39 vs. 2216 ± 132 mosmol L-1 in wild types; P < 0.0001). During water restriction (24 h), urinary osmolarity increased to 1633 ± 153 and 3769 ± 129 mosmol L-1 in ClC-K2-/- and wild-type mice (n = 12; P < 0.0001), accompanied by a loss of body weight of 12 ± 0.4 and 8 ± 0.2% respectively (P < 0.0001). ClC-K2-/- mice showed an increased renal sodium excretion and compromised salt conservation during a salt-restricted diet. The salt-losing phenotype of ClC-K2-/- mice was associated with a reduced plasma volume, hypotension, a slightly reduced glomerular filtration rate, an increased renal prostaglandin E2 generation and a massively stimulated renin-angiotensin system. Clckb-/- mice showed a reduced sensitivity to furosemide and were completely resistant to thiazides. CONCLUSION: Loss of ClC-K2 compromises TAL function and abolishes salt reabsorption in the distal convoluted tubule. Our data suggest that ClC-K2 is crucial for renal salt reabsorption and concentrating ability. ClC-K2-deficient mice in most aspects mimic patients with Bartter's syndrome type 3.
Assuntos
Síndrome de Bartter/genética , Canais de Cloreto/genética , Rim/fisiopatologia , Mutação , Sistema Renina-Angiotensina/genética , Animais , Síndrome de Bartter/metabolismo , Síndrome de Bartter/fisiopatologia , Canais de Cloreto/metabolismo , Dinoprostona/metabolismo , Taxa de Filtração Glomerular/genética , Rim/metabolismo , Camundongos , Camundongos Knockout , FenótipoRESUMO
PURPOSE: Phenotypic overlap exists among type III Bartter syndrome (BS), Gitelman syndrome (GS), and pseudo-BS/GS (p-BS/GS), which are clinically difficult to distinguish. We aimed to clarify the differences between these diseases, allowing accurate diagnosis based on their clinical features. METHODS: A total of 163 patients with genetically defined type III BS (n = 30), GS (n = 90), and p-BS/GS (n = 43) were included. Age at diagnosis, sex, body mass index, estimated glomerular filtration rate, and serum and urine electrolyte concentrations were determined. RESULTS: Patients with p-BS/GS were significantly older at diagnosis than those with type III BS and GS. Patients with p-BS/GS included a significantly higher percentage of women and had a lower body mass index and estimated glomerular filtration rate than did patients with GS. Although hypomagnesemia and hypocalciuria were predominant biochemical findings in patients with GS, 17 and 23% of patients with type III BS and p-BS/GS, respectively, also showed these abnormalities. Of patients with type III BS, GS, and p-BS/GS, 40, 12, and 63%, respectively, presented with chronic kidney disease. CONCLUSIONS: This study clarified the clinical differences between BS, GS, and p-BS/GS for the first time, which will help clinicians establish differential diagnoses for these three conditions.
Assuntos
Síndrome de Bartter/diagnóstico , Síndrome de Gitelman/diagnóstico , Adolescente , Adulto , Síndrome de Bartter/genética , Síndrome de Bartter/fisiopatologia , Pré-Escolar , Cloretos/urina , Análise Mutacional de DNA , Diagnóstico Diferencial , Feminino , Síndrome de Gitelman/genética , Síndrome de Gitelman/fisiopatologia , Humanos , Laxantes/efeitos adversos , Masculino , Sódio/urinaRESUMO
In this article six patients with hypokalemic metabolic alkalosis, classified as Bartter or Gitelman syndrome are presented. Both syndromes result from different gene mutation inducing impaired function of the transporters involved in sodium, chloride and potassium reapsorption in thick ascending limb of the loop of Henle and distal convoluted tubules. These syndromes typically present with hypokalemia, metabolic alkalosis, hyperreninemic hyperaldosteronism without hypertension, polyuria and muscle weakness. Other clinical characteristics may vary considerably, depending on the gene expression. Correct diagnosis is only possible using expensive and not-routinely available genetic testing. Routine laboratory tests, especially those considering serum and urine electrolytes, can help in recognizing these syndromes and therefore in timely beginning of treatment. The most important distinctive laboratory findings are serum magnesium concentration and urine calcium excretion. In Bartter syndrome typically there is hypercalciuria with or without hypomagnesemia, while in Gitelman syndrome typical findings are hypocalciuria and hypomagnesemia. Recognizing and treating these patients is important due to possible increased morbidity and mortality induced by severe electrolyte imbalance.
Assuntos
Alcalose , Síndrome de Bartter , Cálcio/urina , Hipopotassemia , Rim , Magnésio/sangue , Adulto , Alcalose/sangue , Alcalose/etiologia , Alcalose/prevenção & controle , Síndrome de Bartter/complicações , Síndrome de Bartter/diagnóstico , Síndrome de Bartter/genética , Síndrome de Bartter/fisiopatologia , Canais de Cloreto/genética , Intervenção Médica Precoce , Feminino , Testes Genéticos/métodos , Humanos , Hipopotassemia/sangue , Hipopotassemia/etiologia , Hipopotassemia/prevenção & controle , Lactente , Rim/metabolismo , Rim/patologia , Rim/fisiopatologia , Masculino , Pessoa de Meia-Idade , Canais de Potássio/genéticaRESUMO
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.