RESUMEN
Primary aldosteronism (PA) is caused by autonomous overproduction of aldosterone, which induces organ damage directly via activation of the mineralocorticoid receptor (MR); however, no specific or sensitive biomarkers are able to reflect MR activity. Recently, it is found that urinary extracellular vesicles (uEVs) are secreted by multiple cell types in the kidney and are an enriched source of kidney-specific proteins. Here, we evaluate sodium transporters in uEVs as candidates of biomarkers of MR activity in the clinical setting. Sixteen patients were examined to determine their plasma aldosterone concentration (PAC) and renin activity, and their morning urine was collected. The protein levels of two sodium transporters in uEVs, γ-epithelial sodium channel (γENaC) and thiazide-sensitive sodium chloride cotransporter (NCC), were quantified by Western blot analysis, and their clinical correlation with PAC was determined. Consequently, we found PAC was significantly correlated with the γENaC protein level adjusted by the CD9 protein level in uEVs (correlation coefficient = 0.71). PAC was also correlated with the NCC protein level adjusted by the CD9 protein level in uEVs (correlation coefficient = 0.61). In two PA patients, treatment with an MR antagonist or adrenalectomy reduced γENaC/CD9 in uEVs. In conclusion, γENaC/CD9 in uEVs is a valuable biomarker of MR activity in PA patients and may be a useful biomarker for other MR-associated diseases.
Asunto(s)
Canales Epiteliales de Sodio/orina , Vesículas Extracelulares/metabolismo , Hiperaldosteronismo/diagnóstico , Receptores de Mineralocorticoides/fisiología , Tetraspanina 29/orina , Adulto , Anciano , Aldosterona/metabolismo , Biomarcadores/análisis , Biomarcadores/orina , Estudios de Cohortes , Canales Epiteliales de Sodio/análisis , Femenino , Células HEK293 , Humanos , Hiperaldosteronismo/orina , Riñón/metabolismo , Pruebas de Función Renal/métodos , Masculino , Persona de Mediana Edad , Tetraspanina 29/análisisRESUMEN
BACKGROUND: Concentration of the urine is primarily regulated via vasopressin dependent aquaporin-2 water channels in the apical membrane of kidney principal cells. It is unclear whether urine concentration ability in ADPKD differs from other patients with similar degree of impaired renal function (non-ADPKD patients). The purpose of this case control study was to measure urine concentration ability in ADPKD patients compared to non-ADPKD patients and healthy controls. METHODS: A seventeen hour long water deprivation test was carried out in 17 ADPKD patients (CKD I-IV), 16 non-ADPKD patients (CKD I-IV), and 18 healthy controls. Urine was collected in 4 consecutive periods during water deprivation (12 h, 1 h, 2 h and 2 h, respectively) and analyzed for osmolality (u-Osm), output (UO), fractional excretion of sodium (FENa), aquaporin2 (u-AQP2) and ENaC (u-ENaC). Blood samples were drawn trice (after 13-, 15-, and 17 h after water deprivation) for analyses of osmolality (p-Osm), vasopressin (p-AVP), and aldosterone (p-Aldo). RESULTS: U-Osm was significantly lower and FENa significantly higher in both ADPKD patients and non-ADPKD patients compared to healthy controls during the last three periods of water deprivation. During the same periods, UO was higher and secretion rates of u-AQP2 and u-ENaC were lower and at the same level in the two groups of patients compared to controls. P-AVP and p-Osm did not differ significantly between the three groups. P-Aldo was higher in both groups of patients than in controls. CONCLUSIONS: Urine concentration ability was reduced to the same extent in patients with ADPKD and other chronic kidney diseases with the same level of renal function compared to healthy controls. The lower urine excretion of AQP2 and ENaC suggests that the underlying mechanism may be a reduced tubular response to vasopressin and aldosterone. TRIAL REGISTRATION: Current Controlled Trial NCT04363554 , date of registration: 20.08.2017.
Asunto(s)
Capacidad de Concentración Renal/fisiología , Riñón Poliquístico Autosómico Dominante/fisiopatología , Insuficiencia Renal Crónica/fisiopatología , Adulto , Anciano , Aldosterona/sangre , Acuaporina 2/orina , Estudios de Casos y Controles , Canales Epiteliales de Sodio/orina , Femenino , Humanos , Masculino , Persona de Mediana Edad , Concentración Osmolar , Riñón Poliquístico Autosómico Dominante/metabolismo , Eliminación Renal , Insuficiencia Renal Crónica/metabolismo , Índice de Severidad de la Enfermedad , Sodio/orina , Vasopresinas/sangre , Privación de AguaRESUMEN
Albuminuria predicts adverse renal outcome in kidney transplant recipients. The present study addressed the hypothesis that albuminuria is associated with increased urine serine proteases with the ability to activate the epithelial sodium channel (ENaC) and with greater extracellular volume and higher blood pressure. In a cross-sectional design, kidney transplant recipients with ( n = 18) and without ( n = 19) albuminuria were included for office blood pressure measurements, estimation of volume status by bioimpedance, and collection of spot urine and plasma samples. Urine was analyzed for serine proteases and for the ability to activate ENaC current in vitro. Urine exosome protein was immunoblotted for prostasin and γ-ENaC protein. In the present study, it was found that, compared with nonalbuminuria (8.8 mg/g creatinine), albuminuric (1,722 mg/g creatinine) kidney transplant recipients had a higher systolic and diastolic blood pressure, despite receiving significantly more antihypertensives, and a greater urinary total plasminogen, active plasmin, active urokinase-type plasminogen activator, and prostasin protein abundance, which correlated significantly with u-albumin. Fluid overload correlated with systolic blood pressure, urinary albumin/creatinine, and plasminogen/creatinine. Urine from albuminuric kidney transplant recipients evoked a greater amiloride- and aprotinin-sensitive inward current in single collecting duct cells (murine cell line M1). γENaC subunits at 50 and 75 kDa showed increased abundance in urine exosomes from albuminuric kidney transplant recipients when compared with controls. These findings show that albuminuria in kidney transplant recipients is associated with hypertension, ability of urine to proteolytically activate ENaC current, and increased abundance of γENaC. ENaC activity could contribute to hypertension and adverse outcome in posttransplant proteinuria.
Asunto(s)
Albuminuria/orina , Canales Epiteliales de Sodio/orina , Exosomas/enzimología , Trasplante de Riñón/efectos adversos , Serina Proteasas/orina , Receptores de Trasplantes , Albuminuria/enzimología , Albuminuria/etiología , Albuminuria/fisiopatología , Animales , Biomarcadores/orina , Presión Sanguínea , Células Cultivadas , Estudios Transversales , Femenino , Humanos , Hipertensión/etiología , Hipertensión/fisiopatología , Hipertensión/orina , Masculino , Potenciales de la Membrana , Ratones , Persona de Mediana Edad , Proteolisis , Factores de Riesgo , Resultado del Tratamiento , Equilibrio Hidroelectrolítico , Desequilibrio Hidroelectrolítico/etiología , Desequilibrio Hidroelectrolítico/fisiopatología , Desequilibrio Hidroelectrolítico/orinaRESUMEN
OBJECTIVE: Nitric oxide is a key player in regulating vascular tone. Impaired endothelial nitric oxide synthesis plays an important role in hypertension. Replenishing of nitric oxide by sodium nitrite (NaNO2) has not been investigated in patients with essential hypertension (EHT). We aimed to determine the effects of NaNO2 on blood pressure (BP) and renal sodium and water regulation in patients with EHT compared with healthy control study participants (CON). METHODS: In a placebo-controlled, crossover study, we infused 240âµg NaNO2/kg/h or isotonic saline for 2âh in 14 EHT and 14 CON. During infusion, we measured changes in brachial and central BP, free water clearance, fractional sodium excretion, and urinary excretion rate of γ-subunit of the epithelial sodium channel (U-ENaCγ), and aquaporin-2 (U-AQP2). RESULTS: Placebo-adjusted brachial SBP decreased 18âmmHg (Pâ<â0.001) during NaNO2 infusion in EHT and 12âmmHg (Pâ<â0.001) in CON (Pbetweenâ=â0.024). Brachial DBP and central SBP decreased equally in both groups during NaNO2. In EHT, we found a decrease in U-ENaCγ during NaNO2 infusion. In both groups, we observed a decrease in fractional sodium excretion, free water clearance, and U-AQP2 during NaNO2 infusion. CONCLUSION: This study demonstrated an augmented BP-lowering effect of NaNO2 in patients with EHT. We observed an antinatriuretic and antidiuretic effect of NaNO2 in both groups, and a decrease in U-ENaCγ, solely in EHT. In both groups, we detected a nonvasopressin mediated decrease in U-AQP2, which is most likely compensatory to the decline in diuresis.
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Hipertensión Esencial/fisiopatología , Conservantes de Alimentos/farmacología , Tasa de Filtración Glomerular/efectos de los fármacos , Óxido Nítrico/metabolismo , Nitrito de Sodio/farmacología , Adulto , Acuaporina 2/orina , Estudios Cruzados , Método Doble Ciego , Canales Epiteliales de Sodio/orina , Femenino , Humanos , Riñón/fisiología , Masculino , Persona de Mediana Edad , Natriuresis/efectos de los fármacos , Método Simple Ciego , Sodio/orina , Adulto JovenRESUMEN
BACKGROUND: Tolvaptan slows progression of autosomal dominant polycystic kidney disease (ADPKD) by antagonizing the vasopressin-cAMP axis. Nitric oxide (NO) stimulates natriuresis and diuresis, but its role is unknown during tolvaptan treatment in ADPKD. METHODS: Eighteen patients with ADPKD received tolvaptan 60 mg or placebo in a randomized, placebo-controlled, double blind, crossover study. L-NMMA (L-NG-monomethyl-arginine) was given as a bolus followed by continuous infusion during 60 min. We measured: GFR, urine output (UO), free water clearance (CH2O), fractional excretion of sodium (FENa), urinary excretion of aquaporin-2 channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma concentrations of vasopressin (p-AVP), renin (PRC), angiotensinII (p-AngII), aldosterone (p-Aldo), and central blood pressure (cBP). RESULTS: During tolvaptan with NO-inhibition, a more pronounced decrease was measured in UO, CH2O (61% vs 43%) and FENa (46% vs 41%) after placebo than after tolvaptan; GFR and u-AQP2 decreased to the same extent; p-AVP increased three fold, whereas u-ENaCγ, PRC, p-AngII, and p-Aldo remained unchanged. After NO-inhibition, GFR increased after placebo and remained unchanged after tolvaptan (5% vs -6%). Central diastolic BP (CDBP) increased to a higher level after placebo than tolvaptan. Body weight fell during tolvaptan treatment. CONCLUSIONS: During NO inhibition, tolvaptan antagonized both the antidiuretic and the antinatriuretic effect of L-NMMA, partly via an AVP-dependent mechanism. U-AQP2 was not changed by tolvaptan, presumeably due to a counteracting effect of elevated p-AVP. The reduced GFR during tolvaptan most likely is caused by the reduction in extracellular fluid volume and blood pressure. TRIAL REGISTRATION: Clinical Trial no: NCT02527863 . Registered 18 February 2015.
Asunto(s)
Benzazepinas/uso terapéutico , Canales Epiteliales de Sodio/orina , Tasa de Filtración Glomerular/fisiología , Hemodinámica/fisiología , Óxido Nítrico/antagonistas & inhibidores , Riñón Poliquístico Autosómico Dominante/orina , Adulto , Antagonistas de los Receptores de Hormonas Antidiuréticas/farmacología , Antagonistas de los Receptores de Hormonas Antidiuréticas/uso terapéutico , Acuaporina 2/orina , Benzazepinas/farmacología , Estudios Cruzados , Método Doble Ciego , Femenino , Tasa de Filtración Glomerular/efectos de los fármacos , Hemodinámica/efectos de los fármacos , Humanos , Masculino , Tasa de Depuración Metabólica/efectos de los fármacos , Tasa de Depuración Metabólica/fisiología , Persona de Mediana Edad , Óxido Nítrico/metabolismo , Riñón Poliquístico Autosómico Dominante/tratamiento farmacológico , Sodio/metabolismo , Tolvaptán , Resultado del Tratamiento , Agua/metabolismo , Adulto JovenRESUMEN
Preeclampsia is characterized by hypertension, proteinuria, suppression of plasma renin-angiotensin-aldosterone, and impaired urine sodium excretion. Aberrantly filtered plasmin in urine may activate proteolytically the γ-subunit of the epithelial sodium channel (ENaC) and promote Na+ reabsorption and urine K+ loss. Plasma and urine was sampled from patients with preeclampsia, healthy pregnant controls and non-pregnant women, and from patients with nephrostomy catheters. Aldosterone concentration, urine plasminogen, and protein were determined. Exosomes were isolated by ultracentrifugation. Immunoblotting was used to detect exosome markers; γ-ENaC (two different epitopes within the inhibitory peptide tract), α-ENaC, and renal outer medullary K-channel (ROMK) and compared with human kidney cortex homogenate. Urine total plasmin(ogen) was significantly increased in preeclampsia, plasma and urine aldosterone was higher in pregnancy compared to non-pregnancy, and the urine Na/K ratio was lower in preeclampsia compared to healthy pregnancy. Exosome markers ALIX and AQP-2 were stably associated with exosomes across groups. Exosomal α-ENaC-subunit migrated at 75 kDa and dominantly at 50 kDa and was significantly elevated in pregnancy. In human kidney cortex tissue and two of four pelvis catheter urine, ~90-100 kDa full-length γ-ENaC was detected while no full-length γ-ENaC but 75, 60, and 37 kDa variants dominated in voided urine exosomes. There was no difference in γ-ENaC protein abundances between healthy pregnancy and preeclampsia. ROMK was detected inconsistently in urine exosomes. Pregnancy and preeclampsia were associated with increased abundance of furin-cleaved α-ENaC subunit while γ-subunit appeared predominantly in cleaved form independently of conditions and with a significant contribution from post-renal cleavage.
Asunto(s)
Canales Epiteliales de Sodio/orina , Exosomas/metabolismo , Hipertensión/orina , Subunidades de Proteína/orina , Orina/fisiología , Adulto , Aldosterona/orina , Canales Epiteliales de Sodio/metabolismo , Femenino , Fibrinolisina/orina , Humanos , Hipertensión/metabolismo , Riñón/metabolismo , Potasio/orina , Preeclampsia/metabolismo , Preeclampsia/orina , Embarazo , Subunidades de Proteína/metabolismo , Proteinuria/metabolismo , Proteinuria/orina , Sodio/orinaRESUMEN
Urinary exosomes secreted by multiple cell types in the kidney may participate in intercellular signaling and provide an enriched source of kidney-specific proteins for biomarker discovery. Factors that alter the exosomal protein content remain unknown. To determine whether endogenous and exogenous hormones modify urinary exosomal protein content, we analyzed samples from 14 mildly hypertensive patients in a crossover study during a high-sodium (HS, 160 mmol/d) diet and low-sodium (LS, 20 mmol/d) diet to activate the endogenous renin-angiotensin-aldosterone system. We further analyzed selected exosomal protein content in a separate cohort of healthy persons receiving intravenous aldosterone (0.7 µg/kg per hour for 10 hours) versus vehicle infusion. The LS diet increased plasma renin activity and aldosterone concentration, whereas aldosterone infusion increased only aldosterone concentration. Protein analysis of paired urine exosome samples by liquid chromatography-tandem mass spectrometry-based multidimensional protein identification technology detected 2775 unique proteins, of which 316 exhibited significantly altered abundance during LS diet. Sodium chloride cotransporter (NCC) and α- and γ-epithelial sodium channel (ENaC) subunits from the discovery set were verified using targeted multiple reaction monitoring mass spectrometry quantified with isotope-labeled peptide standards. Dietary sodium restriction or acute aldosterone infusion similarly increased urine exosomal γENaC[112-122] peptide concentrations nearly 20-fold, which correlated with plasma aldosterone concentration and urinary Na/K ratio. Urine exosomal NCC and αENaC concentrations were relatively unchanged during these interventions. We conclude that urinary exosome content is altered by renin-angiotensin-aldosterone system activation. Urinary measurement of exosomal γENaC[112-122] concentration may provide a useful biomarker of ENaC activation in future clinical studies.
Asunto(s)
Aldosterona/farmacología , Canales Epiteliales de Sodio/efectos de los fármacos , Canales Epiteliales de Sodio/orina , Exosomas/efectos de los fármacos , Sistema Renina-Angiotensina/fisiología , Adulto , Estudios Cruzados , Femenino , Humanos , Masculino , Sodio en la DietaRESUMEN
BACKGROUND: The renal distal nephron plays an important role in the maintenance of sodium balance, extra cellular volume and blood pressure. The degree of water transport, via aquaporin2 water channels (AQP2), and sodium transport, via epithelial sodium channels (ENaC) in renal collecting duct principal cells are reflected by the level of urinary excretion of AQP2 (u-AQP2) and the γ-fraction of ENaC (u-ENaCγ). The effects of an acute intravenous volume load with isotonic saline, hypertonic saline and glucose on u-AQP2, u-ENaCγ and underlying mechanisms have never been studied in a randomized, placebo-controlled trial in healthy humans. METHODS: We studied the effects of 0.9% saline (23 ml/kg), 3% saline (7 ml/kg) and 5% glucose (23 ml/kg) on u-AQP2 and u-ENaCγ, fractional sodium excretion (FENa), free water clearance (CH2O), and plasma concentrations of vasopressin (AVP), renin (PRC), angiotensin II (ANG II) and aldosterone (Aldo) in a randomized, crossover study of 23 healthy subjects, who consumed a standardized diet, regarding calories, sodium and fluid for 4 days before each examination day. RESULTS: After isotonic saline infusion, u-AQP2 increased (27%). CH2O and u-ENaCγ were unchanged, whereas FENa increased (123%). After hypertonic saline infusion, there was an increase in u-AQP2 (25%), u-ENaCγ (19%) and FENa (96%), whereas CH2O decreased (-153%). After isotonic glucose infusion, there was a decrease in u-AQP2 (-16%), ENaCγ (-10%) and FENa (-44%) whereas CH2O increased (164%). AVP remained unchanged after isotonic saline and glucose, but increased after hypertonic saline (139%). PRC, AngII and p-Aldo decreased after isotonic and hypertonic saline infusion, but not after glucose infusion. CONCLUSIONS: Volume expansion with 3% and 0.9% saline increased u-AQP2, while isotonic glucose decreased u-AQP2. Infusion of hypertonic saline increased u-ENaCγ, whereas u-ENaCγ was not significantly changed after isotonic saline and tended to decrease after glucose. Thus, the transport of water and sodium is changed both via the aquaporin 2 water channels and the epithelial sodium channels during all three types of volume expansion to regulate and maintain water- and sodium homeostasis in the body. TRIAL REGISTRATION: Clinical Trial no: NCT01414088.
Asunto(s)
Acuaporina 2/orina , Agua Corporal/metabolismo , Canales Epiteliales de Sodio/orina , Solución Hipertónica de Glucosa/farmacología , Riñón/metabolismo , Solución Salina Hipertónica/farmacología , Sodio/metabolismo , Volumen Sanguíneo/efectos de los fármacos , Estudios Cruzados , Femenino , Humanos , Soluciones Isotónicas/farmacología , Riñón/citología , Riñón/efectos de los fármacos , Túbulos Renales/efectos de los fármacos , Túbulos Renales/metabolismo , Masculino , Nefronas/efectos de los fármacos , Nefronas/metabolismoRESUMEN
BACKGROUND: Dysregulation of the expression/shuttling of the aquaporin-2 water channel (AQP2) and the epithelial sodium channel (ENaC) in renal collecting duct principal cells has been found in animal models of hypertension. We tested whether a similar dysregulation exists in essential hypertension. METHODS: We measured urinary excretion of AQP2 and ENaC ß-subunit corrected for creatinine (u-AQP2(CR), u-ENaC(ß-CR)), prostaglandin E2 (u-PGE2) and cyclic AMP (u-cAMP), fractional sodium excretion (FE(Na)), free water clearance (C(H2O)), as well as plasma concentrations of vasopressin (AVP), renin (PRC), angiotensin II (Ang II), aldosterone (Aldo), and atrial and brain natriuretic peptide (ANP, BNP) in 21 patients with essential hypertension and 20 normotensive controls during 24-h urine collection (baseline), and after hypertonic saline infusion on a 4-day high sodium (HS) diet (300 mmol sodium/day) and a 4-day low sodium (LS) diet (30 mmol sodium/day). RESULTS: At baseline, no differences in u-AQP2(CR) or u-ENaC(ß-CR) were measured between patients and controls. U-AQP2(CR) increased significantly more after saline in patients than controls, whereas u-ENaC(ß-CR) increased similarly. The saline caused exaggerated natriuretic increases in patients during HS intake. Neither baseline levels of u-PGE2, u-cAMP, AVP, PRC, Ang II, Aldo, ANP, and BNP nor changes after saline could explain the abnormal u-AQP2(CR) response. CONCLUSIONS: No differences were found in u-AQP2(CR) and u-ENaC(ß-CR) between patients and controls at baseline. However, in response to saline, u-AQP2(CR) was abnormally increased in patients, whereas the u-ENaC(ß-CR) response was normal. The mechanism behind the abnormal AQP2 regulation is not clarified, but it does not seem to be AVP-dependent. Clinicaltrial.gov identifier: NCT00345124.
Asunto(s)
Acuaporina 2/orina , Canales Epiteliales de Sodio/orina , Hipertensión/sangre , Hipertensión/orina , Adulto , Aldosterona/sangre , Angiotensina II/sangre , Factor Natriurético Atrial/sangre , Estudios Cruzados , AMP Cíclico/orina , Dinoprostona/orina , Femenino , Tasa de Filtración Glomerular , Humanos , Hipertensión/fisiopatología , Modelos Lineales , Masculino , Persona de Mediana Edad , Péptido Natriurético Encefálico/sangre , Concentración Osmolar , Renina/sangre , Sodio/orina , Sodio en la Dieta , Vasopresinas/sangreRESUMEN
Renal handling of sodium and water is abnormal in chronic kidney diseases. To study the function and regulation of the aquaporin-2 water channel (AQP2) and the epithelial sodium channel (ENaC) in autosomal dominant polycystic kidney disease (ADPKD), we measured urinary excretion of AQP2 (u-AQP2), the ß-subunit of ENaC (u-ENaC(ß)), cAMP (u-cAMP), and prostaglandin E(2) (u-PGE(2)); free water clearance (C(H2O)); fractional sodium excretion (FE(Na)); and plasma vasopressin (p-AVP), renin (p-Renin), angiotensin II (p-ANG II), aldosterone (p-Aldo), and atrial and brain natriuretic peptide (p-ANP, p-BNP) in patients with ADPKD and healthy controls during 24-h urine collection and after hypertonic saline infusion during high sodium intake (HS; 300 mmol sodium/day) and low sodium intake (LS; 30 mmol sodium/day). No difference in u-AQP2, u-ENaC(ß), u-cAMP, u-PGE(2), C(H2O), and vasoactive hormones was found between patients and controls at baseline, but during HS the patients had higher FE(Na). The saline caused higher increases in FE(Na) in patients than controls during LS, but the changes in u-ENaC(ß), p-Aldo, p-ANP, p-BNP, p-Renin, and p-ANG II were similar. Higher increases in u-AQP2 and p-AVP were seen in patients during both diets. In conclusion, u-AQP2 and u-ENaC(ß) were comparable in patients with ADPKD and controls at baseline. In ADPKD, the larger increase in u-AQP2 and p-AVP in response to saline could reflect an abnormal water absorption in the distal nephron. During LS, the larger increase in FE(Na) in response to saline could reflect a defective renal sodium retaining capacity in ADPKD, unrelated to changes in u-ENaC(ß).
Asunto(s)
Acuaporina 2/orina , Canales Epiteliales de Sodio/orina , Riñón Poliquístico Autosómico Dominante/orina , Solución Salina Hipertónica/administración & dosificación , Adolescente , Adulto , Anciano , Aldosterona/sangre , Angiotensina II/sangre , Factor Natriurético Atrial/sangre , Enfermedad Crónica , Estudios Cruzados , AMP Cíclico/orina , Dinoprostona/orina , Femenino , Humanos , Masculino , Persona de Mediana Edad , Péptido Natriurético Encefálico/sangre , Renina/sangre , Sodio/orina , Vasopresinas/sangre , Adulto JovenRESUMEN
BACKGROUND: Potassium is the main intracellular cation, which contributes to keeping the intracellular membrane potential slightly negative and elicits contraction of smooth, skeletal and cardiac muscle. A change in potassium intake modifies both cardiovascular and renal tubular function. The purpose of the trial was to investigate the effect of dietary potassium supplementation, 100 mmol daily in a randomized, placebo-controlled, crossover trial of healthy participants during two periods of 28 days duration. The participants (N = 21) received a diet that was standardized regarding energy requirement, and sodium and water intake. METHODS: 24-hour ambulatory blood pressure (ABP) and applanation tonometry were used to assess blood pressure, pulse wave velocity (PWV), augmentation index (AIx) and central blood pressure (CBP). Immunoassays were used for measurements of plasma concentrations of vasoactive hormones: renin (PRC), angiotensin II (Ang II), aldosterone (Aldo), atrial natriuretic peptide (ANP), vasopressin (AVP), pro-brain natriuretic peptide (pro-BNP),endothelin (Endo), urinary excretions of aquaporin 2 (AQP2), cyclic AMP (cAMP), and the ß-fraction of the epithelial sodium channel (ENaC(ß)). RESULTS: AQP2 excretion increased during potassium supplementation, and free water clearance fell. The changes in urinary potassium excretion and urinary AQP2 excretion were significantly and positively correlated. Aldo increased. GFR, u-ENaC- ß, PRC, Ang II, ANP, BNP, Endo, blood pressure and AI were not significantly changed by potassium supplementation, whereas PWV increased slightly. CONCLUSIONS: Potassium supplementation changed renal tubular function and increased water absorption in the distal part of the nephron. In spite of an increase in aldosterone in plasma, blood pressure remained unchanged after potassium supplementation.
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Tasa de Filtración Glomerular , Rigidez Vascular/efectos de los fármacos , Adolescente , Adulto , Aldosterona/sangre , Angiotensina II/sangre , Acuaporina 2/orina , Arginina Vasopresina/sangre , Factor Natriurético Atrial/sangre , Estudios Cruzados , AMP Cíclico/orina , Suplementos Dietéticos , Endotelinas/sangre , Canales Epiteliales de Sodio/orina , Femenino , Humanos , Masculino , Péptido Natriurético Encefálico/sangre , Potasio/farmacología , Potasio/orina , Renina/sangre , Sodio/orina , Adulto JovenRESUMEN
BACKGROUND: Terlipressin is a vasopressin analogue used for its potent V1a effects in cirrhotic patients. Recent data suggest that terlipressin has affinity to renal V2 receptors and modulates Aquaporin 2 (AQP2) expression and free water clearance. Stimulation of renal V2 receptors may also affect sodium transport via the Epithelial Sodium Channel (ENaC). Furthermore, endothelial V2 receptors may indirectly affect proximal sodium handling by increasing plasma cAMP. METHODS: We investigated 18 patients with cirrhosis and ascites before and after infusion of 2 mg of terlipressin. Plasma cAMP and urine AQP2 were measured and a newly developed radioimmunoassay was used to quantify ENaC in the urine. RESULTS: Mean arterial blood pressure increased from 87 ± 15 to 105 ± 19 mmHg, p < 0.001 after terlipressin infusion and GFR increased from 52 ± 6 to 69 ± 9 mL/min, p < 0.01. Urine-ENaC in ng/mmol creatinine increased from 42 ± 6 to 50 ± 7 ng/mmol creatinine, p = 0.05. Urine sodium increased from 43 ± 8 to 62 ± 9 mmol/L, p < 0.01. Plasma cAMP was not affected by terlipressin, 106 (63-673) vs. 103.5 (69-774) pmol/mL, NS. The rise in ENaC excretion correlated with the rise in AQP2 excretion, r = 0.63, p < 0.01. There was a weak correlation between the change in MAP and the rise in AQP2 excretion (p < 0.05). CONCLUSIONS: Increased ENaC excretion suggests increased abundance of ENaC and resultant increased distal sodium reabsorption. The V2 effects of terlipressin are insufficient to stimulate the endothelial V2 receptors since plasma cAMP is unaltered. Despite pronounced V1a and some V2 effects of terlipressin, additional effects on proximal sodium handling are therefore not likely.
Asunto(s)
Antihipertensivos/farmacología , AMP Cíclico/sangre , Canales Epiteliales de Sodio/orina , Cirrosis Hepática/sangre , Cirrosis Hepática/orina , Lipresina/análogos & derivados , Vasopresinas/agonistas , Equilibrio Hidroelectrolítico/efectos de los fármacos , Demografía , Femenino , Humanos , Riñón/efectos de los fármacos , Riñón/metabolismo , Cirrosis Hepática/fisiopatología , Lipresina/farmacología , Masculino , Persona de Mediana Edad , Receptores de Vasopresinas/metabolismo , Sodio/metabolismo , TerlipresinaRESUMEN
BACKGROUND: Treatment with prostaglandin inhibitors can reduce renal function and impair renal water and sodium excretion. We tested the hypotheses that a reduction in prostaglandin synthesis by ibuprofen treatment during fasting decreased renal water and sodium excretion by increased absorption of water and sodium via the aquaporin2 water channels and the epithelial sodium channels. METHODS: The effect of ibuprofen, 600 mg thrice daily, was measured during fasting in a randomized, placebo-controlled, double-blinded crossover study of 17 healthy humans. The subjects received a standardized diet on day 1, fasted at day 2, and received an IV infusion of 3% NaCl on day 3. The effect variables were urinary excretions of aquaporin2 (u-AQP2), the beta-fraction of the epithelial sodium channel (u-ENaCbeta), cyclic-AMP (u-cAMP), prostaglandin E2 (u-PGE2). Free water clearance (CH2O), fractional excretion of sodium (FENa), and plasma concentrations of vasopressin, angiotensin II, aldosterone, atrial-, and brain natriuretic peptide. RESULTS: Ibuprofen decreased u-AQP2, u-PGE2, and FENa at all parts of the study. During the same time, ibuprofen significantly increased u-ENaCbeta. Ibuprofen did not change the response in p-AVP, u-c-AMP, urinary output, and free water clearance during any of these periods. Atrial-and brain natriuretic peptide were higher. CONCLUSION: During inhibition of prostaglandin synthesis, urinary sodium excretion decreased in parallel with an increase in sodium absorption and increase in u-ENaCbeta. U-AQP2 decreased indicating that water transport via AQP2 fell. The vasopressin-c-AMP-axis did not mediate this effect, but it may be a consequence of the changes in the natriuretic peptide system and/or the angiotensin-aldosterone system TRIAL REGISTRATION: Clinical Trials Identifier: NCT00281762.
Asunto(s)
Acuaporina 2/efectos de los fármacos , Canales Epiteliales de Sodio/efectos de los fármacos , Canales Epiteliales de Sodio/orina , Ibuprofeno/farmacología , Riñón/fisiología , Natriuresis/efectos de los fármacos , Antagonistas de Prostaglandina/farmacología , Prostaglandinas/metabolismo , Sodio/farmacocinética , Adolescente , Adulto , Anciano , Albúminas/efectos de los fármacos , Acuaporina 2/orina , Arginina Vasopresina/sangre , Presión Sanguínea/efectos de los fármacos , Peso Corporal/efectos de los fármacos , Estudios Cruzados , AMP Cíclico/orina , Dinoprostona/orina , Ayuno , Femenino , Humanos , Masculino , Persona de Mediana Edad , Péptido Natriurético Encefálico/sangre , Péptido Natriurético Encefálico/efectos de los fármacos , Solución Salina Hipertónica , Adulto JovenRESUMEN
BACKGROUND: Glucocorticoids influence renal concentrating and diluting ability. We tested the hypothesis that methylprednisolone treatment increased renal water and sodium absorption by increased absorption via the aquaporin-2 (AQP2) water channels and the epithelial sodium channels (ENaCs) respectively. METHODS: The effect of methylprednisolone was measured during fasting in a randomized, placebo-controlled, single-blinded cross-over study of 15 healthy humans. The subjects received a standardized diet on day 1, fasted on day 2, and received 500 mg methylprednisolone intravenously on day 3. The effect variables were urinary excretions of AQP2 (u-AQP2), urinary excretion of the beta-fraction of the ENaC (u-ENaC(beta)), cAMP (u-cAMP), prostaglandin E(2) (u-PGE(2)), free water clearance (C(H2O)), and fractional excretion of sodium (FE(Na)), and plasma vasopressin (p-AVP), angiotensin II (p-Ang II), aldosterone (p-Aldo), atrial natriuretic peptide (p-ANP), and brain natriuretic peptide (p-BNP). RESULTS: Methylprednisolone treatment increased u-AQP2, u-ENaC(beta), and p-AVP significantly, but did not change u-cAMP, c(H2O), and FE(Na). P-ANP increased during methylprednisolone treatment, but after the increase in u-AQP2 and u-ENaC(beta). U-PGE(2), p-Ang II, and p-BNP were unchanged. Heart rate increased and diastolic blood pressure fell. CONCLUSIONS: Methylprednisolone increased u-AQP2 and u-ENaC. Neither the AVP-cAMP axis nor changes in the renin-angiotensin-Aldo system, or the natriuretic peptide system seems to bear a causal relationship with the increase in either u-AQP2 or u-ENaC. Most probably, the effect is mediated via a direct effect of methylprednisolone on the principal cells. The lack of decrease in urinary output and sodium reabsorption most likely can be attributed to the diuretic and natriuretic properties of the increased secretion of ANP.