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Hinrichs GR, Nielsen JR, Birn H, Bistrup C, Jensen BL. Amiloride evokes significant natriuresis and weight loss in kidney transplant recipients with and without albuminuria. Am J Physiol Renal Physiol 2023; 325:F426-F435. [PMID: 37560772 DOI: 10.1152/ajprenal.00108.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 07/14/2023] [Accepted: 08/03/2023] [Indexed: 08/11/2023] Open
Abstract
Albuminuria in kidney transplant recipients (KTRs) is associated with hypertension and aberrant glomerular filtration of serine proteases that may proteolytically activate the epithelial Na+ channel (ENaC). The present nonrandomized, pharmacodynamic intervention study aimed to investigate if inhibition of ENaC increases Na+ excretion and reduces extracellular volume in KTRs dependent on the presence of albuminuria. KTRs with and without albuminuria (albumin-to-creatinine ratio > 300 mg/g, n = 7, and <30 mg/g, n = 7, respectively) were included and ingested a diet with fixed Na+ content (150 mmol/day) for 5 days. On the last day, amiloride at 10 mg was administered twice. Body weight, 24-h urine electrolyte excretion, body water content, and ambulatory blood pressure as well as plasma renin, angiotensin II, and aldosterone concentrations were determined before and after amiloride. Amiloride led to a significant decrease in body weight, increase in 24-h urinary Na+ excretion, and decrease in 24-h urinary K+ excretion in both groups. Urine output increased in the nonalbuminuric group only. There was no change in plasma renin, aldosterone, and angiotensin II concentrations after amiloride, whereas a significant decrease in nocturnal systolic blood pressure and increase in 24-h urine aldosterone excretion was observed in albuminuric KTRs only. There was a significant correlation between 24-h urinary albumin excretion and amiloride-induced 24-h urinary Na+ excretion. In conclusion, ENaC activity contributes to Na+ and water retention in KTRs with and without albuminuria. ENaC is a relevant pharmacological target in KTRs; however, larger and long-term studies are needed to evaluate whether the magnitude of this effect depends on the presence of albuminuria.NEW & NOTEWORTHY Amiloride has a significant natriuretic effect in kidney transplant recipients (KTRs) that relates to urinary albumin excretion. The epithelial Na+ channel may be a relevant direct pharmacological target to counter Na+ retention and hypertension in KTRs. Epithelial Na+ channel blockers should be further investigated as a mean to mitigate Na+ and water retention and to potentially obtain optimal blood pressure control in KTRs.
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Affiliation(s)
- Gitte Rye Hinrichs
- Department of Molecular Medicine, Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
- Department of Nephrology, Odense University Hospital, Odense, Denmark
- Department of Nephrology, University Hospital of Southern Denmark, Esbjerg, Denmark
| | | | - Henrik Birn
- Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Claus Bistrup
- Department of Nephrology, Odense University Hospital, Odense, Denmark
- Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Boye Lagerbon Jensen
- Department of Molecular Medicine, Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
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Ydegaard R, Andersen H, Oxlund CS, Jacobsen IA, Hansen PBL, Jürgensen JF, Peluso AA, Vanhoutte PM, Staehr M, Svenningsen P, Jensen BL. The acute blood pressure-lowering effect of amiloride is independent of endothelial ENaC and eNOS in humans and mice. Acta Physiol (Oxf) 2019; 225:e13189. [PMID: 30240139 DOI: 10.1111/apha.13189] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 09/11/2018] [Accepted: 09/17/2018] [Indexed: 01/15/2023]
Abstract
AIMS The epithelial sodium channel (ENaC) is expressed in cultured endothelial cells and inhibitory coupling to eNOS activity has been proposed. The present study tested the hypothesis that ENaC blockers increase systemic NO-products and lower blood pressure in patients and mice, depending on eNOS. METHODS NO-products and cGMP were measured in diabetes patient urine and plasma samples before and after amiloride treatment (20-40 mg for two days, plasma n = 22, urine n = 12 and 5-10 mg for eight weeks, plasma n = 52, urine n = 55). Indwelling catheters were implanted in the femoral artery and vein in mice for continuous arterial blood pressure and heart rate recordings and infusion. RESULTS Treatment with amiloride for two days increased plasma and urine NO-products, while plasma cGMP decreased and urinary cGMP was unchanged in patient samples. Eight weeks of treatment with amiloride did not alter NO-products and cGMP. In mice, amiloride boli of 5, 50, and 500 µg/kg lowered heart rate and arterial blood pressure significantly and acutely. Benzamil had no effect on pressure and raised heart rate. In hypertensive eNOS-/- and L-NAME-treated mice, amiloride lowered blood pressure significantly. L-NAME infusion significantly decreased NO-products in plasma; amiloride and eNOS-deletion had no effect. An acetylcholine bolus resulted in acute blood pressure drop that was attenuated in eNOS-/- and L-NAME mice. ENaC subunit expressions were not detected consistently in human and mouse arteries and endothelial cells. CONCLUSION Amiloride has an acute hypotensive action not dependent on ENaC and eNOS and likely related to the heart.
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Affiliation(s)
- Rikke Ydegaard
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Henrik Andersen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | | | - Ib A. Jacobsen
- Department of Endocrinology; Odense University Hospital; Odense Denmark
| | - Pernille B. L. Hansen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
- Cardiovascular and Metabolic Disease, IMED Biotech Unit; AstraZeneca; Gothenburg Sweden
| | - Jonathan F. Jürgensen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Antonio Augusto Peluso
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Paul M. Vanhoutte
- Department of Pharmacology and Pharmacy; Hong Kong University; China
| | - Mette Staehr
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Per Svenningsen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Boye L. Jensen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
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Packer M. Activation and Inhibition of Sodium-Hydrogen Exchanger Is a Mechanism That Links the Pathophysiology and Treatment of Diabetes Mellitus With That of Heart Failure. Circulation 2017; 136:1548-1559. [PMID: 29038209 DOI: 10.1161/circulationaha.117.030418] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The mechanisms underlying the progression of diabetes mellitus and heart failure are closely intertwined, such that worsening of one condition is frequently accompanied by worsening of the other; the degree of clinical acceleration is marked when the 2 coexist. Activation of the sodium-hydrogen exchanger in the heart and vasculature (NHE1 isoform) and the kidneys (NHE3 isoform) may serve as a common mechanism that links both disorders and may underlie their interplay. Insulin insensitivity and adipokine abnormalities (the hallmarks of type 2 diabetes mellitus) are characteristic features of heart failure; conversely, neurohormonal systems activated in heart failure (norepinephrine, angiotensin II, aldosterone, and neprilysin) impair insulin sensitivity and contribute to microvascular disease in diabetes mellitus. Each of these neurohormonal derangements may act through increased activity of both NHE1 and NHE3. Drugs used to treat diabetes mellitus may favorably affect the pathophysiological mechanisms of heart failure by inhibiting either or both NHE isoforms, and drugs used to treat heart failure may have beneficial effects on glucose tolerance and the complications of diabetes mellitus by interfering with the actions of NHE1 and NHE3. The efficacy of NHE inhibitors on the risk of cardiovascular events may be enhanced when heart failure and glucose intolerance coexist and may be attenuated when drugs with NHE inhibitory actions are given concomitantly. Therefore, the sodium-hydrogen exchanger may play a central role in the interplay of diabetes mellitus and heart failure, contribute to the physiological and clinical progression of both diseases, and explain certain drug-drug and drug-disease interactions that have been reported in large-scale randomized clinical trials.
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Affiliation(s)
- Milton Packer
- From Baylor Heart and Vascular Institute, Baylor University Medical Center, Dallas, TX.
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Significant natriuretic and antihypertensive action of the epithelial sodium channel blocker amiloride in diabetic patients with and without nephropathy. J Hypertens 2017; 34:1621-9. [PMID: 27214087 DOI: 10.1097/hjh.0000000000000967] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Diabetic nephropathy is associated with aberrant glomerular filtration of serine proteases. The study was designed to test the hypothesis that the epithelial sodium channel is activated proteolytically by urine plasmin in diabetic nephropathy and mediates renal sodium retention. METHODS In an open-label intervention study on type 1 diabetes patients on standardized NaCl intake (200 mmol/day) with (n = 15) and without diabetic nephropathy (control, n = 12), urinary Na excretion in response to oral amiloride (20 or 40 mg/day for 2 days) was compared. RESULTS A total of 27 patients completed the study and nine diabetic nephropathy and eight control study participants were compliant (24-h urine Na excretion of 200 mmol ± 30%). Amiloride increased significantly total and fractional Na excretion in both groups. Total natriuresis and weight loss were significantly larger in the control group compared with diabetic nephropathy at day 1 of amiloride, whereas fractional Na excretion did not differ. Amiloride intervention increased plasma renin concentration only in diabetic nephropathy group; it reduced SBP in both groups, whereas DBP was reduced in diabetic nephropathy group only. Albuminuria was reduced significantly by amiloride in diabetic nephropathy group. Urine total amiloride concentration was not different between groups (12 ± 1 and 16 ± 1 μmol/l, respectively). Urine total plasminogen and active plasmin were reduced after amiloride in diabetic nephropathy. CONCLUSION Amiloride increased renal Na excretion, reduced blood pressure, albuminuria, and total and active plasmin in urine. It is concluded that epithelial sodium channel is an attractive target to attain blood pressure control in long-term type I diabetes with no enhanced activity associated with nephropathy.
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Korte S, Wiesinger A, Straeter AS, Peters W, Oberleithner H, Kusche-Vihrog K. Firewall function of the endothelial glycocalyx in the regulation of sodium homeostasis. Pflugers Arch 2011; 463:269-78. [PMID: 22057584 DOI: 10.1007/s00424-011-1038-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 09/30/2011] [Accepted: 10/03/2011] [Indexed: 12/15/2022]
Abstract
Plasma sodium, slightly above normal and in presence of aldosterone, stiffens vascular endothelium and reduces nitric oxide release with the consequence of endothelial dysfunction. This process is mediated by epithelial sodium channels (ENaC) and, most likely, the endothelial Na(+)/K(+)-ATPase. Both, ENaC and Na(+)/K(+)-ATPase, are located in the plasma membrane of endothelial cells and embedded in the endothelial glycocalyx (eGC). This negatively charged biopolymer is directly exposed to the blood stream and selectively buffers sodium ions. We hypothesize that the glycocalyx could interfere with endothelial sodium transport when extracellular sodium varies in the physiological range. Therefore, we modeled the endothelial cell as a pump-leak system measuring changes of intracellular sodium in cultured human endothelial cells. Experiments were performed under low/high extracellular sodium conditions before and after enzymatic eGC removal, and with inhibition of Na(+)/K(+)-ATPase and ENaC, respectively. Three major observations were made: (1) eGC removal by heparinase treatment facilitates sodium to enter/exit the endothelial cells. (2) The direction of net sodium movement across the endothelial plasma membrane depends on the concentration of extracellular sodium which regulates both the Na(+)/K(+)-ATPase and ENaC activity. (3) Removal of eGC and inhibition of sodium transport modify the electrical resistance of endothelial cells. We conclude that the eGC serves as a potential "firewall" preventing uncontrolled access of sodium to the pump-leak system of the endothelial cell. After eGC removal, sodium access to the system is facilitated. Thus the pump-leak system could be regulated by ambient sodium and control vascular permeability in pathophysiological conditions.
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Affiliation(s)
- Stefanie Korte
- Institute of Physiology II, University of Muenster, Robert-Koch-Strasse 27 b, 48149, Münster, Germany
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Vargas P, Wangensteen R, Rodríguez-Gómez I, Perez-Abud R, Osuna A, Quesada A, Vargas F. Contribution of the amiloride-sensitive component and the Na+/H+ exchanger to renal responsiveness to vasoconstrictors. Pharmacology 2011; 88:142-8. [PMID: 21934350 DOI: 10.1159/000330455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 06/21/2011] [Indexed: 11/19/2022]
Abstract
AIMS This study analyzed the role of the amiloride-sensitive component and the participation of the Na(+)/H(+) exchanger in renal responsiveness to vasoconstrictors in the isolated perfused rat kidney. METHODS The renal responses to vasoconstrictors (angiotensin II, phenylephrine, vasopressin and KCl) were studied under baseline conditions and after the administration of amiloride (10 and 100 μmol/l) or the specific Na(+)/H(+) exchange inhibitor ethylisopropylamiloride (EIPA, 10 μmol/l). The effects of amiloride and EIPA on renal responsiveness to vasoconstrictors were also analyzed in endothelium-denuded preparations. RESULTS Amiloride reduced renal responsiveness to all vasoconstrictors in a dose-related manner, whereas EIPA did not affect the renal pressor response to KCl. The inhibitory effects of amiloride and EIPA on renal responsiveness to vasoconstrictors persisted after endothelium removal. CONCLUSION These results indicate that the amiloride-sensitive component and the Na(+)/H(+) exchanger play an important role in responsiveness to the main endogenous vasoconstrictors in the renal vasculature. These results also suggest that amiloride might be useful as an inhibitor of renal vasoconstriction, even in diseases with endothelial dysfunction.
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Affiliation(s)
- Pablo Vargas
- Departamento de Fisiología, Facultad de Medicina, Universidad de Granada, Granada, Spain.
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Rennings AJ, Russel FG, Li Y, Deen PM, Masereeuw R, Tack CJ, Smits P. Preserved Response to Diuretics in Rosiglitazone-Treated Subjects With Insulin Resistance: A Randomized Double-Blind Placebo-Controlled Crossover Study. Clin Pharmacol Ther 2011; 89:587-94. [DOI: 10.1038/clpt.2010.360] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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van der Heijden AG, Huysmans FTM, van Hamersvelt HW. Foot volume increase on nifedipine is not prevented by pretreatment with diuretics. J Hypertens 2004; 22:425-30. [PMID: 15076203 DOI: 10.1097/00004872-200402000-00029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Despite their natriuretic effects, dihydropyridine calcium-channel blockers (CCBs) often induce ankle oedema, probably due to vasodilation in the dependent legs. Since concomitant administration of frusemide does not prevent the acute increase in foot volume on nifedipine, we investigated whether diuretic pretreatment attenuates foot swelling on CCBs. METHODS In four separate experiments, 10 healthy volunteers received: (i) 20 mg of nifedipine without active pretreatment (pretreatment with placebo only); (ii) 20 mg of nifedipine after 5 days' treatment with amiloride 5 mg twice daily; (iii) 20 mg of nifedipine after 5 days' treatment with chlorthalidone 50 mg once daily; and (iv) no active drugs (pretreatment with placebo and placebo in place of nifedipine) as the control. Foot volumes were measured using an accurate water displacement technique (intra-individual coefficient of variance 0.27%). RESULTS Amiloride and chlorthalidone pretreatment induced marked volume depletion, with a 2-3% reduction in body weight, a 5-10% increase in haematocrit and a 14-23% increase in plasma colloid osmotic pressure. In addition, the mean +/- SEM foot volume after both chlorthalidone (1282 +/- 37 ml) and amiloride (1289 +/- 40 ml) was lower than without pretreatment (1315 +/- 38 ml) (P < 0.05). Neither amiloride nor chlorthalidone significantly influenced the acute increase in foot volume on nifedipine. However, due to pretreatment effects, the foot volume after nifedipine was higher (P < 0.05) without pretreatment (1356 +/- 36 ml) than after amiloride (1318 +/- 38 ml) or chlorthalidone (1319 +/- 37 ml). Amiloride significantly attenuated the natriuretic effect of nifedipine, whereas chlorthalidone prevented the nifedipine-induced rise in colloid osmotic pressure and haematocrit. CONCLUSIONS Diuretic pretreatment and the concomitant volume depletion did not prevent acute foot swelling on nifedipine, although the absolute foot volume remained lower after such pretreatment. Therefore diuretics mitigate the oedema of CCBs, but do not directly interfere with oedema formation.
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Schweda F, Seebauer H, Krämer BK, Kurtz A. Functional role of sodium-calcium exchange in the regulation of renal vascular resistance. Am J Physiol Renal Physiol 2001; 280:F155-61. [PMID: 11133525 DOI: 10.1152/ajprenal.2001.280.1.f155] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our study aimed to assess a possible functional role of the Na(+)/Ca(2+) exchanger in the regulation of renal vascular resistance (RVR). Therefore, we investigated the effects of an inhibition of the Na(+)/Ca(2+) exchanger either by lowering the extracellular sodium concentration ([Na(+)](e)) or, pharmacologically on RVR, by using isolated perfused rat kidneys. Graded decreases in [Na(+)](e) led to dose-dependent increases in RVR to 4.3-fold (35 mM Na(+)). This vasoconstriction was markedly attenuated by lowering the extracellular calcium concentration, by the L-type calcium channel blocker amlodipine or by the chloride channel blocker niflumic acid. Further lowering of [Na(+)](e) to 7 mM led to an increase in RVR to 7.5-fold. In this setting, amlodipine did not influence the magnitude but did influence the velocity of vasoconstriction. Pharmacological blockade of the Na(+)/Ca(2+) exchanger with KB-R7943, benzamil, or nickel resulted in significant vasoconstriction (RVR 2.5-, 1.8-, and 4.2-fold of control, respectively). Our data suggest a functional role of the Na(+)/Ca(2+) exchanger in the renal vascular bed. In conditions of partial replacement of [Na(+)](e), vasoconstriction is dependent on chloride and L-type calcium channels. A total replacement of [Na(+)](e) leads to a vasoconstriction that is nearly independent of L-type calcium channels. This might be due to an active calcium transport into the cell by the Na(+)/Ca(2+) exchanger.
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Affiliation(s)
- F Schweda
- Institut für Physiologie I, Universität Regensburg, D-93040 Regensburg, Germany.
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