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Bargagli M, Anderegg MA, Fuster DG. Effects of thiazides and new findings on kidney stones and dysglycemic side effects. Acta Physiol (Oxf) 2024; 240:e14155. [PMID: 38698738 DOI: 10.1111/apha.14155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 04/08/2024] [Accepted: 04/22/2024] [Indexed: 05/05/2024]
Abstract
Thiazide and thiazide-like diuretics (thiazides) belong to the most frequently prescribed drugs worldwide. By virtue of their natriuretic and vasodilating properties, thiazides effectively lower blood pressure and prevent adverse cardiovascular outcomes. In addition, through their unique characteristic of reducing urine calcium, thiazides are also widely employed for the prevention of kidney stone recurrence and reduction of bone fracture risk. Since their introduction into clinical medicine in the early 1960s, thiazides have been recognized for their association with metabolic side effects, particularly impaired glucose tolerance, and new-onset diabetes mellitus. Numerous hypotheses have been advanced to explain thiazide-induced glucose intolerance, yet underlying mechanisms remain poorly defined. Regrettably, the lack of understanding and unpredictability of these side effects has prompted numerous physicians to refrain from prescribing these effective, inexpensive, and widely accessible drugs. In this review, we outline the pharmacology and mechanism of action of thiazides, highlight recent advances in the understanding of thiazide-induced glucose intolerance, and provide an up-to-date discussion on the role of thiazides in kidney stone prevention.
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Affiliation(s)
- Matteo Bargagli
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Swiss National Centre of Competence in Research (NCCR) Kidney.CH, University of Zürich, Zürich, Switzerland
- Department for Biomedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Manuel A Anderegg
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Swiss National Centre of Competence in Research (NCCR) Kidney.CH, University of Zürich, Zürich, Switzerland
- Department for Biomedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Daniel G Fuster
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Swiss National Centre of Competence in Research (NCCR) Kidney.CH, University of Zürich, Zürich, Switzerland
- Department for Biomedical Research (DBMR), University of Bern, Bern, Switzerland
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2
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AlShanableh Z, Ray EC. Magnesium in hypertension: mechanisms and clinical implications. Front Physiol 2024; 15:1363975. [PMID: 38665599 PMCID: PMC11044701 DOI: 10.3389/fphys.2024.1363975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Accepted: 03/25/2024] [Indexed: 04/28/2024] Open
Abstract
Hypertension is associated with increased risk of cardiovascular disease and death. Evidence suggests that Mg2+ depletion contributes to hypertension. It is estimated that 25% or more of the United States population experiences chronic, latent Mg2+ depletion. This review explores mechanisms by which Mg2+ influences blood pressure, modifying risk of hypertension and complicating its treatment. Mechanisms addressed include effects upon i) sympathetic tone, via the modulation of N-methyl-D-aspartate (NMDA) receptor and N-type Ca2+ channel activity, influencing catecholamine release from sympathetic nerve endings; ii) vascular tone, via alteration of L-type Ca2+ and endothelial nitric oxide synthase (eNOS) activity and prostacyclin release; iii) renal K+ handling, influencing systemic K+ balance and potentially indirectly influencing blood pressure; iv) aldosterone secretion from the adrenal cortex; and v) modulation of pro-hypertensive inflammatory processes in dendritic cells and macrophages, including activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome and stimulation of isolevuglandin (IsoLG) production. Discovery of these mechanisms has furthered our understanding of the pathogenesis of hypertension, with implications for treatment and has highlighted the role of Mg2+ balance in hypertension and cardiovascular disease.
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Affiliation(s)
| | - Evan C. Ray
- Renal-Electrolyte Division, UPMC and University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
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3
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Sriperumbuduri S, Welling P, Ruzicka M, Hundemer GL, Hiremath S. Potassium and Hypertension: A State-of-the-Art Review. Am J Hypertens 2024; 37:91-100. [PMID: 37772757 DOI: 10.1093/ajh/hpad094] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 09/25/2023] [Accepted: 09/27/2023] [Indexed: 09/30/2023] Open
Abstract
Hypertension is the single most important and modifiable risk factor for cardiovascular morbidity and mortality worldwide. Non pharmacologic interventions, in particular dietary modifications have been established to decrease blood pressure (BP) and hypertension related adverse cardiovascular events. Among those dietary modifications, sodium intake restriction dominates guidelines from professional organizations and has garnered the greatest attention from the mainstream media. Despite guidelines and media exhortations, dietary sodium intake globally has not noticeably changed over recent decades. Meanwhile, increasing dietary potassium intake has remained on the sidelines, despite similar BP-lowering effects. New research reveals a potential mechanism of action, with the elucidation of its effect on natriuresis via the potassium switch effect. Additionally, potassium-substituted salt has been shown to not only reduce BP, but also reduce the risk for stroke and cardiovascular mortality. With these data, we argue that the focus on dietary modification should shift from a sodium-focused to a sodium- and potassium-focused approach with an emphasis on intervention strategies which can easily be implemented into clinical practice.
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Affiliation(s)
- Sriram Sriperumbuduri
- Division of Nephrology, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Paul Welling
- Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Marcel Ruzicka
- Division of Nephrology, Department of Medicine, University of Ottawa and the Ottawa Hospital Research Institute, Ottawa, Canada
| | - Gregory L Hundemer
- Division of Nephrology, Department of Medicine, University of Ottawa and the Ottawa Hospital Research Institute, Ottawa, Canada
| | - Swapnil Hiremath
- Division of Nephrology, Department of Medicine, University of Ottawa and the Ottawa Hospital Research Institute, Ottawa, Canada
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4
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Ayasse N, Berg P, Svendsen SL, Rousing AQ, Sørensen MV, Fedosova NU, Leipziger J. Trimethoprim inhibits renal H +-K +-ATPase in states of K + depletion. Am J Physiol Renal Physiol 2024; 326:F143-F151. [PMID: 37942538 DOI: 10.1152/ajprenal.00273.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/23/2023] [Accepted: 11/06/2023] [Indexed: 11/10/2023] Open
Abstract
There is growing consensus that under physiological conditions, collecting duct H+ secretion is independent of epithelial Na+ channel (ENaC) activity. We have recently shown that the direct ENaC inhibitor benzamil acutely impairs H+ excretion by blocking renal H+-K+-ATPase. However, the question remains whether inhibition of ENaC per se causes alterations in renal H+ excretion. To revisit this question, we studied the effect of the antibiotic trimethoprim (TMP), which is well known to cause K+ retention by direct ENaC inhibition. The acute effect of TMP (5 µg/g body wt) was assessed in bladder-catheterized mice, allowing real-time measurement of urinary pH, electrolyte, and acid excretion. Dietary K+ depletion was used to increase renal H+-K+-ATPase activity. In addition, the effect of TMP was investigated in vitro using pig gastric H+-K+-ATPase-enriched membrane vesicles. TMP acutely increased natriuresis and decreased kaliuresis, confirming its ENaC-inhibiting property. Under control diet conditions, TMP had no effect on urinary pH or acid excretion. Interestingly, K+ depletion unmasked an acute urine alkalizing effect of TMP. This finding was corroborated by in vitro experiments showing that TMP inhibits H+-K+-ATPase activity, albeit at much higher concentrations than benzamil. In conclusion, under control diet conditions, TMP inhibited ENaC function without changing urinary H+ excretion. This finding further supports the hypothesis that the inhibition of ENaC per se does not impair H+ excretion in the collecting duct. Moreover, TMP-induced urinary alkalization in animals fed a low-K+ diet highlights the importance of renal H+-K+-ATPase-mediated H+ secretion in states of K+ depletion.NEW & NOTEWORTHY The antibiotic trimethoprim (TMP) often mediates K+ retention and metabolic acidosis. We suggest a revision of the underlying mechanism that causes metabolic acidosis. Our results indicate that TMP-induced metabolic acidosis is secondary to epithelial Na+ channel-dependent K+ retention. Under control dietary conditions, TMP does not per se inhibit collecting duct H+ secretion. These findings add further argument against a physiologically relevant voltage-dependent mechanism of collecting duct H+ excretion.
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Affiliation(s)
- Niklas Ayasse
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
- Vth Department of Medicine, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Peder Berg
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - Samuel L Svendsen
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | | | | | - Natalya U Fedosova
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
| | - Jens Leipziger
- Department of Biomedicine, Physiology, Aarhus University, Aarhus, Denmark
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Do C, Vasquez PC, Soleimani M. Metabolic Alkalosis Pathogenesis, Diagnosis, and Treatment: Core Curriculum 2022. Am J Kidney Dis 2022; 80:536-551. [PMID: 35525634 PMCID: PMC10947768 DOI: 10.1053/j.ajkd.2021.12.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 12/03/2021] [Indexed: 02/02/2023]
Abstract
Metabolic alkalosis is a widespread acid-base disturbance, especially in hospitalized patients. It is characterized by the primary elevation of serum bicarbonate and arterial pH, along with a compensatory increase in Pco2 consequent to adaptive hypoventilation. The pathogenesis of metabolic alkalosis involves either a loss of fixed acid or a net accumulation of bicarbonate within the extracellular fluid. The loss of acid may be via the gastrointestinal tract or the kidney, whereas the sources of excess alkali may be via oral or parenteral alkali intake. Severe metabolic alkalosis in critically ill patients-arterial blood pH of 7.55 or higher-is associated with significantly increased mortality rate. The kidney is equipped with sophisticated mechanisms to avert the generation or the persistence (maintenance) of metabolic alkalosis by enhancing bicarbonate excretion. These mechanisms include increased filtration as well as decreased absorption and enhanced secretion of bicarbonate by specialized transporters in specific nephron segments. Factors that interfere with these mechanisms will impair the ability of the kidney to eliminate excess bicarbonate, therefore promoting the generation or impairing the correction of metabolic alkalosis. These factors include volume contraction, low glomerular filtration rate, potassium deficiency, hypochloremia, aldosterone excess, and elevated arterial carbon dioxide. Major clinical states are associated with metabolic alkalosis, including vomiting, aldosterone or cortisol excess, licorice ingestion, chloruretic diuretics, excess calcium alkali ingestion, and genetic diseases such as Bartter syndrome, Gitelman syndrome, and cystic fibrosis. In this installment in the AJKD Core Curriculum in Nephrology, we will review the pathogenesis of metabolic alkalosis; appraise the precipitating events; and discuss clinical presentations, diagnoses, and treatments of metabolic alkalosis.
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Affiliation(s)
- Catherine Do
- Division of Nephrology, University of New Mexico, and Veterans Administration Medical Center, Albuquerque, New Mexico
| | - Pamela C Vasquez
- Division of Nephrology, University of New Mexico, and Veterans Administration Medical Center, Albuquerque, New Mexico
| | - Manoocher Soleimani
- Division of Nephrology, Department of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
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6
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McDonough AA, Fenton RA. Potassium homeostasis: sensors, mediators, and targets. Pflugers Arch 2022; 474:853-867. [PMID: 35727363 PMCID: PMC10163916 DOI: 10.1007/s00424-022-02718-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 06/08/2022] [Accepted: 06/12/2022] [Indexed: 12/16/2022]
Abstract
Transmembrane potassium (K) gradients are key determinants of membrane potential that can modulate action potentials, control muscle contractility, and influence ion channel and transporter activity. Daily K intake is normally equal to the amount of K in the entire extracellular fluid (ECF) creating a critical challenge - how to maintain ECF [K] and membrane potential in a narrow range during feast and famine. Adaptations to maintain ECF [K] include sensing the K intake, sensing ECF [K] vs. desired set-point and activating mediators that regulate K distribution between ECF and ICF, and regulate renal K excretion. In this focused review, we discuss the basis of these adaptions, including (1) potential mechanisms for rapid feedforward signaling to kidney and muscle after a meal (before a rise in ECF [K]), (2) how skeletal muscles sense and respond to changes in ECF [K], (3) effects of K on aldosterone biosynthesis, and (4) how the kidney responds to changes in ECF [K] to modify K excretion. The concepts of sexual dimorphisms in renal K handling adaptation are introduced, and the molecular mechanisms that can account for the benefits of a K-rich diet to maintain cardiovascular health are discussed. Although the big picture of K homeostasis is becoming more clear, we also highlight significant pieces of the puzzle that remain to be solved, including knowledge gaps in our understanding of initiating signals, sensors and their connection to homeostatic adjustments of ECF [K].
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Affiliation(s)
- Alicia A McDonough
- Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA, USA.
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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7
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Cuthbert JJ, Brown OI, Urbinati A, Pan D, Pellicori P, Dobbs K, Bulemfu J, Kazmi S, Sokoreli I, Pauws SC, Riistama JM, Cleland JGF, Clark AL. Hypochloraemia following admission to hospital with heart failure is common and associated with an increased risk of readmission or death: a report from OPERA-HF. EUROPEAN HEART JOURNAL. ACUTE CARDIOVASCULAR CARE 2022; 11:43-52. [PMID: 34897402 DOI: 10.1093/ehjacc/zuab097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 09/19/2021] [Accepted: 10/11/2021] [Indexed: 06/14/2023]
Abstract
AIMS Hypochloraemia is common in patients hospitalized with heart failure (HF) and associated with a high risk of adverse outcomes during admission and following discharge. We assessed the significance of changes in serum chloride concentrations in relation to serum sodium and bicarbonate concentrations during admission in a cohort of 1002 consecutive patients admitted with HF and enrolled into an observational study based at a single tertiary centre in the UK. METHODS AND RESULTS Hypochloraemia (<96 mmol/L), hyponatraemia (<135 mmol/L), and metabolic alkalosis (bicarbonate >32 mmol/L) were defined by local laboratory reference ranges. Outcomes assessed were all-cause mortality, all-cause mortality or all-cause readmission, and all-cause mortality or HF readmission. Cox regression and Kaplan-Meier curves were used to investigate associations with outcome. During a median follow-up of 856 days (interquartile range 272-1416), discharge hypochloraemia, regardless of serum sodium, or bicarbonate levels was associated with greater all-cause mortality [hazard ratio (HR) 1.44, 95% confidence interval (CI) 1.15-1.79; P = 0.001], all-cause mortality or all-cause readmission (HR 1.26, 95% CI 1.04-1.53; P = 0.02), and all-cause mortality or HF readmission (HR 1.41, 95% CI 1.14-1.74; P = 0.002) after multivariable adjustment. Patients with concurrent hypochloraemia and natraemia had lower haemoglobin and haematocrit, suggesting congestion; those with hypochloraemia and normal sodium levels had more metabolic alkalosis, suggesting decongestion. CONCLUSION Hypochloraemia is common at discharge after a hospitalization for HF and is associated with worse outcome subsequently. It is an easily measured clinical variables that is associated with morbidity or mortality of any cause.
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Affiliation(s)
- J J Cuthbert
- Department of Cardiorespiratory Medicine, Centre for Clinical Sciences, Hull York Medical School, University of Hull, Kingston-Upon-Hull, East Riding of Yorkshire HU6 7RX, UK
- Department of Cardiology, Castle Hill Hospital, Hull University Teaching Hospitals Trust, Castle Road, Cottingham, Kingston-Upon-Hull, East Riding of Yorkshire HU3 2JZ, UK
| | - O I Brown
- Department of Cardiorespiratory Medicine, Centre for Clinical Sciences, Hull York Medical School, University of Hull, Kingston-Upon-Hull, East Riding of Yorkshire HU6 7RX, UK
- Department of Cardiology, Castle Hill Hospital, Hull University Teaching Hospitals Trust, Castle Road, Cottingham, Kingston-Upon-Hull, East Riding of Yorkshire HU3 2JZ, UK
| | - A Urbinati
- Department of Cardiorespiratory Medicine, Centre for Clinical Sciences, Hull York Medical School, University of Hull, Kingston-Upon-Hull, East Riding of Yorkshire HU6 7RX, UK
| | - D Pan
- Department of Cardiorespiratory Medicine, Centre for Clinical Sciences, Hull York Medical School, University of Hull, Kingston-Upon-Hull, East Riding of Yorkshire HU6 7RX, UK
| | - P Pellicori
- Robertson Centre for Biostatistics, Glasgow Clinical Trials Unit, University of Glasgow, Glasgow G12 8QQ, UK
| | - K Dobbs
- Department of Cardiorespiratory Medicine, Centre for Clinical Sciences, Hull York Medical School, University of Hull, Kingston-Upon-Hull, East Riding of Yorkshire HU6 7RX, UK
| | - J Bulemfu
- Department of Cardiorespiratory Medicine, Centre for Clinical Sciences, Hull York Medical School, University of Hull, Kingston-Upon-Hull, East Riding of Yorkshire HU6 7RX, UK
| | - S Kazmi
- Department of Cardiorespiratory Medicine, Centre for Clinical Sciences, Hull York Medical School, University of Hull, Kingston-Upon-Hull, East Riding of Yorkshire HU6 7RX, UK
| | - I Sokoreli
- Remote Patient Management & Chronic Care, Philips Research, Eindhoven 5656 AE, the Netherlands
| | - S C Pauws
- Remote Patient Management & Chronic Care, Philips Research, Eindhoven 5656 AE, the Netherlands
- Department of Communication and Cognition, Tilburg University, Tilburg 5037 AB, the Netherlands
| | - J M Riistama
- Philips Image Guided Therapy Devices, Best 1096 BC, The Netherlands
| | - J G F Cleland
- Robertson Centre for Biostatistics, Glasgow Clinical Trials Unit, University of Glasgow, Glasgow G12 8QQ, UK
| | - A L Clark
- Department of Cardiology, Castle Hill Hospital, Hull University Teaching Hospitals Trust, Castle Road, Cottingham, Kingston-Upon-Hull, East Riding of Yorkshire HU3 2JZ, UK
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Stone MS, Martin BR, Weaver CM. Short-Term RCT of Increased Dietary Potassium from Potato or Potassium Gluconate: Effect on Blood Pressure, Microcirculation, and Potassium and Sodium Retention in Pre-Hypertensive-to-Hypertensive Adults. Nutrients 2021; 13:1610. [PMID: 34064968 PMCID: PMC8151047 DOI: 10.3390/nu13051610] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 05/07/2021] [Accepted: 05/08/2021] [Indexed: 01/04/2023] Open
Abstract
Increased potassium intake has been linked to improvements in cardiovascular and other health outcomes. We assessed increasing potassium intake through food or supplements as part of a controlled diet on blood pressure (BP), microcirculation (endothelial function), and potassium and sodium retention in thirty pre-hypertensive-to-hypertensive men and women. Participants were randomly assigned to a sequence of four 17 day dietary potassium treatments: a basal diet (control) of 60 mmol/d and three phases of 85 mmol/d added as potatoes, French fries, or a potassium gluconate supplement. Blood pressure was measured by manual auscultation, cutaneous microvascular and endothelial function by thermal hyperemia, utilizing laser Doppler flowmetry, and mineral retention by metabolic balance. There were no significant differences among treatments for end-of-treatment BP, change in BP over time, or endothelial function using a mixed-model ANOVA. However, there was a greater change in systolic blood pressure (SBP) over time by feeding baked/boiled potatoes compared with control (-6.0 mmHg vs. -2.6 mmHg; p = 0.011) using contrast analysis. Potassium retention was highest with supplements. Individuals with a higher cardiometabolic risk may benefit by increasing potassium intake. This trial was registered at ClinicalTrials.gov as NCT02697708.
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Affiliation(s)
| | | | - Connie M. Weaver
- Nutrition Science, Purdue University, West Lafayette, IN 47907, USA; (M.S.S.); (B.R.M.)
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9
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Cuthbert JJ, Bhandari S, Clark AL. Hypochloraemia in Patients with Heart Failure: Causes and Consequences. Cardiol Ther 2020; 9:333-347. [PMID: 32772346 PMCID: PMC7584710 DOI: 10.1007/s40119-020-00194-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Indexed: 12/19/2022] Open
Abstract
Hypochloraemia is a common electrolyte abnormality in patients with heart failure (HF). It has a strong association with adverse outcome regardless of HF phenotype and independent of other prognostic markers. How hypochloraemia develops in a patient with HF and how it might influence outcome are not clear, and in this review we explore the possible mechanisms. Patients with HF and hypochloraemia almost invariably take higher doses of loop diuretic than patients with normal chloride levels. However, renal chloride and bicarbonate homeostasis are closely linked, and the latter may be influenced by neurohormonal activation: it is likely that the etiology of hypochloraemia in patients with HF is multifactorial and due to more than just diuretic-induced urinary losses. There are multiple proposed mechanisms by which low chloride concentrations may lead to an adverse outcome in patients with HF: by increasing renin release; by a stimulatory effect on the with-no-lysine kinases which might increase renal sodium-chloride co-transporter activity; and by an adverse effect on myocardial conduction and contractility. None of these proposed mechanisms are proven in humans with HF. However, if true, it might suggest that hypochloraemia is a therapeutic target that might be amenable to treatment with acetazolamide or chloride supplementation.
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Affiliation(s)
- Joseph J Cuthbert
- Department of Academic Cardiology, Hull York Medical School, Hull and East Yorkshire Medical Research and Teaching Centre, Castle Hill Hospital, Cottingham, Kingston upon Hull, HU16 5JQ, UK.
| | - Sunil Bhandari
- Department of Academic Nephrology, Hull University Teaching Hospitals NHS Trust and Hull York Medical School, Anlaby Road, Kingston upon Hull, HU3 2JZ, UK
| | - Andrew L Clark
- Department of Academic Cardiology, Hull York Medical School, Hull and East Yorkshire Medical Research and Teaching Centre, Castle Hill Hospital, Cottingham, Kingston upon Hull, HU16 5JQ, UK
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10
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Urinary Sodium and Potassium Levels and Blood Pressure in Population with High Sodium Intake. Nutrients 2020; 12:nu12113442. [PMID: 33182633 PMCID: PMC7697285 DOI: 10.3390/nu12113442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/16/2020] [Accepted: 11/06/2020] [Indexed: 12/23/2022] Open
Abstract
The purpose of this study was to examine the association of urinary sodium-to-creatinine ratio and potassium-to-creatinine ratio with blood pressure in a cross-sectional study comprising Korean adults who participated in the Healthy Twin Study. The participants consisted of 2653 men and women in the Healthy Twin Study aged ≥19 years. Participants’ urinary excretion of sodium, potassium, and creatinine was measured from overnight half-day urine samples. Food intake was assessed using a validated food frequency questionnaire. We examined systolic and diastolic blood pressures according to sodium- or potassium-to-creatinine ratios using the generalized linear model. We determined food groups explaining high urinary sodium- or potassium-to-creatinine ratio using the reduced rank regression and calculated sodium- or potassium-contributing food score. We observed that systolic blood pressure was higher among men and women in the highest quintile of urinary sodium-to-creatinine ratio or sodium-to-potassium ratio than it was in the lowest quintile. Geometric means (95% CIs) of the lowest and the highest quintiles of systolic blood pressure (mmHg) were 113.4 (111.8–115.0) and 115.6 (114.1–117.2; P for trend = 0.02), respectively, for sodium-to-creatinine ratio. The association between urinary sodium-to-creatinine and systolic blood pressure was more pronounced among individuals whose body mass index (BMI) was less than 25 kg/m2 (P for interaction = 0.03). We found that vegetables, kimchi and seaweed intake contributed to high sodium intake and a sodium-contributing food score were associated with increased blood pressure. In our study, we identified the food groups contributing to high sodium intake and found that high urinary sodium levels were associated with increasing blood pressure among Korean adults.
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11
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Hoorn EJ, Gritter M, Cuevas CA, Fenton RA. Regulation of the Renal NaCl Cotransporter and Its Role in Potassium Homeostasis. Physiol Rev 2020; 100:321-356. [DOI: 10.1152/physrev.00044.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Daily dietary potassium (K+) intake may be as large as the extracellular K+ pool. To avoid acute hyperkalemia, rapid removal of K+ from the extracellular space is essential. This is achieved by translocating K+ into cells and increasing urinary K+ excretion. Emerging data now indicate that the renal thiazide-sensitive NaCl cotransporter (NCC) is critically involved in this homeostatic kaliuretic response. This suggests that the early distal convoluted tubule (DCT) is a K+ sensor that can modify sodium (Na+) delivery to downstream segments to promote or limit K+ secretion. K+ sensing is mediated by the basolateral K+ channels Kir4.1/5.1, a capacity that the DCT likely shares with other nephron segments. Thus, next to K+-induced aldosterone secretion, K+ sensing by renal epithelial cells represents a second feedback mechanism to control K+ balance. NCC’s role in K+ homeostasis has both physiological and pathophysiological implications. During hypovolemia, NCC activation by the renin-angiotensin system stimulates Na+ reabsorption while preventing K+ secretion. Conversely, NCC inactivation by high dietary K+ intake maximizes kaliuresis and limits Na+ retention, despite high aldosterone levels. NCC activation by a low-K+ diet contributes to salt-sensitive hypertension. K+-induced natriuresis through NCC offers a novel explanation for the antihypertensive effects of a high-K+ diet. A possible role for K+ in chronic kidney disease is also emerging, as epidemiological data reveal associations between higher urinary K+ excretion and improved renal outcomes. This comprehensive review will embed these novel insights on NCC regulation into existing concepts of K+ homeostasis in health and disease.
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Affiliation(s)
- Ewout J. Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Catherina A. Cuevas
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Robert A. Fenton
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
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12
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Lee HW, Harris AN, Romero MF, Welling PA, Wingo CS, Verlander JW, Weiner ID. NBCe1-A is required for the renal ammonia and K + response to hypokalemia. Am J Physiol Renal Physiol 2019; 318:F402-F421. [PMID: 31841393 DOI: 10.1152/ajprenal.00481.2019] [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] [Indexed: 12/26/2022] Open
Abstract
Hypokalemia increases ammonia excretion and decreases K+ excretion. The present study examined the role of the proximal tubule protein NBCe1-A in these responses. We studied mice with Na+-bicarbonate cotransporter electrogenic, isoform 1, splice variant A (NBCe1-A) deletion [knockout (KO) mice] and their wild-type (WT) littermates were provided either K+ control or K+-free diet. We also used tissue sections to determine the effect of extracellular ammonia on NaCl cotransporter (NCC) phosphorylation. The K+-free diet significantly increased proximal tubule NBCe1-A and ammonia excretion in WT mice, and NBCe1-A deletion blunted the ammonia excretion response. NBCe1-A deletion inhibited the ammoniagenic/ammonia recycling enzyme response in the cortical proximal tubule (PT), where NBCe1-A is present in WT mice. In the outer medulla, where NBCe1-A is not present, the PT ammonia metabolism response was accentuated by NBCe1-A deletion. KO mice developed more severe hypokalemia and had greater urinary K+ excretion during the K+-free diet than did WT mice. This was associated with blunting of the hypokalemia-induced change in NCC phosphorylation. NBCe1-A KO mice have systemic metabolic acidosis, but experimentally induced metabolic acidosis did not alter NCC phosphorylation. Although KO mice have impaired ammonia metabolism, experiments in tissue sections showed that lack of ammonia does impair NCC phosphorylation. Finally, urinary aldosterone was greater in KO mice than in WT mice, but neither expression of epithelial Na+ channel α-, β-, and γ-subunits nor of H+-K+-ATPase α1- or α2-subunits correlated with changes in urinary K+. We conclude that NBCe1-A is critical for the effect of diet-induced hypokalemia to increase cortical proximal tubule ammonia generation and for the expected decrease in urinary K+ excretion.
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Affiliation(s)
- Hyun-Wook Lee
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Autumn N Harris
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Paul A Welling
- Nephrology Division, Departments of Medicine and Physiology, Johns Hopkins Medical School, Baltimore, Maryland
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida.,Nephrology and Hypertension Section, Gainesville Veterans Affairs Medical Center, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida.,Nephrology and Hypertension Section, Gainesville Veterans Affairs Medical Center, Gainesville, Florida
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Kamel KS, Schreiber M, Halperin ML. Renal potassium physiology: integration of the renal response to dietary potassium depletion. Kidney Int 2018; 93:41-53. [PMID: 29102372 DOI: 10.1016/j.kint.2017.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/31/2017] [Accepted: 08/03/2017] [Indexed: 01/30/2023]
Abstract
We summarize the current understanding of the physiology of the renal handling of potassium (K+), and present an integrative view of the renal response to K+ depletion caused by dietary K+ restriction. This renal response involves contributions from different nephron segments, and aims to diminish the rate of excretion of K+ as a result of: decreasing the rate of electrogenic (and increasing the rate of electroneutral) reabsorption of sodium in the aldosterone-sensitive distal nephron (ASDN), decreasing the abundance of renal outer medullary K+ channels in the luminal membrane of principal cells in the ASDN, decreasing the flow rate in the ASDN, and increasing the reabsorption of K+ in the cortical and medullary collecting ducts. The implications of this physiology for the association between K+ depletion and hypertension, and K+ depletion and formation of calcium kidney stones are discussed.
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Affiliation(s)
- Kamel S Kamel
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
| | - Martin Schreiber
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Mitchell L Halperin
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
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Olushola AI, Aderibigbe KO, Stephen SO, Ayodeji OS. Biochemical Effects of Aqueous Extract of Persea americana (Mill) on the Myocardium of Left Ventricle of High Salt-Fed Adult Wistar Rats. J Evid Based Complementary Altern Med 2017; 22:765-769. [PMID: 29228805 PMCID: PMC5871313 DOI: 10.1177/2156587217733884] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Accepted: 08/07/2017] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The cardioprotective effects of Persea americana extract was investigated on biochemical activities of high salt-fed adult Wistar rats in this study. METHOD Forty healthy Wistar rats of both sexes weighing 120 to 150 g were randomly assigned into 8 groups of 5 rats each (groups A, B, C, D, E, F, G, and H). Rats in groups A, F, G, and H were fed with standard laboratory pellets, while groups B, C, D, and E were fed on the high-salt diet for 4 weeks. Concomitantly, daily administration of 50, 100, and 150 mg/kg of the P americana extract were given orally to groups C and F, D and G, and E and H, respectively, while rats in groups A and B were administered distilled water. Blood samples were taken by cardiac puncture; concentration of sodium ion, potassium ion, nitric oxide, and activity of lactate dehydrogenase were determined. One-way analysis of variance was used to analyze data, followed by Student-Newman-Keuls (SNK) test for multiple comparison. RESULTS Results revealed that concentration of potassium ion and nitric oxide was significantly lower ( P < .05) in high salt-fed groups. Sodium ion concentration and activity of lactate dehydrogenase were higher in high salt-fed group while P americana prevented biochemical perturbations in other experimental groups. CONCLUSION In conclusion, high salt-diet induced biochemical alterations which were significantly protected by oral administration of P americana extract.
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Biber J, Murer H, Mohebbi N, Wagner C. Renal Handling of Phosphate and Sulfate. Compr Physiol 2014; 4:771-92. [DOI: 10.1002/cphy.c120031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Koliaki C, Katsilambros N. Dietary sodium, potassium, and alcohol: key players in the pathophysiology, prevention, and treatment of human hypertension. Nutr Rev 2013; 71:402-11. [PMID: 23731449 DOI: 10.1111/nure.12036] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Western industrialized societies are currently experiencing an epidemic expansion of hypertension (HTN), which extends alarmingly even to children and adolescents. HTN constitutes an independent risk factor for cardiorenal disease and represents an extremely common comorbidity of diabetes and obesity. Numerous randomized clinical trials and meta-analyses have provided robust scientific evidence that reduced dietary salt intake, increased dietary potassium intake, moderation of alcohol consumption, optimal weight maintenance, and the adoption of "heart-friendly" dietary patterns such as the Dietary Approaches to Stop Hypertension or the Mediterranean diet can effectively lower blood pressure. Interestingly, the susceptibility of blood pressure to nutritional interventions is greatly variable among individuals, depending on age, race, genetic background, and comorbidities. The purpose of this review is to provide a comprehensive overview of currently available scientific evidence in the constantly evolving field of diet and HTN, placing particular emphasis on the key role of dietary sodium, dietary potassium, and alcohol intake in the pathophysiology, prevention, and treatment of human hypertension.
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Affiliation(s)
- Chrysi Koliaki
- Eugenideion Hospital, Athens University Medical School, 11141 Athens, Greece.
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Parker MD, Boron WF. The divergence, actions, roles, and relatives of sodium-coupled bicarbonate transporters. Physiol Rev 2013; 93:803-959. [PMID: 23589833 PMCID: PMC3768104 DOI: 10.1152/physrev.00023.2012] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.
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Affiliation(s)
- Mark D Parker
- Dept. of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4970, USA.
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Kovacevic L, Wolfe-Christensen C, Edwards L, Sadaps M, Lakshmanan Y. From Hypercalciuria to Hypocitraturia—A Shifting Trend in Pediatric Urolithiasis? J Urol 2012; 188:1623-7. [PMID: 22910255 DOI: 10.1016/j.juro.2012.02.2562] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Indexed: 11/26/2022]
Affiliation(s)
- Larisa Kovacevic
- Department of Pediatric Urology, Children's Hospital of Michigan, Detroit, Michigan
| | | | - Luke Edwards
- Department of Pediatric Urology, Children's Hospital of Michigan, Detroit, Michigan
| | - Meena Sadaps
- Department of Pediatric Urology, Children's Hospital of Michigan, Detroit, Michigan
| | - Yegappan Lakshmanan
- Department of Pediatric Urology, Children's Hospital of Michigan, Detroit, Michigan
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Zárate Méndez LH, Valenzuela Montero A. Sodium-potassium balance in the regulation of high blood pressure. Medwave 2012. [DOI: 10.5867/medwave.2012.02.5301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Affiliation(s)
- Alan M. Weinstein
- Department of Physiology and Biophysics, Department of Medicine, Weill Medical College of Cornell University, New York, New York
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Kris-Etherton PM, Grieger JA, Hilpert KF, West SG. Milk products, dietary patterns and blood pressure management. J Am Coll Nutr 2009; 28 Suppl 1:103S-19S. [PMID: 19571168 DOI: 10.1080/07315724.2009.10719804] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
High blood pressure (BP) is a major risk factor for heart disease, stroke, congestive heart failure, and kidney disease. Inverse associations between dairy product consumption and systolic blood pressure (SBP) and diastolic blood pressure (DBP) have been observed in cross-sectional studies; some studies, however, have reported an inverse association with only one BP parameter, predominantly SBP. Randomized clinical trials examining the effect of calcium and the combination of calcium, potassium and magnesium provide evidence for causality. In these studies, reductions in BP were generally modest (-1.27 to -4.6 mmHg for SBP, and -0.24 to -3.8 mmHg for DBP). Dairy nutrients, most notably calcium, potassium and magnesium, have been shown to have a blood pressure lowering effect. A low calcium intake increases intracellular calcium concentrations which increases 1,25-dihydroxyvitamin D(3) and parathyroid hormone (PTH), causing calcium influx into vascular smooth muscle cells, resulting in greater vascular resistance. New research indicates that dairy peptides may act as angiotensin converting enzyme (ACE) inhibitors, thereby inhibiting the renin angiotensin system with consequent vasodilation. A growing evidence base shows that dairy product consumption is involved in the regulation of BP. Consequently, inclusion of dairy products in a heart healthy diet is an important focal point to attain BP benefits.
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Affiliation(s)
- Penny M Kris-Etherton
- Department of Nutritional Sciences, 110 Chandlee Laboratory, Penn State University, University Park, PA 16802, USA.
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Busque SM, Wagner CA. Potassium restriction, high protein intake, and metabolic acidosis increase expression of the glutamine transporter SNAT3 (Slc38a3) in mouse kidney. Am J Physiol Renal Physiol 2009; 297:F440-50. [PMID: 19458124 DOI: 10.1152/ajprenal.90318.2008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Kidneys produce ammonium to buffer and excrete acids through metabolism of glutamine. Expression of the glutamine transporter Slc38a3 (SNAT3) increases in kidney during metabolic acidosis (MA), suggesting a role during ammoniagenesis. Potassium depletion and high dietary protein intake are known to elevate renal ammonium excretion. In this study, we examined SNAT3, phosphate-dependent glutaminase (PDG), and phosphoenolpyruvate carboxykinase (PEPCK) regulation during a control (0.36%) or low-K(+) (0.02%) diet for 7 or 14 days or a control (20%) or high-protein (50%) diet for 7 days. MA was induced in control and low-K(+) groups by addition of NH(4)Cl. Urinary ammonium excretion increased during MA, after 14-day K(+) restriction alone, and during high protein intake. SNAT3, PDG, and PEPCK mRNA abundance were elevated during MA and after 14-day K(+) restriction but not during high protein intake. SNAT3 protein abundance was enhanced during MA (both control and low K(+)), after 14-day low-K(+) treatment alone, and during high protein intake. Seven-day dietary K(+) depletion alone had no effect. Immunohistochemistry showed SNAT3 staining in earlier parts of the proximal tubule during 14-day K(+) restriction with and without NH(4)Cl treatment and during high protein intake. In summary, SNAT3, PDG, and PEPCK mRNA expression were congruent with urinary ammonium excretion during MA. Chronic dietary K(+) restriction, high protein intake, and MA enhance ammoniagenesis, an effect that may involve enhanced SNAT3 mRNA and protein expression. Our data suggest that SNAT3 plays an important role as the glutamine uptake mechanism in ammoniagenesis under these conditions.
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Affiliation(s)
- Stephanie M Busque
- Institute of Physiology, Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Zuckerman JM, Assimos DG. Hypocitraturia: pathophysiology and medical management. Rev Urol 2009; 11:134-144. [PMID: 19918339 PMCID: PMC2777061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Low urinary citrate excretion is a known risk factor for the development of kidney stones. Citrate inhibits stone formation by complexing with calcium in the urine, inhibiting spontaneous nucleation, and preventing growth and agglomeration of crystals. Hypocitraturia is a common metabolic abnormality found in 20% to 60% of stone formers. It is most commonly idiopathic in origin but may be caused by distal renal tubular acidosis, hypokalemia, bowel dysfunction, and a high-protein, low-alkali diet. Genetic factors, medications, and other comorbid disorders also play a role. Hypocitraturia should be managed through a combination of dietary modifications, oral alkali, and possibly lemonade or other citrus juice-based therapy. This review concerns the pathophysiology of hypocitraturia and the management of stone formers afflicted with this abnormality.
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Affiliation(s)
- Jack M Zuckerman
- Department of Urology, Wake Forest University School of Medicine Winston-Salem, NC
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Tavichakorntrakool R, Prasongwattana V, Sriboonlue P, Puapairoj A, Wongkham C, Wiangsimma T, Khunkitti W, Triamjangarun S, Tanratanauijit M, Chamsuwan A, Khunkitti W, Yenchitsomanus PT, Thongboonkerd V. K+, Na+, Mg2+, Ca2+, and water contents in human skeletal muscle: correlations among these monovalent and divalent cations and their alterations in K+ -depleted subjects. Transl Res 2007; 150:357-66. [PMID: 18022598 DOI: 10.1016/j.trsl.2007.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 08/23/2007] [Accepted: 08/25/2007] [Indexed: 11/26/2022]
Abstract
None of previous studies had simultaneously analyzed the K(+), Na(+), Mg(2+), and Ca(2+) contents in human skeletal muscle. We examined extensively and simultaneously the levels of all these cations and examined water content in vastus lateralis and pectoralis major muscles in 30 northeastern Thai men who were apparently healthy but died from an accident. Specimen collection was performed within 6 h of death. We used atomic absorption or flame photometry to measure the level of muscle cation. Histopathology of muscle and kidney was also evaluated. K(+), Na(+), Mg(2+), and Ca(2+) contents in vastus lateralis were 84.74 +/- 1.50, 38.64 +/- 0.77, 7.58 +/- 0.17, and 0.94 +/- 0.06 micromol/g wet weight, respectively, whereas K(+), Na(+), and Mg(2+) contents in pectoralis major were 82.83 +/- 1.54, 37.57 +/- 0.72, and 7.30 +/- 0.17 micromol/g wet weight, respectively. The water component was comparable in vastus lateralis and pectoralis major (78.66 +/- 0.41 and 78.09 +/- 0.56 %, respectively). Based on muscle K(+) levels, we divided the subjects into 2 main groups: K(+)-depleted (KD) group (K(+) < 80 micromol/g wet weight; n = 7) and non-K(+)-depleted (NKD) group (K(+) > or = 80 micromol/g wet weight; n = 23). In the KD muscle, Na(+) and Ca(2+) levels were significantly higher, whereas the level of Mg(2+) was significantly lower. Linear regression analysis showed significant correlations of K(+) and Mg(2+) levels and between Na(+) and Ca(2+). However, K(+) and Mg(2+) had the negative correlation with Na(+) and Ca(2+). Histopathologic examination showed no change in the KD muscles, whereas 29% (2 of 7) of the KD kidneys had vacuolization in proximal renal tubular cells. Our study not only provided the descriptive data but also implied the balance or homeostasis of these monovalent and divalent cations in their muscle pools.
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Abstract
Although significant contributions to the understanding of metabolic alkalosis have been made recently, much of our knowledge rests on data from clearance studies performed in humans and animals many years ago. This article reviews the contributions of these studies, as well as more recent work relating to the control of renal acid-base transport by mineralocorticoid hormones, angiotensin, endothelin, nitric oxide, and potassium balance. Finally, clinical aspects of metabolic alkalosis are considered.
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Affiliation(s)
- Melvin E Laski
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79413, USA.
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Xia VW, Du B, Tran A, Liu L, Hu KQ, Hiatt JR, Busuttil RW, Steadman RH. Intraoperative Hypokalemia in Pediatric Liver Transplantation: Incidence and Risk Factors. Anesth Analg 2006; 103:587-93. [PMID: 16931666 DOI: 10.1213/01.ane.0000229650.23931.0c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this retrospective study of 268 children undergoing liver transplantation, we investigated the incidence of intraoperative potassium (K+) disturbances and the risk factors for hypokalemia in the preperfusion and postreperfusion periods. Overall, hypokalemia was the predominant disturbance, occurring in 72.0% of pediatric patients during liver transplantation. Hypokalemia was more common during the postreperfusion period than the prereperfusion period. Hyperkalemia, though a commonly cited complication, was infrequent during pediatric liver transplantation. Using multivariate logistic regression analysis, baseline serum K+ < or =3.5 mmol/L, base excess >5 mmol/L, and creatinine < or =0.5 mg/dL were found to be predictors for hypokalemia in the prereperfusion period; and body weight < or =15 kg, K+ < or =3.5 mmol/L, fresh-frozen plasma transfusion >90 mL/kg, and absence of ascites at surgery were independent predictors for hypokalemia in the postreperfusion period. These findings support the use of K+ replacement to maintain normokalemia and avoid the potential complications related to hypokalemia in pediatric liver transplantation, especially in children with the risk factors for hypokalemia.
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Affiliation(s)
- Victor W Xia
- Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-1778, USA.
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Takakura S, Nozaki T, Nomura Y, Koreeda C, Urabe H, Kawai K, Takii M, Kubo C. Factors related to renal dysfunction in patients with anorexia nervosa. Eat Weight Disord 2006; 11:73-7. [PMID: 16809978 DOI: 10.1007/bf03327754] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVE Anorexia nervosa (AN) patients were surveyed to determine which disease factors were related to AN influenced renal dysfunction. METHODS Data were from forty-five AN patients hospitalized in our department between 1995 and 2002. The patients were classified into three groups based on the type of anorexia: restricting (n=18), self-induced vomiting (n=13), and laxative abuse (n=14). Twenty-four hour-creatinine clearance (Ccr) was calculated within two weeks of hospitalization for comparison among the three groups. RESULTS The Ccr level of the laxative abuse group was significantly lower than that of the restricting group (65.8+/-31.4 ml/min vs restricting type: 104+/-23.3 ml/min, p=0.002). The laxative abuse group had a significantly longer duration of illness than the restricting group (p<0.0001). Multiple regression analysis revealed the duration of illness to be a risk factor for renal function deterioration in AN patients (r=0.580, p<0.001). DISCUSSION Renal function should be carefully followed during the treatment of AN patients with a long duration of illness, especially those with long-term laxative abuse.
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Affiliation(s)
- S Takakura
- Department of Psychosomatic Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
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Xu J, Worrell RT, Li HC, Barone SL, Petrovic S, Amlal H, Soleimani M. Chloride/Bicarbonate Exchanger SLC26A7 Is Localized in Endosomes in Medullary Collecting Duct Cells and Is Targeted to the Basolateral Membrane in Hypertonicity and Potassium Depletion. J Am Soc Nephrol 2006; 17:956-67. [PMID: 16524946 DOI: 10.1681/asn.2005111174] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
SLC26A7 is a Cl(-)/HCO(3)(-) exchanger that is expressed on the basolateral membrane and in the cytoplasm of two distinct acid-secreting epithelial cells: The A-intercalated cells in the kidney outer medullary collecting duct and the gastric parietal cells. The intracellular localization of SLC26A7 suggests the possibility of trafficking between cell membrane and intracellular compartments. For testing this hypothesis, full-length human SLC26A7 cDNA was fused with green fluorescence protein and transiently expressed in MDCK epithelial cells. In monolayer cells in isotonic medium, SLC26A7 showed punctate distribution throughout the cytoplasm. However, in medium that was made hypertonic for 16 h, SLC26A7 was detected predominantly in the plasma membrane. The presence of mitogen-activated protein kinase inhibitors blocked the trafficking of SLC26A7 to the plasma membrane. Double-labeling studies demonstrated the localization of SLC26A7 to the transferrin receptor-positive endosomes. A chimera that was composed of the amino terminal fragment of SLC26A7 and the carboxyl terminal fragment of SLC26A1, and a C-terminal-truncated SLC26A7 were retained in the cytoplasm in hypertonicity. In separate studies, SLC26A7 showed predominant localization in plasma membrane in potassium-depleted isotonic medium (0.5 or 2 mEq/L KCl) versus cytoplasmic distribution in normal potassium isotonic medium (4 mEq/L). It is concluded that SLC26A7 is present in endosomes, and its targeting to the basolateral membrane is increased in hypertonicity and potassium depletion. The trafficking to the cell surface suggests novel functional upregulation of SLC26A7 in states that are associated with hypokalemia or increased medullary tonicity. Additional studies are needed to ascertain the role of SLC26A7 in enhanced bicarbonate absorption in outer medullary collecting duct in hypokalemia and in acid-base regulation in conditions that are associated with increased medullary tonicity.
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Affiliation(s)
- Jie Xu
- Division of Nephrology and Hypertension, Department of Medicine, University of Cincinnati, 231 Albert Sabin Way, MSB 259G, Cincinnati, OH 45267-0585, USA
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Unwin RJ, Capasso G, Shirley DG. An Overview of Divalent Cation and Citrate Handling by the Kidney. ACTA ACUST UNITED AC 2004; 98:p15-20. [PMID: 15499218 DOI: 10.1159/000080259] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Urinary calcium, magnesium and citrate levels are important in promoting or inhibiting renal stone formation. Here we review current information on the tubular handling of these ions. Most filtered calcium is reabsorbed in the proximal tubule and the thick ascending limb (TAL) of the loop of Henle, largely paracellularly; most of the remainder is reabsorbed in the distal tubule, transcellularly. Calcium reabsorption in the TAL and distal tubule is stimulated by parathyroid hormone and vitamin D; other factors influencing its renal handling include extracellular volume status and acid-base balance. Little filtered magnesium is reabsorbed in the proximal tubule; the bulk is reabsorbed paracellularly in the TAL, while most of the remainder is reabsorbed transcellularly in the distal tubule. Dietary intake, peptide hormones and chronic potassium depletion can all influence magnesium reabsorption in the TAL and distal tubule. Most filtered citrate is taken up across the apical membrane of the proximal tubule via a sodium-dicarboxylate co-transporter (NaDC-1). It also enters proximal tubular cells across the basolateral membrane; citrate contributes to the cells' oxidative metabolism. Citrate excretion is affected by acid-base balance, acetazolamide treatment, chronic potassium depletion and urinary excretion of calcium and magnesium. Where possible, we have indicated the mechanisms of these complex interactions.
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Affiliation(s)
- R J Unwin
- Centre for Nephrology, Department of Medicine, Royal Free and University College Medical School, London, UK
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Elkjaer ML, Kwon TH, Wang W, Nielsen J, Knepper MA, Frøkiaer J, Nielsen S. Altered expression of renal NHE3, TSC, BSC-1, and ENaC subunits in potassium-depleted rats. Am J Physiol Renal Physiol 2002; 283:F1376-88. [PMID: 12388387 DOI: 10.1152/ajprenal.00186.2002] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to examine whether hypokalemia is associated with altered abundance of major renal Na+ transporters that may contribute to the development of urinary concentrating defects. We examined the changes in the abundance of the type 3 Na+/H+ exchanger (NHE3), Na+ - K+-ATPase, the bumetanide-sensitive Na+ - K+ - 2Cl- cotransporter (BSC-1), the thiazide-sensitive Na+ - Cl- cotransporter (TSC), and epithelial sodium channel (ENaC) subunits in kidneys of hypokalemic rats. Semiquantitative immunoblotting revealed that the abundance of BSC-1 (57%) and TSC (46%) were profoundly decreased in the inner stripe of the outer medulla (ISOM) and cortex/outer stripe of the outer medulla (OSOM), respectively. These findings were confirmed by immunohistochemistry. Moreover, total kidney abundance of all ENaC subunits was significantly reduced in response to the hypokalemia: alpha-subunit (61%), beta-subunit (41%), and gamma-subunit (60%), and this was confirmed by immunohistochemistry. In contrast, the renal abundance of NHE3 in hypokalemic rats was dramatically increased in cortex/OSOM (736%) and ISOM (210%). Downregulation of BSC-1, TSC, and ENaC may contribute to the urinary concentrating defect, whereas upregulation of NHE3 may be compensatory to prevent urinary Na+ loss and/or to maintain intracellular pH levels.
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Affiliation(s)
- Marie-Louise Elkjaer
- The Water and Salt Research Center, University of Aarhus, DK-8000 Aarhus C, Denmark
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Wagner CA, Finberg KE, Stehberger PA, Lifton RP, Giebisch GH, Aronson PS, Geibel JP. Regulation of the expression of the Cl-/anion exchanger pendrin in mouse kidney by acid-base status. Kidney Int 2002; 62:2109-17. [PMID: 12427135 DOI: 10.1046/j.1523-1755.2002.00671.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Pendrin belongs to a superfamily of Cl-/anion exchangers and is expressed in the inner ear, the thyroid gland, and the kidney. In humans, mutations in pendrin cause Pendred syndrome characterized by sensorineural deafness and goiter. Recently pendrin has been localized to the apical side of non-type A intercalated cells of the cortical collecting duct, and reduced bicarbonate secretion was demonstrated in a pendrin knockout mouse model. To investigate a possible role of pendrin in modulating acid-base transport in the cortical collecting duct, we examined the regulation of expression of pendrin by acid-base status in mouse kidney. METHODS Mice were treated orally either with an acid or bicarbonate load (0.28 mol/L NH4Cl or NaHCO3) or received a K+-deficient diet for one week. Immunohistochemistry and Western blotting was performed. RESULTS Acid-loading caused a reduction in pendrin protein expression levels within one day and decreased expression to 23% of control levels after one week. Concomitantly, pendrin protein was shifted from the apical membrane to the cytosol, and the relative abundance of pendrin positive cells declined. Similarly, in chronic K+-depletion, known to elicit a metabolic alkalosis, pendrin protein levels decreased and pendrin expression was shifted to an intracellular pool with the relative number of pendrin positive cells reduced. In contrast, following oral bicarbonate loading pendrin was found exclusively in the apical membrane and the relative number of pendrin positive cells increased. CONCLUSIONS These results are in agreement with a potential role of pendrin in bicarbonate secretion and regulation of acid-base transport in the cortical collecting duct.
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Affiliation(s)
- Carsten A Wagner
- Department of Cellular and Molecular Physiology, Yale University, School of Medicine, New Haven, Connecticut, USA.
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Eladari D, Leviel F, Pezy F, Paillard M, Chambrey R. Rat proximal NHE3 adapts to chronic acid-base disorders but not to chronic changes in dietary NaCl intake. Am J Physiol Renal Physiol 2002; 282:F835-43. [PMID: 11934693 DOI: 10.1152/ajprenal.00188.2001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the proximal tubule, the apical Na(+)/H(+) exchanger identified as NHE3 mediates most NaCl and NaHCO(3) absorption. The purpose of this study was to analyze the long-term regulation of NHE3 during alkalosis induced by dietary NaHCO(3) loading and changes in NaCl intake. Sprague-Dawley rats exposed to a low-NaCl, high-NaCl, or NaHCO(3) diet for 6 days were studied. Renal cortical apical membrane vesicles (AMV) were prepared from treated and normal rats. Na(+)/H(+) exchange was assayed as the initial rate of (22)Na(+) uptake in the presence of an outward H(+) gradient. (22)Na(+) uptake measured in the presence of high-dose 5-(N-ethyl-N-isopropyl) amiloride was not different among models. Changes in NaCl intake did not affect NHE3 activity, whereas NaHCO(3) loading inhibited (22)Na(+) uptake by 30%. AMV NHE3 protein abundance assessed by Western blot analysis was unaffected during changes in NaCl intake. During NaHCO(3) loading, NHE3 protein abundance was decreased by 65%. We conclude that proximal NHE3 adapts to chronic metabolic acid-base disorders but not to changes in dietary NaCl intake.
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Affiliation(s)
- Dominique Eladari
- Institut National de la Santé et de la Recherche Médicale Unité 356, Institut Fédératif de Recherche 58, Université Pierre et Marie Curie, 75270 Paris Cedex 06, France
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Abstract
Disturbances in potassium homoeostasis presenting as low or high serum potassium are common, especially among hospitalised patients. Given the fact that untreated hypokalaemia or hyperkalaemia is associated with high morbidity and mortality, it is critical to recognise and treat these disorders promptly. In this article, normal potassium homoeostasis is reviewed initially and then a pathophysiological approach to work-up and management of hypokalaemia and hyperkalaemia is presented. Recent advances with respect to the role of kidney in handling of the potassium, the regulation of renal ion transporters in hypokalaemia, and treatment of hypokalaemia and hyperkalaemia will be discussed.
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Affiliation(s)
- A Rastegar
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
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Amlal H, Chen Q, Greeley T, Pavelic L, Soleimani M. Coordinated down-regulation of NBC-1 and NHE-3 in sodium and bicarbonate loading. Kidney Int 2001; 60:1824-36. [PMID: 11703600 DOI: 10.1046/j.1523-1755.2001.00995.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Bicarbonate reabsorption in the kidney proximal tubule is predominantly mediated via the apical Na+/H+ exchanger (NHE-3) and basolateral Na+: HCO(-3) cotransporter (NBC-1). The purpose of these studies was to examine the effects of Na+ load and altered acid-base status on the expression of NHE-3 and NBC-1 in the kidney. METHODS Rats were placed on 280 mmol/L of NaHCO(3), NaCl, or NH(4)Cl added to their drinking water for 5 days and examined for the expression of NHE-3 and NBC-1 in the kidney. RESULTS Serum [HCO(-3)] was unchanged in NaHCO(-3) and NaCl-loaded animals versus control (P> 0.05). However, a significant hyperchloremic metabolic acidosis was developed in NH4Cl-loaded animals. A specific polyclonal antibody against NBC-1 recognized a 130 kD band, which was exclusively expressed in the basolateral membrane of proximal tubules. Immunoblot studies indicated that the protein abundance of NBC-1 and NHE-3 in the cortex decreased by 74% (P < 0.04) and 66% (P < 0.03), respectively, in NaHCO(3) loading and by 72% (P < 0.003) and 55% (P < 0.04), respectively, in NaCl loading. Switching from NaHCO(3) to distilled water resulted in rapid recovery of NHE-3 and NBC-1 protein expression toward normal levels. Metabolic acidosis increased the abundance of NHE-3 (P < 0.0001) but not NBC-1 (P> 0.05). CONCLUSIONS NaHCO(-3) or NaCl loading coordinately down-regulates the apical NHE-3 and basolateral NBC-1 in rat kidney proximal tubule, presumably due to increased Na+ load. We propose that the down-regulation of these two Na+- and HCO(3)-absorbing transporters is, to a large degree, responsible for enhanced excretion of excess of Na+ and alkaline load and prevention of metabolic alkalosis in rats subjected to NaHCO(-3) loading.
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Affiliation(s)
- H Amlal
- Department of Medicine, University of Cincinnati Medical Center, 231 Albert Sabin Way, Cincinnati, OH 45267-0585, USA
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Steinbrecher KA, Mann EA, Giannella RA, Cohen MB. Increases in guanylin and uroguanylin in a mouse model of osmotic diarrhea are guanylate cyclase C-independent. Gastroenterology 2001; 121:1191-202. [PMID: 11677212 DOI: 10.1053/gast.2001.28680] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Guanylin and uroguanylin are peptide hormones that are homologous to the diarrhea-causing Escherichia coli enterotoxins. These secretagogues are released from the intestinal epithelia into the intestinal lumen and systemic circulation and bind to the receptor guanylate cyclase C (GC-C). We hypothesized that a hypertonic diet would result in osmotic diarrhea and cause a compensatory down-regulation of guanylin/uroguanylin. METHODS Gut-to-carcass weights were used to measure fluid accumulation in the intestine. Northern and/or Western analysis was used to determine the levels of guanylin, uroguanylin, and GC-C in mice with osmotic diarrhea. RESULTS Wild-type mice fed a polyethylene glycol or lactose-based diet developed weight loss, diarrhea, and an increased gut-to-carcass ratio. Unexpectedly, 2 days on either diet resulted in increased guanylin/uroguanylin RNA and prohormone throughout the intestine, elevated uroguanylin RNA, and prohormone levels in the kidney and increased levels of circulating prouroguanylin. GC-C-deficient mice given the lactose diet reacted with higher gut-to-carcass ratios. Although they did not develop diarrhea, GC-C-sufficient and -deficient mice on the lactose diet responded with elevated levels of guanylin and uroguanylin RNA and protein. A polyethylene glycol drinking water solution resulted in diarrhea, higher gut-to-carcass ratios, and induction of guanylin and uroguanylin in both GC-C heterozygous and null animals. CONCLUSIONS We conclude that this model of osmotic diarrhea results in a GC-C-independent increase in intestinal fluid accumulation, in levels of these peptide ligands in the epithelia of the intestine, and in prouroguanylin in the kidney and blood.
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Affiliation(s)
- K A Steinbrecher
- Division of Pediatric Gastroenterology, Hepatology and Nutrition and Graduate Program in Molecular and Developmental Biology, Children's Hospital Research Foundation, Cincinnati, Ohio, USA
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Zajicek HK, Wang H, Puttaparthi K, Halaihel N, Markovich D, Shayman J, Béliveau R, Wilson P, Rogers T, Levi M. Glycosphingolipids modulate renal phosphate transport in potassium deficiency. Kidney Int 2001; 60:694-704. [PMID: 11473652 DOI: 10.1046/j.1523-1755.2001.060002694.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Potassium (K) deficiency (KD) and/or hypokalemia have been associated with disturbances of phosphate metabolism. The purpose of the present study was to determine the cellular mechanisms that mediate the impairment of renal proximal tubular Na/Pi cotransport in a model of K deficiency in the rat. METHODS K deficiency in the rat was achieved by feeding rats a K-deficient diet for seven days, which resulted in a marked decrease in serum and tissue K content. RESULTS K deficiency resulted in a marked increase in urinary Pi excretion and a decrease in the V(max) of brush-border membrane (BBM) Na/Pi cotransport activity (1943 +/- 95 in control vs. 1184 +/- 99 pmol/5 sec/mg BBM protein in K deficiency, P < 0.02). Surprisingly, the decrease in Na/Pi cotransport activity was associated with increases in the abundance of type I (NaPi-1), and type II (NaPi-2) and type III (Glvr-1) Na/Pi protein. The decrease in Na/Pi transport was associated with significant alterations in BBM lipid composition, including increases in sphingomyelin, glucosylceramide, and ganglioside GM3 content and a decrease in BBM lipid fluidity. Inhibition of glucosylceramide synthesis resulted in increases in BBM Na/Pi cotransport activity in control and K-deficient rats. The resultant Na/Pi cotransport activity in K-deficient rats was the same as in control rats (1148 +/- 52 in control + PDMP vs. 1152 +/- 61 pmol/5 sec/mg BBM protein in K deficiency + PDMP). These changes in transport activity occurred independent of further changes in BBM NaPi-2 protein or renal cortical NaPi-2 mRNA abundance. CONCLUSION K deficiency in the rat causes inhibition of renal Na/Pi cotransport activity by post-translational mechanisms that are mediated in part through alterations in glucosylceramide content and membrane lipid dynamics.
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Affiliation(s)
- H K Zajicek
- Department of Internal Medicine, The University of Texas Southwestern Medical Center and VA Medical Center, Dallas, Texas 75216, USA
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Soleimani M, Greeley T, Petrovic S, Wang Z, Amlal H, Kopp P, Burnham CE. Pendrin: an apical Cl-/OH-/HCO3- exchanger in the kidney cortex. Am J Physiol Renal Physiol 2001; 280:F356-64. [PMID: 11208611 DOI: 10.1152/ajprenal.2001.280.2.f356] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The identities of the apical Cl-/base exchangers in kidney proximal tubule and cortical collecting duct (CCD) cells remain unknown. Pendrin (PDS), which is expressed at high levels in the thyroid and its mutation causes Pendred's syndrome, is shown to be an anion exchanger. We investigated the renal distribution of PDS and its function. Our results demonstrate that pendrin mRNA expression in the rat kidney is abundant and limited to the cortex. Proximal tubule suspensions isolated from kidney cortex were highly enriched in pendrin mRNA. Immunoblot analysis studies localized pendrin to cortical brush-border membranes. Nephron segment RT-PCR localized pendrin mRNA to proximal tubule and CCD. Expression studies in HEK-293 cells demonstrated that pendrin functions in the Cl-/OH-, Cl-/HCO3-, and Cl-/formate exchange modes. The conclusion is that pendrin is an apical Cl-/base exchanger in the kidney proximal tubule and CCD and mediates Cl-/OH-, Cl-/HCO3-, and Cl-/formate exchange.
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Affiliation(s)
- M Soleimani
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0585, USA
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Amlal H, Habo K, Soleimani M. Potassium deprivation upregulates expression of renal basolateral Na(+)-HCO(3)(-) cotransporter (NBC-1). Am J Physiol Renal Physiol 2000; 279:F532-43. [PMID: 10966933 DOI: 10.1152/ajprenal.2000.279.3.f532] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of the present experiments was to examine the effect of potassium deprivation on the expression of the renal basolateral Na(+)-HCO(3)(-) cotransporter (NBC-1). Rats were placed on a K(+)-free diet for various time intervals and examined. NBC-1 mRNA levels increased by about threefold in the cortex (P < 0.04) at 72 h of K(+) deprivation and remained elevated at 21 days. NBC activity increased by approximately 110% in proximal tubule suspensions, with the activity increasing from 0.091 in control to 0.205 pH/min in the K(+)-deprived group (P < 0.005). The inner stripe of outer medulla and cells of medullary thick ascending limb of Henle (mTAL) showed induction of NBC-1 mRNA and activity in K(+)-deprived rats, with the activity in mTAL increasing from 0.010 in control to 0.133 pH/min in the K(+)-deprived group (P < 0.004). K(+) deprivation also increased NBC-1 mRNA levels in the renal papilla (P < 0.02). We conclude that 1) K(+) deprivation increases NBC-1 expression and activity in proximal tubule and 2) K(+) deprivation causes induction of NBC-1 expression and activity in mTAL tubule and inner medulla. We propose that NBC-1 likely mediates enhanced HCO(3)(-) reabsorption in proximal tubule, mTAL, and inner medullary collecting duct in K(+) deprivation and contributes to the maintenance of metabolic alkalosis in this condition.
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Affiliation(s)
- H Amlal
- Department of Medicine, University of Cincinnati School of Medicine, Cincinnati, Ohio 45267-0585, USA
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Ali R, Amlal H, Burnham CE, Soleimani M. Glucocorticoids enhance the expression of the basolateral Na+:HCO3- cotransporter in renal proximal tubules. Kidney Int 2000; 57:1063-71. [PMID: 10720958 DOI: 10.1046/j.1523-1755.2000.00933.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Studies have shown that glucocorticoids enhance HCO3- reabsorption in proximal tubules. Functional and molecular studies indicate that HCO3- reabsorption in proximal tubules is mediated via luminal H(+)-ATPase and Na+/H+ exchanger (NHE-3), and basolateral Na+:HCO3- cotransporter (NBC) acting in series. The purpose of these experiments was to examine the effect of adrenal steroids on NBC-1 and NHE-3 expression and activity in rat renal proximal tubules. METHODS Rats were injected subcutaneously with dexamethasone (100 mu/day) or deoxycorticosterone acetate (30 mg/kg), potent glucocorticoid, or mineralocorticoid analogues, respectively. Animals were sacrificed after two or four days, and NBC-1 and NHE-3 mRNA expression and activities were measured in cortex and proximal tubules. RESULTS Northern hybridizations indicated that cortical NBC-1 mRNA expression increased by approximately 92% in rats treated with dexamethasone for four days (N = 6, P < 0.03) but not two days. NHE-3 mRNA expression remained unchanged. NBC and NHE-3 activities were measured as the Na-dependent pHi recovery from an acid load in the presence or absence of HCO3-, respectively, and appropriate inhibitors in proximal tubule suspensions loaded with BCECF. NBC activity increased by approximately 80% in rats treated with dexamethasone for four days (P < 0.01, N = 5) but not two days. NHE-3 activity increased by 34 and 42% in rats treated with dexamethasone for two and four days, respectively (P < 0.05 and P < 0.02 for each group vs. control). Treatment with deoxycorticosterone acetate did not alter NBC-1 expression. CONCLUSION Glucocorticoids at pharmacologic concentrations enhance the mRNA expression and functional activity of renal proximal tubule NBC-1. Enhanced NBC and NHE-3 activities could result in increased HCO3- reabsorption in proximal tubule and could contribute to the maintenance of metabolic alkalosis in pathophysiologic states associated with increased glucocorticoid production.
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Affiliation(s)
- R Ali
- Department of Internal Medicine, University of Cincinnati, Ohio, USA
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Soleimani M, Burnham CE. Physiologic and molecular aspects of the Na+:HCO3- cotransporter in health and disease processes. Kidney Int 2000; 57:371-84. [PMID: 10652014 DOI: 10.1046/j.1523-1755.2000.00857.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Approximately 80% of the filtered load of HCO3- is reabsorbed in the proximal tubule via a process of active acid secretion by the luminal membrane. The major mechanism for the transport of HCO3- across the basolateral membrane is via the electrogenic Na+:3HCO3- cotransporter (NBC). Recent molecular cloning experiments have identified the existence of three NBC isoforms (NBC-1, NBC-2, and NBC-3).1 Functional and molecular studies indicate the presence of all three NBC isoforms in the kidney. All are presumed to mediate the cotransport of Na+ and HCO3- under normal conditions and may be functionally altered in certain pathophysiologic states. Specifically, NBC-1 may be up-regulated in metabolic acidosis and potassium depletion and in response to glucocorticoid excess and may be down-regulated in response to HCO3- loading or alkalosis. Recent studies provide molecular evidence indicating the expression of NBC-1 in pancreatic duct cells. NBC is activated by cystic fibrosis transmembrane conductance regulator (CFTR) and plays an important role in HCO3- secretion in the agonist-stimulated state in pancreatic duct cells. The purpose of this review is to summarize recent functional and molecular studies on the regulation of NBCs in physiologic and pathophysiologic states. Possible signals responsible for the regulation of NBCs in these conditions are examined. Furthermore, the possible role of this transporter in acid-base disorders (such as proximal renal tubular acidosis) is discussed.
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Affiliation(s)
- M Soleimani
- Department of Medicine, University of Cincinnati, and the Veterans Affairs Medical Center, Cincinnati, Ohio 45267-0585, USA.
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Chapter 12 Molecular physiology of mammalian epithelial Na+/H+ exchangers NHE2 and NHE3. CURRENT TOPICS IN MEMBRANES 2000. [DOI: 10.1016/s1063-5823(00)50014-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Silver RB, Soleimani M. H+-K+-ATPases: regulation and role in pathophysiological states. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:F799-811. [PMID: 10362769 DOI: 10.1152/ajprenal.1999.276.6.f799] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Molecular cloning experiments have identified the existence of two H+-K+-ATPases (HKAs), colonic and gastric. Recent functional and molecular studies indicate the presence of both transporters in the kidney, which are presumed to mediate the exchange of intracellular H+ for extracellular K+. On the basis of these studies, a picture is evolving that indicates differential regulation of HKAs at the molecular level in acid-base and electrolyte disorders. Of the two transporters, gastric HKA is expressed constitutively along the length of the collecting duct and is responsible for H+ secretion and K+ reabsorption under normal conditions and may be stimulated with acid-base perturbations and/or K+ depletion. This regulation may be species specific. To date there are no data to indicate that the colonic HKA (HKAc) plays a role in H+ secretion or K+ reabsorption under normal conditions. However, HKAc shows adaptive regulation in pathophysiological conditions such as K+ depletion, NaCl deficiency, and proximal renal tubular acidosis, suggesting an important role for this exchanger in potassium, HCO-3, and sodium (or chloride) reabsorption in disease states. The purpose of this review is to summarize recent functional and molecular studies on the regulation of HKAs in physiological and pathophysiological states. Possible signals responsible for regulation of HKAs in these conditions will be discussed. Furthermore, the role of these transporters in acid-base and electrolyte homeostasis will be evaluated in the context of genetically altered animals deficient in HKAc.
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Affiliation(s)
- R B Silver
- Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021, USA
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Amemiya M, Tabei K, Kusano E, Asano Y, Alpern RJ. Incubation of OKP cells in low-K+ media increases NHE3 activity after early decrease in intracellular pH. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C711-6. [PMID: 10069999 DOI: 10.1152/ajpcell.1999.276.3.c711] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic hypokalemia increases the activity of proximal tubule apical membrane Na+/H+ antiporter NHE3. The present study examined the effect of the incubation of OKP cells (an opossum kidney, clone P cell line) in control medium (K+ concn ([K+]) = 5.4 mM) or low-K+ medium ([K+] = 2.7 mM) on NHE3. The activity of an ethylisopropyl amiloride-resistant Na+/H+ antiporter, whose characteristics were consistent with those of NHE3, was increased in low-K+ cells beginning at 8 h. NHE3 mRNA and NHE3 protein abundance were increased 2.2-fold and 62%, respectively, at 24 h but not at 8 h. After incubation in low-K+ medium, intracellular pH (pHi) decreased by 0.27 pH units (maximum at 27 min) and then recovered to the control level. Intracellular acidosis induced by 5 mM sodium propionate increased Na+/H+ antiporter activity at 8 and 24 h. Herbimycin A, a tyrosine kinase inhibitor, blocked low-K+- and sodium propionate-induced activation of the Na+/H+ antiporter at 8 and 24 h. Our results demonstrate that low-K+ medium causes an early decrease in pHi, which leads to an increase in NHE3 activity via a tyrosine kinase pathway.
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Affiliation(s)
- M Amemiya
- Division of Nephrology, Department of Internal Medicine, Jichi Medical School, Tochigi, Japan 329-0498, USA
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Markovich D, Wang H, Puttaparthi K, Zajicek H, Rogers T, Murer H, Biber J, Levi M. Chronic K depletion inhibits renal brush border membrane Na/sulfate cotransport. Kidney Int 1999; 55:244-51. [PMID: 9893133 DOI: 10.1046/j.1523-1755.1999.00255.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The purpose of this study was to determine if dietary potassium (K) deficiency regulates renal proximal tubular sodium gradient-dependent sulfate transport (Na/Si cotransport) in the rat and, furthermore, determine if the regulation takes place at the level of the recently cloned Na/Si cotransport system (NaSi-1). Methods and Results. Rats treated chronically (seven days) with a K-deficient diet had a significant decrease in serum Si levels and an increase in fractional excretion of ultrafilterable Si, which paralleled a significant decrease in brush border membrane (BBM) Na/Si cotransport activity. The decrease in BBM Na/Si cotransport activity was associated with decreases in BBM NaSi-1 protein and renal cortical NaSi-1 mRNA abundance. In addition, in Xenopus oocytes injected with mRNA from kidney cortex slices of K-deficient rats, there was a significant reduction in the induced Na/Si cotransport, whereas there was no alteration in l-leucine uptake, suggesting that in K-deficient rats, there is a specific decrease in functional mRNA encoding the NaSi-1 mRNA. CONCLUSION These findings indicate that chronic K deficiency leads to a reduction in serum Si levels and an increase fractional excretion of Si, and reduces Si reabsorption by down-regulating the expression of the proximal tubular Na/Si-1 cotransporter protein and mRNA.
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Affiliation(s)
- D Markovich
- Department of Physiology and Pharmacology, University of Queensland, Australia; Institute of Physiology, University of Zurich, Zurich, Switzerland.
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Laghmani K, Chambrey R, Froissart M, Bichara M, Paillard M, Borensztein P. Adaptation of NHE-3 in the rat thick ascending limb: effects of high sodium intake and metabolic alkalosis. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:F18-26. [PMID: 9887076 DOI: 10.1152/ajprenal.1999.276.1.f18] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present studies examined the effects of chronic NaCl administration and metabolic alkalosis on NHE-3, an apical Na+/H+ exchanger of the rat medullary thick ascending limb of Henle (MTAL). NaCl administration had no effect on NHE-3 mRNA abundance as assessed by competitive RT-PCR, as well as on NHE-3 transport activity estimated from the Na+-dependent cell pH recovery of Na+-depleted acidified MTAL cells, in the presence of 50 microM Hoe-694, which specifically blocks NHE-1 and NHE-2. Two models of metabolic alkalosis were studied, one associated with high sodium intake, i.e., NaHCO3 administration, and one not associated with high sodium intake, i.e., chloride depletion alkalosis (CDA). In both cases, the treatment induced a significant metabolic alkalosis that was associated with a decrease in NHE-3 transport activity (-27% and -25%, respectively). Negative linear relationships were observed between NHE-3 activity and plasma pH or bicarbonate concentration. NHE-3 mRNA abundance and NHE-3 protein abundance, assessed by Western blot analysis, also decreased by 35 and 25%, respectively, during NaHCO3-induced alkalosis, and by 47 and 33%, respectively, during CDA. These studies demonstrate that high sodium intake has per se no effect on MTAL NHE-3. In contrast, chronic metabolic alkalosis, regardless of whether it is associated with high sodium intake or not, leads to an appropriate adaptation of NHE-3 activity, which involves a decrease in NHE-3 protein and mRNA abundance.
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Affiliation(s)
- K Laghmani
- Laboratoire de Physiologie et Endocrinologie Cellulaire Rénale, Institut National de la Santé et de la Recherche Médicale Unité 356, Broussais, 75270 Paris
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Nakamura S, Amlal H, Galla JH, Soleimani M. Colonic H+-K+-ATPase is induced and mediates increased HCO3- reabsorption in inner medullary collecting duct in potassium depletion. Kidney Int 1998; 54:1233-9. [PMID: 9767539 DOI: 10.1046/j.1523-1755.1998.00105.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Potassium depletion increases HCO3- reabsorption in outer medullary collecting duct (OMCD) by activation of colonic (c) H-K-ATPase (HKA). The purpose of the current experiments was to examine the role of the isoforms of HKA in HCO3- reabsorption by terminal inner medullary collecting duct (IMCD) cells in potassium depletion. METHODS Sprague-Dawley rats were fed a potassium-free diet and studied after 8 to 10 days. mRNA expression of HKA isoforms in terminal portion of inner medulla was examined and correlated with HCO3- reabsorption in the terminal IMCD. RESULTS Gastric (g) HKA mRNA decreased whereas colonic (c) HKA mRNA expression was heavily induced in terminal portion of inner medulla in potassium depleted rats. Net HCO3- flux (JtCO2) in terminal IMCD increased in potassium depletion (4.56 to 7.06 pmol/min/mm tubule length, P < 0.001). In normal rats, 1 mM ouabain in perfusate had no effect on JtCO2, whereas 10 microM Schering 28080 (SCH) decreased JtCO2 to 2.4 (P < 0.002). In KD rats, 1 mM ouabain decreased JtCO2 to 4.9 (P < 0.005) and 10 microM SCH decreased JtCO2 to 3.3 (P < 0.001). However, the inhibitory effects of SCH and ouabain on JtCO2 in potassium depleted animals were not additive. CONCLUSIONS The data indicate that gHKA is suppressed whereas cHKA is induced in potassium depletion and mediates increased HCO3- reabsorption in terminal IMCD. The results further indicate that cHKA in vivo is sensitive to both SCH and ouabain.
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Affiliation(s)
- S Nakamura
- Department of Medicine, University of Cincinnati School of Medicine, and Veterans Affairs Medical Center, Ohio, USA
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