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Kanbay M, Copur S, Guldan M, Ozbek L, Hatipoglu A, Covic A, Mallamaci F, Zoccali C. Proximal tubule hypertrophy and hyperfunction: a novel pathophysiological feature in disease states. Clin Kidney J 2024; 17:sfae195. [PMID: 39050867 PMCID: PMC11267238 DOI: 10.1093/ckj/sfae195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2024] [Indexed: 07/27/2024] Open
Abstract
The role of proximal tubules (PTs), a major component of the renal tubular structure in the renal cortex, has been examined extensively. Along with its physiological role in the reabsorption of various molecules, including electrolytes, amino acids and monosaccharides, transcellular transport of different hormones and regulation of homeostasis, pathological events affecting PTs may underlie multiple disease states. PT hypertrophy or a hyperfunctioning state, despite being a compensatory mechanism at first in response to various stimuli or alterations at tubular transport proteins, have been shown to be critical pathophysiological events leading to multiple disorders, including diabetes mellitus, obesity, metabolic syndrome and congestive heart failure. Moreover, pharmacotherapeutic agents have primarily targeted PTs, including sodium-glucose cotransporter 2, urate transporters and carbonic anhydrase enzymes. In this narrative review, we focus on the physiological role of PTs in healthy states and the current understanding of the PT pathologies leading to disease states and potential therapeutic targets.
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Affiliation(s)
- Mehmet Kanbay
- Department of Internal Medicine, Division of Nephrology, Koç University School of Medicine, Istanbul, Turkey
| | - Sidar Copur
- Department of Medicine, Koç University School of Medicine, Istanbul, Turkey
| | - Mustafa Guldan
- Department of Internal Medicine, Division of Internal Medicine, Koç University School of Medicine, Istanbul, Turkey
| | - Lasin Ozbek
- Department of Internal Medicine, Division of Internal Medicine, Koç University School of Medicine, Istanbul, Turkey
| | - Alper Hatipoglu
- Department of Internal Medicine, Division of Internal Medicine, Koç University School of Medicine, Istanbul, Turkey
| | - Adrian Covic
- Nephrology, Dialysis and Transplantation, University Grigore T Popa, Iasi, Romania
| | - Francesca Mallamaci
- Nephrology, Dialysis and Transplantation Unit, Grande Ospedale Metropolitano, Reggio Calabria, Italy
- CNR-IFC, Research Unit of Clinical Epidemiology and Physiopathology of Renal Diseases and Hypertension, Institute of Clinical Physiology, Reggio Calabria, Italy
| | - Carmine Zoccali
- Renal Research Institute, New York, NY, USA
- Institute of Molecular Biology and Genetics, Ariano Irpino, Italy
- Associazione Ipertensione Nefrologia Trapianto Renale, Grande Ospedale Metropolitano, c/o Nefrologia, Reggio Calabria, Italy
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2
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Zhang Q, Wang X, Chao Y, Liu L. Focus on oliguria during renal replacement therapy. J Anesth 2024:10.1007/s00540-024-03342-4. [PMID: 38777933 DOI: 10.1007/s00540-024-03342-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 04/29/2024] [Indexed: 05/25/2024]
Abstract
Oliguria is a clinical symptom characterized by decreased urine output, which can occur at any stage of acute kidney injury and also during renal replacement therapy. In some cases, oliguria may resolve with adjustment of blood purification dose or fluid management, while in others, it may suggest a need for further evaluation and intervention. It is important to determine the underlying cause of oliguria during renal replacement therapy and to develop an appropriate treatment plan. This review looks into the mechanisms of urine production to investigate the mechanism of oliguria during renal replacement therapy from two aspects: diminished glomerular filtration rate and tubular abnormalities. The above conditions all implying a renal oxygen supply-demand imbalance, which is the signal of worsening kidney injury. It also proposes a viable clinical pathway for the treatment and management of patients with acute kidney injury receiving renal replacement therapy.
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Affiliation(s)
- Qian Zhang
- Department of Intensive Care Unit (ICU), The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou, 550004, People's Republic of China
| | - Xiaoting Wang
- Department of Intensive Care Unit (ICU), Peking Union Medical College Hospital, Beijing, 100005, People's Republic of China
| | - Yangong Chao
- Department of Intensive Care Unit (ICU), The First Affiliated Hospital of Tsinghua University, Beijing, 100016, People's Republic of China
| | - Lixia Liu
- Department of Intensive Care Unit (ICU), The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei, 050011, People's Republic of China.
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3
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Clemente-Suárez VJ, Martín-Rodríguez A, Redondo-Flórez L, Villanueva-Tobaldo CV, Yáñez-Sepúlveda R, Tornero-Aguilera JF. Epithelial Transport in Disease: An Overview of Pathophysiology and Treatment. Cells 2023; 12:2455. [PMID: 37887299 PMCID: PMC10605148 DOI: 10.3390/cells12202455] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/11/2023] [Accepted: 10/13/2023] [Indexed: 10/28/2023] Open
Abstract
Epithelial transport is a multifaceted process crucial for maintaining normal physiological functions in the human body. This comprehensive review delves into the pathophysiological mechanisms underlying epithelial transport and its significance in disease pathogenesis. Beginning with an introduction to epithelial transport, it covers various forms, including ion, water, and nutrient transfer, followed by an exploration of the processes governing ion transport and hormonal regulation. The review then addresses genetic disorders, like cystic fibrosis and Bartter syndrome, that affect epithelial transport. Furthermore, it investigates the involvement of epithelial transport in the pathophysiology of conditions such as diarrhea, hypertension, and edema. Finally, the review analyzes the impact of renal disease on epithelial transport and highlights the potential for future research to uncover novel therapeutic interventions for conditions like cystic fibrosis, hypertension, and renal failure.
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Affiliation(s)
- Vicente Javier Clemente-Suárez
- Faculty of Sports Sciences, Universidad Europea de Madrid, Tajo Street, s/n, 28670 Madrid, Spain;
- Group de Investigación en Cultura, Educación y Sociedad, Universidad de la Costa, Barranquilla 080002, Colombia
| | | | - Laura Redondo-Flórez
- Department of Health Sciences, Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, C/Tajo s/n, Villaviciosa de Odón, 28670 Madrid, Spain; (L.R.-F.); (C.V.V.-T.)
| | - Carlota Valeria Villanueva-Tobaldo
- Department of Health Sciences, Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, C/Tajo s/n, Villaviciosa de Odón, 28670 Madrid, Spain; (L.R.-F.); (C.V.V.-T.)
| | - Rodrigo Yáñez-Sepúlveda
- Faculty of Education and Social Sciences, Universidad Andres Bello, Viña del Mar 2520000, Chile;
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4
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Nakagawa Y, Kaseda R, Suzuki Y, Watanabe H, Otsuka T, Yamamoto S, Kaneko Y, Goto S, Terada Y, Haishi T, Sasaki S, Narita I. Sodium Magnetic Resonance Imaging Shows Impairment of the Counter-current Multiplication System in Diabetic Mice Kidney. KIDNEY360 2023; 4:582-590. [PMID: 36963113 PMCID: PMC10278814 DOI: 10.34067/kid.0000000000000072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 01/17/2023] [Indexed: 03/26/2023]
Abstract
Key Points 23Na MRI allows us to noninvasively assess sodium distribution. We propose the utility of 23Na MRI for evaluating functional changes in diabetic kidney disease and not as a marker reflecting structural damage. 23Na MRI may be an early marker for structures beyond the glomeruli, enabling prompt intervention with novel efficacious tubule-targeting therapies. Background Sodium magnetic resonance imaging can noninvasively assess sodium distribution, specifically sodium concentration in the countercurrent multiplication system in the kidney, which forms a sodium concentration gradient from the cortex to the medulla, enabling efficient water reabsorption. This study aimed to investigate whether sodium magnetic resonance imaging can detect changes in sodium concentrations under normal conditions in mice and in disease models, such as a mouse model with diabetes mellitus. Methods We performed sodium and proton nuclear magnetic resonance imaging using a 9.4-T vertical standard-bore superconducting magnet. Results A condition of deep anesthesia, with widened breath intervals, or furosemide administration in 6-week-old C57BL/6JJcl mice showed a decrease in both tissue sodium concentrations in the medulla and sodium concentration gradients from the cortex to the medulla. Furthermore, sodium magnetic resonance imaging revealed reductions in the sodium concentration in the medulla and in the gradient from the cortex to the medulla in BKS.Cg-Leprdb+/+ Leprdb/Jcl mice at very early type 2 diabetes mellitus stages compared with corresponding control BKS.Cg-m+/m+/Jcl mice. Conclusions The kidneys of BKS.Cg-Leprdb+/+ Leprdb/Jcl mice aged 6 weeks showed impairments in the countercurrent multiplication system. We propose the utility of 23Na MRI for evaluating functional changes in diabetic kidney disease and not as a marker that reflects structural damage. Thus, 23Na MRI may be a potentially very early marker for structures beyond the glomerulus; this may prompt intervention with novel efficacious tubule-targeting therapies.
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Affiliation(s)
- Yusuke Nakagawa
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Ryohei Kaseda
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Yuya Suzuki
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Hirofumi Watanabe
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Tadashi Otsuka
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Suguru Yamamoto
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Yoshikatsu Kaneko
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Shin Goto
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
| | - Yasuhiko Terada
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Tomoyuki Haishi
- MRTechnology Inc., Tsukuba, Ibaraki, Japan
- Department of Radiological Sciences, School of Health Sciences at Narita, International University of Health and Welfare, Narita, Chiba, Japan
| | - Susumu Sasaki
- Faculty of Engineering, Niigata University, Niigata, Niigata, Japan
| | - Ichiei Narita
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University, Niigata, Niigata, Japan
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Freemas JA, Worley ML, Gabler MC, Hess HW, Mcdeavitt J, Baker TB, Johnson BD, Chapman CL, Schlader ZJ. Glomerular filtration rate reserve is reduced during mild passive heat stress in healthy young adults. Am J Physiol Regul Integr Comp Physiol 2022; 323:R340-R350. [PMID: 35816723 PMCID: PMC9423723 DOI: 10.1152/ajpregu.00090.2022] [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: 04/27/2022] [Revised: 06/16/2022] [Accepted: 07/07/2022] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that, compared with normothermia, the increase in glomerular filtration rate (GFR) after an oral protein load (defined as the GFR reserve) is attenuated during moderate passive heat stress in young healthy adults. Sixteen participants (5 women; 26 ± 2 yr) completed two experimental visits, heat stress or a normothermic time-control, assigned in a block-randomized crossover design. During the heat stress trial, core temperature was increased by 0.6°C in the first hour before commencing a 2-min cold pressor test (CPT) to assess renal vasoconstrictor responses. One-hour post-CPT, subjects ingested a whey protein shake (1.2 g of protein/kg body wt), and measurements were taken pre-, 75, and 150 min postprotein. Segmental artery vascular resistance was calculated as the quotient of Doppler ultrasound-derived segmental artery blood velocity and mean arterial pressure and provided an estimate of renal vascular tone. GFR was estimated from creatinine clearance. The increase in segmental artery vascular resistance during the CPT was attenuated during heat stress (end CPT: 5.6 ± 0.9 vs. 4.7 ± 1.1 mmHg/cm/s, P = 0.024). However, the reduction in segmental artery vascular resistance in response to an oral protein load did not differ between heat stress (at 150 min: 1.9 ± 0.4 mmHg/cm/s) and normothermia (at 150 min: 1.8 ± 0.5 mmHg/cm/s; P = 0.979). The peak increase in creatinine clearance postprotein, independent of time, was attenuated during heat stress (+26 ± 19 vs. +16 ± 20 mL/min, P = 0.013, n = 13). GFR reserve is diminished by mild passive heat stress. Moreover, renal vasoconstrictor responses are attenuated by mild passive heat stress, but renal vasodilator responses are maintained.
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Affiliation(s)
- Jessica A Freemas
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
| | - Morgan L Worley
- Department of Exercise and Nutrition Sciences, Center for Research and Education in Special Environments, University at Buffalo, Buffalo, New York
| | - Mikaela C Gabler
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
| | - Hayden W Hess
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
| | - Jovi Mcdeavitt
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
| | - Tyler B Baker
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
| | - Blair D Johnson
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
| | - Christopher L Chapman
- Department of Human Physiology, Bowerman Sports Science Center, University of Oregon, Eugene, Oregon
| | - Zachary J Schlader
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
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6
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Selechnik D, Richardson MF, Shine R, DeVore JL, Ducatez S, Rollins LA. Increased Adaptive Variation Despite Reduced Overall Genetic Diversity in a Rapidly Adapting Invader. Front Genet 2019; 10:1221. [PMID: 31850072 PMCID: PMC6901984 DOI: 10.3389/fgene.2019.01221] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 11/05/2019] [Indexed: 01/26/2023] Open
Abstract
Invasive species often evolve rapidly following introduction despite genetic bottlenecks that may result from small numbers of founders; however, some invasions may not fit this “genetic paradox”. The invasive cane toad (Rhinella marina) displays high phenotypic variation across its introduced Australian range. Here, we used three genome-wide datasets to characterize their population structure and genetic diversity. We found that toads form three genetic clusters: 1) native range toads, 2) toads from the source population in Hawaii and long-established areas near introduction sites in Australia, and 3) toads from more recently established northern Australian sites. Although we find an overall reduction in genetic diversity following introduction, we do not see this reduction in loci putatively under selection, suggesting that genetic diversity may have been maintained at ecologically relevant traits, or that mutation rates were high enough to maintain adaptive potential. Nonetheless, toads encounter novel environmental challenges in Australia, and the transition between genetic clusters occurs at a point along the invasion transect where temperature rises and rainfall decreases. We identify environmentally associated loci known to be involved in resistance to heat and dehydration. This study highlights that natural selection occurs rapidly and plays a vital role in shaping the structure of invasive populations.
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Affiliation(s)
- Daniel Selechnik
- School of Life and Environmental Sciences (SOLES), University of Sydney, Sydney, NSW, Australia.,Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Mark F Richardson
- Deakin Genomics Centre, School of Life and Environmental Sciences, Deakin University, Geelong, VIC, Australia.,Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, VIC, Australia
| | - Richard Shine
- School of Life and Environmental Sciences (SOLES), University of Sydney, Sydney, NSW, Australia
| | - Jayna L DeVore
- School of Life and Environmental Sciences (SOLES), University of Sydney, Sydney, NSW, Australia
| | - Simon Ducatez
- School of Life and Environmental Sciences (SOLES), University of Sydney, Sydney, NSW, Australia
| | - Lee A Rollins
- Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
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7
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Turck D, Castenmiller J, de Henauw S, Hirsch-Ernst KI, Kearney J, Knutsen HK, Maciuk A, Mangelsdorf I, McArdle HJ, Pelaez C, Pentieva K, Siani A, Thies F, Tsabouri S, Vinceti M, Aggett P, Fairweather-Tait S, Martin A, Przyrembel H, de Sesmaisons-Lecarré A, Naska A. Dietary reference values for chloride. EFSA J 2019; 17:e05779. [PMID: 32626426 PMCID: PMC7009052 DOI: 10.2903/j.efsa.2019.5779] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) has derived dietary reference values (DRVs) for chloride. There are no appropriate biomarkers of chloride status, no balance studies and no adequate evidence on the relationship between chloride intake and health outcomes that can be used to set DRVs for chloride. There is a close relationship between sodium and chloride balances in the body. Sodium chloride is the main source of both electrolytes in European diets and similar urinary excretion levels of sodium and chloride (on a molar basis) are typically observed in Western populations. Hence, the Panel considered that reference values for chloride can be set at values equimolar to the reference values for sodium for all population groups, and are as follows: 1.7 g/day for children aged 1-3 years, 2.0 g/day for children aged 4-6 years, 2.6 g/day for children aged 7-10 years, 3.1 g/day for children aged 11-17 years and 3.1 g/day for adults including pregnant and lactating women. Consistent with the reference values for sodium, these levels of chloride intake are considered to be safe and adequate for the general EU population, under the consideration that the main dietary source of chloride intake is sodium chloride. For infants aged 7-11 months, an adequate intake of 0.3 g/day is set.
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Turck D, Castenmiller J, de Henauw S, Hirsch-Ernst KI, Kearney J, Knutsen HK, Maciuk A, Mangelsdorf I, McArdle HJ, Pelaez C, Pentieva K, Siani A, Thies F, Tsabouri S, Vinceti M, Aggett P, Fairweather-Tait S, Martin A, Przyrembel H, Ciccolallo L, de Sesmaisons-Lecarré A, Valtueña Martinez S, Martino L, Naska A. Dietary reference values for sodium. EFSA J 2019; 17:e05778. [PMID: 32626425 PMCID: PMC7009309 DOI: 10.2903/j.efsa.2019.5778] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) derived dietary reference values (DRVs) for sodium. Evidence from balance studies on sodium and on the relationship between sodium intake and health outcomes, in particular cardiovascular disease (CVD)-related endpoints and bone health, was reviewed. The data were not sufficient to enable an average requirement (AR) or population reference intake (PRI) to be derived. However, by integrating the available evidence and associated uncertainties, the Panel considers that a sodium intake of 2.0 g/day represents a level of sodium for which there is sufficient confidence in a reduced risk of CVD in the general adult population. In addition, a sodium intake of 2.0 g/day is likely to allow most of the general adult population to maintain sodium balance. Therefore, the Panel considers that 2.0 g sodium/day is a safe and adequate intake for the general EU population of adults. The same value applies to pregnant and lactating women. Sodium intakes that are considered safe and adequate for children are extrapolated from the value for adults, adjusting for their respective energy requirement and including a growth factor, and are as follows: 1.1 g/day for children aged 1-3 years, 1.3 g/day for children aged 4-6 years, 1.7 g/day for children aged 7-10 years and 2.0 g/day for children aged 11-17 years, respectively. For infants aged 7-11 months, an Adequate Intake (AI) of 0.2 g/day is proposed based on upwards extrapolation of the estimated sodium intake in exclusively breast-fed infants aged 0-6 months.
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9
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Brewster LM, van Montfrans GA. Renin and Antihypertensive Drug Therapy in African Ancestry Patients. Am J Hypertens 2019; 32:617-619. [PMID: 30944923 DOI: 10.1093/ajh/hpz045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 03/25/2019] [Indexed: 11/12/2022] Open
Affiliation(s)
- Lizzy M Brewster
- Department of Cardiovascular Disease, Creatine Kinase Foundation, Amsterdam, The Netherlands
| | - Gert A van Montfrans
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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10
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Brewster LM, Oudman I, Nannan Panday RV, Khoyska I, Haan YC, Karamat FA, Clark JF, van Montfrans GA. Creatine kinase and renal sodium excretion in African and European men on a high sodium diet. J Clin Hypertens (Greenwich) 2018; 20:334-341. [PMID: 29357199 DOI: 10.1111/jch.13182] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 09/26/2017] [Accepted: 09/30/2017] [Indexed: 01/11/2023]
Abstract
Creatine kinase (CK) rapidly regenerates ATP for Na+ /K+ -ATPase driven sodium retention throughout the kidney. Therefore, we assessed whether resting plasma CK is associated with sodium retention after a high sodium diet. Sixty healthy men (29 European and 31 African ancestry) with a mean age of 37.2 years (SE 1.2) were assigned to low sodium intake (< 50 mmol/d) during 7 days, followed by 3 days of high sodium intake (> 200 mmol/d). Sodium excretion (mmol/24-h) after high sodium was 260.4 (28.3) in the high CK tertile versus 415.2 (26.3) mmol/24-h in the low CK tertile (P < .001), with a decrease in urinary sodium excretion of 98.4 mmol/24-h for each increase in log CK, adjusted for age and African ancestry. These preliminary results are in line with the energy buffering function of the CK system, but more direct assessments of kidney CK will be needed to further establish whether this enzyme enhances sodium sensitivity.
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Affiliation(s)
- Lizzy M Brewster
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Inge Oudman
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Rani V Nannan Panday
- Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Inna Khoyska
- Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Yentl C Haan
- Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Fares A Karamat
- Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Joseph F Clark
- The Vontz Center for Molecular Studies, University of Cincinnati, Cincinnati, OH, USA
| | - Gert A van Montfrans
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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11
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Layton AT, Laghmani K, Vallon V, Edwards A. Solute transport and oxygen consumption along the nephrons: effects of Na+ transport inhibitors. Am J Physiol Renal Physiol 2016; 311:F1217-F1229. [PMID: 27707706 DOI: 10.1152/ajprenal.00294.2016] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 09/28/2016] [Indexed: 01/11/2023] Open
Abstract
Sodium and its associated anions are the major determinant of extracellular fluid volume, and the reabsorption of Na+ by the kidney plays a crucial role in long-term blood pressure control. The goal of this study was to investigate the extent to which inhibitors of transepithelial Na+ transport (TNa) along the nephron alter urinary solute excretion and TNa efficiency and how those effects may vary along different nephron segments. To accomplish that goal, we used the multinephron model developed in the companion study (28). That model represents detailed transcellular and paracellular transport processes along the nephrons of a rat kidney. We simulated the inhibition of the Na+/H+ exchanger (NHE3), the bumetanide-sensitive Na+-K+-2Cl- transporter (NKCC2), the Na+-Cl- cotransporter (NCC), and the amiloride-sensitive Na+ channel (ENaC). Under baseline conditions, NHE3, NKCC2, NCC, and ENaC reabsorb 36, 22, 4, and 7%, respectively, of filtered Na+ The model predicted that inhibition of NHE3 substantially reduced proximal tubule TNa and oxygen consumption (QO2 ). Whole-kidney TNa efficiency, as reflected by the number of moles of Na+ reabsorbed per moles of O2 consumed (denoted by the ratio TNa/QO2 ), decreased by ∼20% with 80% inhibition of NHE3. NKCC2 inhibition simulations predicted a substantial reduction in thick ascending limb TNa and QO2 ; however, the effect on whole-kidney TNa/QO2 was minor. Tubular K+ transport was also substantially impaired, resulting in elevated urinary K+ excretion. The most notable effect of NCC inhibition was to increase the excretion of Na+, K+, and Cl-; its impact on whole-kidney TNa and its efficiency was minor. Inhibition of ENaC was predicted to have opposite effects on the excretion of Na+ (increased) and K+ (decreased) and to have only a minor impact on whole-kidney TNa and TNa/QO2 Overall, model predictions agree well with measured changes in Na+ and K+ excretion in response to diuretics and Na+ transporter mutations.
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Affiliation(s)
- Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina;
| | - Kamel Laghmani
- Sorbonne Universités, UPMC Univ Paris 06, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and
| | - Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego, La Jolla, California, and San Diego Veterans Affairs Healthcare System, San Diego, California
| | - Aurélie Edwards
- Sorbonne Universités, UPMC Univ Paris 06, Université Paris Descartes, Sorbonne Paris Cité, INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and
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12
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Hughes AD. How do thiazide and thiazide-like diuretics lower blood pressure? J Renin Angiotensin Aldosterone Syst 2016; 5:155-60. [PMID: 15803433 DOI: 10.3317/jraas.2004.034] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Thiazide diuretics are widely used for the treatment of hypertension, but the mechanism by which these drugs lower blood pressure in the long term remains unknown. This article reviews current knowledge about the hypotensive actions of thiazides and thiazide-like diuretics and discusses possible mechanisms of action.
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Affiliation(s)
- Alun D Hughes
- Clinical Pharmacology, Faculty of Medicine, Imperial College London, London W21NY, UK.
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Marx B, Scuvée É, Scuvée-Moreau J, Seutin V, Jouret F. [Mechanisms of caffeine-induced diuresis]. Med Sci (Paris) 2016; 32:485-90. [PMID: 27225921 DOI: 10.1051/medsci/20163205015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Caffeine is an alkaloid which belongs to the family of methylxanthines and is present in beverages, food and drugs. Caffeine competitively antagonizes the adenosine receptors (AR), which are G protein-coupled receptors largely distributed throughout the body, including brain, heart, vessels and kidneys. Caffeine consumption has a well-known diuretic effect. The homeostasis of salt and water involves different segments of the nephron, in which adenosine plays complex roles depending on the differential expression of AR. Hence, caffeine increases glomerular filtration rate by opposing the vasoconstriction of renal afferent arteriole mediated by adenosine via type 1 AR during the tubuloglomerular feedback. Caffeine also inhibits Na(+) reabsorption at the level of renal proximal tubules. In addition, caffeine perturbs the hepatorenal reflex via sensory nerves in Mall's intrahepatic spaces. Here, we review the physiology of caffeine-induced natriuresis and diuresis, as well as the putative pathological implications.
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Affiliation(s)
- Barbara Marx
- Faculté de médecine, université de Liège, 4000 Liège, Belgique
| | - Éléonore Scuvée
- Faculté de médecine, université de Liège, 4000 Liège, Belgique
| | - Jacqueline Scuvée-Moreau
- Service de pharmacologie et laboratoire de neurophysiologie, GIGA neurosciences, université de Liège, 4000 Liège, Belgique
| | - Vincent Seutin
- Service de pharmacologie et laboratoire de neurophysiologie, GIGA neurosciences, université de Liège, 4000 Liège, Belgique
| | - François Jouret
- GIGA cardiovasculaires, université de Liège, Avenue Hippocrate, 13, 4000 Liège, Belgique - Service de néphrologie, CHU de Liège, 4000 Liège Belgique
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LeVine MV, Cuendet MA, Khelashvili G, Weinstein H. Allosteric Mechanisms of Molecular Machines at the Membrane: Transport by Sodium-Coupled Symporters. Chem Rev 2016; 116:6552-87. [PMID: 26892914 DOI: 10.1021/acs.chemrev.5b00627] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Solute transport across cell membranes is ubiquitous in biology as an essential physiological process. Secondary active transporters couple the unfavorable process of solute transport against its concentration gradient to the energetically favorable transport of one or several ions. The study of such transporters over several decades indicates that their function involves complex allosteric mechanisms that are progressively being revealed in atomistic detail. We focus on two well-characterized sodium-coupled symporters: the bacterial amino acid transporter LeuT, which is the prototype for the "gated pore" mechanism in the mammalian synaptic monoamine transporters, and the archaeal GltPh, which is the prototype for the "elevator" mechanism in the mammalian excitatory amino acid transporters. We present the evidence for the role of allostery in the context of a quantitative formalism that can reconcile biochemical and biophysical data and thereby connects directly to recent insights into the molecular structure and dynamics of these proteins. We demonstrate that, while the structures and mechanisms of these transporters are very different, the available data suggest a common role of specific models of allostery in their functions. We argue that such allosteric mechanisms appear essential not only for sodium-coupled symport in general but also for the function of other types of molecular machines in the membrane.
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Affiliation(s)
- Michael V LeVine
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
| | - Michel A Cuendet
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
| | - George Khelashvili
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
| | - Harel Weinstein
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
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15
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Aniort J, Ait Hssain A, Pereira B, Coupez E, Pioche PA, Leroy C, Heng AE, Souweine B, Lautrette A. Daily urinary urea excretion to guide intermittent hemodialysis weaning in critically ill patients. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2016; 20:43. [PMID: 26895760 PMCID: PMC4761179 DOI: 10.1186/s13054-016-1225-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 02/10/2016] [Indexed: 12/18/2022]
Abstract
Background There are no easily available markers of renal recovery to guide intermittent hemodialysis (IHD) weaning. The aim of this study was to identify markers for IHD weaning in critically ill patients with acute kidney injury (AKI). Methods We performed a retrospective single-center cohort study of patients treated with IHD for at least 7 days and four dialysis sessions for AKI between 2006 and 2011 in an intensive care unit (ICU) of a French university hospital. Blood and urinary markers were recorded on the day of the last IHD in the ICU for unweaned patients and 2 days after the last IHD for weaned patients. Factors associated with IHD weaning were identified by multiple logistic regression. The areas under the receiver operating characteristic curve (AUROC) and the characteristics of the best diagnostic thresholds were compared. Results Sixty-seven patients were analyzed, including thirty-seven IHD-weaned patients. Urine output [odds ratio (OR) 1.59, 95 % confidence interval (CI) 1.20–2.10 (per ml/kg/24 h increase); P = 0.01] and urinary urea concentration [OR 1.29, 95 % CI 1.01–1.64 (per 10 mmol/L increase); P = 0.04] were both associated with IHD weaning. The optimal diagnostic thresholds for IHD weaning were urine output greater than 8.5 ml/kg/24 h, urinary urea concentration greater than 148 mmol/L, and daily urea excretion greater than 1.35 mmol/kg/24 h, with accuracy of 82.1 %, 76.1 %, and 92.5 % (P = 0.03), respectively. The AUROC of daily urinary urea excretion (0.96) was greater than the AUROC of urine output (0.86) or the AUROC of urinary urea concentration (0.83) (P < 0.001). Conclusions A daily urinary urea excretion greater than 1.35 mmol/kg/24 h was found to be the best marker for weaning ICU patients with AKI from IHD. Electronic supplementary material The online version of this article (doi:10.1186/s13054-016-1225-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Julien Aniort
- Nephrology, Dialysis and Transplantation Department, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, Clermont-Ferrand, France.
| | - Ali Ait Hssain
- Medical Intensive Care Unit, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, 54 rue Montalembert, BP69, 63003, Clermont-Ferrand, Cedex 1, France.
| | - Bruno Pereira
- Biostatistics and Research Department (DRCI), University Hospital of Clermont-Ferrand, Clermont-Ferrand, France.
| | - Elisabeth Coupez
- Medical Intensive Care Unit, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, 54 rue Montalembert, BP69, 63003, Clermont-Ferrand, Cedex 1, France.
| | - Pierre Antoine Pioche
- Medical Intensive Care Unit, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, 54 rue Montalembert, BP69, 63003, Clermont-Ferrand, Cedex 1, France.
| | - Christophe Leroy
- Medical Intensive Care Unit, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, 54 rue Montalembert, BP69, 63003, Clermont-Ferrand, Cedex 1, France.
| | - Anne Elisabeth Heng
- Nephrology, Dialysis and Transplantation Department, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, Clermont-Ferrand, France.
| | - Bertrand Souweine
- Medical Intensive Care Unit, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, 54 rue Montalembert, BP69, 63003, Clermont-Ferrand, Cedex 1, France. .,Laboratoire Micro-organismes: Génome et Environnement (LMGE), UMR CNRS 6023, Clermont-University, Clermont-Ferrand, France.
| | - Alexandre Lautrette
- Medical Intensive Care Unit, Gabriel Montpied Teaching Hospital, University Hospital of Clermont-Ferrand, 54 rue Montalembert, BP69, 63003, Clermont-Ferrand, Cedex 1, France. .,Laboratoire Micro-organismes: Génome et Environnement (LMGE), UMR CNRS 6023, Clermont-University, Clermont-Ferrand, France.
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16
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Kortenoeven MLA, Pedersen NB, Rosenbaek LL, Fenton RA. Vasopressin regulation of sodium transport in the distal nephron and collecting duct. Am J Physiol Renal Physiol 2015; 309:F280-99. [DOI: 10.1152/ajprenal.00093.2015] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 05/27/2015] [Indexed: 12/22/2022] Open
Abstract
Arginine vasopressin (AVP) is released from the posterior pituitary gland during states of hyperosmolality or hypovolemia. AVP is a peptide hormone, with antidiuretic and antinatriuretic properties. It allows the kidneys to increase body water retention predominantly by increasing the cell surface expression of aquaporin water channels in the collecting duct alongside increasing the osmotic driving forces for water reabsorption. The antinatriuretic effects of AVP are mediated by the regulation of sodium transport throughout the distal nephron, from the thick ascending limb through to the collecting duct, which in turn partially facilitates osmotic movement of water. In this review, we will discuss the regulatory role of AVP in sodium transport and summarize the effects of AVP on various molecular targets, including the sodium-potassium-chloride cotransporter NKCC2, the thiazide-sensitive sodium-chloride cotransporter NCC, and the epithelial sodium channel ENaC.
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Affiliation(s)
- M. L. A. Kortenoeven
- Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark
| | - N. B. Pedersen
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark; and
| | - L. L. Rosenbaek
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - R. A. Fenton
- Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark
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17
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Lee A, Slattery C, Nikolic-Paterson DJ, Hryciw DH, Wilk S, Wilk E, Zhang Y, Valova VA, Robinson PJ, Kelly DJ, Poronnik P. Chloride channel ClC-5 binds to aspartyl aminopeptidase to regulate renal albumin endocytosis. Am J Physiol Renal Physiol 2015; 308:F784-92. [DOI: 10.1152/ajprenal.00322.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 01/04/2015] [Indexed: 12/17/2022] Open
Abstract
ClC-5 is a chloride/proton exchanger that plays an obligate role in albumin uptake by the renal proximal tubule. ClC-5 forms an endocytic complex with the albumin receptor megalin/cubilin. We have identified a novel ClC-5 binding partner, cytosolic aspartyl aminopeptidase (DNPEP; EC 3.4.11.21), that catalyzes the release of N-terminal aspartate/glutamate residues. The physiological role of DNPEP remains largely unresolved. Mass spectrometric analysis of proteins binding to the glutathione- S-transferase (GST)-ClC-5 C terminus identified DNPEP as an interacting partner. Coimmunoprecipitation confirmed that DNPEP and ClC-5 also associated in cells. Further experiments using purified GST-ClC-5 and His-DNPEP proteins demonstrated that the two proteins bound directly to each other. In opossum kidney (OK) cells, confocal immunofluorescence studies revealed that DNPEP colocalized with albumin-containing endocytic vesicles. Overexpression of wild-type DNPEP increased cell-surface levels of ClC-5 and albumin uptake. Analysis of DNPEP-immunoprecipitated products from rat kidney lysate identified β-actin and tubulin, suggesting a role for DNPEP in cytoskeletal maintenance. A DNase I inhibition assay showed a significant decrease in the amount of G actin when DNPEP was overexpressed in OK cells, suggesting a role for DNPEP in stabilizing the cytoskeleton. DNPEP was not present in the urine of healthy rats; however, it was readily detected in the urine in rat models of mild and heavy proteinuria (diabetic nephropathy and anti-glomerular basement membrane disease, respectively). Urinary levels of DNPEP were found to correlate with the severity of proteinuria. Therefore, we have identified another key molecular component of the albumin endocytic machinery in the renal proximal tubule and describe a new role for DNPEP in stabilizing the actin cytoskeleton.
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Affiliation(s)
- Aven Lee
- UQ Centre for Clinical Research, The University of Queensland, Herston, Brisbane, Queensland, Australia
| | - Craig Slattery
- School of Biomolecular and Biomedical Sciences, University College Dublin, Belfield, Dublin, Republic. of Ireland
| | - David J. Nikolic-Paterson
- Department of Nephrology, Monash University Department of Medicine, Monash Medical Centre, Clayton, Victoria, Australia
| | - Deanne H. Hryciw
- Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia
| | - Sherwin Wilk
- Department of Pharmacology, Mount Sinai School of Medicine, New York, New York
| | - Elizabeth Wilk
- Department of Pharmacology, Mount Sinai School of Medicine, New York, New York
| | - Yuan Zhang
- Department of Medicine, Saint Vincent's Hospital, Fitzroy, Victoria, Australia
| | - Valentina A. Valova
- Children's Medical Research Institute, The University of Sydney, Westmead New South Wales, Australia; and
| | - Phillip J. Robinson
- Children's Medical Research Institute, The University of Sydney, Westmead New South Wales, Australia; and
| | - Darren J. Kelly
- Department of Medicine, Saint Vincent's Hospital, Fitzroy, Victoria, Australia
| | - Philip Poronnik
- School of Medical Sciences and the Bosch Institute, The University of Sydney, New South Wales, Australia
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18
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Itoh K, Izumi Y, Inoue T, Inoue H, Nakayama Y, Uematsu T, Fukuyama T, Yamazaki T, Yasuoka Y, Makino T, Nagaba Y, Tomita K, Kobayashi N, Kawahara K, Mukoyama M, Nonoguchi H. Expression of three isoforms of Na-K-2Cl cotransporter (NKCC2) in the kidney and regulation by dehydration. Biochem Biophys Res Commun 2014; 453:356-61. [PMID: 25265491 DOI: 10.1016/j.bbrc.2014.09.089] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 09/19/2014] [Indexed: 10/24/2022]
Abstract
Sodium reabsorption via Na-K-2Cl cotransporter 2 (NKCC2) in the thick ascending limbs has a major role for medullary osmotic gradient and subsequent water reabsorption in the collecting ducts. We investigated intrarenal localization of three isoforms of NKCC2 mRNA expressions and the effects of dehydration on them in rats. To further examine the mechanisms of dehydration, the effects of hyperosmolality on NKCC2 mRNA expression in microdissected renal tubules was studied. RT-PCR and RT-competitive PCR were employed. The expressions of NKCC2a and b mRNA were observed in the cortical thick ascending limbs (CAL) and the distal convoluted tubules (DCT) but not in the medullary thick ascending limbs (MAL), whereas NKCC2f mRNA expression was seen in MAL and CAL. Two-day dehydration did not affect these mRNA expressions. In contrast, hyperosmolality increased NKCC2 mRNA expression in MAL in vitro. Bradykinin dose-dependently decreased NKCC2 mRNA expression in MAL. However, dehydration did not change NKCC2 protein expression in membrane fraction from cortex and outer medulla and in microdissected MAL. These data show that NKCC2a/b and f types are mainly present in CAL and MAL, respectively. Although NKCC2 mRNA expression was stimulated by hyperosmolality in vitro, NKCC2 mRNA and protein expressions were not stimulated by dehydration in vivo. These data suggest the presence of the inhibitory factors for NKCC2 expression in dehydration. Considering the role of NKCC2 for the countercurrent multiplier system, NKCC2f expressed in MAL might be more important than NKCC2a/b.
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Affiliation(s)
- Kazuko Itoh
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan
| | - Yuichiro Izumi
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan
| | - Takeaki Inoue
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan
| | - Hideki Inoue
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan
| | - Yushi Nakayama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan
| | - Takayuki Uematsu
- Biomedical Laboratory, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan
| | - Takashi Fukuyama
- Biomedical Laboratory, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan
| | - Taiga Yamazaki
- Research Center for Medical Environment, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan
| | - Yukiko Yasuoka
- Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan
| | - Takeshi Makino
- Department of Nephrology, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan
| | - Yasushi Nagaba
- Department of Nephrology, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan
| | - Kimio Tomita
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan
| | - Noritada Kobayashi
- Biomedical Laboratory, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan
| | - Katsumasa Kawahara
- Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan
| | - Masashi Mukoyama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan
| | - Hiroshi Nonoguchi
- Department of Internal Medicine and Education & Research Center, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan.
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mTORC1 maintains renal tubular homeostasis and is essential in response to ischemic stress. Proc Natl Acad Sci U S A 2014; 111:E2817-26. [PMID: 24958889 DOI: 10.1073/pnas.1402352111] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) is a key regulator of cell metabolism and autophagy. Despite widespread clinical use of mTORC1 inhibitors, the role of mTORC1 in renal tubular function and kidney homeostasis remains elusive. By using constitutive and inducible deletion of conditional Raptor alleles in renal tubular epithelial cells, we discovered that mTORC1 deficiency caused a marked concentrating defect, loss of tubular cells, and slowly progressive renal fibrosis. Transcriptional profiling revealed that mTORC1 maintains renal tubular homeostasis by controlling mitochondrial metabolism and biogenesis as well as transcellular transport processes involved in countercurrent multiplication and urine concentration. Although mTORC2 partially compensated for the loss of mTORC1, exposure to ischemia and reperfusion injury exaggerated the tubular damage in mTORC1-deficient mice and caused pronounced apoptosis, diminished proliferation rates, and delayed recovery. These findings identify mTORC1 as an important regulator of tubular energy metabolism and as a crucial component of ischemic stress responses.
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20
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Sizova D, Velazquez H, Sampaio-Maia B, Quelhas-Santos J, Pestana M, Desir GV. Renalase regulates renal dopamine and phosphate metabolism. Am J Physiol Renal Physiol 2013; 305:F839-44. [PMID: 23863468 DOI: 10.1152/ajprenal.00616.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Renalase is a kidney-secreted catecholamines-degrading enzyme whose expression and activity are downregulated by increased dietary phosphate. A renalase knockout (KO) mouse model was used to explore the mechanisms mediating renalase's effect on phosphate excretion. Compared with wild-type (WT) mice maintained on a regular diet, KO mice show decreased serum PO4(-) (KO = 5.3 ± 0.2 vs. WT = 6.0 ± 0.1, n = 6; P < 0.04) and increased urinary PO4(-) excretion (urine PO4(-)/creatinine: KO = 7.7 ± 0.3 vs. WT = 6.1 ± 0.3, n = 6; P < 0.02). However, both WT and KO mice respond similarly to PO4(-) restriction by increasing renal COMT-1 activity and markedly decreasing PO4(-) excretion, which excludes an intrinsic renal defect in the KO. Renal sodium-phosphate cotransporter Npt2a, sodium proton exchanger NHE3 expression, and MAO-A and B activity did not differ between WT and KO. Only catechol-O-methyl transferase (COMT) expression and activity were significantly increased in KO mice. Despite that, urinary dopamine increased by twofold, whereas urinary l-DOPA excretion decreased by twofold in the KO mouse, indicating an upregulation of renal dopamine (DA) synthesis. These data indicate that renalase deficiency is associated with increased renal DA synthesis, stimulated PO4(-) excretion, and moderately severe hypophosphatemia. The signal to increase renal DA synthesis is strong since it overcomes a compensatory increase in COMT activity.
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Affiliation(s)
- Daria Sizova
- Section of Nephrology, Dept. of Medicine, Yale School of Medicine, P.O. Box 208029, New Haven, CT 06520-8029.
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Silva GB, Atchison DK, Juncos LI, García NH. Anandamide inhibits transport-related oxygen consumption in the loop of Henle by activating CB1 receptors. Am J Physiol Renal Physiol 2012; 304:F376-81. [PMID: 23220721 DOI: 10.1152/ajprenal.00239.2012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The energy required for active Na chloride reabsorption in the thick ascending limb (TAL) depends on oxygen consumption and oxidative phosphorylation (OXP). In other cells, Na transport is inhibited by the endogenous cannabinoid anandamide through the activation of the cannabinoid receptors (CB) type 1 and 2. However, it is unclear whether anandamide alters TAL transport and the mechanisms that could be involved. We hypothesized that anandamide inhibits TAL transport via activation of CB1 receptors and NO. For this, we measured oxygen consumption (Q(O(2))) in TAL suspensions to monitor the anandamide effects on transport and OXP. Anandamide reduced Q(O(2)) in a concentration-dependent manner. During Na-K-2Cl cotransport and Na/H exchange inhibition, anandamide did not inhibit TAL Q(O(2)). To test the role of the cannabinoid receptors, we used specific agonists and antagonists of CB1 and CB2 receptors. The CB1-selective agonist WIN55212-2 reduced Q(O(2)) in a concentration-dependent manner. Also, the CB1 receptor antagonist rimonabant blocked the effect of anandamide on Q(O(2)). In contrast, the CB2-selective agonist JHW-133 had no effect on Q(O(2)), while the CB2 receptor antagonist AM-630 failed to block the anandamide effects on Q(O(2)). To confirm these results, we measured CB1 and CB2 receptor expression and only CB1 expression was detected. Because CB1 receptors are strong nitric oxide synthase (NOS) stimulators and NO inhibits transport in TALs, we evaluated the role of NO. Anandamide stimulated NO production and the NOS inhibitor N(G)-nitro-L-arginine methyl ester blocked the anandamide effects on Q(O(2)). We conclude that anandamide inhibits TAL Na transport-related Q(O(2)) via activation of CB1 receptor and NOS.
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Affiliation(s)
- Guillermo B Silva
- School of Chemistry Science, Catholic Univ. of Córdoba, Consejo Nacional de Investigaciones Científicas y Técnicas, Córdoba, Argentina.
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Role of renalase in the regulation of blood pressure and the renal dopamine system. Curr Opin Nephrol Hypertens 2011; 20:31-6. [PMID: 21099685 DOI: 10.1097/mnh.0b013e3283412721] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
PURPOSE OF REVIEW Renalase is a secreted amine oxidase that is synthesized in the kidney, and that metabolizes circulating catecholamines. Tissue and plasma renalase levels are decreased in models of chronic kidney disease. Recent data indicate that renalase deficiency is associated with increased blood pressure and elevated circulating catecholamines. The mechanisms of hypertension in renalase deficiency and the possibility that renalase regulates the renal dopamine system are discussed. RECENT FINDINGS Characterization of the renalase knockout mouse model revealed that renalase deficiency increases SBP and DBP. Renal and cardiac functions are unaffected, but there is evidence of sympathetic activation, with elevation of plasma and urine catecholamines. Renalase is continually excreted in urine, and is enzymatically active and could modulate catecholamines levels in tubular fluid. Renalase expression is modulated by salt intake, and recombinant renalase has a potent and prolonged hypotensive effect on blood pressure in Dahl salt-sensitive rats and rats with chronic kidney disease. Plasma renalase levels are inversely associated with SBP in patients with resistant hypertension. A functional mutation in renalase (Glu37Asp) associated with essential hypertension also predicts more severe cardiac hypertrophy, dysfunction, and ischemia in individuals with stable coronary artery disease, comparable blood pressure and normal renal function. SUMMARY Urinary renalase metabolizes urinary catecholamines, and perhaps regulates dopamine concentration in luminal fluid, and modulate proximal tubular sodium transport. Renalase deficiency is associated with increased sympathetic tone and resistant hypertension. Recombinant renalase is a potent antihypertensive agent in Dahl salt-sensitive rats and in rats with chronic kidney disease.
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23
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Silva GB, Garvin JL. Rac1 mediates NaCl-induced superoxide generation in the thick ascending limb. Am J Physiol Renal Physiol 2009; 298:F421-5. [PMID: 19923407 DOI: 10.1152/ajprenal.00472.2009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Superoxide (O(2)(-)) produced by NADPH oxidase regulates Na absorption and renal hemodynamics. Increased NaCl in the thick ascending limb (TAL) stimulates O(2)(-) generation. However, we do not know whether physiological changes in NaCl concentration augment O(2)(-) generation, nor do we know the mediator(s) involved. In other cells, Rac1, a regulatory subunit of NADPH oxidase, is activated by elevated NaCl. We hypothesized that increasing luminal NaCl within the physiological range activates Rac1 and NADPH oxidase and, thereby, increases O(2)(-) production. We increased NaCl from 10 to 57 mM in medullary TAL suspensions and used lucigenin to measure O(2)(-) generation and Western blot to measure Rac1 activity. Increasing NaCl stimulated O(2)(-) generation from 1.41 +/- 0.16 to 2.71 +/- 0.30 nmol O(2)(-) x min(-1) x mg protein(-1) (n = 6, P < 0.05). This increase was blocked by the Na-K-2Cl cotransporter inhibitor furosemide and the NADPH oxidase inhibitor apocynin. To examine the role of Rac1 in NaCl-induced O(2)(-) production, we measured Rac1 translocation by Western blot. When we added NaCl, Rac1 in the particulate fraction increased from 6.8 +/- 0.8 to 11.7 +/- 2.4% of total Rac1 (n = 7, P < 0.05). Then we measured O(2)(-) generation in the presence and absence of the Rac1 inhibitor. In the absence of the Rac1 inhibitor, NaCl increased O(2)(-) generation from 1.07 +/- 0.24 to 2.02 +/- 0.49 nmol O(2)(-) x min(-1) x mg protein(-1), and this increase was completely blocked by the inhibitor. Similarly, in vivo treatment of TALs with adenovirus expressing dominant-negative Rac1 decreased NaCl-induced O(2)(-) generation by 60% compared with control (0.33 +/- 0.04 vs. 0.81 +/- 0.17 nmol O(2)(-) x min(-1) x mg protein(-1), n = 6, P < 0.05). We concluded that physiological increases in NaCl stimulate TAL O(2)(-) generation by activating Rac1.
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Affiliation(s)
- Guillermo B Silva
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Mchigan 48202, USA
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Abstract
Hyponatraemia is a commonly encountered electrolyte abnormality in hospitalised patients and is associated with significant morbidity and mortality. The fact that most cases of hyponatraemia are the result of water imbalance rather than sodium imbalance underscores the role of antidiuretic hormone (ADH) in the pathophysiology. Hyponatraemia can be classified according to the measured plasma osmolality as isotonic, hypertonic or hypotonic. Hyponatraemia with a normal plasma osmolality usually indicates pseudohyponatraemia, while hyponatraemia because of a high plasma osmolality is typically caused by hyperglycaemia. After excluding isotonic and hypertonic causes, hypotonic hyponatraemia is further classified according to the volume status of the patient as hypovolaemic, hypervolaemic or euvolaemic. Hypovolaemic hyponatraemia is accompanied by extracellular fluid (ECF) volume deficit, while hypervolaemic hyponatraemia manifests with ECF volume expansion. The syndrome of inappropriate ADH (SIADH) should be suspected in any patient with euvolaemic hyponatraemia with a urine osmolality above 100 mOsm/kg and urine sodium concentration above 40 mEq/l. In the management of any hyponatraemia regardless of the patient's volume status, it is advised to restrict free water and hypotonic fluid intake. Hypertonic saline and vasopressin antagonists can be used to correct symptomatic hyponatraemia. The rate of correction is dependent upon the duration, degree of hyponatraemia and the presence or absence of symptoms. Symptomatic acute hyponatraemia (< 48 h) is a medical emergency requiring rapid correction to prevent the worsening of brain oedema. In asymptomatic patients with chronic hyponatraemia (> 48 h or unknown duration), fluid restriction and close monitoring alone are sufficient, while a slow correction by 0.5 mEq/l/h may be attempted in symptomatic patients. Excessive rapid correction should be avoided in both acute and chronic hyponatraemia, because it can lead to irreversible neurological complications including central osmotic demyelination.
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Affiliation(s)
- P Reddy
- Department of Medicine, University of Florida College of Medicine, Jacksonville, FL 32209, USA
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Yamada T, Niisato N, Marunaka Y. Effects of extracellular chloride ion on epithelial sodium channel (ENaC) in arginine vasotocin (AVT)-stimulated renal epithelial cells. ACTA ACUST UNITED AC 2009; 30:193-8. [PMID: 19574722 DOI: 10.2220/biomedres.30.193] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The epithelial Na(+) channel (ENaC) contributes to control of blood pressure by reabsorbing Na(+) in the cortical collecting duct of the kidney. The luminal Cl(-) concentration in the duct varies under physiological conditions. As the body Na(+) content is lower, the luminal Cl(-) concentration in the duct becomes lower. Thus, we hypothesized that the extracellular Cl(-) elevates ENaC activity in AVT-stimulated renal epithelial A6 cells (a model cell line of the cortical collecting duct) leading to recovery from a low body Na(+) content. To clarify this point, we studied effects of extracellular Cl(-) concentration on ENaC activity using cell-attached patch clamp technique. We found that ENaC had a single-channel conductance of 4.6 +/- 0.1 pS (mean +/- SE) and channel activity (open probability, Po) of 0.30 +/- 0.02 at a pipette potential of 60 mV. Lowering pipette Cl(-) concentration diminished Po to 0.23 +/- 0.02 associated with a significant decrease in open time from 0.78 +/- 0.03 to 0.61 +/- 0.02 s with no significant change in closed time, and shifted the current-voltage relationship leftward. These results suggest that the extracellular Cl(-) regulates the ENaC-mediated Na(+) reabsorption by affecting ENaC properties in AVT-stimulated renal epithelial cells.
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Affiliation(s)
- Toshiki Yamada
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
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Silva GB, Garvin JL. Extracellular ATP inhibits transport in medullary thick ascending limbs: role of P2X receptors. Am J Physiol Renal Physiol 2009; 297:F1168-73. [PMID: 19710240 DOI: 10.1152/ajprenal.00325.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Absorption of NaCl by the thick ascending limb (TAL) involves active transport and therefore depends on oxidative phosphorylation. Extracellular ATP has pleiotropic effects, including both stimulation and inhibition of transport and inhibition of oxidative phosphorylation. However, it is unclear whether ATP alters TAL transport and how this occurs. We hypothesized that ATP inhibits TAL Na absorption by reducing Na entry. We measured oxygen consumption in TAL suspensions. ATP reduced oxygen consumption in a concentration-dependent manner. The purinergic (P2) receptor antagonist suramin (300 microM) blocked the effect of ATP on TAL oxygen consumption (147 +/- 15 vs. 146 +/- 16 nmol O2 x min(-1) x mg protein(-1)). In contrast, the adenosine receptor antagonist theophylline did not block the effect of ATP on oxygen consumption. When Na-K-2Cl cotransport and Na/H exchange were blocked with furosemide (100 microM) plus dimethyl amiloride (100 microM), ATP did not inhibit TAL oxygen consumption (from 78 +/- 13 to 98 +/- 5 nmol O2 x min(-1) x mg protein(-1)). The Na ionophore nystatin (200 U/ml) increased TAL oxygen consumption to a similar extent in both ATP- and vehicle-treated samples (368 +/- 41 vs. 397 +/- 47 nmol O2 x min(-1) x mg protein(-1)). The nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (3 mM) blocked the ATP effects on TAL oxygen consumption (157 +/- 10 vs. 165 +/- 15 nmol O2 x min(-1) x mg protein(-1)). The P2X-selective receptor antagonist NF023 blocked the effect of ATP on oxygen consumption, whereas the P2X-selective agonist beta-gamma-Me-ATP reduced oxygen consumption in a concentration-dependent manner. We conclude that ATP inhibits Na transport-related oxygen consumption in TALs by reducing Na entry and P2X receptors and nitric oxide mediate this effect.
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Low creatine kinase is associated with a high population incidence of fainting. Clin Auton Res 2009; 19:231-6. [PMID: 19468786 PMCID: PMC2720582 DOI: 10.1007/s10286-009-0013-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 04/03/2009] [Indexed: 11/21/2022]
Abstract
Objective Vasoconstrictor capacity, skeletal muscle tone, and renal sodium retention are involved in the pathogenesis of fainting. As muscle contractility and ion transport are highly energy-demanding processes, we hypothesized that a low activity of the energy-generating enzyme creatine kinase (CK) is associated with a higher risk of fainting. The aim of this observational study was to explore the association of vasovagal syncope with low CK. Methods A random sample of 1,000 subjects aged 34–60 years was drawn from the general population, with 442 subjects eventually included in the study. Data on fainting history were collected with the investigators blinded to participants’ CK level. We prepared this report according to the “Strengthening the Reporting of Observational Studies in Epidemiology” (STROBE) statement. The main outcome was the lifetime cumulative incidence of vasovagal syncope in subjects with low versus high-normal serum CK after a 3 days rest. Results The proportion of fainters within the high CK group was 29 out of 130 (22%) versus 121 out of 312 (39%) in the low CK group; a 73% greater occurrence of fainting with low CK (P = 0.0005). This finding was consistent across recurrent fainters, and in men and women. Interpretation Low CK is associated with a 73% higher incidence of fainting in a random population sample. The association is biologically plausible, as CK enhances cardiovascular and skeletal muscle contractility and salt retention. The presented data suggest that low CK activity is a potential new risk factor for vasovagal syncope.
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Fogelgren B, Yang S, Sharp IC, Huckstep OJ, Ma W, Somponpun SJ, Carlson EC, Uyehara CFT, Lozanoff S. Deficiency in Six2 during prenatal development is associated with reduced nephron number, chronic renal failure, and hypertension in Br/+ adult mice. Am J Physiol Renal Physiol 2009; 296:F1166-78. [PMID: 19193724 DOI: 10.1152/ajprenal.90550.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Br/+ mutant mouse displays decreased embryological expression of the homeobox transcription factor Six2, resulting in hertitable renal hypoplasia. The purpose of this study was to characterize the renal physiological consequences of embryonic haploinsuffiency of Six2 by analyzing renal morphology and function in the adult Br heterozygous mutant. Adult Br/+ kidneys weighed 50% less than those from wild-type mice and displayed glomerulopathy. Stereological analysis of renal glomeruli showed that Br/+ kidneys had an average of 88% fewer glomeruli than +/+ kidneys, whereas individual glomeruli in Br/+ mice maintained an average volume increase of 180% compared with normal nephrons. Immunostaining revealed increased levels of endothelin-1 (ET-1), endothelin receptors A (ET(A)) and B (ET(B)), and Na-K-ATPase were present in the dilated renal tubules of mutant mice. Physiological features of chronic renal failure (CRF) including elevated mean arterial pressure, increased plasma creatinine, and dilute urine excretion were measured in Br/+ mutant mice. Electron microscopy of the Br/+ glomeruli revealed pathological alterations such as hypercellularity, extracellular matrix accumulation, and a thick irregular glomerular basement membrane. These results indicate that adult Br/+ mice suffer from CRF associated with reduced nephron number and renal hypoplasia, as well as glomerulopathy. Defects are associated with embryological deficiencies of Six2, suggesting that proper levels of this protein during nephrogenesis are critical for normal glomerular development and adult renal function.
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Affiliation(s)
- Ben Fogelgren
- Deptartment of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA
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Amaral JS, Pinho MJ, Soares-da-Silva P. Regulation of amino acid transporters in the rat remnant kidney. Nephrol Dial Transplant 2009; 24:2058-67. [PMID: 19155532 DOI: 10.1093/ndt/gfn752] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Partial renal ablation is associated with compensatory renal growth, significant azotaemia, a significant increase in fractional excretion of sodium and changes in solute transport. The present study evaluated the occurrence of adaptations in the remnant kidney, especially in renal amino acid transporters and sodium transporters and their putative role in sodium handling in the early stages (24 h and 1 week) after uninephrectomy. METHODS Wistar rats aged 8 weeks old were submitted to renal ablation of the right kidney--Unx rats (n = 10). 24 hours (n = 5) and 1 week (n = 5) after surgery, rats were anesthetized and the left kidney was removed. Urinary and plasmatic levels of catecholamines, sodium, urea and creatinine were measured. Gene expression of the amino acid and sodium transporters was determined by Real-time reverse transcription PCR. Protein expression was evaluated by Western blot using specific antibodies for the amino acid and sodium transporters. RESULTS Uninephrectomized (Unx) rats for 24 h showed a lower urinary excretion of L-DOPA, dopamine and DOPAC than the corresponding Sham rats, accompanied by an increase in the expression of the Na(+)-K(+)-ATPase protein (64% increase). Unx rats for 1 week presented a hypertrophied remnant kidney, higher urine outflow and a approximately 2-fold increase in the fractional excretion of sodium. The NHE3 mRNA expression was significantly decreased in Unx rats throughout the study (approximately 20% decrease). LAT1 transcript and protein were consistently overexpressed at both 24 h and 1 week after uninephrectomy. In contrast, 4F2hc and LAT2 transcript abundance was lower in 24-h Unx rats than in Sham rats (a 36% decrease in both cases). CONCLUSIONS These results provide evidence that the renal expression of the amino acid transporters LAT1, LAT2 and 4F2hc and the sodium transporters Na(+)-K(+)-ATPase and NHE3 is differently regulated following unilateral nephrectomy. In conclusion, this study allowed us to characterize the renal adaptations in the early stages after uninephrectomy, which showed a combined interaction of multiple mechanisms regulating sodium homeostasis including the renal dopaminergic system, and the abundance of amino acid transporters and sodium transporters.
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Affiliation(s)
- João S Amaral
- Institute of Pharmacology and Therapeutics, Faculty of Medicine, 4200-319 Porto, Portugal
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Neuberger T, Gulani V, Webb A. Sodium renal imaging in mice at high magnetic fields. Magn Reson Med 2007; 58:1067-71. [PMID: 17969112 DOI: 10.1002/mrm.21402] [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] [Received: 02/15/2007] [Accepted: 08/02/2007] [Indexed: 11/05/2022]
Abstract
This work presents the first sodium MRI functional renal study on a mouse model. The tissue sodium concentration was monitored during induced diuresis with furosemide. By using density-weighted chemical shift imaging (DWCSI) at high field strength a temporal resolution of less than 5 min for three dimensional (3D) data sets with high spatial resolution was achieved. A maximum increase of 20% in the cortex and a decrease of 45% of the original signal strength in the medulla were observed. These findings correspond well with experiments conducted on much larger rodent models.
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Affiliation(s)
- Thomas Neuberger
- Department of Experimental Physics V, University of Würzburg, Würzburg, Germany
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Esteva-Font C, Torra Balcells R, Fernández-Llama P. Transportadores de sodio y aquaporinas: ¿futuros biomarcadores renales? Med Clin (Barc) 2007; 129:433-7. [DOI: 10.1157/13110477] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Drumm K, Kress TR, Gassner B, Krug AW, Gekle M. Aldosterone stimulates activity and surface expression of NHE3 in human primary proximal tubule epithelial cells (RPTEC). Cell Physiol Biochem 2006; 17:21-8. [PMID: 16543718 DOI: 10.1159/000091456] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The steroid hormone aldosterone is a major regulator of extracellular volume and blood pressure. Aldosterone effectors are for example the epithelial Na(+) channel (ENaC), the Na(+)-K(+)-ATPase and the proximal tubule Na(+)/H(+) exchanger isoform 3 (NHE3). The aim of this study was to investigate whether aldosterone acts directly on proximal tubule cells to stimulate NHE3 and if so whether the EGF-receptor (EGFR) is involved. For this purpose, primary human renal proximal tubule cells were exposed to aldosterone. NHE3 activity was determined from Na(+)- dependent pH-recovery, NHE3 surface expression was determined by biotinylation and immunoblotting. EGFR-expression was assessed by ELISA. pH(i)- measurements revealed an aldosterone-induced increase in NHE3 activity, which was inhibited by the mineralocorticoid receptor blocker spironolactone and by the EGFR-kinase inhibitor AG1478. Immunoprecipitation and immunoblot analysis showed an aldosterone-induced increase in NHE3 surface expression, which was also inhibited by spironolactone and AG1478. Furthermore, aldosterone enhanced EGFR-expression. In conclusion, aldosterone stimulates NHE3 in human proximal tubule cells. The underlying mechanisms include AG1478 inhibitable kinase and are paralleled by enhanced EGFR expression, which could be compatible with EGF-receptor-pathway-dependent surface expression and activity of NHE3 in human primary renal proximal tubule epithelial cells.
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Affiliation(s)
- Karina Drumm
- Institute of Physiology, University of Wuerzburg, Germany.
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Nascimento Gomes G, Barbosa FT, Radaeli RF, Cavanal MF, Mello Aires M, Zaladek Gil F. Effect of D-alpha-tocopherol on tubular nephron acidification by rats with induced diabetes mellitus. Braz J Med Biol Res 2005; 38:1043-51. [PMID: 16007275 DOI: 10.1590/s0100-879x2005000700007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objective of the present study was to determine if treatment of diabetic rats with D-alpha-tocopherol could prevent the changes in glomerular and tubular function commonly observed in this disease. Sixty male Wistar rats divided into four groups were studied: control (C), control treated with D-alpha-tocopherol (C + T), diabetic (D), and diabetic treated with D-alpha-tocopherol (D + T). Treatment with D-alpha-tocopherol (40 mg/kg every other day, ip) was started three days after diabetes induction with streptozotocin (60 mg/kg, ip). Renal function studies and microperfusion measurements were performed 30 days after diabetes induction and the kidneys were removed for morphometric analyses. Data are reported as means +/- SEM. Glomerular filtration rate increased in D rats but decreased in D + T rats (C: 6.43 +/- 0.21; D: 7.74 +/- 0.45; D + T: 3.86 +/- 0.18 ml min-1 kg-1). Alterations of tubular acidification observed in bicarbonate absorption flux (JHCO3) and in acidification half-time (t/2) in group D were reversed in group D + T (JHCO3, C: 2.30 +/- 0.10; D: 3.28 +/- 0.22; D + T: 1.87 +/- 0.08 nmol cm-2 s-1; t/2, C: 4.75 +/- 0.20; D: 3.52 +/- 0.15; D + T: 5.92 +/- 0.19 s). Glomerular area was significantly increased in D, while D + T rats exhibited values similar to C, suggesting that the vitamin prevented the hypertrophic effect of hyperglycemia (C: 8334.21 +/- 112.05; D: 10,217.55 +/- 100.66; D + T: 8478.21 +/- 119.81 microm(2)). These results suggest that D-alpha-tocopherol is able to protect rats, at least in part, from the harmful effects of diabetes on renal function.
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Affiliation(s)
- G Nascimento Gomes
- Departamento de Fisiologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil.
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Gamba G. Molecular Physiology and Pathophysiology of Electroneutral Cation-Chloride Cotransporters. Physiol Rev 2005; 85:423-93. [PMID: 15788703 DOI: 10.1152/physrev.00011.2004] [Citation(s) in RCA: 572] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Electroneutral cation-Cl−cotransporters compose a family of solute carriers in which cation (Na+or K+) movement through the plasma membrane is always accompanied by Cl−in a 1:1 stoichiometry. Seven well-characterized members include one gene encoding the thiazide-sensitive Na+−Cl−cotransporter, two genes encoding loop diuretic-sensitive Na+−K+−2Cl−cotransporters, and four genes encoding K+−Cl−cotransporters. These membrane proteins are involved in several physiological activities including transepithelial ion absorption and secretion, cell volume regulation, and setting intracellular Cl−concentration below or above its electrochemical potential equilibrium. In addition, members of this family play an important role in cardiovascular and neuronal pharmacology and pathophysiology. Some of these cotransporters serve as targets for loop diuretics and thiazide-type diuretics, which are among the most commonly prescribed drugs in the world, and inactivating mutations of three members of the family cause inherited diseases such as Bartter's, Gitelman's, and Anderman's diseases. Major advances have been made in the past decade as consequences of molecular identification of all members in this family. This work is a comprehensive review of the knowledge that has evolved in this area and includes molecular biology of each gene, functional properties of identified cotransporters, structure-function relationships, and physiological and pathophysiological roles of each cotransporter.
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Affiliation(s)
- Gerardo Gamba
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Universidad Nacional Autónoma de México, Mexico City, Mexico.
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Fernández-Llama P, Ageloff S, Fernández-Varo G, Ros J, Wang X, Garra N, Esteva-Font C, Ballarin J, Barcelo P, Arroyo V, Stokes JB, Knepper MA, Jiménez W. Sodium retention in cirrhotic rats is associated with increased renal abundance of sodium transporter proteins. Kidney Int 2005; 67:622-30. [PMID: 15673309 DOI: 10.1111/j.1523-1755.2005.67118.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
BACKGROUND Liver cirrhosis with ascites is associated with a decrease in renal sodium excretion and therefore sodium retention. METHODS In this paper, we utilize transporter-specific antibodies to address the hypothesis that dysregulation of one or more sodium transporters or channels is associated with sodium chloride (NaCl) retention in a rat model of cirrhosis induced by repeated exposure to carbon tetrachloride. Age-matched controls and cirrhotic rats were pair fed to ensure identical NaCl and water intake for 4 days prior to euthanasia for quantitative immunoblotting studies. RESULTS AND CONCLUSION The rats manifested marked extracellular fluid volume expansion with massive ascites. Plasma aldosterone levels were markedly elevated. Analysis of immunoblots revealed marked increases in the abundances of both of the major aldosterone-sensitive apical transport proteins of the renal tubule, namely the thiazide-sensitive NaCl cotransporter NCC and the epithelial sodium channel alpha subunit (alpha-ENaC). These results are consistent with an important role for hyperaldosteronism in the pathogenesis of sodium retention and ascites formation in cirrhosis. In addition, we observed a large decrease in cortical NHE3 abundance (proximal tubule) and a large increase in NKCC2 abundance (thick ascending limb), potentially shifting premacula densa sodium absorption from proximal tubule to loop of Henle (which powers urinary concentration and dilution).
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Maril N, Margalit R, Mispelter J, Degani H. Functional sodium magnetic resonance imaging of the intact rat kidney. Kidney Int 2004; 65:927-35. [PMID: 14871412 DOI: 10.1111/j.1523-1755.2004.00475.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Renal fluid homeostasis depends to a large extent on the sodium concentration gradient along the corticomedullary axis. The spatial distribution and extent of this gradient were previously determined by invasive methods, which yielded a range of results. We demonstrate here the capacity of sodium magnetic resonance imaging (MRI) to quantify non-invasively renal sodium distribution in the intact kidney. METHODS Sodium MRI was applied to study normal, diuretic, and obstructed rat kidneys in vivo. The images were recorded at 4.7 Tesla using a 3-dimensional gradient echo sequence, with high spatial and temporal resolution. The tissue sodium concentration (TSC) was obtained by taking into account the measured nuclear relaxation rates and MRI visibility relative to a reference saline solution. RESULTS The corticomedullary sodium gradient increased linearly from the cortex to the inner medulla by approximately 31 mmol/L/mm, from a TSC of approximately 60 mmol/L to approximately 360 mmol/L. Furosemide induced a 50% reduction in the inner-medulla sodium and a 25% increase in the cortical sodium. The kinetics of these changes was related to the specific site and mechanism of the loop diuretic. Distinct profiles of the sodium gradient were observed in acute obstructed kidneys, as well as spontaneously obstructed kidneys. The changes in the sodium gradient correlated with the extent of damage and the residual function of the kidneys. CONCLUSION Quantitative assessment of the renal corticomedullary sodium gradient by high resolution sodium MRI may help verify new aspects of the kidney concentrating mechanism and serve as a non-invasive diagnostic method of renal function.
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Affiliation(s)
- Nimrod Maril
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
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Wang W, Li C, Kwon TH, Miller RT, Knepper MA, Frøkiaer J, Nielsen S. Reduced expression of renal Na+transporters in rats with PTH-induced hypercalcemia. Am J Physiol Renal Physiol 2004; 286:F534-45. [PMID: 14625199 DOI: 10.1152/ajprenal.00044.2003] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to evaluate whether the natriuresis and polyuria seen in parathyroid hormone (PTH)-induced hypercalcemia are associated with dysregulation of renal Na transporters. Rats were infused with three different doses of human PTH [PTH ( 1 - 34 ); 7.5, 10, and 15 μg·kg-1·day-1sc] or vehicle for 48 h using osmotic minipumps. The rats treated with PTH developed significant hypercalcemia (plasma total calcium levels: 2.71 ± 0.03, 2.77 ± 0.02, and 3.42 ± 0.06 mmol/l, respectively, P < 0.05 compared with corresponding controls). The rats with severe hypercalcemia induced by high-dose PTH developed a decreased glomerular filtration rate (GFR), increased urine output, reduced urinary osmolality, increased urinary Na excretion, and fractional excretion of Na. This was associated with downregulation (calculated as a fraction of control levels) of whole kidney expression of type 2 Na-Picotransporter (NaPi-2; 16 ± 6%), type 3 Na/H exchanger (NHE3; 42 ± 7%), Na-K-ATPase (55 ± 2%), and bumetanide-sensitive Na-K-2Cl cotransporter (BSC-1; 25 ± 4%). In contrast, an upregulation of the Ca2+-sensing receptor (CaR) was observed. Rats treated with moderate-dose PTH exhibited unchanged GFR but decreased urinary concentration. The whole kidney expression of NHE3 (52 ± 8%) and NaPi-2 (26 ± 5%) was persistently decreased, whereas BSC-1 and Na-K-ATPase protein levels were not altered. CaR expression was also increased. Moreover, rats treated with low-dose PTH showed very mild hypercalcemia but unchanged GFR, normal urinary concentration, and unchanged expression of Na transporters and CaR. In conclusion, the reduced expression of major renal Na transporters is likely to play a role in the increased urinary Na excretion and decreased urinary concentration in rats with PTH-induced hypercalcemia. Moreover, the increase in the CaR in the thick ascending limb (TAL) may indicate a potential role of the CaR in inhibiting Na transport in the TAL.
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Affiliation(s)
- Weidong Wang
- The Water and Salt Research Center, University of Aarhus, DK-8000 Aarhus C, Denmark
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Fekete A, Vannay A, Vér A, Vásárhelyi B, Müller V, Ouyang N, Reusz G, Tulassay T, Szabó AJ. Sex differences in the alterations of Na(+), K(+)-ATPase following ischaemia-reperfusion injury in the rat kidney. J Physiol 2003; 555:471-80. [PMID: 14673189 PMCID: PMC1664838 DOI: 10.1113/jphysiol.2003.054825] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Postischaemic acute renal failure (ARF) is influenced by sex. Na(+), K(+)-ATPase (NKA) plays a crucial role in the pathogenesis of postischaemic ARF. We tested the impact of sex on mRNA, protein expression, cellular distribution and enzyme activity of NKA following renal ischaemia-reperfusion (I-R) injury. The left renal pedicle of uninephrectomized female (F) and male (M) Wistar rats was clamped for 55 min followed by 2 h (T2) and 16 h (T16) of reperfusion. Uninephrectomized, sham-operated F and M rats served as controls (n= 6 per group). Blood urea nitrogen, serum creatinine and renal histology were evaluated to detect the severity of postischaemic ARF. mRNA expression of NKA alpha1 and beta1 subunits were detected by RT-PCR. The effect of I-R on cellular distribution was compared by Triton X-100 extraction. Cellular proteins were divided into Triton-insoluble and Triton-soluble fractions and assessed by Western blot. NKA enzyme activity was also determined. After the ischaemic insult blood urea nitrogen and serum creatinine were higher and renal histology showed more rapid progression in M versus F (P < 0.05). mRNA expression of the NKA alpha1 subunit decreased in I-R groups versus controls, but was higher in F versus M both in control and I-R groups (P < 0.05). However, protein levels of the NKA alpha1 subunit in total tissue homogenate did not differ in controls, but were higher in F versus M in I-R groups (P < 0.05). Triton X-100 extractability was lower in F versus M at T16 (P < 0.05). NKA enzyme activity was the same in controls, but was higher in F versus M in I-R groups (T2: 14.9 +/- 2.3 versus 9.15 +/- 2.21 U) (T16: 11.7 +/- 4.1 versus 5.65 +/- 2.3 U; P < 0.05). mRNA and protein expression of the NKA beta1 subunit did not differ between F and M in any of the protocol. We concluded that NKA is more protected from the detrimental effects of postischaemic injury in females. Higher mRNA and protein expression of the NKA alpha1 subunit and higher enzyme activity might be additional contributing factors to the improved postischaemic renal function of female rats.
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Affiliation(s)
- Andrea Fekete
- Research Laboratory of Paediatrics and Nephrology of 1st Department of Paediatrics and Hungarian Academy of Science, Semmelweis University, 1083 Budapest Bókay u. 53-54, Hungary
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Lee EM, Pollock CA, Drumm K, Barden JA, Poronnik P. Effects of pathophysiological concentrations of albumin on NHE3 activity and cell proliferation in primary cultures of human proximal tubule cells. Am J Physiol Renal Physiol 2003; 285:F748-57. [PMID: 12799307 DOI: 10.1152/ajprenal.00442.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The progression of renal disease correlates strongly with hypertension and the degree of proteinuria, suggesting a link between excessive Na+ reabsorption and exposure of the proximal tubule to protein. The present study investigated the effects of albumin on cell growth and Na+ uptake in primary cultures of human proximal tubule cells (PTC). Albumin (1.0 mg/ml) increased cell proliferation to 134.1 +/- 11.8% (P < 0.001) of control levels with no change in levels of apoptosis. Exposure to 0.1 and 1.0 mg/ml albumin increased total 22Na+ uptake to 119.1 +/- 6.3% (P = 0.005) and 115.6 +/- 5.3% (P < 0.006) of control levels, respectively, because of an increase in Na+/H+ exchanger isoform 3 (NHE3) activity. This was associated with an increase in NHE3 mRNA to 161.1 +/- 15.1% (P < 0.005) of control levels in response to 0.1 mg/ml albumin. Using confocal microscopy with a novel antibody raised against the predicted extracellular NH2 terminus of human NHE3, we observed in nonpermeabilized cells that exposure of PTC to albumin (0.1 and 1.0 mg/ml) increased NHE3 at the cell surface to 115.4 +/- 2.7% (P < 0.0005) and 122.4 +/- 3.7% (P < 0.0001) of control levels, respectively. This effect was paralleled by significant increases in NHE3 in the subplasmalemmal region as measured in permeabilized cells. These albumin-induced increases in expression and activity of NHE3 in PTC suggest a possible mechanism for Na+ retention in response to proteinuria.
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Affiliation(s)
- E M Lee
- Department of Medicine, University of Sydney, Renal Research Group, Kolling Institute of Medical Research, Royal North Shore Hospital, St. Leonard's, New South Wales 2065, Australia
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Meade P, Hoover RS, Plata C, Vázquez N, Bobadilla NA, Gamba G, Hebert SC. cAMP-dependent activation of the renal-specific Na+-K+-2Cl- cotransporter is mediated by regulation of cotransporter trafficking. Am J Physiol Renal Physiol 2003; 284:F1145-54. [PMID: 12604467 DOI: 10.1152/ajprenal.00421.2002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The murine apical bumetanide-sensitive Na(+)-K(+)-2Cl(-) cotransporter gene (mBSC1) exhibits two spliced isoform products that differ at the COOH-terminal domain. A long COOH-terminal isoform (L-mBSC1) encodes the Na(+)-K(+)-2Cl(-) cotransporter, and a short isoform (S-mBSC1) exerts a dominant-negative effect on L-mBSC1 cotransporter activity that is abrogated by cAMP. However, the mechanism of this dominant-negative effect was not clear. In this study, we used confocal microscopic analysis of an enhanced green fluorescent protein (EGFP) fusion construct (L-mBSC1-EGFP) expressed to characterize the surface expression of the L-BSC1 isoform in Xenopus laevis oocytes. Functional expression was also assessed in L-mBSC1-injected oocytes by measuring the bumetanide-sensitive (86)Rb(+) uptake. Oocytes injected with L-mBSC1-EGFP cRNA developed a distinct plasma membrane-associated fluorescence that colocalized with the fluorescent membrane dye FM 4-64. The fluorescence intensity in L-mBSC1-EGFP oocytes did not change after cAMP was added to the extracellular medium. In contrast, L-mBSC1-EGFP fluorescence intensity was reduced in a dose-dependent manner, with coexpression of S-mBSC1. The inhibitory effect of S-mBSC1 was abrogated by cAMP. Finally, the exocytosis inhibitor colchicine blocked the effect of cAMP on the L-mBSC1-EGFP/S-mBSC1-coinjected oocytes. All changes in L-mBSC1 surface expression correlated with modification of bumetanide-sensitive (86)Rb(+) uptake. Our data suggest that the dominant-negative effect of S-mBSC1 on L-mBSC1 transport function is due to the effects of the cotransporter on trafficking.
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Affiliation(s)
- Patricia Meade
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México
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Loffing J, Kaissling B. Sodium and calcium transport pathways along the mammalian distal nephron: from rabbit to human. Am J Physiol Renal Physiol 2003; 284:F628-43. [PMID: 12620920 DOI: 10.1152/ajprenal.00217.2002] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The final adjustment of renal sodium and calcium excretion is achieved by the distal nephron, in which transepithelial ion transport is under control of various hormones, tubular fluid composition, and flow rate. Acquired or inherited diseases leading to deranged renal sodium and calcium balance have been linked to dysfunction of the distal nephron. Diuretic drugs elicit their effects on sodium balance by specifically inhibiting sodium transport proteins in the apical plasma membrane of distal nephron segments. The identification of the major apical sodium transport proteins allows study of their precise distribution pattern along the distal nephron and helps address their cellular and molecular regulation under various physiological and pathophysiological settings. This review focuses on the topological arrangement of sodium and calcium transport proteins along the cortical distal nephron and on some aspects of their functional regulation. The availability of data on the distribution of transporters in various species points to the strengths, as well as to the limitations, of animal models for the extrapolation to humans.
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Affiliation(s)
- Johannes Loffing
- Institute of Anatomy, University of Zurich, CH-8057 Zurich, Switzerland.
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Ko SBH, Luo X, Hager H, Rojek A, Choi JY, Licht C, Suzuki M, Muallem S, Nielsen S, Ishibashi K. AE4 is a DIDS-sensitive Cl(-)/HCO(-)(3) exchanger in the basolateral membrane of the renal CCD and the SMG duct. Am J Physiol Cell Physiol 2002; 283:C1206-18. [PMID: 12225984 DOI: 10.1152/ajpcell.00512.2001] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The renal cortical collecting duct (CCD) plays an important role in systemic acid-base homeostasis. The beta-intercalated cells secrete most of the HCO(-)(3), which is mediated by a luminal, DIDS-insensitive, Cl(-)/HCO(-)(3) exchange. The identity of the luminal exchanger is a matter of debate. Anion exchanger isoform 4 (AE4) cloned from the rabbit kidney was proposed to perform this function (Tsuganezawa H et al. J Biol Chem 276: 8180-8189, 2001). By contrast, it was proposed (Royaux IE et al. Proc Natl Acad Sci USA 98: 4221-4226, 2001) that pendrin accomplishes this function in the mouse CCD. In the present work, we cloned, localized, and characterized the function of the rat AE4. Northern blot and RT-PCR showed high levels of AE4 mRNA in the CCD. Expression in HEK-293 and LLC-PK(1) cells showed that AE4 is targeted to the plasma membrane. Measurement of intracellular pH (pH(i)) revealed that AE4 indeed functions as a Cl(-)/HCO(-)(3) exchanger. However, AE4 activity was inhibited by DIDS. Immunolocalization revealed species-specific expression of AE4. In the rat and mouse CCD and the mouse SMG duct AE4 was in the basolateral membrane. By contrast, in the rabbit, AE4 was in the luminal and lateral membranes. In both, the rat and rabbit CCD AE4 was in alpha-intercalated cells. Importantly, localization of AE4 was not affected by the systemic acid-base status of the rats. Therefore, we conclude that expression and possibly function of AE4 is species specific. In the rat and mouse AE4 functions as a Cl(-)/HCO(-)(3) exchanger in the basolateral membrane of alpha-intercalated cells and may participate in HCO(-)(3) absorption. In the rabbit AE4 may contribute to HCO(-)(3) secretion.
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Affiliation(s)
- Shigeru B H Ko
- Department of Physiology, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Wetzel RK, Sweadner KJ. Immunocytochemical localization of Na-K-ATPase alpha- and gamma-subunits in rat kidney. Am J Physiol Renal Physiol 2001; 281:F531-45. [PMID: 11502602 DOI: 10.1152/ajprenal.2001.281.3.f531] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The gamma-subunit of the Na-K-ATPase is a single-span membrane protein that alters the kinetic properties of the enzyme. It is expressed in the kidney, but our initial observations indicated that it is not present in all nephron segments (Arystarkhova E, Wetzel RK, Asinovski NK, and Sweadner KJ. J Biol Chem 274: 33183-33185, 1999). Here we used triple-label confocal immunofluorescence microscopy in rat kidney with antibodies to Na-K-ATPase alpha1- and gamma-subunits and nephron segment-specific markers. Na-K-ATPase alpha1-subunit stain was low but unambiguous in proximal segments, moderate in macula densa, connecting tubules, and cortical collecting ducts, high in thick ascending limb and distal convoluted tubules, and nearly undetectable in glomeruli, descending and ascending thin limb, and medullary collecting ducts. The gamma-subunit colocalized at staining levels similar to alpha1-subunit in basolateral membranes in all segments except cortical thick ascending limb and cortical collecting ducts, which had alpha1-subunit but no detectable gamma-subunit stain. Selective gamma-subunit expression may contribute to the variations in Na-K-ATPase properties in different renal segments.
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Affiliation(s)
- R K Wetzel
- Laboratory of Membrane Biology, Neuroscience Center, Massachusetts General Hospital, 149 13th St., Charlestown, MA 02129, USA
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Caruso-Neves C, Rangel LB, Lara LS, Lopes AG. Regulation of the renal proximal tubule second sodium pump by angiotensins. Braz J Med Biol Res 2001; 34:1079-84. [PMID: 11471048 DOI: 10.1590/s0100-879x2001000800015] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
For several years it was believed that angiotensin II (Ang II) alone mediated the effects of the renin-angiotensin system. However, it has been observed that other peptides of this system, such as angiotensin-(1-7) (Ang-(1-7)), present biological activity. The effect of Ang II and Ang-(1-7) on renal sodium excretion has been associated, at least in part, with modulation of proximal tubule sodium reabsorption. In the present review, we discuss the evidence for the involvement of Na+-ATPase, called the second sodium pump, as a target for the actions of these compounds in the regulation of proximal tubule sodium reabsorption.
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Affiliation(s)
- C Caruso-Neves
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21949-900 Rio de Janeiro RJ, Brasil
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Mann B, Hartner A, Jensen BL, Kammerl M, Krämer BK, Kurtz A. Furosemide stimulates macula densa cyclooxygenase-2 expression in rats. Kidney Int 2001; 59:62-8. [PMID: 11135058 DOI: 10.1046/j.1523-1755.2001.00466.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND During a low salt intake, maintenance of renal blood flow and renin secretion depends on intact formation of prostaglandins. In the juxtaglomerular apparatus, the inducible isoform of cyclooxygenase, cyclooxygenase-2 (COX-2), is restricted to the macula densa and the cortical thick ascending limb of Henle (cTALH) cells, and is inversely regulated by dietary salt intake. This study aimed to elucidate whether the effect of NaCl on macula densa COX-2 expression is mediated by transepithelial transport of NaCl. METHODS To this end, male Sprague-Dawley rats received subcutaneous infusions of the loop diuretic furosemide (12 mg/day) or were fed with the diuretic hydrochlorothiazide (30 mg/kg day) for seven days each. To compensate for their salt and water loss, the animals had free access to normal water and to salt water (0.9% NaCl, 0.1% KCl). COX-2 expression in kidney cortex was assessed by immunohistochemical staining and by semiquantitative ribonuclease protection assay for COX-2 mRNA. RESULTS After six days of furosemide infusion to salt-substituted rats, there was no change of extracellular volume. Furosemide led to a fivefold and threefold increase of plasma renin activity and renocortical renin mRNA level, respectively. In parallel, there was a threefold increase of renocortical COX-2 abundance, while the COX-1 mRNA level remained unchanged. Moreover, the percentage of juxtaglomerular apparatuses immunopositive for COX-2 increased threefold in response to furosemide compared with vehicle-infused animals. Hydrochlorothiazide treatment increased plasma renin activity twofold but did not change kidney cortical renin mRNA, COX-2 mRNA, or COX-2 immunoreactivity. CONCLUSION Our findings suggest that inhibition of salt transport in the loop of Henle, but not in the distal tubule, causes a selective stimulation of COX-2 expression in the macula densa region. This up-regulation may be of relevance for macula densa signaling, which links tubular salt transport rate with glomerular filtration rate and renin secretion.
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Affiliation(s)
- B Mann
- Institut für Physiologie, Universität Regensburg; Nephrologie, Medizinische Klinik IV, Universität Erlangen-Nürnberg, Erlangen, Germany
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