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Salota R, Lapsley M, Nabi E, Packer S, Hyer S, Dockrell M. Time-resolved fluorescence immunoassay for urine retinol-binding protein is more sensitive than polyclonal and monoclonal assays. Ann Clin Biochem 2021; 58:505-519. [PMID: 34006121 DOI: 10.1177/00045632211020034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Retinol-binding protein4 (RBP) assays using polyclonal antibodies (pRBP) have major problems of non-linearity of dilution and a very small useable dynamic range. Our objective was to develop a specific assay with a wider dynamic range to detect tubular proteinuria. METHODS mRBP (monoclonal capture and second antibody with colorimetric detection) and fluoroimmunoassays for RBP (fRBP) (polyclonal capture and monoclonal second antibody with fluorescence detection) were developed and compared with pRBP. Four hundred and eighty-eight patient samples were collected; 290 samples were analysed by mRBP and 198 samples with fRBP and compared with pRBP. RESULTS mRBP assay has the advantages of better linearity on dilution and wider analytical range over pRBP. It is limited by poor signal in the patients with albuminuria and glomerular proteinuria and inferior discrimination between patient groups. fRBP had an intra-assay and inter-assay CV of <6% and <8%, respectively, and analytical range was 2.3-599 µg/L. fRBP was linear on dilution within the analytical range. Correlation (r) was 0.8722 (95% CI 0.7621 to 0.9333, P< 0.0001); Mann-Whitney test revealed no significant difference (U = 18,877, n = 198, P = 0.5244) asserting that the medians of the two samples were identical. Bland-Altman test between pRBP and fRBP showed a mean negative bias of 16.43 (CI -994 to 1027) µg/mmol. CONCLUSIONS The combination assay with fluorescence detection (fRBP) proved more discriminatory than a purely monoclonal system especially in patients with significant proteinuria and has advantages of better linearity on dilution and wider analytical range than the existing pRBP assay and compared extremely well with pRBP.
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Affiliation(s)
- Rashim Salota
- Department of Clinical Biochemistry, Epsom and St Helier University Hospitals NHS Trust Surrey, UK
| | - Marta Lapsley
- Department of Clinical Biochemistry, Epsom and St Helier University Hospitals NHS Trust Surrey, UK
| | - Ekramun Nabi
- South West Thames Institute for Renal Research, Epsom and St. Helier University Hospitals NHS Trust, Surrey, UK
| | | | - Steve Hyer
- Diabetes and Endocrinology, Epsom and St Helier University Hospitals NHS Trust, Surrey, UK
| | - Mark Dockrell
- South West Thames Institute for Renal Research, Epsom and St. Helier University Hospitals NHS Trust, Surrey, UK
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Development of a multiplex mass spectrometry method for simultaneous quantification of urinary proteins related to respiratory health. Sci Rep 2021; 11:10107. [PMID: 33980897 PMCID: PMC8115669 DOI: 10.1038/s41598-021-89068-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 04/16/2021] [Indexed: 02/03/2023] Open
Abstract
Respiratory health of children is a health priority. Club cell protein (CC16) is an interesting biomarker of lung diseases and adverse effects towards the airway epithelium integrity. Osteopontin (OPN) and nuclear factor-kappa B (NF-κB) also play a role in respiratory health. The use of urine as biomarker source is useful in studies involving children but necessitates proper adjustment for physiological confounders influencing the urinary excretion, potentially characterized with beta-2-microglobulin (β2M), retinol binding protein 4 (RBP4) or myoglobin (MYO), as well as adjustment for possible renal dysfunction, characterized by human serum albumin (HSA). The simultaneous quantification of all these proteins in urine could facilitate children's health monitoring. A multiple reaction monitoring method (MRM) was developed and validated for the relative quantification of the seven mentioned urinary proteins. A total of nine proteotypic peptides were selected and used for the relative quantification of the seven proteins. The MRM method was completely validated for all proteins and partially for OPN. LOQ's ranged from 0.3 to 42.8 ng/ml, a good reproducibility and a good linearity were obtained across the analytical measurement range (r2 > 0.98). The method yielded varying correlations (r2 of 0.78, 0.71, 0.34 and 0.15 for CC16, β2M, RBP4 and HSA respectively) with available immunoassay data. It also allowed the identification and successful quantification of β2M and RBP4 as a protein candidate for adjustment of renal handling and dysfunction. All proteins were detected in the urine samples except for MYO and NF-κB. Our validated MRM-method is able to simultaneously quantify in urine biomarkers of airway epithelium integrity and biomarkers of variation in renal function and urinary dilution. This will allow to investigate further in future studies if urine can be used as a good surrogate source for biomarkers of airway epithelium integrity, and to understand the complex relationship between cause and effect in children's respiratory health monitoring.
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Zeni L, Norden AGW, Cancarini G, Unwin RJ. A more tubulocentric view of diabetic kidney disease. J Nephrol 2017; 30:701-717. [PMID: 28840540 PMCID: PMC5698396 DOI: 10.1007/s40620-017-0423-9] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 07/22/2017] [Indexed: 12/14/2022]
Abstract
Diabetic nephropathy (DN) is a common complication of Diabetes Mellitus (DM) Types 1 and 2, and prevention of end stage renal disease (ESRD) remains a major challenge. Despite its high prevalence, the pathogenesis of DN is still controversial. Initial glomerular disease manifested by hyperfiltration and loss of glomerular size and charge permselectivity may initiate a cascade of injuries, including tubulo-interstitial disease. Clinically, 'microalbuminuria' is still accepted as an early biomarker of glomerular damage, despite mounting evidence that its predictive value for DN is questionable, and findings that suggest the proximal tubule is an important link in the development of DN. The concept of 'diabetic tubulopathy' has emerged from recent studies, and its causative role in DN is supported by clinical and experimental evidence, as well as plausible pathogenetic mechanisms. This review explores the 'tubulocentric' view of DN. The recent finding that inhibition of proximal tubule (PT) glucose transport (via SGLT2) is nephro-protective in diabetic patients is discussed in relation to the tubule's potential role in DN. Studies with a tubulocentric view of DN have stimulated alternative clinical approaches to the early detection of diabetic kidney disease. There are tubular biomarkers considered as direct indicators of injury of the proximal tubule (PT), such as N-acetyl-β-D-glucosaminidase, Neutrophil Gelatinase-Associated Lipocalin and Kidney Injury Molecule-1, and other functional PT biomarkers, such as Urine free Retinol-Binding Protein 4 and Cystatin C, which reflect impaired reabsorption of filtered proteins. The clinical application of these measurements to diabetic patients will be reviewed in the context of the need for better biomarkers for early DN.
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Affiliation(s)
- Letizia Zeni
- Department of Medical and Surgical Specialities, Radiological Sciences and Public Health, University of Brescia, Piazza del Mercato 15, 25121, Brescia, Italy.
- UCL Centre for Nephrology, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK.
- Operative Unit of Nephrology, ASST Spedali Civili, Piazzale Spedali Civili 1, Brescia, Italy.
| | - Anthony G W Norden
- UCL Centre for Nephrology, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
| | - Giovanni Cancarini
- Department of Medical and Surgical Specialities, Radiological Sciences and Public Health, University of Brescia, Piazza del Mercato 15, 25121, Brescia, Italy
- Operative Unit of Nephrology, ASST Spedali Civili, Piazzale Spedali Civili 1, Brescia, Italy
| | - Robert J Unwin
- UCL Centre for Nephrology, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
- Cardiovascular and Metabolic Diseases iMED ECD, AstraZeneca Gothenburg, Mölndal, Sweden
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4
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Argyropoulos CP, Chen SS, Ng YH, Roumelioti ME, Shaffi K, Singh PP, Tzamaloukas AH. Rediscovering Beta-2 Microglobulin As a Biomarker across the Spectrum of Kidney Diseases. Front Med (Lausanne) 2017; 4:73. [PMID: 28664159 PMCID: PMC5471312 DOI: 10.3389/fmed.2017.00073] [Citation(s) in RCA: 150] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 05/26/2017] [Indexed: 12/28/2022] Open
Abstract
There is currently an unmet need for better biomarkers across the spectrum of renal diseases. In this paper, we revisit the role of beta-2 microglobulin (β2M) as a biomarker in patients with chronic kidney disease and end-stage renal disease. Prior to reviewing the numerous clinical studies in the area, we describe the basic biology of β2M, focusing in particular on its role in maintaining the serum albumin levels and reclaiming the albumin in tubular fluid through the actions of the neonatal Fc receptor. Disorders of abnormal β2M function arise as a result of altered binding of β2M to its protein cofactors and the clinical manifestations are exemplified by rare human genetic conditions and mice knockouts. We highlight the utility of β2M as a predictor of renal function and clinical outcomes in recent large database studies against predictions made by recently developed whole body population kinetic models. Furthermore, we discuss recent animal data suggesting that contrary to textbook dogma urinary β2M may be a marker for glomerular rather than tubular pathology. We review the existing literature about β2M as a biomarker in patients receiving renal replacement therapy, with particular emphasis on large outcome trials. We note emerging proteomic data suggesting that β2M is a promising marker of chronic allograft nephropathy. Finally, we present data about the role of β2M as a biomarker in a number of non-renal diseases. The goal of this comprehensive review is to direct attention to the multifaceted role of β2M as a biomarker, and its exciting biology in order to propose the next steps required to bring this recently rediscovered biomarker into the twenty-first century.
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Affiliation(s)
- Christos P Argyropoulos
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Shan Shan Chen
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Yue-Harn Ng
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Maria-Eleni Roumelioti
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Kamran Shaffi
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Pooja P Singh
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Antonios H Tzamaloukas
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States.,Raymond G. Murphy VA Medical Center Albuquerque, Albuquerque, NM, United States
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5
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Kuwata K, Nakamura I, Ide M, Sato H, Nishikawa S, Tanaka M. Comparison of changes in urinary and blood levels of biomarkers associated with proximal tubular injury in rat models. J Toxicol Pathol 2015. [PMID: 26441477 DOI: 10.1293/tox.2014-0039.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
To investigate useful biomarkers associated with proximal tubular injury, we assessed changes in levels of a focused set of biomarkers in urine and blood. Male rats administered a single dose or four doses of gentamicin (GM, 240 mg/kg/day) or a single dose of cisplatin (CDDP, 5 mg/kg) were euthanized on days 2 (the day after initial dosing) 5, or 12. At each time point, histopathological examination of the kidney and immunohistochemistry for biomarkers, kidney injury molecule-1 (Kim-1), lipocalin (NGAL), clusterin (CLU), cystatin C (CysC) and β2-microglobulin (β2M) were performed. Biomarker levels were measured in urine and blood. In both treatment groups, degenerated/necrotic proximal tubules and regenerated tubules were mainly observed on days 5 and 12, respectively. At the same time as these tubular injuries, urinary Kim-1, CysC and β2M levels were increased. Moreover, urinary levels of CysC and β2M in GM-treated animals and Kim-1 in CDDP-treated animals increased (on day 2) prior to tubular injury on day 5. This was considered to reflect the characteristics of drug toxicity. Although almost all of the biomarkers in blood were not sufficiently sensitive to detect proximal tubular injury, urinary and plasma β2M levels simultaneously increased. Therefore, in addition to urinary Kim-1, CysC and β2M levels, plasma β2M levels were also considered useful for detecting proximal tubular injury.
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Affiliation(s)
- Kazunori Kuwata
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
| | - Itsuko Nakamura
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 2-2-50 Kawagishi, Toda, Saitama 335-8505, Japan
| | - Mika Ide
- Research Strategy & Planning Department, Research Division, Mitsubishi Tanabe Pharma Corporation, 2-2-50 Kawagishi, Toda, Saitama 335-8505, Japan
| | - Hiroko Sato
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
| | - Satomi Nishikawa
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
| | - Masaharu Tanaka
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
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Kuwata K, Nakamura I, Ide M, Sato H, Nishikawa S, Tanaka M. Comparison of changes in urinary and blood levels of biomarkers associated with proximal tubular injury in rat models. J Toxicol Pathol 2015; 28:151-64. [PMID: 26441477 PMCID: PMC4588209 DOI: 10.1293/tox.2014-0039] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 05/05/2015] [Indexed: 11/19/2022] Open
Abstract
To investigate useful biomarkers associated with proximal tubular injury, we assessed
changes in levels of a focused set of biomarkers in urine and blood. Male rats
administered a single dose or four doses of gentamicin (GM, 240 mg/kg/day) or a single
dose of cisplatin (CDDP, 5 mg/kg) were euthanized on days 2 (the day after initial dosing)
5, or 12. At each time point, histopathological examination of the kidney and
immunohistochemistry for biomarkers, kidney injury molecule-1 (Kim-1), lipocalin (NGAL),
clusterin (CLU), cystatin C (CysC) and β2-microglobulin (β2M) were performed. Biomarker
levels were measured in urine and blood. In both treatment groups, degenerated/necrotic
proximal tubules and regenerated tubules were mainly observed on days 5 and 12,
respectively. At the same time as these tubular injuries, urinary Kim-1, CysC and β2M
levels were increased. Moreover, urinary levels of CysC and β2M in GM-treated animals and
Kim-1 in CDDP-treated animals increased (on day 2) prior to tubular injury on day 5. This
was considered to reflect the characteristics of drug toxicity. Although almost all of the
biomarkers in blood were not sufficiently sensitive to detect proximal tubular injury,
urinary and plasma β2M levels simultaneously increased. Therefore, in addition to urinary
Kim-1, CysC and β2M levels, plasma β2M levels were also considered useful for detecting
proximal tubular injury.
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Affiliation(s)
- Kazunori Kuwata
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
| | - Itsuko Nakamura
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 2-2-50 Kawagishi, Toda, Saitama 335-8505, Japan
| | - Mika Ide
- Research Strategy & Planning Department, Research Division, Mitsubishi Tanabe Pharma Corporation, 2-2-50 Kawagishi, Toda, Saitama 335-8505, Japan
| | - Hiroko Sato
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
| | - Satomi Nishikawa
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
| | - Masaharu Tanaka
- Safety Research Laboratories, Research Division, Mitsubishi Tanabe Pharma Corporation, 1-1-1 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan
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7
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Chehade H, Parvex P, Poncet A, Werner D, Mosig D, Cachat F, Girardin E. Urinary low-molecular-weight protein excretion in pediatric idiopathic nephrotic syndrome. Pediatr Nephrol 2013; 28:2299-306. [PMID: 23949592 DOI: 10.1007/s00467-013-2569-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Revised: 05/28/2013] [Accepted: 07/01/2013] [Indexed: 11/27/2022]
Abstract
BACKGROUND Minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) are the most common causes of idiopathic nephrotic syndrome (INS). We have evaluated the reliability of urinary neutrophil-gelatinase-associated lipocalin (uNGAL), urinary alpha1-microglobulin (uα1M) and urinary N-acetyl-beta-D-glucosaminidase (uβNAG) as markers for differentiating MCD from FSGS. We have also evaluated whether these proteins are associated to INS relapses or to glomerular filtration rate (GFR). METHODS The patient cohort comprised 35 children with MCD and nine with FSGS; 19 healthy age-matched children were included in the study as controls. Of the 35 patients, 28 were in remission (21 MCD, 7 FSGS) and 16 were in relapse (14 MCD, 2 FSGS). The prognostic accuracies of these proteins were assessed by receiver operating characteristic (ROC) curve analyses. RESULTS The level of uNGAL, indexed or not to urinary creatinine (uCreat), was significantly different between children with INS and healthy children (p = 0.02), between healthy children and those with FSGS (p = 0.007) and between children with MCD and those with FSGS (p = 0.01). It was not significantly correlated to proteinuria or GFR levels. The ROC curve analysis showed that a cut-off value of 17 ng/mg for the uNGAL/uCreat ratio could be used to distinguish MCD from FSGS with a sensitivity of 0.77 and specificity of 0.78. uβNAG was not significantly different in patients with MCD and those with FSGS (p = 0.86). Only uα1M, indexed or not to uCreat, was significantly (p < 0.001) higher for patients in relapse compared to those in remission. CONCLUSIONS Our results indicate that in our patient cohort uNGAL was a reliable biomarker for differentiating MCD from FSGS independently of proteinuria or GFR levels.
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Affiliation(s)
- Hassib Chehade
- Division of Pediatric Nephrology, Department of Pediatrics, Lausanne University Hospital, Rue Bugnon 46, 1011, Lausanne, Switzerland,
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8
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Lee D, Gleich K, Fraser SA, Katerelos M, Mount PF, Power DA. Limited capacity of proximal tubular proteolysis in mice with proteinuria. Am J Physiol Renal Physiol 2013; 304:F1009-19. [PMID: 23344573 DOI: 10.1152/ajprenal.00601.2012] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Albuminuria is associated with the additional loss in the urine of small molecular weight proteins normally degraded by the proximal convoluted tubule (PCT), and competition for binding to the megalin/cubilin reuptake system has been considered the likely cause. We have previously reported that deficiency of the intrinsic lysosomal protein Limp-2 causes tubular proteinuria due to reduced fusion of endosomes with lysosomes in the PCT leading to inadequate proteolysis. To determine whether this mechanism also contributes to the tubular proteinuria induced by albumin overload in normal mice, wild-type (WT) mice received daily BSA injections intraperitoneally for 10 days, using untreated Limp-2(-/-) mice as positive controls for inadequate proteolysis. BSA overload induced significant urinary loss of megalin and cubilin ligands in WT mice. Tubular uptake of Alexa-conjugated BSA, administered by intravenous injection, was not reduced in the PCT of mice receiving intraperitoneal BSA. Expression of the tubular protein receptor megalin was also unchanged. There was a delay in proteolysis of reabsorbed proteins in WT mice receiving BSA, evidenced by an increased quantity of retinol-binding protein (RBP) in the kidney cortex, increased basal distribution of endocytosed RBP in cells of the PCT, and persistence of exogenous Alexa-conjugated BSA and RBP after injection. Upregulation of cathepsin L and normal fusion of lysosomes with endosomes were apparently not sufficient to maintain normal clearance of endocytosed proteins. The data suggest that in the presence of competition from albumin overload, reabsorption of filtered proteins is limited by the capacity of lysosomal degradation rather than receptor-mediated endocytosis.
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Affiliation(s)
- D Lee
- Department of Nephrology, Austin Health, Studley Rd., Heidelberg, Victoria 3084, Australia.
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Haddam N, Samira S, Dumont X, Taleb A, Lison D, Haufroid V, Bernard A. Confounders in the assessment of the renal effects associated with low-level urinary cadmium: an analysis in industrial workers. Environ Health 2011; 10:37. [PMID: 21569589 PMCID: PMC3118317 DOI: 10.1186/1476-069x-10-37] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 05/14/2011] [Indexed: 05/19/2023]
Abstract
BACKGROUND Associations of proteinuria with low-level urinary cadmium (Cd) are currently interpreted as the sign of renal dysfunction induced by Cd. Few studies have considered the possibility that these associations might be non causal and arise from confounding by factors influencing the renal excretion of Cd and proteins. METHODS We examined 184 healthy male workers (mean age, 39.5 years) from a zinc smelter (n = 132) or a blanket factory (n = 52). We measured the concentrations of Cd in blood (B-Cd) and the urinary excretion of Cd (U-Cd), retinol-binding protein (RBP), protein HC and albumin. Associations between biomarkers of metal exposure and urinary proteins were assessed by simple and multiple regression analyses. RESULTS The medians (interquartile range) of B-Cd (μg/l) and U-Cd (μg/g creatinine) were 0.80 (0.45-1.16) and 0.70 (0.40-1.3) in smelter workers and 0.66 (0.47-0.87) and 0.55 (0.40-0.90) in blanket factory workers, respectively. Occupation had no influence on these values, which varied mainly with smoking habits. In univariate analysis, concentrations of RBP and protein HC in urine were significantly correlated with both U-Cd and B-Cd but these associations were substantially weakened by the adjustment for current smoking and the residual influence of diuresis after correction for urinary creatinine. Albumin in urine did not correlate with B-Cd but was consistently associated with U-Cd through a relationship, which was unaffected by smoking or diuresis. Further analyses showed that RBP and albumin in urine mutually distort their associations with U-Cd and that the relationship between RBP and Cd in urine was almost the replicate of that linking RBP to albumin CONCLUSIONS Associations between proteinuria and low-level urinary Cd should be interpreted with caution as they appear to be largely driven by diuresis, current smoking and probably also the co-excretion of Cd with plasma proteins.
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Affiliation(s)
- Nahida Haddam
- Laboratory of Medical Toxicology, Faculty of Medicine, University Abou Bekr Belkaid, Tlemcen, Algeria
- Institute of Biology, Faculty of Science, University Abou Bekr Belkaid, Tlemcen, Algeria
| | - Sekkal Samira
- Laboratory of Medical Toxicology, Faculty of Medicine, University Abou Bekr Belkaid, Tlemcen, Algeria
| | - Xavier Dumont
- Unit of Toxicology and Applied Pharmacology, Catholic University of Louvain, Brussels, Belgium
| | - Abdesselem Taleb
- Laboratory of Medical Toxicology, Faculty of Medicine, University Abou Bekr Belkaid, Tlemcen, Algeria
| | - Dominique Lison
- Unit of Toxicology and Applied Pharmacology, Catholic University of Louvain, Brussels, Belgium
| | - Vincent Haufroid
- Unit of Toxicology and Applied Pharmacology, Catholic University of Louvain, Brussels, Belgium
| | - Alfred Bernard
- Unit of Toxicology and Applied Pharmacology, Catholic University of Louvain, Brussels, Belgium
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Nejat M, Hill JV, Pickering JW, Edelstein CL, Devarajan P, Endre ZH. Albuminuria increases cystatin C excretion: implications for urinary biomarkers. Nephrol Dial Transplant 2011; 27 Suppl 3:iii96-103. [PMID: 21551085 DOI: 10.1093/ndt/gfr222] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Low-molecular weight (LMW) proteins, including albumin and novel urinary biomarkers of acute kidney injury (AKI) such as cystatin C and neutrophil gelatinase-associated lipocalin (NGAL), are normally absorbed from the glomerular filtrate by receptor-mediated transport. We evaluated the effect of albuminuria on urinary excretion of novel biomarkers. METHODS Sprague-Dawley rats given four injections over 2 days of 5 mg/g body wt/day bovine serum albumin (BSA) in saline were compared with controls given saline alone. Urinary cystatin C, albumin and protein excretion rates were compared prior to treatment (Day -1), after treatment (Day 2) and 4 days later (Day 6). A preliminary assessment of the clinical effect of proteinuria on the filtered urinary biomarkers cystatin C and NGAL was made by comparison with the effect on urinary interleukin-18 (IL-18) that is not absorbed from the glomerular filtrate, in a cohort of intensive care unit patients. RESULTS BSA induced transient increases in albuminuria, proteinuria and cystatinuria (P < 0.01, P < 0.001 and P < 0.001, respectively). Beyond a threshold 6-fold increase in albuminuria, cystatin C absorption was reduced by competitive inhibition. The excretion rates of all analytes returned to preinjection levels by Day 6. Clinical proteinuria was associated with increasing cystatin C and NGAL concentrations (n = 90, P < 0.0001) but not IL-18 (P = 0.12). CONCLUSIONS Proteinuria may increase the threshold for detection of AKI by increasing the excretion of LMW protein biomarkers.
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Affiliation(s)
- Maryam Nejat
- Christchurch Kidney Research Group, Department of Medicine, University of Otago, Christchurch, New Zealand
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11
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Chaumont A, De Winter F, Dumont X, Haufroid V, Bernard A. The threshold level of urinary cadmium associated with increased urinary excretion of retinol-binding protein and beta 2-microglobulin: a re-assessment in a large cohort of nickel-cadmium battery workers. Occup Environ Med 2011; 68:257-64. [PMID: 20935291 PMCID: PMC3060309 DOI: 10.1136/oem.2009.054122] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2010] [Indexed: 11/04/2022]
Abstract
OBJECTIVE To evaluate the threshold value of urinary cadmium (CdU) for renal dysfunction on the basis of relationships unconfounded by protein degradation, diuresis and the renal effects associated with chronic smoking. Methods We studied 599 workers (451 men, mean age 45.4 years) who were employed in four nickel-cadmium battery plants for 18.8 years on average. After adjustment for covariates by multiple regression, the CdU threshold values for increased concentrations of retinol-binding protein (RBPU) and b(2)-microglobulin (b(2)-mU) were assessed by logistic regression and benchmark dose analyses using as referents workers with CdU<1 μg/g creatinine. Results Relationships between urinary proteins and CdU (μg/g creatinine) were influenced by sex, age, diuresis and especially smoking. When considering all workers, odds for abnormal RBPU and b(2)-mU were significantly increased from CdU of 6-10 and >10, respectively. The benchmark dose (BMD5) and the benchmark dose lower limit (BMDL5) for a 5% excess in the background prevalence of abnormal RBPU and b(2)-mU were estimated at 5.1/3.0 and 9.6/5.9. When excluding ever smokers, odds for abnormal RBPU and b(2)-mU were both increased only among workers with CdU>10 (OR, 21.8, 95% CI, 6.4-74.4 and OR, 15.1, 95% CI, 3.6-63.1, respectively). In never smokers, these BMD5/BMDL5 of CdU were estimated at 12.6/6.6 and 12.2/5.5 while in ever smokers they were 6.2/4.9 and 4.3/3.5. Conclusions On the basis of associations undistorted by smoking and adjusted for covariates, the BMDL5 of CdU for low-molecular-weight proteinuria induced by occupational exposure to Cd can be reliably estimated between 5.5 and 6.6 μg/g creatinine.
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Affiliation(s)
- Agnès Chaumont
- Unit of Toxicology and Applied Pharmacology, Catholic University of Louvain, Avenue E Mounier 53.02, Brussels B-1200, Belgium
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Patel TV, Rennke HG, Sloan JM, DeAngelo DJ, Charytan DM. A forgotten cause of kidney injury in chronic myelomonocytic leukemia. Am J Kidney Dis 2009; 54:159-64. [PMID: 19185401 DOI: 10.1053/j.ajkd.2008.11.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Accepted: 11/03/2008] [Indexed: 11/11/2022]
Affiliation(s)
- Tejas V Patel
- Renal Division, Brigham and Women's Hospital, Boston, MA 02120, USA
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Klassen RB, Crenshaw K, Kozyraki R, Verroust PJ, Tio L, Atrian S, Allen PL, Hammond TG. Megalin mediates renal uptake of heavy metal metallothionein complexes. Am J Physiol Renal Physiol 2004; 287:F393-403. [PMID: 15126248 DOI: 10.1152/ajprenal.00233.2003] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although several heavy metal toxins are delivered to the kidney on the carrier protein metallothionein (MT), uncertainty as to how MT enters proximal tubular cells limits treatment strategies. Prompted by reports that MT-I interferes with renal uptake of the megalin ligand β2-microglobulin in conscious rats, we tested the hypothesis that megalin binds MT and mediates its uptake. Three lines of evidence suggest that binding of MT to megalin is critical in renal proximal tubular uptake of MT-bound heavy metals. First, MT binds megalin, but not cubilin, in direct surface plasmon resonance studies. Binding of MT occurs at a single site with a Kd∼10−4and, as with other megalin ligands, depends on divalent cations. Second, antisera and various known megalin ligands inhibit the uptake of fluorescently labeled MT in model cell systems. Anti-megalin antisera, but not control sera, displace >90% bound MT from rat renal brush-border membranes. Megalin ligands including β2-microglobulin and also recombinant MT fragments compete for uptake by megalin-expressing rat yolk sac BN-16 cells. Third, megalin and fluorescently labeled MT colocalize in BN-16 cells, as shown by fluorescent microscopic techniques. Follow-up surface plasmon resonance and flow cytometry studies using overlapping MT peptides and recombinant MT fragments identify the hinge SCKKSCC region of MT as a critical site for megalin binding. These findings suggest that disruption of the SCKKSCC motif can inhibit proximal tubular MT uptake and thereby eliminate much of the renal accumulation and toxicity of heavy metals such as cadmium, gold, copper, and cisplatinum.
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Affiliation(s)
- R Bryan Klassen
- Department of Chemistry, Xavier University of Louisiana, New Orleans, Louisiana 70125-1098, USA.
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Klassen RBS, Allen PL, Batuman V, Crenshaw K, Hammond TG. Light chains are a ligand for megalin. J Appl Physiol (1985) 2004; 98:257-63. [PMID: 15286052 DOI: 10.1152/japplphysiol.01090.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cubilin and megalin are giant glycoprotein receptors abundant on the luminal surface of proximal tubular cells of the kidney. We showed previously that light chains are a ligand for cubilin. As cubilin and megalin share a number of common ligands, we further investigated the ligand specificity of these receptors. Three lines of evidence suggest that light chains can also bind megalin: 1) anti-megalin antiserum largely displaces brush-border light chain binding and megalin-expressing BN-16 cell uptake more than anti-cubilin antiserum, 2) direct binding studies on isolated proteins using surface plasmon resonance techniques confirm that megalin binds light chains, and 3) light chains compete with known megalin ligands for brush-border membrane binding and BN-16 cell uptake. The megalin-light chain interaction is divalent ion dependent and similar for both kappa- and lambda-light chains. A fit of the data on light chain binding to megalin over a concentration range 0.078-2.5 mg/ml leads to an estimated dissociation constant of 6 x 10(-5) M, corresponding approximately to one light chain-binding site per megalin and in the same range for dissociation constants for cubilin binding. These data suggest that light chains bind the tandem megalin-cubilin complex. Megalin is the major mediator of light chain entry into megalin-expressing membrane such as the apical surface of proximal tubular epithelial cells.
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Affiliation(s)
- R Bryan S Klassen
- Dept. of Chemistry, Box 114-B, Xavier University of Louisiana, 1 Drexel Drive, New Orleans, LA 70125-1098, USA.
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Carcoana OV, Mathew JP, Davis E, Byrne DW, Hayslett JP, Hines RL, Garwood S. Mannitol and dopamine in patients undergoing cardiopulmonary bypass: a randomized clinical trial. Anesth Analg 2003; 97:1222-1229. [PMID: 14570627 DOI: 10.1213/01.ane.0000086727.42573.a8] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
UNLABELLED In this prospective, randomized, placebo-controlled, double-blinded study, we determined the effects of two commonly used adjuncts, mannitol and dopamine, on beta(2)-microglobulin (beta(2)M) excretion rates in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass (CPB). beta(2)M excretion rate has been described as a sensitive marker of proximal renal tubular function. One-hundred patients with a preoperative serum creatinine level <or=1.5 mg/dL were prospectively randomized into 4 groups: 1). placebo, 2). mannitol 1 g/kg added to the CPB prime, 3). dopamine 2 microg kg(-1x. min(-1) from the induction of anesthesia to 1 h post-CPB, or 4). mannitol plus dopamine. The primary outcome measure was beta(2)M excretion rate at 1 h post-CPB. Secondary outcome measures included beta(2)M excretion rate at 6 and 24 h post-CPB; urinary flow rate and creatinine clearance at 1, 6, and 24 h post-CPB; and the highest postoperative serum creatinine level. Length of intensive care stay and hospitalization, as well as adverse events, were also considered secondary outcomes. Dopamine significantly increased beta(2)M excretion rate at 1 h post-CPB (2.48 +/- 3.61 microg/min) compared with placebo (0.59 +/- 1.04 microg/min; P = 0.001). This effect was not ameliorated by the addition of mannitol (beta(2)M excretion rate, 2.05 +/- 2.77 microg/min; P = 0.007 compared with placebo). beta(2)M excretion rate was similar in patients given placebo or mannitol alone (P = 0.831). Rather than being a protective drug in the setting of CPB, dopamine alone or in combination with mannitol increases beta(2)M excretion rate, which may be a measure of renal tubular dysfunction. The clinical implications of this increase and whether it is also seen in patients with established renal dysfunction undergoing CPB require additional investigation. IMPLICATIONS In many clinical settings, an increased beta-2-microglobulin (beta(2)M) excretion rate indicates renal tubular injury. In this cardiopulmonary bypass (CPB) study, a dopamine infusion (alone or with mannitol) resulted in an increased beta(2)M excretion rate. It is unclear whether this dopamine-related increase implies renal injury after CPB, and further investigations are required to examine the mechanism/clinical relevance of this observation.
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Affiliation(s)
- Olivia V Carcoana
- *Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut; †Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina; ‡Department of Internal Medicine, Vanderbilt University Medical Center, Nashville, TN; and §Department of Internal Medicine (Section of Nephrology), Yale University School of Medicine, New Haven, Connecticut
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Saw S, Aw TC, Sinniah R. Urine laminin and kallikrein, markers of tubulointerstitial damage in experimental protein overload on pre-existing renal damage. Pathology 2001. [DOI: 10.1080/00313020125043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Wang Y, Shia MA, Christensen TG, Borkan SC. Hepatic alpha 2 mu-globulin localizes to the cytosol of rat proximal tubule cells. Kidney Int 2000; 57:1015-26. [PMID: 10720954 DOI: 10.1046/j.1523-1755.2000.00929.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Alpha 2 mu-Globulin (A2), an 18.6 kD protein of hepatic origin, accumulates in the proximal tubule as an abundant, 15.5 kD cleavage product termed "A2-fragment" (A2-f). A2-f facilitates proximal tubule fatty acid oxidation, presumably by binding hydrophobic ligands. This requires some A2-f to enter the cytosol of the renal epithelial cell (REC). The localization of A2/A2-f in the proximal tubule cell was evaluated in this study. METHODS Immunoblot analysis of renal cortical homogenates separated by differential centrifugation and quantitative immunoelectron microscopy (IEM) was performed to localize A2/A2-f using an affinity-purified antibody that detects both proteins. To evaluate A2 as a physiologically relevant ligand, the accumulation of A2-f in the female rat kidney (normally devoid of A2-f) was examined after the induction of hepatic A2 synthesis. Ligand binding, uptake, and degradation assays were used to assess A2 processing by RECs in vitro. RESULTS Although A2 and A2-f were detected in the "lysosomal" fraction, only A2-f was found in the soluble protein fraction. IEM confirmed the presence of significant signal in the vesicular and lysosomal as well as the cytosolic compartments. In contrast, both beta 2 mu globulin (B2) and cathepsin B were restricted to endosomes. In the female rat, induction of hepatic A2 production resulted in A2-f accumulation in the renal cortex. In RECs in culture, uptake of A2 and B2 demonstrated nonsaturable, nondisplacable surface binding and similar uptake rates. Compared with B2, A2 was markedly resistant to degradation. CONCLUSIONS A fraction of A2 escapes lysosomal degradation, permitting A2-f to accumulate in the cytosol of the proximal tubule epithelial cell. A2 may represent an unusual example of a physiologic protein capable of accumulating in a distant cell type.
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Affiliation(s)
- Y Wang
- Renal Section, Boston Medical Center, Massachusetts, USA
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Thakkar H, Lowe PA, Price CP, Newman DJ. Measurement of the kinetics of protein uptake by proximal tubular cells using an optical biosensor. Kidney Int 1998; 54:1197-205. [PMID: 9767535 DOI: 10.1046/j.1523-1755.1998.00098.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The affinity and specificity of protein reabsorption by proximal tubular cells have been investigated using techniques for monitoring endocytosis, demonstrating a high capacity but low affinity process. It is not known whether uptake is through binding to a single binding site/receptor with differing affinities, or if there are several classes of binding sites receptors, each specific for differing proteins or groups, such as, high or low molecular weight proteins. METHODS We have developed a novel technique for analyzing the kinetics of protein binding to tubular cells using a optical biosensor system. We have studied the binding of cultured LLCPK cells to albumin and RBP immobilized onto the sensor. By adding increasing concentrations of competing proteins [varying in molecular weight from 66,000 to 11,800 D and pI from 4.6 to 9.2 as represented by albumin, alpha1-microglobulin (alpha1M), retinol binding protein (RBP), cystatin C and beta2-microglobulin (beta2m)], specific and inhibitable cell binding was demonstrated. RESULTS Equilibrium constants, KA, could be calculated from the reciprocal of the protein concentration causing 50% inhibition in binding rate. These were: albumin = 8.0 x 10(4) M(-1), alpha1M = 2.0 x 10(5) M(-1), RBP = 2.7 x 10(4) M(-1), cystatin C = 2.0 x 10(4) M(-1), beta2m = 4.2 x 10(3) M(-1). There were no significant differences between the measured KA's whether RBP or albumin were immobilized on the surface. CONCLUSIONS All the proteins gave similar shaped inhibition profiles, suggesting that there is one binding site/receptor for all proteins studied, regardless of molecular weight or charge, but there are differing affinities for each protein.
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Affiliation(s)
- H Thakkar
- Department of Clinical Biochemistry, St. Bartholomew's and The Royal London School of Medicine and Dentistry, England, United Kingdom
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Poon R, Park G, Viau C, Chu I, Potvin M, Vincent R, Valli V. Inhalation toxicity of methanol/gasoline in rats: effects of 13-week exposure. Toxicol Ind Health 1998; 14:501-20. [PMID: 9664642 DOI: 10.1177/074823379801400402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The subchronic inhalation toxicity of a methanol/gasoline blend (85% methanol, 15% gasoline, v/v) was studied in rats. Sprague Dawley rats (10 animals per group) of both sexes were exposed to vapours of methanol/gasoline at 50/3, 500/30 and 5000/300ppm for 6 hours per day, 5 days per week, for 13 weeks. Control animals inhaled filtered room air only. Control recovery and high dose recovery groups were also included which inhaled room air for an extra 4 weeks following the treatment period. No clinical signs of toxicity were observed in the treatment group and their growth curves were not significantly different from the control. Except for decreased forelimb grip strength in high dose females, no treatment-related neurobehavioural effects (4-6 hours post inhalation) were observed using screening tests which included cage-side observations, righting reflex, open field activities, and forelimb and hindlimb grip strength. At necropsy, the organ to body weight ratios for the liver, spleen, testes, thymus and lungs were not significantly different from the control group. There were no treatment-related effects in the hematological endpoints and no elevation in serum formate levels. Minimal serum biochemical changes were observed with the only treatment-related change being the decreased creatinine in the females. A dose-related increase in urinary ascorbic acid was detected in males after 2, 4 and 8 weeks of exposure, but not after the 12th week, and in females only at week-2. Increased urinary albumin was observed in treated males starting at the lowest dose and at all exposure periods, but not in females. A treatment-related increase in urinary beta 2-microglobulin was detected in males at week-2 only. Except for mild to moderate mucous cell metaplasia in nasal septum B, which occurred more often and with a slightly higher degree of severity in the low dose groups of both sexes, and presence of a minimal degree of interstitial lymphocyte infiltration in the prostate glands in the high dose males. No other significant microscopic changes were observed in the tissues of treated animals. Based on the marked increase in urinary ascorbic acid and albumin in the high dose males and the decreased forelimb grip strength in the high dose females, we concluded that the no-observed adverse effect level (NOAEL) of methanol/gasoline vapour is 500/30 ppm.
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Affiliation(s)
- R Poon
- Environmental Health Directorate, Health Protection Branch, Ottawa, Canada.
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Gburek J, Zabel M, Osada J. Immunohistochemical localization of haemoglobin binding sites in the distal tubule of the rat kidney. THE HISTOCHEMICAL JOURNAL 1998; 30:421-4. [PMID: 10192541 DOI: 10.1023/a:1003272209740] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Although it is well established that haemoglobin can be taken up by kidney tubular epithelium, the exact mechanism of the process has not been elucidated so far. We have undertaken a study to determine whether any specific binding sites for haemoglobin are present on the membranes of renal tubular cells. Paraffin sections of rat kidney cortex were incubated with haemoglobin, and the bound molecules were detected by means of a combined avidin-peroxidase and ImmunoMax method. Haemoglobin binding sites were observed in the apical membrane of distal tubules. Binding occurred for both rat haemoglobin and swine and human haemoglobins, and the proteins could compete with each other. Competition experiments with other proteins showed that the binding is specific for haemoglobin and that the net charge of the protein is not critical for the interaction. We failed to detect the binding sites in proximal tubules, where most of the filtered proteins are reabsorbed. The role of the binding sites in the distal nephron is unclear. Our findings may be essential for the further understanding of the pathomechanism of haemoglobin-induced acute renal failure.
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Affiliation(s)
- J Gburek
- Department of Pharmaceutical Biochemistry, Wroclaw University of Medicine, Poland
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Kabanda A, Vandercam B, Bernard A, Lauwerys R, van Ypersele de Strihou C. Low molecular weight proteinuria in human immunodeficiency virus-infected patients. Am J Kidney Dis 1996; 27:803-8. [PMID: 8651244 DOI: 10.1016/s0272-6386(96)90517-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
To determine whether human immunodeficiency virus (HIV) infection is associated with incipient tubular or glomerular defects, we determined the urinary excretion of four low molecular weight proteins (LMWP); beta2-microglobulin (U-beta2-m), cystatin C (U-cyst C), Clara cell protein (U-CC16), and retinol-binding protein (U-RBP), the markers of tubular dysfunction, the excretion of albumin (U-Alb), a marker of glomerular defect, and the excretion of N-acetyl-beta-D-glucosaminidase (U-NAG), a marker of structural damage of the proximal tubular epithelium. Their determinants have been assessed by stepwise regression analysis using as possible predictors age, sex, serum-beta2-m (S-beta2-m), CD4 lymphocyte count, or HIV infection stage and therapy. The study involved 76 HIV-infected patients without renal disease, 56 with S-beta2-m < 5 mg/L (Group B1), 20 with S-beta2-m > or = 5 mg/L (Group B2), and 30 HIV-negative controls. Fourteen patients (18.4%) had no abnormal urinary protein loss, and 62 (81.6%) had elevated urinary excretion of at least one protein (Alb, LMWP, or NAG). A single urinary protein was abnormal in 21 patients (U-beta2-m, n = 9; U-RBP, n = 2; U-CC16, n = 4; and U-Alb, n = 6). At least two LMWP were abnormal without increased U-Alb in 23 patients (12 with increased and 11 with normal U-NAG). Ten patients had an increased urinary excretion of at least one LMWP together with U-Alb (5 with increased and 5 with normal U-NAG). An increased urinary excretion of all proteins was observed in the last 8 patients. The average urinary excretion of all proteins (except cyst C) was significantly higher in HIV than in the control group. As expected, U-beta2-m and the prevalence of abnormal U-beta2-m values were higher in the B2 than in the B1 group (P = 0.0001), whereas the average urinary excretion and the prevalence of elevated values of Alb, LMWP (except beta2-m) or NAG were the same in both HIV groups. By stepwise regression analysis, age emerged as a significant determinant of urinary excretion of beta2-m and CC16, whereas male sex was associated with increased U-CC16. S-beta2-m, CD4-lymphocyte count, or HIV infection stage emerged as significant determinants only for U-beta2-m as a consequence of a close correlation between S-beta2-m and either HIV infection stage (r = -0.52, P = 0.0001), or CD4 count (r = -0.45, P = 0.0002). Over 80% of HIV-infected patients without overt renal disease have evidence of glomerular permeability defects or tubular dysfunction, whatever the stage of the disease. U-Alb, RBP, and CC16 appear as the most sensitive and reliable early markers of these abnormalities. Their cause and prognostic value remain to be determined.
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Affiliation(s)
- A Kabanda
- Nephrology Unit, Catholic University of Louvain, Medical School, Brussels, Belgium
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Takakura Y, Morita T, Fujikawa M, Hayashi M, Sezaki H, Hashida M, Borchardt RT. Characterization of LLC-PK1 kidney epithelial cells as an in vitro model for studying renal tubular reabsorption of protein drugs. Pharm Res 1995; 12:1968-72. [PMID: 8786975 DOI: 10.1023/a:1016256325921] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE The purpose of this study was to assess whether LLC-PK1 renal epithelial cells could serve as an in vitro model for studying the renal tubular reabsorption of protein drugs. METHODS The association of 111In-labeled model protein drugs, bovine serum albumin (BSA), superoxide dismutase (SOD), soybean trypsin inhibitor (STI), and [Asu1.7]-eel calcitonin (Asu-ECT), with the monolayers of LLC-PK1 renal epithelial cells was characterized under various conditions. RESULTS The cellular association of these proteins was temperature-dependent and varied according to the protein. Saturation kinetics were observed for STI association, with the apparent Km and Vmax values determined to be 66.3 micrograms/ml and 250 ng/mg protein/min, respectively. The association of STI decreased with increases in medium pH from 5.4 to 8.4 and was inhibited significantly by 2,4-dinitrophenol, sodium azide, cytochalasin B, and colchicine, suggesting that the cellular association involved endocytosis. Mutual inhibition was observed in competitive binding experiments with the four protein drugs, suggesting that they shared a common binding site on the luminal membrane of LLC-PK1 cells. Taken together, these findings show that a variety of protein drugs bind to LLC-PK1 cells in a non-specific manner and possibly undergo endocytosis, a phenomenon that is similar to in vivo proximal tubular reabsorption. CONCLUSIONS LLC-PK1 renal epithelial cells would be a suitable model system for the study of the renal proximal tubular reabsorption of protein drugs.
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Affiliation(s)
- Y Takakura
- Department of Drug Delivery Research, Kyoto University, Japan
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Kabanda A, Jadoul M, Lauwerys R, Bernard A, van Ypersele de Strihou C. Low molecular weight proteinuria in Chinese herbs nephropathy. Kidney Int 1995; 48:1571-6. [PMID: 8544416 DOI: 10.1038/ki.1995.449] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Urinary excretion of five low molecular weight proteins (LMWP) [beta 2-microglobulin (beta 2m), cystatin C (cyst C), Clara cell protein (CC16), retinol-binding protein (RBP) and alpha 1-microglobulin (alpha 1m)], albumin and N-acetyl-beta-D-glucosaminidase (NAG) were quantified in 16 patients who followed a weight reduction program which included Chinese herbs, which have been incriminated in the genesis of Chinese herbs nephropathy (CHN). An additional group of four patients transplanted for CHN were investigated. Urinary data were obtained for comparison purpose in five groups of proteinuric patients: two groups with normal serum creatinine (SCr) and glomerular albuminura [12 patients with diabetes mellitus and microalbuminuria (DN), 10 patients with primary nephrotic syndrome (NS)]; two groups with normal SCr and toxic nephropathy [6 patients with analgesic (AN), 9 patients with cadmium nephropathy (CdN)]; and one group of seven patients with glomerular diseases and increased SCr (GN). Patients were classified according to serum level S beta 2m to take into account the possibility of overflow proteinuria at S beta 2m > or = 5 mg/liter. Three patients (CHN0) with a S beta 2m < 5 mg/liter, had a normal urinary protein pattern including NAG and a normal S beta 2m. Eight patients (CHN1) with a S beta 2m < 5 mg/liter had various abnormalities of their urinary protein pattern. In four of them (CHN1a) only beta 2m, RBP and CC16 were increased while total proteinuria and SCr were normal. In the other four (CHN1b and c) albumin, cyst C, alpha 1m and NAG were also elevated, while total proteinuria and SCr were moderately raised. Five patients (CHN2) with a S beta 2m > or = 5 mg/liter had a markedly increased excretion of all LMWP, albumin and NAG (CHN1 vs. CHN2, P < 0.05) as well as a further increase in total proteinuria and SCr. The urinary LMWP/albumin concentration ratio was strikingly higher in CHN patients than in patients with glomerular albuminuria (CHN1 vs. DN and NS, P < 0.01) or moderate renal failure with elevated S beta 2m level (CHN2 vs. GN, P < 0.01), confirming the existence of a tubular proteinuria independent of glomerular albuminuria or overflow proteinuria. A similar proteinuria pattern was present in the two toxic nephropathies (CdN and AN). This pattern was no longer recognizable after transplantation. In conclusion, CHN exhibits various profiles of tubular proteinuria which are the hallmarks of the disease. This pattern is still detectable in patients with renal failure and/or glomerular albuminuria. It is identical to that observed in cadmium and analgesic nephropathies. It does not recur after transplantation. Its most sensitive and reliable marker is a raised urinary level of CC16 or RBP.
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Affiliation(s)
- A Kabanda
- Nephrology Unit, Catholic University of Louvain, Medical School, Brussels, Belgium
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Simonnet H, Gauthier C, Gire V, Baverel G. Protein endocytosis by a kidney tubule suspension: metabolic requirements. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1189:152-62. [PMID: 8292619 DOI: 10.1016/0005-2736(94)90060-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Endocytosis in the renal tubular cell is a permanent process serving the role of saving nitrogen from plasma peptides that are continuously cleared away by kidney glomerulus. Since small proteins appear in urine after strenuous exercise, it was hypothesized that renal ischemia impairs the tubular endocytic reabsorption of proteins. The aim of this paper is to describe a simple in vitro model of renal endocytosis and to use it in studies of endocytic metabolic requirements. The results show that rabbit renal proximal tubules in suspension are able to take up 125I-lysozyme, as well as RITC-lactalbumin. The fluorescent protein was taken up only by the ends of the everted tubule fragments, and accumulated into intracellular vesicles, demonstrating the luminal pathway of endocytosis. The amount of 125I-lysozyme taken up was equivalent to that taken up by isolated perfused tubules (Nielsen et al. (1986) Am. J. Physiol. 251, F822-F830). Anoxia decreased 12-fold the intracellular accumulation of 125I-lysozyme; however, the time-course of inhibition shows that only the late steps of endocytic accumulation are energy-dependent. Substrate deprivation studies suggest a specific role of glucose to sustain endocytosis. Lastly, renal uptake of 125I-lysozyme was shown to be strongly depressed by chloroquine, an alkalinizing agent of endosomes and lysosomes. We conclude that (1) renal tubules in suspension are a satisfactory model for endocytic studies in kidney; (2) suppressing oxygen and substrate supplies to kidney impairs endocytic tubular reabsorption of proteins.
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Affiliation(s)
- H Simonnet
- Laboratoire de Physiopathologie Rénale et Métabolique, CNRS EP 18, Faculté de Médecine Alexis Carrel, Lyon, France
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Abstract
Trichosanthin (TCS) is a ribosome-inactivating protein that has a wide range of biological and pharmacological activities. Due to its small molecular size, TCS is filtered by the glomerulus and can be recovered from urine. A previous experiment showed that the kidney is an important organ for its elimination. However, urine TCS recovery was unexpectedly small, suggesting renal reabsorption of this compound. To substantiate renal TCS reabsorption, different doses of TCS were injected intravenously into rats. Increasing the dose from 0.375 mg/kg to 12 mg/kg enhanced the percentage urine recovery from less than 0.29 +/- 0.06% to 39.07 +/- 2.46%. This demonstrated that TCS is reabsorbed by a saturable mechanism. Reabsorption of most small molecular weight filterable proteins shares a common endocytotic process. It is very likely that TCS utilizes the same process for reabsorption. When a filterable protein such as hemoglobin was infused with TCS, it competed with TCS for reabsorption and therefore increased the percentage urine TCS recovery to 35 +/- 2%. Infusion of another filterable protein, lysozyme, increased recovery to 3.2 +/- 0.8%. This supports the proposal that renal TCS uptake utilizes the common endocytotic mechanism. It was also found in this study that injection of TCS depressed the glomerular filtration rate (GFR), implying renal toxicity. This effect can be attributed to ribosome inactivation which takes place inside the cells. Should reabsorption of TCS be reduced, renal toxicity will disappear. For this purpose, dextran-trichosanthin (DXTCS) conjugate was synthesized to increase its effective molecular size.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- W H Ko
- Department of Physiology, Chinese University of Hong Kong
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Bernard A, Ouled Amor A, Lauwerys R. Charge-dependent renal uptake of beta 2-microglobulin in conscious rats. Scand J Clin Lab Invest 1992; 52:415-23. [PMID: 1325071 DOI: 10.3109/00365519209088377] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The influence of molecular charge on the tubular reabsorption of proteins was studied in conscious rats injected intravenously with beta 2-microglobulins of different isoelectric points (pI). Native human beta 2-microglobulin (pI 5.8), two anionized (pI 4.85 and 5.55) and three cationized derivatives (pI 7.2, 8.35 and 8.7) were used. The six forms of beta 2-microglobulin had a molecular radius between 15.7 and 15.9 A. The renal uptake was estimated by measuring the amount excreted in urine with a sensitive immunoassay. The ability of rat kidney to reabsorb beta 2-microglobulin was clearly related to the net charge of the protein. Increasing the pI of the protein significantly reduced the urinary excretion, whereas lowering it had the opposite effect. Anionization was particularly effective in reducing the beta 2-microglobulin uptake, since a decrease of the pI of one unit enhanced the urinary output by two orders of magnitude. This charge-dependency persisted when the tubular reabsorption of proteins was partly inhibited by lysozyme. By contrast, it was practically abolished by lysine, probably because the inhibitory effect of this amino acid on protein tubular reabsorption is not competitive. The administration of ammonium chloride in rats produced an immediate and transient elevation of rat beta 2-microglobulinuria. This phenomenon, which was partly inhibited by the subsequent administration of sodium bicarbonate, presumably results from a competition between the NH4+ ion and beta 2-microglobulin for tubular binding sites. These data support the hypothesis that proteins bind to the luminal membrane of tubular cells mainly via positively charged amino groups.
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Affiliation(s)
- A Bernard
- Unit of Industrial Toxicology and Occupational Health, University of Louvain, Brussels, Belgium
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Bernard A, Lauwerys R, Ouled Amor A. Loss of glomerular polyanion correlated with albuminuria in experimental cadmium nephropathy. Arch Toxicol 1992; 66:272-8. [PMID: 1514926 DOI: 10.1007/bf02307173] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The relationship between proteinuria and glomerular polyanion (GPA) charge has been studied in a model of experimental cadmium (Cd) nephropathy. Female Sprague-Dawley rats were administered Cd in drinking water for up to 18 months. From month 2, the animals showed an elevation of albuminuria preceding by about 6 months the rise of urinary beta 2-microglobulin and IgG. The nephrotoxic action of Cd was not readily detectable on the basis of the urinary output of beta-N-acetylglucosaminidase, alanine aminopeptidase and lactate dehydrogenase. These enzymes showed either little variation or were affected late in the intoxication process. Administration of Cd for 12 or 18 months did not impair the GFR. The glomerular origin of the albuminuria induced by Cd was demonstrated by estimating the glomerular filtration of rat or human (injected intravenously) albumin in rats whose tubular reabsorption had been blocked by a saturating dose of cytochrome C. The GPA charge was assessed by measuring the binding of the cationic dye, Alcian blue (AB), to membranes of isolated glomeruli. The sialic and sulfate content of these membranes was also determined. The Cd induced-albuminuria was negatively correlated (r = -0.73; n = 37) with the AB binding to glomerular membranes, their sialic acid content (r = -0.39) but not with their sulfate content (r = -0.15). A negative correlation (r = -0.62; n = 37) was also observed between the albuminuria and red blood cell membrane negative charges largely contributed by sialic acid. All these observations can be interpreted as the evidence that Cd enhances the glomerular filtration of proteins through a GPA depletion involving mainly sialic acid.
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Affiliation(s)
- A Bernard
- Unit of Industrial Toxicology and Occupational Medicine, Catholic University of Louvain, Clos Chapelle-aux-Champs, Brussels, Belgium
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Ginevri F, Mutti A, Ghiggeri GM, Alinovi R, Ciardi MR, Bergamaschi E, Verrina E, Gusmano R. Urinary excretion of brush border antigens and other proteins in children with vesico-ureteric reflux. Pediatr Nephrol 1992; 6:30-2. [PMID: 1311186 DOI: 10.1007/bf00856825] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
This study was designed to evaluate the occurrence and the type of proteinuria in 82 children with vesico-ureteric reflux (VUR) with or without renal scars. The urinary excretion of the high molecular weight protein albumin was taken as an index of glomerular alterations and the excretion of retinol-binding protein (RBP), beta 2-microglobulin and brush border antigens (BBA) (measured by monoclonal antibody-based enzyme-linked immunosorbent assay) was taken as an index of tubular alterations. All such markers were increased in children with VUR and were related to the degree of renal function. Patients showing reduced creatinine clearance had very high levels of albuminuria, microproteinuria and BBA, with all these variables reciprocally correlated. In children with normal renal function however, only microproteins (not albumin or BBA) were slightly increased, thus indicating an isolated tubular defect without involvement of the proximal segment of the tubule. However, microprotein excretion did not correlate with the grade of scarring (99mtechnetium-dimercaptosuccinic acid scan), both RBP and beta 2-microglobulin excretion being normal in 75% of children with radioisotopic signs of renal lesions but increased in 17% of children without scars. Therefore, tubular proteinuria identifies different groups of children with VUR but is not related to renal scarring. Prospective studies will define the usefulness of proteinuria as a reliable indicator of renal outcome.
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Affiliation(s)
- F Ginevri
- Department of Nephrology, G. Gaslini Institute of Genoa, Italy
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Ko WH, Wong CC, Yeung HW, Yung MH, Shaw PC, Tam SC. Increasing the plasma half-life of trichosanthin by coupling to dextran. Biochem Pharmacol 1991; 42:1721-8. [PMID: 1718284 DOI: 10.1016/0006-2952(91)90508-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Trichosanthin (TCS) is a plant protein which has a wide spectrum of pharmacological activities. It was demonstrated recently that this compound suppressed the replication of human immunodeficiency virus (HIV-1) in vitro. The mechanism of action is believed to be inhibition of protein synthesis. Trichosanthin is a low molecular weight protein which is expected to be easily filtered and eliminated through the kidney. To minimize renal loss, the molecular size of trichosanthin can be increased by coupling to dextran. The larger complex will not undergo glomerular filtration and therefore renal loss can be prevented. This study investigates the kidney's role in trichosanthin elimination and the beneficial effect afforded by coupling to dextran in prolonging plasma half-life. For this purpose, a radioimmunoassay has been developed to determine the concentration of TCS in plasma and urine. The sensitivity of this assay is in the nanogram range. Trichosanthin was coupled to dextran T40 by a dialdehyde method and successful coupling was confirmed by gel filtration chromatography. The complex retained specific binding to trichosanthin antibodies with decreased affinity which can be partially reversed after incubation with dextranase; an enzyme that digested dextran. The pharmacokinetics of intravenously administered trichosanthin (0.75 mg/kg) was compared between two groups of rats with normal and impaired renal function (bilateral renal arterial ligation). Rats with ligation showed a decrease in plasma clearance from 4780 +/- 570 to 220 +/- 20 microL/min and an increase in the mean residence time from 9 +/- 1 to 145 +/- 16 min. Despite the several-fold difference in these parameters, recovery of trichosanthin from normal rat urine was only 0.38 +/- 0.05%. This value can be increased by using higher injection doses. The data indicate that the kidney is an important organ for the elimination of trichosanthin. When the dextran-trichosanthin complex was injected into normal rats trichosanthin activity was not detected in the urine. All the pharmacokinetic parameters suggest that the dextran-trichosanthin complex stayed longer in the body and maintained a much higher plasma concentration than trichosanthin.
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Affiliation(s)
- W H Ko
- Department of Physiology, Chinese University of Hong Kong, Shatin
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Bernard A, Lauwerys R, Noel A, Vandeleene B, Lambert A. Determination by latex immunoassay of protein 1 in normal and pathological urine. Clin Chim Acta 1991; 201:231-45. [PMID: 1756596 DOI: 10.1016/0009-8981(91)90374-l] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A sensitive latex particle assay has been developed to study the occurrence of protein 1 in human urine. The coefficients of variation (CVs) of the method which is fully automated vary between 3 and 11.5%. The assayable concentration range is 0.3 to 40 micrograms/l. Protein 1 is clearly a sex-dependent protein. In contrast to urinary retinol-binding protein (RBP) which shows no variation with age or sex, protein 1 is excreted in greater amounts in males from the puberty. In adults, the mean concentration of protein 1 in urine of men is approximately 5 times that of women. In the urine from both sexes, protein 1 occurs as a single component with a Mr around 21,000 and an pI of about 4.8. Protein 1 is correlated with RBP in the urine from female or male patients with impaired proximal tubular function, which suggests that it is handled by the kidney in a similar manner as RBP. Diabetics, however, show elevations of urinary protein 1 which do not correlate with the RBP excretion but with the albuminuria. A competition between albumin and protein 1 for renal tubular uptake might explain this paradoxical behaviour of protein 1 in the course of diabetic nephropathy.
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Affiliation(s)
- A Bernard
- Unité de Toxicologie Industrielle et de Médecine du Travail, Université Catholique de Louvain, Brussels, Belgium
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Abstract
During the last few decades, considerable progress has been made in the understanding of the pathophysiological mechanisms of proteinuria. A great variety of hemodynamic or biochemical mechanisms acting at different sites of the nephron have been shown to alter the renal handling and the urinary excretion of proteins. The finding which perhaps has had most practical implications is that the pattern of protein excretion quantitatively and qualitatively varies with the site and severity of renal damage. This has led to the development of a large array of methods for the identification and quantitation of specific urinary proteins. These methods have been most extensively used by toxicologists in experimental, epidemiological, or clinical studies on potentially nephrotoxic chemicals (e.g., drugs, heavy metals, solvents, etc.). The present review summarizes the current state of knowledge on the mechanisms of proteinuria and the use of urinary proteins as indicators of nephrotoxicity.
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Affiliation(s)
- A Bernard
- Unit of Industrial Toxicology and Occupational Medicine, Catholic University of Louvain, Brussels, Belgium
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Tomlinson PA, Dalton RN, Turner C, Chantler C. Measurement of beta 2-microglobulin, retinol-binding protein, alpha 1-microglobulin and urine protein 1 in healthy children using enzyme-linked immunosorbent assay. Clin Chim Acta 1990; 192:99-106. [PMID: 1705872 DOI: 10.1016/0009-8981(90)90073-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Enzyme-linked immunosorbent assays (ELISA) have been developed for the measurement of beta 2-microglobulin (B2M), retinol-binding protein (RBP), alpha 1-microglobulin (A1M) and urine protein 1 (UP1) in children. Results from random urine samples in 43 children (31 for B2M) are, when corrected for urine creatinine (geometric mean (range)): B2M 9.8 (6.0-40.7) micrograms/mmol, RBP 8.1 (less than 1-24.5) micrograms/mmol, A1M 0.4 (0.1-2.2) mg/mmol and UP1 17.8 (less than 2-309.4) micrograms/mmol. Fractional excretions (FE) in 23 children (14 for B2M) are (geometric mean (range)): FEB2M 0.04% (0.02-0.10%) and FEUP1 0.10% (0.01-1.21%). Results in overnight urine collections are also presented. Our results extend existing data for normal ranges in adults to include children and provide data on UP1 concentrations.
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Affiliation(s)
- P A Tomlinson
- Evelina Children's Unit, Guy's Hospital, United Medical and Dental School, London, UK
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Roberts DS, Haycock GB, Dalton RN, Turner C, Tomlinson P, Stimmler L, Scopes JW. Prediction of acute renal failure after birth asphyxia. Arch Dis Child 1990; 65:1021-8. [PMID: 2241220 PMCID: PMC1590244 DOI: 10.1136/adc.65.10_spec_no.1021] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Twenty-one babies of 34-41 weeks' gestational age with birth asphyxia (5 minute Apgar score less than or equal to 5 or umbilical artery pH less than or equal to 7.2) were studied during the first two days of life to find out whether the urinary excretion of tubular markers of renal function is of value in the early diagnosis of acute renal failure. Urinary retinol binding protein, myoglobin, and N-acetyl-beta-D-glucosaminidase (NAG), expressed as a ratio with urinary creatinine, were measured and excretion profiles repeated at 3-6 days in 15 infants and at 7-14 days in 11 infants. Plasma creatinine concentration, creatinine clearance, plasma myoglobin concentration, and fractional sodium excretion were measured where possible in asphyxiated infants. Control data were obtained from 50 healthy infants: 28 gave urine samples alone, 17 urine and blood, and five blood alone. Normal urinary values were derived from 17, 25, and three infants, respectively, for the three time periods. The number of control samples was limited for ethical reasons. Four asphyxiated infants had acute renal failure (group 1), four had tubular dysfunction without glomerular disturbance (group 2) and 13 had normal renal function (group 3). Group 1 were clearly identified by greatly increased urinary retinol binding protein (greater than 27,000 micrograms/mmol creatinine) and myoglobin (greater than 1500 micrograms/mmol creatinine) excretion measured in the first two days of life. In control infants the range of excretion of retinol binding protein within the same time period was 3 to 967 micrograms/mmol creatinine and urinary myoglobin was undetectable. Excretion of NAG failed to discriminate between groups 1 and 2. Acute renal failure occurred only in infants who had heavy myoglobinaemia. Tubular dysfunction in group 2 was transient and not accompanied by plasma electrolyte disturbances. We conclude that measurement of urinary excretion of retinol binding protein or myoglobin after birth is helpful in the early diagnosis of acute renal failure.
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Affiliation(s)
- D S Roberts
- Department of Paediatrics, United Medical School, St Thomas's Hospital, London
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Bernard AM, de Russis R, Normand JC, Lauwerys RR. Evaluation of the subacute nephrotoxicity of cyclohexane and other industrial solvents in the female Sprague-Dawley rat. Toxicol Lett 1989; 45:271-80. [PMID: 2645690 DOI: 10.1016/0378-4274(89)90018-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The subacute nephrotoxicity of more than 20 industrial solvents has been compared in female Sprague-Dawley rats. The animals were given 5 i.p. injections of the solvents per week for 2 weeks at doses ranging from 1/20 to 1/5 of the i.p. or oral LD50 and the urinary excretion of N-acetyl-beta-D-glucosaminidase, beta 2-microglobulin and albumin was determined. Under these experimental conditions, two solvents, cyclohexane and styrene, were found to cause some tubular injury as evidenced by a statistically significant increase of beta 2-microglobulinuria. At the same dose, styrene was more tubulotoxic than cyclohexane but the opposite was observed when the solvents were administered proportionally to their LD50. The increased beta 2-microglobulinuria caused by cyclohexane was both time- and dose-dependent. It was not accompanied by changes in the glomerular filtration rate and the renal plasma flow, but at the highest dose (1.5 g/kg) the renal concentrating ability was depressed. These renal tubular effects can most likely be ascribed to cyclohexanol, the main metabolite of cyclohexane. As cyclohexane is a widely used industrial solvent with a relatively high threshold limit value (TWA-TLV: 300 ppm) it might represent an underestimated risk for the renal function of exposed populations.
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Affiliation(s)
- A M Bernard
- Unit of Industrial Toxicology and Occupational Medicine, Catholic University of Louvain, Brussels, Belgium
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