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Query: UMLS:C0033687 (proteinuria)
 24,015 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four commonly used methods for the determination of total protein in urine were compared. These were two biuret methods using different precipitants, a Ponceau S method and a Coomassie Brilliant Blue method. The protein content of the urines was also evaluated by sodium dodecylsulphate polyacrylamide gel electrophoresis. The biuret method with ethanolic phosphotungstic acid as precipitant correlated best with the Coomassie Brilliant Blue method (r = 0.944; p less than 0.001) but less well with the Ponceau S (r = 0.895; p less than 0.001) or biuret-trichloroacetic acid (r = 0.874; p less than 0.001) methods. For urines with normal electrophoretic protein patterns, the imprecise biuret-trichloroacetic acid method (cv = 18.5%) gave the greatest number of false high results (23 in 36 urines) as assessed by electrophoresis. False low results were common in low relative molecular mass (Mr) proteinuria, especially with the biuret-tricholoroacetic acid and Ponceau S methods. High Mr proteinuria rarely caused false low results. Discrepancies between methods appear to have resulted from incomplete precipitation of low Mr protein by trichloroacetic acid.
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PMID:Effects of low and high relative molecular protein mass on four methods for total protein determination in urine. 170 Mar 58

A two-step screening of urine samples for Bence-Jones proteins is described. The proposed method is fast and fully mechanized; quantitative results are obtained within minutes. As a first step alpha 1-microglobulin, albumin, transferrin and IgG are measured immunonephelometrically. Then the cumulative concentration of the four markers is compared with that of total protein, which is determined by nephelometry during trichloroacetic acid protein precipitation. Bence-Jones proteinuria is indicated by large concentrational differences (greater than 31%) between the four markers and total protein. As a second step, Bence-Jones proteins are assessed directly if they are present. Immunoglobulin light-chains are measured immunonephelometrically and the kappa:lambda ratio is used to discriminate between monoclonal and polyclonal forms. Using this strategy, urine samples from 84 patients with monoclonal gammopathia or multiple myeloma were screened. Bence-Jones proteinuria was detected in 40 cases. In a reference collective (69 patients with different types of renal proteinuria) Bence-Jones proteinuria was not observed. Comparing the results with those obtained by immunofixation, the nephelometric method has a sensitivity of 100% and a specificity of 97%, differing only in a single false-positive result. Additional information about renal forms of proteinuria is supplied by the first screening step. This permits an assessment of the renal involvement in Bence-Jones proteinuria, and the method can also be used for nephrological diagnosis.
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PMID:Identification and quantification of Bence-Jones proteinuria by automated nephelometric screening. 231 35

A reduction in prostacyclin (PGI2) production by vascular wall may cause platelet hyperaggregability in diabetics, which is considered to be a possible pathogenesis of diabetic vascular complications. In the present study, the presence of PGI2-stimulatory activity (PSA) in rat and human plasma-derived serum (PDS) was confirmed by cultured bovine aortic endothelial cells. PSA in PDS was significantly decreased in streptozotocin-induced diabetic rats and in patients with non-insulin-dependent diabetes mellitus (NIDDM). PDS from patients with NIDDM showed less PSA prior to the clinical onset of diabetic vascular complications, such as retinopathy and proteinuria. The reduction in PSA was still observed in dialyzed PDS from the patients with NIDDM. The nondialyzable PSA was heat-stable at 56 degrees C for 30 minutes and partially stable at 100 degrees C for five minutes. This activity was not extractable with diethylether and was precipitable with trichloroacetic acid. The study of Sephadex G-50 column chromatography showed that a major part of PSA in dialyzed PDS was found in the area of the molecular weight of 12,000 to 17,000 daltons. In conclusion, the reduction in PSA from diabetics may cause a reduction of PGI2 production by vascular wall, subsequently contributing to the development of diabetic vascular complications.
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PMID:Abnormality in prostacyclin-stimulatory activity in sera from diabetics. 250 15

Glomerular epithelial cells (GECs) in vitro provide a useful model for the study of the mechanism(s) underlying the nephrotic syndrome of rats induced by the aminonucleoside of puromycin (PAN). Some of the toxicities of PAN are nonspecific, in that the constituent molecules of PAN (adenosine and puromycin) cause similar effects in vitro. These include GEC blebbing and rounding, reduced uptake of precursors of protein (leucine) and glycoprotein (glucosamine) synthesis, and increased permeability of the GEC membrane to adenosine. Some of the effects of PAN are not reproduced by adenosine or puromycin and are inhibited by the simultaneous presence of N6-monomethyl adenosine (MMA), a PAN analog and an in vivo blocker of nephrosis due to PAN. These processes may be related to the nephrotic syndrome and include the loss of adhesion to plastic; a reduction in the incorporation of 14C-glucosamine and 35S-sulfate both into molecules removable from the GEC surface by neuraminidase and into those moieties precipitated from the culture media by TCA; a marked reduction in the "ordering" of the lipids of the rigid GEC membrane, which is possibly dependent upon cell-surface proteins. These morphologic alterations in GECs and in the distribution of negatively charged molecules, which are either secreted or on the cell surface, correlate with observations made in PAN-induced nephrosis in rats in vivo. These include changes in the turnover and the array of sialic acid and heparan sulfate glycoprotein on the GECs and the glomerular basement membrane. The in vitro sensitivity of GECs to PAN and the effects of MMA suggest a role for these cells in in vivo aminonucleoside nephrotoxicity, where alterations in both the morphology and the anionic topology of GECs participate in the development of proteinuria.
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PMID:Effects of the aminonucleoside of puromycin on glomerular epithelial cells in vitro. 397 43

A turbidimetric method for the determination of total urinary proteins is proposed that uses a specimen blank for each urine. The precipitant, trichloroacetic acid (TCA), is introduced into the blank and the sample in the same amount. The blank is the supernatant of the TCA-treated urine for each specimen. Turbidity is measured by reading the 420-nm absorbance 35 minutes after the TCA addition when the turbidity curves for most urine samples plateau. This improved method was compared with an established procedure that uses water to prepare the blanks and that measures turbidity 5 minutes after the TCA addition. Of the 69 urine specimens that were analyzed by the two methods, the revised procedure yielded higher values (greater than or equal to 150%) for 5 samples, while 21 samples had lower values (less than or equal to 50%). In the latter group, four cases would have been classified erroneously as having significant proteinuria by the established method.
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PMID:Turbidimetric measurement of total urinary proteins: a revised method. 672 Jun 31

Gentamicin and other aminoglycoside antibiotics in high doses may produce proteinuria and other signs of nephrotoxicity. Proteinuria may result from general renal damage or may reflect alterations in specific steps in the renal handling of proteins. To distinguish between these two possibilities, experiments were designed to quantify the effects of nephrotoxic doses of several aminoglycosides on the renal handling of proteins in the isolated perfused rat kidney with the cationic low-molecular-weight protein lysozyme as a representative protein. Each aminoglycoside was administered ip to male Wistar rats (30 mg/kg/day) for 7 days. Lysozyme and 125I-lysozyme were added to the perfusate to achieve a lysozyme perfusate concentration of about 100 mg/liter. Clearances of inulin and lysozyme, release of tyrosine and trichloroacetic acid-soluble radioactive metabolites into the perfusate, and the glomerular sieving coefficient of lysozyme were determined. Scanning and transmission electron microscopy indicated that gentamicin and tobramycin decreased the number and diameter of the endothelial fenestrae of the glomerular capillaries. Concurrently, gentamicin and tobramycin decreased the glomerular sieving coefficient of lysozyme from 0.8 to 0.6 and 0.5, respectively. Netilmicin did not affect the percentage reabsorption of lysozyme whereas gentamicin and tobramycin decreased lysozyme reabsorption from 71.7 to 35.4 and 34.4% of the filtered load, respectively. Lysozyme degradation, estimated by the release of tyrosine into the perfusate during a 150-min perfusion period, was decreased from a control value of 12 mumol/liter to 4.43 and 4.65 mumol/liter in kidneys from rats treated with gentamicin and tobramycin, respectively. This study demonstrates that polycationic aminoglycosides may affect several processes involved in renal handling of lysozyme including glomerular permeability, tubular reabsorption, and intracellular proteolytic degradation.
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PMID:Effects of aminoglycosides on glomerular permeability, tubular reabsorption, and intracellular catabolism of the cationic low-molecular-weight protein lysozyme. 684 78

Total urinary protein was measured by five methods: BioRad Total Protein Test (TPT), pyrogallol red, benzethonium chloride, sulfosalicylic acid, trichloroacetic acid, and the results compared to those obtained by a method combining preparative ultrafiltration and the biuret reaction. TPT was linear to 1.5 g protein/l, the detection limit 0.0135 g/l, and it was 3-5 times more sensitive than the other methods. Within-day precision (CV) was 4.3%, (0.60 g/l), the day-to-day precision was 4.5%. The protein contents of 35 selected urine samples assigned to one of five groups according to their electrophoretic pattern were assayed by the five methods. No method accurately measured physiological proteinuria, but the values for light chain (Bence Jones), glomerular, tubular and overload proteinurias measured by TPT did not differ significantly from the biuret value. The other methods differed significantly for at least three groups. Alpha 1 acid glycoprotein slightly inhibited TPT, but peptones, amino acids, antibiotics or normal urine constituents had little or no effect. The TPT method has been automated (Kone Progress); normal 24-h urinary protein excretion was 36 mg/day (range 12-114), the protein creatinine ratio was 34 mg/g (12-106 mg/g).
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PMID:Measuring urinary protein with the new BioRad reagent kit: evaluation and comparison with five other methods. 785 35

Proximal tubule-derived opossum kidney (OK) cells are a suitable model to study proximal tubular protein endocytosis by using fluorescein-isothiocyanate-albumin as substrate. We used OK cells to investigate several steps of the endocytotic process in control cells and in ochratoxin A (OTA)-treated cells. OTA is a mycotoxin which causes proteinuria. When OTA was present only during the 15-min period in which uptake was studied, it had no effect on albumin endocytosis. Preincubation of OK cells with OTA (10 mumol/l) for 24 hr led to a reduction of transport capacity (Jmax to approximately 50% of control) and of apparent affinity (Km to approximately 200% of control). Specific binding of albumin to the apical cell surface was reduced also. Maximum binding capacity was reduced to 72% of control. By contrast, endocytotic uptake of the fluid-phase marker dextran was not affected by OTA. Preincubation of OK cells for 24 hr with 10 mumol/l of OTA reduced degradation of fluorescein-isothiocyanate-albumin to trichloroacetic acid-soluble fluorescence to 59% of control. We could not detect any difference in endosomal pH (6.13 +/- 0.05 in controls vs. 6.04 +/- 0.10 in OTA-treated cells). Furthermore, the rate of re-exocytosis of albumin taken up was significantly greater in OTA-treated cells. We conclude that: 1) OK cells are a suitable model to study several steps of the endocytotic process separately and thus to investigate the pathophysiology of reduced tubular protein reabsorption and 2) 24-hr exposure to OTA reduces protein uptake because of a decrease of specific binding sites and of enhanced exocytosis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The mycotoxin ochratoxin-A impairs protein uptake in cells derived from the proximal tubule of the kidney (opossum kidney cells). 796 1

Fractional dextran clearances have been extensively used to study glomerular size selectivity. We report on an analysis of different laboratory procedures involved in measuring fractional dextran clearances. The deproteinization of plasma samples by 20% trichloroacetic acid (TCA) revealed a protein contamination of 0.2% +/- 0.3%, whereas both 5% TCA and zinc sulfate deproteinization revealed a significantly higher remaining sample protein content (2.5% +/- 0.4% and 3.4% +/- 0.1%, respectively). Only zinc sulfate revealed incomplete deproteinization of urine samples (0.6% +/- 0.2%). Dextran recovery in plasma and urine supernatants was significantly lower after 5% TCA and zinc sulfate deproteinization when compared with 20% TCA deproteinization. Gel permeation chromatography (GPC) and high-performance liquid chromatography (HPLC) showed a variance of calibration smaller than 5% over 1 year. The use of 3 different sets of standard dextrans revealed significant differences in calibration. GPC and HPLC followed by anthrone assay showed a comparable variance in dextran concentration in plasma, from 3 to 6 nm (14% to 25%), whereas the variance in urine was lower for the GPC and anthrone assay, especially from 5.4 to 6 nm (23% to 43% versus 50% to 78%). HPLC and online refractometry showed the lowest variance of dextran concentration in plasma, from 3 to 6 nm (<4%), and in urine, from 3 to 5.2 nm (<7%), whereas it showed a higher variance in urine, from 5.4 to 6 nm, in comparison with GPC and HPLC with the anthrone assay. The GPC and anthrone assay revealed higher fractional dextran clearances in comparison with the HPLC and anthrone assay in healthy subjects (3 to 5.4 nm) as well as in patients with nondiabetic proteinuria (4.2 to 5.8 nm), and lower clearances in patients from 3 to 3.4 nm. The HPLC and anthrone assay revealed higher clearances in comparison with HPLC and online refractometry in healthy subjects (3.6 to 5.4 nm) and in patients (3.6 to 5.2 nm). The GPC and anthrone assay revealed characteristic differences in fractional dextran clearances between healthy subjects and patients. The HPLC and anthrone assay showed no significant differences between both groups, whereas HPLC and online refractometry showed only an increased clearance of dextrans from 4.6 to 5.2 nm in patients. Fractional clearances of dextran 5.6 nm as estimated by all 3 dextran assays were not significantly related to the fractional immunoglobulin G clearance or the immunoglobulin-to-albumin clearance index in our patients. Quantitative and qualitative differences in fractional dextran clearances may be induced by differences in laboratory procedures. We recommend sample preparation by 20% TCA deproteinization, frequent calibration with 1 set of dextran standards with low polydispersity, size-exclusion chromatography by GPC, and dextran detection by anthrone assay for optimal measurement of fractional dextran clearances. Even with such an approach, however, the variability in the measurement remains extremely high in the important range of dextrans greater than 5 nm.
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PMID:A comparison of analytic procedures for measurement of fractional dextran clearances. 982 28

Genetic inactivation of ClC-5, a voltage-gated chloride channel prominently expressed in the kidney, leads to proteinuria because of defective apical endocytosis in proximal tubular cells. Because thyroid hormone secretion depends on apical endocytosis of thyroglobulin (Tg), we investigated whether ClC-5 is expressed in the thyroid and affects its function, using Clcn5-deficient knockout (KO) mice. We found that ClC-5 is highly expressed in wild-type mouse thyroid ( approximately 40% of mRNA kidney level). The protein was immunolocalized at the apical pole of thyrocytes. In Percoll gradients, ClC-5 overlapped with plasma membrane and early endosome markers, but best codistributed with the late endosomal marker, Rab7. ClC-5 KO mice were euthyroid (normal T4 and TSH serum levels) but developed a goiter with parallel iodine and Tg accumulation (i.e. normal Tg iodination level). When comparing ClC-5 KO with wild-type mice, thyroid 125I uptake after 1 h was doubled, incorporation into Tg was decreased by approximately 2-fold, so that trichloroacetic acid-soluble 125I increased approximately 4-fold. Enhanced 125I- efflux upon perchlorate and presence of 125I-Tg as autoradiographic rings at follicle periphery demonstrated delayed iodide organification. Endocytic trafficking of 125I-Tg toward lysosomes was not inhibited. Expression of pendrin, an I-/Cl- exchanger involved in apical iodide efflux, was selectively decreased by 60% in KO mice at mRNA and protein levels. Thus, ClC-5 is well expressed in the thyroid but is not critical for apical endocytosis, contrary to the kidney. Instead, the goiter associated with ClC-5 KO results from impaired rate of apical iodide efflux by down-regulation of pendrin expression.
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PMID:The loss of the chloride channel, ClC-5, delays apical iodide efflux and induces a euthyroid goiter in the mouse thyroid gland. 1630 76


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