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PubMed1976

The morphometry of the glomerular epithelial cell and its foot processes after the injection of bovine serum albumin or egg albumin.

The intraperitoneal injection of 1 g of bovine serum albumin daily for 5 days was shown by electron-microscope morphometry to cause swelling of the glomerular epithelial cells and very severe loss of foot processes. However, these changes were found in only 70 per cent. of glomeruli and the other 30 per cent. remained normal. After 7 days' recovery following five daily injections of 1 g of bovine serum albumin, the swelling of the glomerular epithelial cells had subsided and the foot process reappeared. These changes were accompanied by severe proteinuria which resolved only slowly when the injections were stopped. After daily injections of 0-8 g of egg albumin for 5 days there was no swelling of the glomerular epithelial cells and only very slight loss of foot processes detectable only by morphometry. There was a less severe proteinuria than after injections of bovine serum albumin and it resolved more rapidly when injections were stopped. It is suggested that these differences arise from the fact that bovine serum albumin is reabsorbed by the glomerular epithelial cell but egg albumin is not. Two of four rats allowed to recover for 7 days after five daily injections of 1 g of bovine serum albumin had unusual glomerular lesions.

Animals↗
PubMed1997

Drug binding sites on chicken albumin: a comparison to human albumin.

Mammalian albumins have two main structurally selective ligand binding sites. Site I binds drugs such as azapropazone, phenylbutazone and warfarin; whereas benzodiazepines, some dansyl amino acids, such as dansylsarcosine, and short chain fatty acids like octanoic acid interact with site II. However, it is not known if non-mammalian albumins have similar binding loci. In this study, drug binding sites on chicken albumin were investigated using site selective fluorescent probes (warfarin and dansylsarcosine) and p-nitrophenyl acetate (NPA); the hydrolysis of which is selectively inhibited by site II ligands. Azapropazone and phenylbutazone decreased the binding of warfarin and dansylsarcosine to a similar extent. Diazepam and octanoic acid also inhibited binding of the two fluorescent probes in a non-selective manner. However, the fluorescence intensity of the warfarin-chicken albumin complex decreased when the pH was increased from 6.0-9.0; but by contrast, the fluorescence of bound dansylsarcosine remained unchanged. Furthermore, the hydrolysis of NPA was selectively inhibited by dansylsarcosine, diazepam and octanoic acid (ligands selective for site II on mammalian albumins), but not by site I selective ligands such as azapropazone and warfarin. Overall, the results suggest that chicken albumin, like mammalian albumins, has discrete binding sites for warfarin and dansylsarcosine.

Albumins↗
PubMed2003

Albumin fragments in normal rat urine are derived from rapidly degraded filtered albumin.

Filtered albumin is excreted as a heterogeneous population of albumin-derived molecules resulting from degradation during renal passage. In order to understand the dynamics of this degradation process, albumin clearance was studied over a short-term (minutes) and a long-term (7 days) by both radioactivity and radioimmunoassay. The radiolabelled material in the urine was also analysed extensively by using size exclusion chromatography, size selective filtration and high performance liquid chromatography. These studies demonstrate that during renal passage, albumin degradation to fragments in the size range of 500-10,000 occurs in a matter of minutes. The fragments are not detected by using radioimmunoassay. Steady state excretion rates or fractional clearance of radiolabelled albumin occur over a similar time period. Both rates of degradation and approach to steady-state clearance, while rapid, were considerably slower than the transit time for molecules in the Bowman's capsule and early tubular lumen. The results are consistent with an extremely rapid lysosomal uptake of filtered albumin, and degradation and regurgitation of the albumin-derived peptide fragments into the tubular lumen prior to excretion.

Albumins↗
PubMed1994

Binding of serum albumin on tumor cells and characterization of the albumin binding protein.

The binding of bovine (BSA) and human serum albumin (HSA) to the surface of human and mouse tumor cells in vitro was examined by flow cytometry using monoclonal antibodies against these albumins. Both isologous and heterologous types of albumin bound firmly on several lines of human and mouse tumor cells. The cell-bound albumin was removable by protease (actinase) treatment or by culture in albumin-free medium for more than 2 days, but not by simple washing. The amount of albumin capable of binding to the tumor cell surface differed among the 9 tumor cell lines tested. As determined with radioiodinated BSA, about 2.6 x 10(6) BSA molecules/cell could bind to MDA-MB-453 human mammary cancer cells, which exhibit high binding capacity as to BSA. A unique peptide having a molecular weight of 18 kDa was detected on gel electrophoresis in extracts of tumor cells or normal aortic endothelial cells which had been treated with radioiodinated, photocross-linker-labeled BSA or HSA, followed by UV-irradiation. This peptide was also immuno-precipitated with an anti-BSA or anti-HSA monoclonal antibody. With both methods, the yield of the peptide was decreased by previous addition of an excess amount of unlabeled BSA or HSA. These findings indicated that the 18-kDa peptide expressed on both normal aortic endothelial cells and tumor cells is a principal serum albumin-binding protein, and that this protein binds both BSA and HSA.

Animals↗
PubMed1976

Immunoelectrophoretic 'tailing' of albumin line due to albumin-IgG antibody complexes: a side effect of nitrofurantoin treatment?

The immunochemical analysis of sera of 10 patients in which immunoelectrophoresis showed a cathodic, elongated, 'tailing' albumin (TA) line is described. Eight of the 10 patients had been treated with nitrofurantoin, and withdrawal of the drug was followed by disappearance of the phenomenon in 5 cases. Most of the patients had polyclonally elevated IgG and IgA levels and a decreased albumin level; IgM; C3, C4, and C1-INH were normal. Antinuclear activity of IgG type was demonstrated in the sera of 9 patients. The TA phenomenon was due to noncovalently bound complexes between IgG and albumin. The combining sites of the IgG molecules were in the Fab fragment. The antibody-like activity of the IgG was directed towards autologous albumin. The anti-albumin activity remained unchanged after absorption of the antinuclear activity. The nitrofurantoin-induced albumin-anti-albumin system may prove useful as a human model of autoimmune response of known aetiology.

Aged↗
PubMed1997

Heparin-induced structural modifications and oxidative cleavage of human serum albumin in the absence and presence of glucose--implications for transcapillary leakage of albumin in hyperglycaemia.

Both unfractionated and fractionated, low-molecular-mass heparins were tested on human serum albumin in the absence and presence of glucose at concentrations similar to those frequently found in diabetic hyperglycaemic patients, to ascertain whether heparin and glucose interfered with each other in affecting the conformation of albumin. Reproducible results were obtained with both heparins when used at equal masses, but not when used at equal molar concentrations, suggesting a crucial role of the amount of the saccharide units in determining the observed effects. Spectroscopic studies showed that the binding sites of glucose and heparin on albumin do not overlap and that changes in protein structure depend on complex and mutual interference of glucose and heparin with the protein, although the effects of heparin in modifying the chromophore environment and increasing the ordered structure of the protein also prevailed in the presence of glucose. Heparin binding to albumin rapidly gave rise to oxidative reactions, which were responsible for the increase in the carbonyl content of the protein together with its higher susceptibility to tryptic digestion. Glucose enhanced and prolonged the production of heparin-induced oxidants. Oxidation caused peptide bond cleavage at Lys323 in the primary structure of albumin, yielding two large fragments of 27.5 kDa and 35 kDa which aggregated to form disulphide-linked homodimers visible in SDS/PAGE as two new bands of 54 kDa and 74 kDa, respectively. This was accompanied with a reduction in Val, Glu, and Gly residues, only partially counterbalanced by an increase in Thr and Ser residues. While only a small percentage of albumin molecules underwent fragmentation in the presence of heparin with glucose, albumin turned out to display in an even higher proportion structural modifications consistent with a higher degree of ordered structure. The mechanism(s) underlying this heparin-driven effect and possible physiopathological implications in vivo are discussed.

Capillary Permeability↗
PubMed1993

Protamine-mediated transport of albumin into brain and other organs of the rat. Binding and endocytosis of protamine-albumin complex by microvascular endothelium.

High doses of intravenous protamine cause generalized vascular permeability changes in brain and other organs, and concomitant hypoproteinemia. The present investigations test the hypothesis that protamine has a dual action of both binding serum proteins and of undergoing absorptive-mediated transcytosis through microvascular endothelial barriers. Binding of albumin to protamine was demonstrated using equilibrium dialysis, and protamine was shown to selectively augment the uptake of albumin, but not sucrose, in isolated bovine or human brain capillaries. In contrast, the anionic macromolecule, dextran sulfate, resulted in an increased capillary uptake of both albumin and sucrose in vitro. The selective effects of protamine on albumin transport were also documented in vivo using an external organ technique; the intravenous injection of 1.5 mg/kg protamine resulted in a marked and selective influx of albumin into brain, heart, kidney, lung, and liver, and the increased albumin transport exceeded the increased sucrose uptake in some organs by an order of magnitude. The transcytosis of protamine through the cerebral microvascular barrier was documented with an internal carotid artery perfusion technique. In summary, these studies provide evidence for protamine-mediated vectorial transport of albumin through microvascular barriers in brain and other organs.

Animals↗
PubMed2000

Cubilin is an albumin binding protein important for renal tubular albumin reabsorption.

Using affinity chromatography and surface plasmon resonance analysis, we have identified cubilin, a 460-kDa receptor heavily expressed in kidney proximal tubule epithelial cells, as an albumin binding protein. Dogs with a functional defect in cubilin excrete large amounts of albumin in combination with virtually abolished proximal tubule reabsorption, showing the critical role for cubilin in the uptake of albumin by the proximal tubule. Also, by immunoblotting and immunocytochemistry we show that previously identified low-molecular-weight renal albumin binding proteins are fragments of cubilin. In addition, we find that mice lacking the endocytic receptor megalin show altered urinary excretion, and reduced tubular reabsorption, of albumin. Because cubilin has been shown to colocalize and interact with megalin, we propose a mechanism of albumin reabsorption mediated by both of these proteins. This process may prove important for understanding interstitial renal inflammation and fibrosis caused by proximal tubule uptake of an increased load of filtered albumin.

Adsorption↗
PubMedDate not supplied

The role of albumin in human physiology and pathophysiology, Part III: Albumin and disease states.

The serum albumin level is one of several clinical parameters of the status of general health. There is a marked correlation between low albumin levels and the incidence of morbidity and mortality in hospitalized patients. Therefore, it is not surprising to find that hypoalbuminemia is a common finding among hospitalized patients. This results from alterations in the catabolic or anabolic rates, losses of albumin, or redistribution between the various fluid compartments of the body. Somewhat less well defined than the role of albumin as a prognostic indicator is its role in compounding pathophysiology. Hypoalbuminemia is known to be associated with delayed wound healing. The hypoalbuminemic state interferes with the normal functioning of the gastrointestinal tract. Qualitative changes in the albumin molecule which occur in renal disease may damage the nephron. Low serum albumin levels may adversely affect the coagulation system. Further investigation into the role of albumin in pathophysiology is warranted.

Ascites↗
PubMedDate not supplied

Increased levels of albumin in bronchial washing fluid of patients with bronchial carcinoma. Could albumin be considered as a tumor marker?

BACKGROUND: The aim of this study was to evaluate the significance of albumin in bronchial washing fluid (BWF) and its relationship to three tumor markers (CEA, CA 19-9 and NSE). METHODS: Serum and BWF samples were collected in a group of 60 patients. Albumin and tumor markers in the BWF and serum of three groups: a control group (CG), a chronic bronchitis group (CBG) and a lung cancer group (CaG), were analyzed in a prospective cross-sectional study. The diagnostic yields of the tests in each environment (serum and BWF) were evaluated by using as cutoff points the values of the corresponding 90th percentile of CG and CBG taken together. RESULTS: A significant difference in albumin level (p < 0.001) was noted in the BWF of patients with cancer compared with the other two groups. In addition, a significant difference in CEA level (p < 0.001) was observed in the serum of cancer patients compared with the other two groups. The cutoff values for CEA in serum and albumin in BWF were 2.20 ng/mL and 2.00 g/dL, respectively. The areas under the corresponding ROC curves were 93% and 97%. Combination of CEA-serum and albumin-BWF by logistic regression analysis increased their diagnostic value. CONCLUSION: Measurement of albumin levels in BWF could be a useful additional diagnostic tool to differentiate malignant from non-malignant lung diseases. Moreover, the combined measurement of CEA in serum and albumin in BWF could be of aid in the follow-up of lung cancer patients.

Aged↗
PubMed2006

Evaluation of the albumin cobalt binding (ACB) assay for measurement of ischaemia-modified albumin (IMA) on the Beckman Coulter LX-20.

BACKGROUND: In the presence of ischaemia, albumin undergoes changes resulting in the formation of ischaemia-modified albumin (IMA). Increased serum concentrations of IMA have been found in patients with myocardial ischaemia. The purpose of this study was threefold: to evaluate the albumin cobalt binding (ACB) assay for measurement of IMA on the Beckman Coulter LX-20; to establish a reference range for IMA; and to investigate the relationship between IMA and total albumin concentrations. METHODS: The ACB assay was evaluated under the following headings: imprecision, accuracy and reliability. A reference range was established on a population of 81 healthy subjects. RESULTS: The within-batch coefficient of variation (CV) at IMA concentrations of 88, 99 and 120 KU/L were 1.4, 2.0 and 2.5%, respectively. The between-batch CVs at 74, 84 and 123 KU/L were 3.4, 3.3 and 3.0%, respectively. Comparison with the Cobas Mira Plus showed a mean negative bias of 7 KU/L. The 97.5th percentile established on our reference population was 110 KU/L. A significant inverse relationship was found between total serum albumin and IMA concentrations (r = -0.66, P < 0.0001). Correcting the IMA concentrations for total albumin in our reference population, using a formula devised in this study, yielded a range similar to that of uncorrected IMA. CONCLUSIONS: The ACB assay was found to have acceptable precision and performed very satisfactorily on the Beckman Coulter LX-20. A correction to measured IMA concentrations, to take into account total albumin concentrations, may need to be applied for the proper interpretation of IMA results.

Autoanalysis↗
PubMed1988

Lack of albumin as genotypic marker of preneoplastic analbuminemic rat hepatocytes transplanted within albumin-positive liver.

In analbuminemic rats, preneoplastic hepatocytes lack the capability to produce albumin. On the other hand, the hepatocytes of F1 hybrids born from parents of analbuminemic rats and normal rats retain their capability to produce albumin, since the analbuminemia is inherited as a recessive trait in rats. We isolated hyperplastic nodule cells from Nagase's analbuminemic rats and transplanted them into the livers of F1 hybrid rats by infusion into the mesenteric vein. The host rats were subjected to a short term dietary 2-acetylaminofluorene and underwent a two-thirds partial hepatectomy to promote the growth of preneoplastic hepatocytes. Within 10 to 13 days after transplantation, may albumin-negative hepatocytic nodules were formed in the albumin-positive host livers. Almost all the albumin-negative nodules expressed conventional biochemical markers for preneoplastic hepatocytes. Eight to 9 weeks after the transplantation, almost the same number of albumin-negative nodules were observed as on days 10-13. However, roughly a half of the albumin-negative nodules showed no biochemical markers. The results indicate that the majority of early preneoplastic lesions revert to become phenotypically normal after removal of the promoting stimuli.

Albumins↗
PubMed1989

The molecular mechanism of the neutral-to-base transition of human serum albumin. Acid/base titration and proton nuclear magnetic resonance studies on a large peptic and a large tryptic fragment of albumin.

In order to obtain a better understanding of the neutral-to-base (N-B) transition of human serum albumin, we performed acid/base titration experiments and 500-MHz 1H NMR experiments on albumin and on a large peptic (residues 1-387) and large tryptic (residues 198-585) fragment of albumin. The acid/base titration experiments revealed that Ca2+ ions induce a downward pK shift of several histidine residues of the peptic (P46) fragment and of albumin. By contrast, Ca2+ has very little influence on the pK of histidine residues of the tryptic (T45) fragment. In albumin, the pH-dependent His C-2 proton resonances, observed with 1H NMR experiments, have been allotted the numbers 1-17. It proved possible to locate these resonances in the P46 and the T45 fragments. A correspondence was found between the number of histidines detected by the acid/base titration and by the 1H NMR experiments. The results of the experiments lead us to conclude that in domain 1 at least the histidines corresponding to the His C-2 proton resonances 1-5 play a dominant role in the N-B transition. The Cu2+-binding histidine residue 3 (resonance 8) of the albumin molecule is not involved in the N-B transition. In addition, we were able to assign His C-2 proton resonance 9 to histidine 464 of the albumin molecule. The role of the N-B transition in the transport and cellular uptake mechanisms of endogenous and exogenous compounds is discussed.

Binding Sites↗
PubMed1994

Physical and biochemical characterization of Albunex, a new ultrasound contrast agent consisting of air-filled albumin microspheres suspended in a solution of human albumin.

Albunex is a new ultrasound contrast agent for medical imaging. The product consists of air-filled albumin microspheres suspended in a solution of 5% (w/v) human albumin. The suspension is sterile, non-pyrogenic and isotonic, with a pH of 7.0 and a viscosity of 1.4 relative to water. The contrast effect is caused by the air-filled microspheres, which range in diameter from 1 to 15 microns, with less than 5% being larger than 10 microns. The product contains a total of about 7 x 10(8) microspheres/ml of suspension. The number concentration of microspheres with diameters between 4 and 10 microns is about 2 x 10(8)/ml. The latter microsphere fraction is assumed to give the main contribution to the ultrasound signal in the left ventricle of the heart after intravenous injection. The air-filled microspheres are prepared by sonication of a heated solution of 5% (w/v) human albumin. During the sonication process, microbubbles of air are formed which become encapsulated in a thin shell of aggregated albumin about 15 nm in thickness. Due to the stabilizing effect of the albumin shell, the air-filled microsphere suspension is stable for at least 2 years when stored refrigerated. The microsphere protein represents about 1.5% of the total protein in the suspension. The remaining protein is soluble albumin molecules which behave like the albumin molecules in the starting material when analysed by a number of biochemical techniques.

Albumins↗
PubMed1980

Albumin extravasation in bicuculline-induced blood-brain barrier dysfunction. A comparison between endogeneous and 125I-labeled exogeneous serum albumin.

The extravasation of endogeneous rat albumin and exogeneous 125I-labeled human serum albumin was compared in rats subjected to bicuculline-induced blood-brain barrier dysfunction. The correlation between rocket immunoelectrophoretic assays of endogeneous rat albumin and 125I-labeled human serum albumin, assayed by gamma scintillation counting, was good respective of whether 125I-labeled albumin was studies in whole brain tissue or in brain homogenates. The ratio of brain to serum albumin was similar with the two assay methods.

Albumins↗
PubMed1973

Experience with a commercial preparation of 125I-labelled human albumin for study of albumin metabolism.

Evaluation of a commercial preparation of (125)I-labelled albumin for use in the study of albumin metabolism is described. In eight subjects with normal albumin metabolism the proportion of the dose of radioiodide excreted was stable throughout a period of 17 days, indicating that there was no excessive denaturation of the iodinated albumin. Characteristics of albumin metabolism-pool sizes, catabolic rate, etc-were in agreement with currently accepted normal values. It is concluded that this preparation of iodinated albumin is suitable for metabolic use.

Adult↗
PubMed2004

Association between urinary albumin excretion and serum dehydroepiandrosterone sulfate concentration in male patients with type 2 diabetes: a possible link between urinary albumin excretion and cardiovascular disease.

OBJECTIVE: Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in patients with type 2 diabetes. Both elevated urinary albumin excretion and low serum concentrations of dehydroepiandrosterone (DHEA) are associated with increased CVD mortality. This raises the possibility of DHEA as a causal intermediate linking urinary albumin excretion to CVD. RESEARCH DESIGN AND METHODS: Relationships of urinary albumin excretion to serum DHEA sulfate (DHEA-S) concentration and to major cardiovascular risk factors, including blood pressure, serum lipid concentration, glycemic control (HbA1c), and BMI, were investigated in 357 consecutive men with type 2 diabetes. RESULTS: Serum DHEA-S concentrations were lower in patients with macroalbuminuria (866.5 +/- 523.8 ng/ml, P <0.0001) and in those with microalbuminuria (1,014.4 +/- 525.3 ng/ml, P=0.0006) than in patients with normoalbuminuria (1,232.6 +/- 542.4 ng/ml). Serum DHEA-S concentration correlated inversely with log (urinary albumin excretion) (r=-0.227, P <0.0001). Multiple regression analysis demonstrated that duration of diabetes (beta=0.147, P=0.0075), HbA1c (beta=0.156, P=0.0048), BMI (beta=0.194, P=0.0007), systolic blood pressure (beta=0.195, P=0.0005), and serum DHEA-S concentration (beta=-0.192, P=0.0010) were independent determinants of log (urinary albumin excretion). CONCLUSIONS: Serum DHEA-S concentration, which correlated inversely with degree of urinary albumin excretion, may contribute to the link between elevated urinary albumin excretion and higher CVD mortality in male patients with type 2 diabetes.

Age of Onset↗
PubMedDate not supplied

Urinary excretion of glycated albumin in insulin-dependent diabetic patients with normal urinary albumin excretion.

Glycation involves both circulating proteins, such as albumin, and structural proteins, such as the components of the glomerular basement membrane. A preferential excretion of glycated albumin (more anionic at physiological pH compared with unmodified plasma albumin) has been reported by some authors, but not by others. We therefore investigated the selectivity index (renal clearance of non-glycated albumin/clearance of glycated albumin) in 25 insulin-dependent diabetic patients with normal urinary albumin excretion and in 19 well-matched control subjects. The selectivity index was significantly higher in diabetic patients than in control subjects: 1.38 +/- 0.05 SEM vs 0.98 +/- 0.02, p less than 0.0001. This result is not consistent with a preferential urinary excretion of glycated albumin, at least in normoalbuminuric uncomplicated insulin-dependent diabetic patients.

Adult↗