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PubMed1982

Undermethylation at the 5' end of the albumin gene is necessary but not sufficient for albumin production by rat hepatoma cells in culture.

We have measured methylation of the albumin gene in clones of rat hepatoma cells that vary quantitatively in their rates of synthesis of albumin and in variant and hybrid cells that produce no albumin. Although the albumin gene is undermethylated for its entire length in rat liver, only the 5' end is ever undermethylated in hepatoma cells. Moreover, undermethylation of the 5' end of the gene appears to be necessary for stable expression of the albumin gene in hepatoma cells. Since undermethylation of this region is found in some variant cells that fail to produce albumin, it is not a sufficient condition for albumin gene expression. Despite the excellent correlation between undermethylation of the 5' end of the albumin gene and its stable expression, the results argue against the possibility that the methylated state of such genes during development determines whether they will or will not be expressed.

Albumins↗
PubMed1992

gp60 is an albumin-binding glycoprotein expressed by continuous endothelium involved in albumin transcytosis.

Albumin reduces capillary permeability and acts as a carrier for various small molecules. Recently, we identified a 60-kDa sialoglycoprotein (gp60) on the surface of cultured rat microvascular endothelial cells (MEC) that binds albumin and antiglycophorin serum (alpha-gp). We verified that alpha-gp recognizes the albumin-binding gp60 by affinity, purifying proteins from MEC extracts using immobilized albumin. gp60 was immunoblotted with alpha-gp only when the MEC extract was reacted with albumin and not in controls. We immunoprecipitated gp60 from biosynthetically radiolabeled MEC lysates and from extracts containing endothelial surface proteins of isolated rat hearts that were radioiodinated in situ. gp60 was immunoblotted selectively in rat tissue microvascular beds lined with continuous endothelium (heart, lung, diaphragm, fat, skeletal muscle, mesentery, and duodenal muscularis but not cortical brain) and not those exclusively lined with fenestrated or sinusoidal endothelium (adrenal, pancreas, liver, and small intestinal mucosa). MEC isolated from rat heart, lung, and epididymal fat pad expressed gp60 and bound albumin, whereas various nonendothelial cells and brain-derived MEC did not. gp60 is an albumin-binding glycoprotein expressed specifically on the surface of continuous endothelium that binds albumin apparently not only to initiate its transcytosis via plasmalemmal vesicles but also to increase capillary permselectivity.

Animals↗
PubMed1980

Renal handling of albumin: clearance studies with bovine and rat serum albumin in conscious rats.

The reabsorption capacity of albumin was determined by a clearance technique following a single load of bovine or rat serum albumin in conscious rats. The maximum reabsorption capacity of both albumin amounted to 5.6--6.2 micrograms/min . 100 g BW and there seemed to be a nonselective mechanism for the two albumins. The tubular reabsorption capacity was reached at normal physiological plasma albumin concentration. The renal excretion threshold of both albumins amounted to 31.8 mg/ml, the sieving coefficient phi was calculated to be 2.0 . 10(-4). The glomerular filtration rate, controlled by the total plasma slope clearance of 51Cr-EDTA, remained unchanged following a load of rat serum albumin (54.8 +/- 12.2 ml/min . m2 body surface) but decreased significantly after the administration of bovine serum albumin.

Albuminuria↗
PubMed1997

Immunochemical approach to characterize post-translational modification of serum albumin using anti-glutaraldehyde-treated serum albumin antibodies.

Polyclonal antibodies against glutaraldehyde-treated rabbit serum albumin (pRSA) and human serum albumin (pHSA) were prepared from rabbit and mouse, respectively. Anti-pRSA antibody had the structural determinant depending on the polymerization process of RSA and showed only a weak cross-reactivity with the other glutaraldehyde-treated albumins. Anti-pHSA antibody (after adsorption of anti-HSA antibody) recognized only pHSA, but not HSA and the other treated albumins. The cross-reactivity of those antibodies was examined with albumins treated by other methods such as modification of glucose and fructose, carbodiimide, and transglutaminase. Among the, RSA and HSA modified with glucose and fructose had an affinity for each antibody and the reactivity depended on the extent of formation of the polymerized albumin. The results suggests that functional groups involved in cross-linking of albumin are important for formation of the cross-reactivity with the antibody and that a definite structure immunochemically similar to glutaraldehyde-treated albumin could be formed by the Maillard reaction.

Animals↗
PubMed2003

Biological variability of albumin excretion rate and albumin-to-creatinine ratio in hypertensive type 2 diabetic patients.

The importance of measuring microalbuminuria is well established. However, only scanty data are available concerning the biological variability of albumin excretion in type 2 diabetic subjects. We report our experience from a large clinical trial of a new antihypertensive drug (Lercanidipine) designed to reduce albumin excretion and blood pressure in type 2 diabetic patients with hypertension and microalbuminuria. Eighty seven patients with persistent microalbuminuria were studied within 1 year of the clinical trial. The measurements were performed on blood and timed urine samples frozen at -80 degrees C and shipped to a central laboratory unit. Preliminary experiments were performed to assess albumin stability in urine under various conditions (4 degrees C, -20 degrees C and -80 degrees C), particularly with regard to the albumin/creatinine ratio. Urine samples can be stored up to 3 weeks at 4 degrees C or up to 2 months at -80 degrees C. The biological variability of the albumin excretion rate was 25.7%, while that of the albumin/creatinine ratio was 13.4%. These data are useful in defining the analytical goals of imprecision for microalbuminuria (CV = 13% for albumin, and CV = 6% for albumin/creatinine ratio). No correlation between albumin/creatinine ratio and HbA1c was found in the cohort of 61 microalbuminuric patients who completed the trial. The results of this study confirm that the albumin/ creatinine ratio is much more suitable for monitoring albumin excretion in longitudinal studies than the albumin excretion rate.

Albuminuria↗
PubMedDate not supplied

Albumin impregnated vascular grafts: albumin resorption and tissue reactions.

This study aimed to determine the kinetics of albumin resorption from and the healing of two types of albumin impregnated Vasculour II (Bard Cardiovascular) Dacron grafts (ACG-A and ACG-B) using whole blood preclotted Vasculour II Dacron grafts (without albumin) as controls (PCC). Prostheses measuring 4 mm ID x 50 mm length were implanted in the aortoiliac position in 24 dogs (ACG-A n = 12, ACG-B n = 24, PCC n = 12) and explanted after 1, 2 4, and 6 months. Platelet count, platelet aggregometry to 10(-5) M ADP, prothrombin time (PT), and partial thromboplastin time (PTT) were determined preoperatively and at explantation. Sections of the explanted grafts were assayed for human albumin by immunohistochemical techniques utilizing a rabbit polyclonal mono-specific antibody for human albumin followed by the addition of a biotinylated goat anti-rabbit IgG. Immunoperoxidase staining was then performed using Avidin D horse-radish peroxidase. Histology of the grafts (light microscopy, scanning electron microscopy, and transmission electron microscopy) as well as percent thrombus free surface area (TFSA) by computerized planimetry were also determined. Seven of 48 grafts were occluded (85.4% patency) with no difference among the three groups. Platelet aggregometry was not predictive of graft patency. No change in PT or PTT occurred nor was there any difference among the three groups. Retained albumin was detected in every one-month explant but not beyond that time, with the sensitivity for detecting human albumin in this assay being 20 mg albumin per gram of Dacron. All ACG explants at one month revealed inner capsular fibrin coagula not present in PCC specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1990

Influence of insulin on albumin and non-albumin protein fractional synthetic rates in post-absorptive type I diabetic patients.

Two 8-h primed continuous infusions of L-[1-13C] leucine were used to determine fractional synthesis rates of albumin and non-albumin plasma protein in post-absorptive Type I diabetic patients during insulin infusion and its withdrawal. Fractional protein synthetic rates were calculated from the rate of incorporation of 13C-label into protein and employing plasma 13C-alpha-ketoisocaproic acid enrichment to represent the precursor pools label. Incorporation of 13C into albumin and non-albumin plasma protein was linear over the latter 6 h of the 8-h L-[1-13C] leucine infusion. Fractional synthetic rates of plasma albumin and non-albumin proteins were similar during insulin withdrawal and its infusion. The increased whole-body protein synthesis observed during insulin withdrawal in Type I diabetic patients appears unrelated to events in albumin and non-albumin plasma protein fractions. These data are further evidence that insulin per se does not stimulate protein synthesis in man.

Adult↗
PubMedDate not supplied

[The role of epsilon-amino groups of lysine of human serum albumin in heat-induced protein denaturation. Increased stability of glycosylated and alkylated albumin in aggregation during heating].

Human serum albumin was glycosidated by prolonged protein incubation in phosphate buffer, pH 6.8-7.0, with excess glucose at 37 degrees C. epsilon-amino groups of lysine residues of the albumin molecule were alkylated by pyridoxal-5-phosphate in the presence of NaBH4. The solutions of glycosidated and alkylated serum albumin were incubated at different temperature values in the range of 20 to 80 degrees C in phosphate buffer, pH 7.0, over 30 min. The nondenatured monomer and the resulting aggregated were isolated by TSK-HW-55-gel column chromatography and polyacrylamide gel electrophoresis. The stability of modified proteins elevated in parallel to the increase in the number of the ligand molecules covalently bound to albumin amino groups. The 1-3% aqueous solutions of glycosidated serum albumin containing 3-4 glucose residues and those of alkylated albumin containing 6-7 residues of pyridoxal-5-phosphate were stable on heating up to 80 degrees C and did not form aggregates. Under these conditions the initial serum albumin completely aggregated. Preincubation of the aggregated albumin with glucose at 37 degrees C resulted in protein "renaturation" to the monomeric form with a small number of dimers and trimers.

Alkylation↗
PubMed1988

[Bilirubin-albumin-binding function of 2 human albumin preparations (placental and plasma). Comparison of their efficacy in the icteric premature infant].

Two albumin preparations obtained by Cohn fractionation of either plasma of blood donors (plasmatic albumin) or human placental blood (placental albumin) were studied in vitro and in vivo regarding their bilirubin-binding function. Analysis of this function during the industrial processing of the two preparations indicated that alcoholic fractionation and, to a lesser extent, stabilizers, were responsible for the decrease of (a) the association constants between albumin and bilirubin, (b) bilirubin-binding capacity of albumin. Unexpectedly, improvement of bilirubin-binding parameters was observed after the final heating stage. Stabilizers were reversibly bound as suggested by a further improvement of binding function seen after a brief contact of the preparations with red blood cells. The changes were similar for the two preparations. Fifty-one sick premature hyperbilirubinemic neonates were randomly infused either with placental or plasmatic albumin (1.5 g/kg). Albuminemia, bilirubinemia, erythrocytic bilirubin, unbound bilirubin (peroxidase method) were evaluated before and 3 hours after infusion. Improvement of bilirubin-binding parameters was frequently observed but without clear-cut relation with change in bilirubin/albumin molar ratio. No difference was noted between the two albumin preparations. In spite of a decrease of their association constants with bilirubin, the two albumins retained a high binding potency for bilirubin in vivo.

Bilirubin↗
PubMed1978

The influence of increasing albumin concentrations on the determination of the binding of sulfamethoxy-pyridazine to human and bovine serum albumin.

The binding of sulfamethoxypyridazine to human and bovine serum albumin was determined at eight constant molar drug/albumin ratios for seven different albumin concentrations ranging from 0.1% to 1.5%. The serum albumin concentration affects the determination of the albumin binding of the drug in two different ways. 1. The relative affinity of the albumins for the drug increases with increasing albumin concentrations, while the numbers of binding sites remain constant. 2. The association constants taken from Scatchard plots decrease with increasing albumin concentrations. It is concluded that a direct comparison of binding constants obtained with different albumin concentrations, as widely done, can lead to misinterpretations and should be avoided.

Animals↗
PubMed1981

The gene frequency of serum albumin variants in Chinese and the electrophoretic characterization of several serum albumin variants.

By screening a Chinese population of 1025 unrelated persons in Beijing, three serum albumin variants were discovered, and the gene frequency of serum albumin variants of Chinese is estimated as 0.0015. These albumin variants can be distinguished electrophoretically from each other, and were named tentatively as albumin Hanzhong, albumin Changzhi and albumin LXX respectively. A polyacrylamide gel electrophoresis procedure has been developed to characterize albumin variants by determining the relative mobilities (Rm) of albumin variants in a tris-succinate buffer system.

Asian People↗
PubMed1994

Effect of albumin on proluminal movement of 3H-androgen into seminiferous and epididymal tubules and androgen binding in the interstitium of the testis and epididymis after perifusion with fluid containing albumin.

Effect of albumin on proluminal androgen movement from the peritubular space to the intratubular fluids of the adult rat testis and epididymis was examined by using in vivo microperifusion and subsequent micro-puncture of the seminiferous tubules and caput epididymal tubules. Tubules were perfused with four different fluids: (1) Minimum Essential Medium (MEM) containing 3H-testosterone and 14C-polyethyleneglycol (PEG) alone; (2) MEM + 8 mg/ml Bovine Serum Albumin (BSA) containing the same radiolabeled compounds as above; (3) MEM + 80 mg/ml albumin containing the same radiolabeled compounds as above; and (4) Testosterone-free rat serum containing the same radiolabeled compounds as above. Bound 3H-androgens in the interstitial fluids of the testis and epididymis after one-hour perifusion with the four different fluids above were measured by charcoal assay. In the testis, proluminal 3H-androgen movement was not significantly altered by addition of albumin to the perifusion fluid (p = 0.08). Bound 3H-androgens in the interstitial fluid after perifusion were significantly increased with increasing albumin concentrations in the perifusion fluid. In the caput epididymis, proluminal 3H-androgen movement was significantly decreased with increasing albumin concentration in the perifusion fluid. Bound 3H-androgens in the interstitial fluid after perifusion were significantly increased with increasing albumin concentrations in the perifusion fluid (p < 0.05). These findings suggest that proluminal transepithelial movement of 3H-androgens in the reproductive tract could be influenced by the presence of albumin, androgen-binding protein or some other binding protein in the peritubular space.

Animals↗
PubMed1975

Normal serum albumin transfer from blood to small intestine and its role in albumin breakdown.

131I-albumin transfer into isolated segments of the small intestine has been determined following the intravenous injection of human 131I-albumin in 23 dogs. The importance of different intestinal segments in the normal degradation of albumin has been established. The slope of the serum disappearance curve was unaltered with proves that the applied technique had no damaging effect. Albumin leakage was not uniform in the whole length of the small intestine. It was highest in the duodenum (0.241 +/- 0.014 ml/10 cm intestine/hour). This was followed by the jejunum (0.142 +/- 0.022 ml/10 cm intestine/hour), and the smallest vally quantity of albumin leakage corresponded to a plasma volume of 14.49 ml in the duodenum, 27.16 ml in the jejunum, and to 23.76 ml in the ileum. The relationship of albumin leakage and catabolism revealed that protein bound activity (transferred and regained) in the dudodenum, in spite of the shortness of this section of the intestine, was responsible for 11.72 +/- 1.70% of total catabolism, that in the jejunum for 21.28 +/- 3.69%, and that in the ileum for 19.24 +/- 3.64%. The sum of the catabolism of the three intestinal segments yielded 52.26 +/- 6.65% of the total catabolism. After correction with a proteolytic factor, this value was 68.44%. Our examinations have established that the small intestine is the main region of normal albumin breakdown.

Albumins↗
PubMed1975

Albumin synthesis and catabolism following partial hepatectomy in the rat. The effects of amino acids and adrenocortical steroids on albumin synthesis after partial hepatectomy.

Plasma albumin levels were measured in partially hepatectomized, sham operated and control rats. The levels fell in both the partially hepatectomized and sham operated groups; while the latter group returned to normal within a few days, the low plasma albumin in the partially hepatectomized animals was sustained. Albumin synthesis rates in the isolated perfused rat liver were measured in the three groups of animals at varying intervals after partial hepatectomy. There was a significant depression of albumin synthesis rate in terms of both liver and whole animal weights when compared to the sham operated and control animals. This depression was almost completely reversed by the addition of arginine, asparagine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan and valine added together to 10 times their normal plasma concentrations. The addition of hydrocortisone had no effect on the albumin synthesis rate after partial hepatectomy. Studies in vivo in the three groups of animals (partially hepatectomized, sham operated and control animals) revealed a fall in the albumin catabolic rate after partial hepatectomy coinciding with the fall in the albumin synthesis rate. An hypothesis whereby the amino acids may have their stimulatory effect is proposed.

Albumins↗
PubMed1997

Acute phase proteins and peritoneal dialysate albumin loss are the main determinants of serum albumin in peritoneal dialysis patients.

Hypoalbuminemia predicts mortality in dialysis patients. It has been postulated that hypoalbuminemia in the dialysis population is a consequence of poor protein intake resulting from inadequate dialysis. To establish the cause of hypoalbuminemia in a group of 27 patients on peritoneal dialysis (PD), we determined the relationship between serum albumin concentration and a group of parameters including dialysis dose delivered (Kt/V), normalized protein catabolic rate (PCRn), transperitoneal and urinary albumin losses, and the serum concentration of two acute-phase proteins, C-reactive protein (CRP), and serum amyloid A (SAA). Serum albumin concentration could be predicted by a combination of transperitoneal albumin loss and either the serum concentration of CRP or of SAA. There was no relationship between weekly Kt/V or PCRn and serum albumin concentration. CRP and SAA significantly correlated with one another, but neither correlated with transperitoneal albumin losses. Hypoalbuminemia in PD patients is a consequence of transperitoneal albumin losses and of the acute phase response.

Acute-Phase Reaction↗
PubMed1993

Albumin-binding proteins on the surface of the Streptococcus milleri group and characterization of the albumin receptor of Streptococcus intermedius C5.

Members of the Streptococcus milleri group (SMG) that react with Lancefield group C antisera were shown to bind large amounts of albumin although there was no direct relation between these two properties as polyclonal antisera to Lancefield group C antigen did not prevent the binding of albumin. There was a specificity for albumin binding, with albumin from man, monkeys, cat, dog and mouse being bound to a greater degree than albumin from cow, horse, goat or rabbit. Gold-labelled albumin was shown to be located close to the surface of strains by transmission electron microscopy. A cell-surface protein of M(r) 24,000, which was liberated by lysozyme treatment of cells, was shown to be the cell-surface receptor on Streptococcus intermedius C5. The receptor was physically dissimilar from protein G, an albumin- and IgG-binding protein of 'large-colony' Lancefield group C and G streptococci.

Animals↗
PubMed1963

SPECTROPHOTOMETRIC TITRATIONS OF HUMAN SERUM ALBUMIN AND REDUCED CARBOXYMETHYLATED ALBUMIN.

The tyrosyl groups of reduced and carboxymethylated human serum albumin, in which all disulfide bonds are broken, ionize at lower pH than those of native albumin, in spite of the greater negative charge on the protein produced by the S-carboxy-methyl groups. The heat and entropy of ionization of these groups in the reduced albumin are also "normal," in contrast to native albumin. Spectro-photometric titrations at 244 and 295 mmicro give equivalent results. The more open structure of the reduced albumin, as compared with the native protein, presumably allows the tyrosine groups to come freely into contact with solvent. In acid solutions the heights of the two peaks at 236 and 287 mmicro in the difference spectrum (albumin at pH 7 against albumin at a lower pH) are strictly proportional over the whole course of the titration. Both peaks apparently arise from changes in the environment of tyrosyl residues, rather than from more general conformational changes.

Humans↗
PubMed2002

Mechanical properties of coagulated albumin and failure mechanisms of liver repaired with the use of an argon-beam coagulator with albumin.

Hemostasis in the traumatized liver has been achieved by thermally denaturing topically applied albumin. In this article, the mechanical properties of liver and denatured albumin (solder) were measured, and the failure methods of liver repaired with albumin were identified. The ultimate tensile strength and Young's modulus were measured for healthy liver (N = 20) and thermally damaged liver (N = 20). The ultimate tensile strength and Young's modulus were measured for three concentrations of coagulated albumin (25, 38, and 53%) in a single layer and for two layers of denatured 38% albumin. Failure under tension of argon-beam coagulator soldered liver on the parenchymal surface (N = 30) with 38% albumin in two layers had a 70% occurrence for tearing at a mean stress of 39 kPa and a 23% occurrence for shearing at a mean stress of 7 kPa. Liver repaired on the interior surface (N = 11) failed in tension by tearing (64%) at a mean stress of 34 kPa and by shearing (36%) at a mean stress of 6 kPa. Argon-beam coagulator soldering with 38% albumin took 6 s/cm(2) for two layers of solder and gave the best balance of usability, strength, and matching of mechanical properties with those of the liver.

Albumins↗