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Immunologic tolerance in the chicken. I. Isolation of two suppressive fractions from serum of chickens tolerant to bovine serum albumin.

Serum from 14-day-old chickens rendered tolerant at hatching with 1250 mg bovine serum albumin (BSA)/KBW was found to suppress an adoptive secondary response to BSA and an in vitro response to sheep red blood cells (SRBC). Chromatographic separation resulted in three fractions: I, II, and III. The suppressive activity was found to be contained in fraction I (m.w. greater than 1 X 10(6)) and fraction III (m.w. less than 2.5 X 10(4)). Analysis of fraction I by affinity chromatographic techniques revealed that it was composed of soluble BSA-antibody complexes and their removal removed the suppressive activity. Analysis of peak III revealed that the suppressive activity could only be removed by BSA and anti-Line 3 antiserum columns.

Animals

Bovine serum albumin chronic serum sickness nephropathy in rats.

We administered bovine serum albumin (BSA) 1 or 3 mg i.v. into hyper-immune Sprague-Dawley rats weekly for up to 6 months. Animals with free circulating antibody 1 h after BSA developed mesangial deposits of IgG and C-3 without proteinuria. Rats without free antibody at 1 h developed either mesangial or mesangial and glomerular basement membrane (GBM) deposits. Rats given 3 mg BSA tended to have GBM deposits, proteinuria and undetectable antibody at 1 h. By electronmicroscopy, all rats had mesangial and subendothelial dense deposits, while those with GBM lesions had intramembranous and subepithelial deposits with foot process obliteration. Light microscopic evaluation of kidney tissue revealed only mild histological changes similar to those in age-matched control rats. The present studies demonstrate that prolonged i.v. administration of BSA into rats results in the development of a chronic non-inflammatory nephropathy. Despite certain parallels to chronic serum sickness nephropathy in rabbits, species differences appear to modify the nephropathy in rats.

Animals

Serum amyloid A (SAA) protein-interaction with itself and serum albumin.

Serum amyloid A (SAA) protein is a 12,000 dalton protein that exists in serum under physiologic conditions as an 85,000 dalton complex and under certain conditions, as a 170,000 dalton component. To study the reason for this finding, the behavior of 125I-SAA was studied in the presence of cold SAA and several serum proteins. SAA caused a shift of some of the radioactivity to the region of albumin. Addition of normal human serum or albumin caused a shift of a significant fraction of the radioactivity to a peak eluting slightly ahead of albumin (80.000 daltons). This interaction could be blocked by the addition of cold SAA. No shift was noted when IgG or Bence Jones proteins were added. Thus, it appears that low molecular SAA protein has a tendency to aggregate with itself and to bind to albumin but not to human IgG or Bence Jones proteins.

Amyloid

Brdicka currents observed with bovine serum albumin and completely reduced bovine serum albumin in the presence of urea.

In ammonia buffers of varying composition and pH, native bovine serum albumin and completely reduced bovine serum albumin, denoted by p(SH)35, yield quite different Brdicka current-voltage (i-E) curves, but they are identical in the presence of 5 mM calcium chloride. This means that in the presence of calcium, bovine serum albumin becomes completely reduced to p(SH)35. In 8 M urea and ammonia buffers the Brdicka i-E patterns of serum albumin and p(SH)35 are identical even in the absence of calcium, the effect of calcium on the first wave being negligible while calcium slightly increases the second wave. The maximum polarographic effect is attained at urea concentrations of about 5-6 M. Quite generally, the appearance of a second Brdicka wave is attributed to complexation of Co(II) with S- and a group of ligands that is different on the second than on the first wave. The effect of calcium on Brdicka currents of bovine serum albumin in the absence of urea is attributed to an orientation of the protein on the surface of the electrode such that all disulfide groups are reduced and with other ligands can complex with Co(ii). Denaturation of bovine serum albumin in buffers with a pH less than 10.5, and which are 8 M in area, is (polarographically) completely reversible if dilution is made within 15 minutes after preparation. Changes in Brdlcka I-E patterns upon longer aging at varying pH are attributed-in part at least-to dimerization of the denatured protein by interaction of pS- in one molecule with -S-S-in another.

Ammonia

Delayed type hypersensitivity to bovine serum albumin and to lipid-conjugated bovine serum albumin in mice.

Delayed type hypersensitivity (DTH) to bovine serum albumin (BSA) and to lipid-conjugated BSA were studied comparatively. Unlike the case of BSA with which no DTH can be detected with native antigen, injection of butyric-conjugated BSA (Bu-BSA) in sensitized mice provokes a typical DTH for an early and limited period. Alum-precipitated Bu-BSA (Al-Bu-BSA) provokes from the beginning a stronger DTH which persists a much longer period.

Alum Compounds

Antibody as an immunological probe for studying the refolding of bovine serum albumin. I. The catalysis of reoxidation of reduced bovine serum albumin by glutathione and a disulfide interchange enzyme.

We have used an immunochemical approach to study the refolding of bovine serum albumin. Using antibody as a probe for return of native structure, we have been able to demonstrate the regeneration of native structure at several sites on the surface of the molecule. Using this technique, we have shown that the rate of refolding of reduced bovine serum albumin catalyzed by either glutathione or rat liver disulfide interchange enzyme is greater than the rate of air reoxidation of albumin. The half-regeneration times for albumin, however, are substantially greater than those obtained with smaller proteins that have fewer disulfide bonds. We have also demonstrated that the reoxidized monomers isolated at the end of the refolding process are immunologically identical to native monomers. In addition, the tryptophan fluorescence emission maxima were the same as that of the native monomers.

Antibodies

Immunochemistry of serum albumin. VI. A dynamic approach to the immunochemical cross reactions of proteins using serum albumins from various species as models.

Antisera against bovine serum albumin were raised in two rabbits. Serial bleedings were obtained at different times after the first immunization, and antisera from these serial bleedings were not mixed but were kept and studied separately. The immunochemical cross-reactions of these antisera with serum albumins from bovine, goat, sheep, porcine, horse, human and chicken were determined by immunoadsorbent studies. These were done by titration so that the values of maximum (plateau) binding by each albumin of radioiodinated antibodies were determined. In each rabbit, the immunochemical cross-reactivity was not static but increased progressievly with time after the first immunization. In the interval 7 days to 398 days the increases in cross-reaction were extremely large. pH dissociation studies revealed that, together with the increase in cross-reactivity of a given albumin with time after immunization, there was a restriction in the antibody heterogeneity towards populations possessing higher affinity. These results provide a rational explanation for the different values of cross-reactivities for a given albumin from different laboratories. The findings are analyzed in relation to the antigenic structure of albumin and their significance in evolutionary studies discussed.

Animals

Steroid-protein interactions. 40. The effect of fatty acids on progesterone binding to human serum albumin.

Human serum albumin was delipidated by solvent extraction or by treatment with charcoal. Progesterone complexes formed with these albumin preparations had higher association constants than those formed with the untreated samples. The charcoal method of delipidation resulted in somewhat higher affinity constants than extraction with chloroform/methanol. Addition of 5 mol lauric acid per mol albumin reduced the association constant of the progesterone complex by approx. 50%. Studies with lauric, myristic, and palmitic acid showed that the decrease of binding affinity for progesterone was proportional to the amount of fatty acid added to albumin, and to its chain length. These results confirm and extend our previous findings of inhibition of progesterone binding to human albumin by long-chain fatty acids.

Binding Sites

Correlation between arginyl residue modification and benzodiazepine binding to human serum albumin.

Human serum albumin (HSA) has been chemically modified with 1,2-cyclohexanedione and N-acetylimidazole under nondenaturing conditions. Derivatives, in which 10 arginine residues (1,2-dihydroxycyclohex-1,2-ylene (DHCH)-HSA), 56 to 57 lysine and 5 tyrosine residues (acetyl-HSA), or 56 to 57 lysine residues alone (O-deacetyl-HSA) are modified, have been isolated. Their conformation has been tested by circular dichroism measurement, gel filtration on Sephadex G-150, and ultracentrifugation. From these analyses and binding studies it is concluded that only insignificant changes of conformation have occurred. The binding properties of the HSA derivatives have been tested with bilirubin, diazepam (a benzodiazepine drug), phenylbutazone, and indomethacin by circular dichroism. The binding of diazepam to DHCH-HSA is almost completely inhibited and that of phenylbutazone and indomethacin decreased, while the binding of bilirubin is essentially unaffected. In acetyl-HSA and O-deacetyl-HSA, the bilirubin binding is significantly decreased, while the binding of the drugs mentioned is less affected. It is concluded that bilirubin and the drugs bind to two separate sites which contain positive charges essential for the binding properties. The charge(s) in the benzodiazepine site from arginine.

Arginine

Equilibrium saturation chromatographic method for studying the binding of ligands to human serum albumin by high-performance liquid chromatography. Influence of fatty acids and sodium dodecyl sulphate on warfarin-human serum albumin binding.

A size exclusion chromatographic method for studying ligand-macromolecule binding parameters is described. This equilibrium saturation method allows the determination of the concentrations of constituents in equilibrium and is specially useful for characterizing ligand--protein binding under conditions that can be compared with physiological conditions. The method has been used for measuring warfarin--human serum albumin (HSA) binding and for studying the influence of free fatty acids (FFA) and sodium dodecyl sulphate on warfarin--HSA binding. Some comparisons with the Hummel and Dreyer method are given. The influence of the FFA is strongly dependent on their chain length, with an inversion of the effect for a 10-carbon chain.

Chromatography, High Pressure Liquid

[Determination of drug-albumin binding in buffered bovine serum albumin solutions applying a modified ultrafiltration process (author's transl)].

The construction of two ultrafiltration devices which, under application of high-pressure liquid chromatographic (HPLC) technique, allow the determination of unbound portions of drugs in albumin solutions is described. The usefulness of this method and its advantages compared with prevailing methods are demonstrated by means of determination of the unbound portion of carbamazepine, chlorpromazine, phenobarbital and phenprocoumon in buffered bovine serum albumin solutions (4%). The binding of each drug to albumin was characterised by determining the overall binding constant (K1), the apparent binding constant (k+), the free reaction energy (delta F0), the number of binding sites per albumin molecule (n), the rate of taking up of drug by albumin (V) and the unbound portions of the drug (alpha).

Animals

The fluorescence decay of human serum albumin and its subfractions.

Human serum albumin does not decay monoexponentially although it contains a single tryptophan residue per molecule. The molecular population is thus heterogeneous with respect to the tryptophan emission. The separated monomeric and dimeric molecules of this protein, as well as various fractions isolated by the procedures of Foster and his coworkers, exhibit deviations from monoexponential decay which are comparable to those of the unfractionated protein; thus, the heterogeneity in molecular population of human serum albumin persists in the various fractions. By comparing the fluorescence decay data of this protein in the presence of thyroxine with the corresponding quenching data it was found that the fluorescence of the protein does not respond uniformly to the binding for all protein molecules. Qualitatively similar behavior was found for bovine serum albumin. In view of the above, binding studies followed by fluorescence should be viewed as averages over a heterogeneous population of the molecules of the serum albumin.

Acetates