Species-specific heterogeneity for molecular weight estimates of serum extracellular superoxide dismutase activities.

1. Several apparent molecular weights (mol. wt) are reported for plasma or serum extracellular superoxide dismutase (EC SOD) activity. This study found species-dependent heterogeneity for apparent mol. wt using gel filtration with Sephadex G-150. 2. EC SOD activity in rabbit and guinea-pig serum, measured by a modified pyrogallol assay, eluted just before ceruloplasmin activity, but rat and bovine serum activity eluted after ceruloplasmin (apparent mol. wt of 142,000 and 73,000, respectively). 3. The heterogeneity between rat and rabbit serum was not eliminated by substituting a cytochrome-c-based SOD assay for the pyrogallol method, by substituting lung extracts for serum, by analysing a mixture of rat and rabbit serums, nor by analysing hemolysed serum. The apparent mol. wt of bovine serum EC SOD activity was not duplicated by gel filtration analysis of a mixture of bovine cytosolic SOD and albumin. 4. In conclusion, species-specific variation in apparent mol. wt for serum EC SOD activity was demonstrated under several circumstances.     

Thermodynamic parameters of the binding of retinol to binding proteins and to membranes

Retinol (vitamin A alcohol) is a hydrophobic compound and distributes in vivo mainly between binding proteins and cellular membranes. To better clarify the nature of the interactions of retinol with these phases which have a high affinity for it, the thermodynamic parameters of these interactions were studied. The temperature-dependence profiles of the binding of retinol to bovine retinol binding protein, bovine serum albumin, unilamellar vesicles of dioleoylphosphatidylcholine, and plasma membranes from rat liver were determined. It was found that binding of retinol to retinol binding protein is characterized by a large increase in entropy (T delta S degrees = +10.32 kcal/mol) and no change in enthalpy. Binding to albumin is driven by enthalpy (delta H degrees = -8.34 kcal/mol) and is accompanied by a decrease in entropy (T delta S degrees = -2.88 kcal/mol). Partitioning of retinal into unilamellar vesicles and into plasma membranes is stabilized both by enthalpic (delta H degrees was -3.3 and -5.5 kcal/mol, respectively) and by entropic (T delta S degrees was +4.44 and +2.91 kcal/mol, respectively) components. The implications of these finding are discussed.     

Nucleocytoplasmic exchange of macromolecules

Quantitative measurements of the cytoplasm-to-nucleus exchange of specific protein tracers were correlated with known physical properties (size and electrical charge) of the proteins. Tracers differing in their molecular parameters were produced by fluorescence labelling of wellcharacterized proteins (bovine serum albumin, mol. wt 67 500; ovalbumin, mol. wt 45 000; myoglobin, mol. wt 17 500; lysozyme, mol. wt 14 500; and cytochrome c, mol. wt 13 000) with fluorescein isothiocyanate. The labelled proteins were microinjected into the cytoplasm of living cells, and their uptake into the nucleus was followed by quantitative fluorescence microscopy. In addition, the distribution of cytoplasmically injected ferritin (mol. wt 465 000) was observed with the electron microscope.     

Binding of norgestrel to human plasma proteins.

Binding of [14, 15-3H](+/-)-norgestrel to human plasma proteins has been investigated. Norgestrel showed greater affinity to plasma than to human serum albumin indicating specific norgestrel binding protein(s) in the plasma. alpha1-acid glycoprotein showed high affinity for norgestrel when compared with human serum albumin. The binding protein was eluted at pH 5.8 by step by step elution on a DEAE-cellulose column. Norgestrel binding to plasma proteins was not affected at 60 degrees C. The optimal binding occurred between pH 7 and 8. Ligand specificity of the binding protein revealed that progesterone was able to compete for the norgestrel binding sites, whereas corticosterone, testosterone, oestradiol, and norethindrone acetate did not show much competition. The molecular weight of the binding protein was found to be approximately 43 000. Sucrose density gradient analysis indicated that norgestrel bound to a macromolecular component of sedimentation coefficient 2.9 S. The association constant (Kass) and dissociation constant (Kdiss) of norgestrel-binding plasma protein was found to be 1.4-10(6) M-1 and 0.7-10(-6) M respectively. The number of binding sites was 0.5-10(-9) mol/mg protein. Norgestrel-binding protein in the plasma appeared to be a protein different from human serum albumin, corticosteroid-binding globulin and sex-steroid-binding protein. This binding protein showed some similarities to alpha1-acid glycoprotein.     

On the possible presence of a beta 2-microglobulin-like protein in extracts of livers from normal chickens and chickens with erythroblastosis-IV. Homology of small molecular weight (mol.wt 11,000) protein with serum albumin based on the content of amino acid residues

A small molecular weight (mol.wt 11,000) protein (SMWP) was obtained from the livers of normal chickens and chickens infected with erythroblastosis virus. SMWP, which had been shown to have no biochemical homology with beta 2-microglobulin, is homologous with chicken serum albumin. SMWP shows a similar order of homology with another small molecular weight protein isolated by others from chicken plasma. Like chicken albumin, SMWP is more closely homologous with bovine albumin than with human albumin.     

A comparative binding of platinum anti-tumour compounds to plasma proteins in the rat (in vivo) and mouse (in vitro).

Plasma protein binding of 195mPt-labelled cisplatin, carboplatin and iproplatin has been studied in vivo in rat and in vitro in mouse, using both electrophoresis and trichloroacetic acid precipitation. After intravenous injection plasma clearance rates were biphasic for all 3 compounds, (t1/2 alpha, 13-17 min) but cisplatin was retained thereafter longer than the others. By 5 min, gel electrophoresis showed protein labelling with all 3 drugs but none involved low mol.wt. proteins (< 16 kDa). At 2 h a notable proportion of the protein bound platinum was associated with the latter components. There was a general resemblance between the distribution patterns of cisplatin and carboplatin whereas iproplatin showed a persistent retention of the label with time to higher mol. wt. proteins. From in vitro incubation with mouse plasma, rates of interaction respectively were cisplatin t1/2 alpha, 35 min, beta 8 h, carboplatin t1/2, 44 h and iproplatin t1/2, 104 h. By electrophoresis the protein bound fraction pattern (1 h) was again similar for cisplatin and carboplatin with virtually no binding to low mol. wt. proteins. After 24 h these were now involved to a high degree (40%). Iproplatin showed relatively marked binding to proteins of higher mol. wt. but no transfer with time to the low mol. wt. protein zone. A possible explanation is the need for in vivo metabolism for this compound as manifest in the rat. It is suggested that the significance of interaction with low mol. wt. proteins merits further investigation in relation to the antitumour and toxicological actions of these drugs.     

The effect of soluble rat liver proteins on the activity of microsomal stearoyl-CoA and linoleoyl-CoA desaturase.

1. The influence of bovine serum albumin and soluble rat liver proteins on the activity of rat liver microsomal delta9 and delta6 desaturases has been studied. 2. In the absence of bovine serum albumin, the delta9 desaturase which converts stearoyl-CoA into oleoyl-CoA, shows a non-linear correlation between enzyme activity and protein concentration. 3. Optimum concentrations of bovine serum albumin have three main effects on the enzyme activity: (i) establishes a linear relationship between enzyme activity and protein concentration, (ii) stimulates the enzyme activity 2--3-fold and (iii) raises the optimum substrate concentration from 10 to 100 muM. 4. A highly purified soluble liver protein of molecular weight 24 000 also stimulated the enzyme activity and brought about a linear relationship between enzyme activity and protein concentration. 5. It was concluded that the non-linear kinetics were due to limiting amounts of substrate binding protein in the microsomal preparations. 6. The delta6 desaturase which converts linoleoyl-CoA into gamma-linolenoyl-CoA was also stimulated by bovine serum albumin and soluble liver proteins. 7. The significance of the fatty acid-binding proteins is discussed.     

The effect of ligand presaturation on the interaction of serum albumins with an immobilized Cibacron Blue 3G-A studied by affinity gel electrophoresis.

The interaction of the immobilized triazine dye Cibacron Blue 3G-A with rat, rabbit, sheep, goat, bovine and human serum albumins was studied by affinity gel electrophoresis. Dissociation constants were estimated in each instance and showed human serum albumin to have a significantly higher affinity for the dye than did albumin from any other species. Pretreatment of the defatted proteins with bilirubin (3 mol of bilirubin/mol of protein) did not increase the dissociation constants of the serum albumins, whereas pretreatment with palmitate (7 mol of palmitate/mol of protein) increased the dissociation constant in all cases: 3-fold for human serum albumin, 15-fold for other serum albumins. Increasing the bilirubin/albumin ratio (to 7:1) did not affect the dissociation constant of the albumins studied. Decreasing the palmitate/albumin ratio decreased the dissociation constant for human serum albumin, but did not affect those of bovine and rat albumins. Altering the chain length of the presaturating fatty acid dramatically changed the dissociation constant of both human and bovine serum albumins. Butyrate, hexanoate, octanoate and decanoate did not significantly influence the dissociation constants of bovine and human serum albumins for Cibacron Blue, whereas laurate, myristate and palmitate greatly increased the dissociation constant. These data are discussed in relationship to the behaviour of albumins during dye--agarose column chromatography. In Addendum the effect of nucleotide presaturation on the interaction between Bacillus stearothermophilus 6-phosphogluconate dehydrogenase and the immobilized triazine dyes Cibacron Blue 3G-A and Procion Red HE-3B was examined, and the implications for dye--ligand chromatography are discussed.     

Protein-phosphate complexes as an inhibitor of iron-induced lipid peroxidation

Effect of phosphate buffer (pH 6.2) alone or in the presence of bovine serum albumin and other proteins on iron (II)-induced lipid peroxidation was studied. Phosphate buffer alone and in the presence of bovine serum albumin was found to inhibit lipid peroxidation. The inhibition was higher when bovine serum albumin was also present. Other proteins also inhibited lipid peroxidation in the presence of phosphate. Inhibition by proteins in the presence of phosphate seems to be due to binding of iron with phosphate and with protein-phosphate complexes. Reversal in inhibition was observed with an increase in iron concentration in reaction mixture. Equilibrium dialysis showed more binding of iron to protein in the presence of phosphate than in the presence of chloride ions.     

Crossed immunoelectrophoretic analysis of ARDS lavage proteins

Serum proteins in normal and ARDS bronchoalveolar lavages were analyzed using crossed immunoelectrophoresis. Normal lavages demonstrated relatively few proteins (albumin, alpha 1-antitrypsin, transferrin, and haptoglobin) in low concentrations. In contrast, substantial amounts of all identifiable serum proteins were detected in ARDS lavages. IgA was apparently locally produced. Two of the largest proteins, beta-lipoprotein (mol wt greater than 2 million) and IgM (mol wt approximately 900,000) were found to be complexed as evidenced by their coprecipitation in a single spike in ARDS lavage. Electrophoretic modifications of ARDS albumin and alpha 1-antitrypsin precipitation peaks and partial identity spurring of the alpha 1-lipoprotein peak with other precipitation loops indicated possible complex formation between these proteins and other possibly pathogenic lung fluid constituents. Similarly, modifications of orosomucoid and Gc-globulin peaks indicated possible molecular alterations resulting from interactions with other components. The relatively few protein modifications exhibited in ARDS lavages together with alpha 1-antitrypsin-protease complex formation confirm the relative absence of substantial proteolytic activity in ARDS edema fluids obtained within 12 hr of the onset of the syndrome demonstrated in previous studies.     

Interaction of prostaglandins with blood plasma proteins. Comparative binding of prostaglandins A2, F2α and E2 to human plasma proteins

1. The binding of prostaglandin A(2) and prostaglandin F(2alpha) to human plasma proteins was investigated by DEAE-Sephadex chromatography and polyacrylamide-gel electrophoresis. Both prostaglandins, when added to human plasma in vitro, were found to become bound mainly to plasma albumin. 2. The extent of binding of prostaglandins added to human plasma in low to moderate concentrations was found to be approx. 88, 73 and 58% for prostaglandins A(2), E(2) and F(2alpha) respectively. The order of affinities for the binding of the three prostaglandins to albumin appear to be A(2)>E(2)>F(2alpha). 3. The apparent association constants for the binding of these prostaglandins to human serum albumin were estimated to be approx. 4.8x10(4), 2.4x10(4) and 0.9x10(4) litre/mol for prostaglandins A(2), E(2) and F(2alpha) respectively. The results are compared with previously reported association constants for the binding of long-chain fatty acids to both human and bovine albumins.     

Adenosine 3'':5''-cyclic monophosphate-binding proteins in bovine and rat tissues.

1. At least two classes of high-affinity cyclic AMP-binding proteins have been identified: those derived from cyclic AMP-dependent protein kinases (regulatory subunits) and those that bind a wide range of adenine analogues (adenine analogue-binding proteins). 2. In fresh-tissue extracts, regulatory subunits could be further subdivided into 'type I or 'type II' depending on whether they were derived from 'type I' or 'type II' protein kinase [see Corbin et al. (1975) J. Biol. Chem. 250, 218-225]. 3. The adenine analogue-binding protein was detected in crude tissue supernatant fractions of bovine and rat liver. It differed from the regulatory subunit of cyclic AMP-dependent protein kinase in many of its properties. Under the conditions of assay used, the protein accounted for about 45% of the binding of cyclic AMP to bovine liver supernatants. 4. The adenine analogue-binding protein from bovine liver was partially purified by DEAE-cellulose and Sepharose 6B chromatography. It had mol.wt. 185000 and was trypsin-sensitive. As shown by competition and direct binding experiments, it bound adenosine and AMP in addition to cyclic AMP. At intracellular concentrations of adenine nucleotides, binding of cyclic AMP was essentially completely inhibited in vitro. Adenosine binding was inhibited by only 30% under similar conditions. 5. Rat tissues were examined for the presence of the adenine analogue-binding protein, and, of those examined (adipose tissue, heart, brain, testis, kidney and liver), significant amounts were only found in the liver. The possible physiological role of the adenine analogue-binding protein is discussed. 6. Because the adenine analogue-binding protein or other cyclic AMP-binding proteins in tissues may be products of partial proteolysis of the regulatory subunit of cyclic AMP-dependent protein kinase, the effects of trypsin and aging on partially purified protein kinase and its regulatory subunit from bovine liver were investigated. In all studies, the effects of trypsin and aging were similar. 7. In fresh preparations, the cyclic AMP-dependent protein kinase had mol.wt. 150000. Trypsin treatment converted it into a form of mol.wt 79500. 8. The regulatory subunit of the protein kinase had mol.wt. 87000. It would reassociate with and inhibit the catalytic subunit of the enzyme. Trypsin treatment of the regulatory subunit produced a species of mol.wt. 35500 which bound cyclic AMP but did not reassociate with the catalytic subunit. Trypsin treatment of the protein kinase and dissociation of the product by cyclic AMP produced a regulatory subunit of mol.wt. 46500 which reassociated with the catalytic subunit. 9. These results may be explained by at least two trypsin-sensitive sites on the regulatory subunit. A model for the effects of trypsin is described.     

Association equilibrium of d-methamphetamine and l-methamphetamine with serum albumin

The association equilibria for complex formation between serum albumin (bovine, rat) and the optical isomers of methamphetamine (MAMP) was determined using an ultrafiltration method. It was found that serum albumin/d-MAMP and serum albumin/l-MAMP complexes had distinctly different Scatchard plots with bovine and rat albumin. The binding parameters of each association equilibrium were estimated from the Scatchard plots by Rosenthal's graphic method. This distinguished two kinds of specific binding sites in terms of the association equilibrium between bovine serum albumin and d-MAMP, and one binding site for rat serum albumin and d-MAMP. One specific binding site was found between serum albumin and l-MAMP in both bovine and rat. Molar ellipticities, [θ], of peaks were decreased in the CD spectra of the complexes formed between bovine serum albumin and d-MAMP or l-MAMP when compared with the CD spectrum of bovine serum albumin alone. However, no difference in [θ] was found between the CD spectra of the enantiomers of MAMP in the measured wavelength range. The non-specific binding site was distinct from the specific binding site and resulting from altered tertiary structure of the albumin molecule. Chirality 10:742–746, 1998. © 1998 Wiley-Liss, Inc.     

Affinity of uterine luminal proteins for rat blastocysts.

The binding of 125I-labelled rat uterine luminal proteins from Day-5 pregnant rats showed higher binding affinity to blastocysts than did the binding of proteins in uterine fluid from pro-oestrous rats (Day 0), rat serum albumin (RSA) or bovine serum albumin (BSA). Apparently little uptake of proteins into cells by phagocytosis or entry into the blastocoelic cavity occurred since similar results were obtained in the presence of sodium azide or cytochalasin B. Autoradiographic studies showed that the proteins were localized on the outer surface of the blastocyst. The binding was Ca2+-dependent. Denaturation of Day-5 uterine proteins at 80 degrees C reduced the counts to the values obtained with undenatured RSA and Day-0 fluids; this residual binding was considered as non-specific. The binding of labelled Day-5 uterine proteins was substantially reduced in the presence of unlabelled Day-5 proteins but to a lesser extent in the presence of RSA or rat serum. The dissociation of the bound labelled Day-5 uterine proteins occurred most rapidly in the presence of unlabelled Day-5 proteins. However, dissociation occurred within 2 h in the presence of other macromolecules, suggesting that the binding was not strong.     

Comparison of biotin binding protein of pregnant rat serum with rat serum albumin

The purified biotin binding protein of pregnant rat serum was shown to be immunologically similar to rat serum albumin as assessed by a sensitive radioimmunoassay. In radioimmunoassay for rat biotin binding protein, the binding of [¹²⁵I] rat biotin binding protein to anti-chicken egg yolk biotin binding protein antibodies was displaced by both rat serum (10–100 nl) and purified rat serum albumin (0.1–10 ng). Similarly, in radioimmunoassay for rat serum albumin the binding of [¹²⁵I] rat serum albumin to either anti-rat serum albumin antibodies or anti-chicken egg yolk biotin binding protein antibodies was displaced by unlabelled rat biotin binding protein at comparable concentration range (0·5–10 ng). Significant fractions of radioiodinated rat biotin binding protein and rat serum albumin bound to antibodies to chicken egg yolk biotin binding protein. In immature rats, the circulating half-lives of rat biotin binding protein and rat serum albumin were determined to be 12 and 17 h respectively. The rat biotin binding protein and rat serum albumin were analysed by techniques that exploit their physicochemical properties. They displayed similar electrophoretic mobilities in alkaline as well as denaturing sodium dodecyl sulphate-polyacrylamide gels. However, in nonequilibrium pH gradient polyacrylamide gel electrophoresis, they resolved clearly. In two-dimensional tryptic peptide map analysis, the two proteins showed similarities as well as significant differences in the relative distribution patterns of their iodopeptides. These results showed that the primary structure of rat biotin binding protein and rat serum albumin were different in finer details despite the fact that they shared significant immunological cross-reactivity.     

γ-Glutamyl semialdehyde and 2-amino-adipic semialdehyde: biomarkers of oxidative damage to proteins

Reactive oxygen species are formed in the body by several natural processes and by induced oxidative stress. The reactive oxygen species may react with the various biomolecules of the body, including proteins. In order to assess the impact of oxidative damage to proteins, we have tried to identify oxidized amino acids in blood proteins which might serve as biomarkers of oxidative damage. When oxidative damage is induced into bovine serum albumin by metal-catalysed oxidation systems, the aldehyde groups formed can be derivatized by fluoresceinamine (FINH₂). Following acid hydrolysis of FINH₂-derivatized protein, two major oxidation products, γ-glutamyl semialdehyde (GGS) and 2-amino-adipic semialdehyde (AAS), were found and identified by HPLC and MS. Isolation and identification of oxidized amino acids from homopolymers (poly-Arg,-Pro,-Lys,-Trp or -Leu) confirmed that GGS can originate from Arg or Pro, while AAS is an oxidation product of Lys. When oxidative stress was induced in rats by treatments with t-butyl hydroperoxide or acrolein, rat plasma protein levels of GGS and AAS were found to be significantly higher compared with control rats. The AAS-content in serum albumin or in total plasma proteins collected from eight different mammalian species was found to be inversely proportional to their maximum lifespan potential. The content of AAS in plasma proteins of untreated adult rats showed a positive correlation with the age of the rat. In young rats a negative correlation with age was found for both GGS and AAS. We conclude that GGS or AAS may be useful novel biomarkers of oxidative damage to proteins in vivo.     

Calmodulin-binding proteins: visualization by 125I-calmodulin overlay on blots quenched with Tween 20 or bovine serum albumin and poly(ethylene oxide)

To streamline detection of calmodulin-binding proteins, blotting techniques for the electrophoretic transfer of proteins onto nitrocellulose filters, followed by overlay with 125I-calmodulin, have been adapted. Autoradiography of the 125I-calmodulin-labeled blots allows the identification and quantitation of proteins that possess affinity for calmodulin. Five protocols for suppressing nonspecific binding and for enhancing specific interactions of 125I-calmodulin with electrophoretically separated proteins were investigated. Tween 20 and bovine serum albumin alone, as well as combinations of bovine serum albumin and poly(ethylene oxide) or hemoglobin and gelatin, were evaluated as quenching and enhancing agents. Tween 20 proved highly effective for quenching nonspecific binding and for enhancing specific 125I-calmodulin binding of a 61,000-Mr rat brain protein, which was only faintly observed on blots quenched with proteins alone. However, Tween 20 dissociated 50% of 68,000-Mr proteins and 80% of 21,000-Mr 125I-labeled protein standards from the nitrocellulose filter. An alternative, the combination of bovine serum albumin followed by incubation with 15,000- to 20,000-Mr poly(ethylene oxide), proved satisfactory for the recovery of 61,000-Mr calmodulin-binding activity and for the detection of calmodulin-binding peptides (50,000 to 14,000 Mr) produced by limited proteolysis of rat brain 51,000-Mr calmodulin-binding protein. These blotting procedures for detection of calmodulin-binding proteins are compatible with a variety of one-dimensional and two-dimensional electrophoresis systems, including a two-dimensional electrophoresis system utilizing urea and sodium dodecyl sulfate in the first dimension and nonurea sodium dodecyl sulfate electrophoresis in the second, a system which proved useful for resolving calmodulin-binding proteins displaying anomalous electrophoretic migration in the presence of urea.     

γ-Glutamyl semialdehyde and 2-amino-adipic semialdehyde: biomarkers of oxidative damage to proteins

Reactive oxygen species are formed in the body by several natural processes and by induced oxidative stress. The reactive oxygen species may react with the various biomolecules of the body, including proteins. In order to assess the impact of oxidative damage to proteins, we have tried to identify oxidized amino acids in blood proteins which might serve as biomarkers of oxidative damage. When oxidative damage is induced into bovine serum albumin by metal-catalysed oxidation systems, the aldehyde groups formed can be derivatized by fluoresceinamine (FINH₂). Following acid hydrolysis of FINH₂-derivatized protein, two major oxidation products, γ-glutamyl semialdehyde (GGS) and 2-amino-adipic semialdehyde (AAS), were found and identified by HPLC and MS. Isolation and identification of oxidized amino acids from homopolymers (poly-Arg,-Pro,-Lys,-Trp or -Leu) confirmed that GGS can originate from Arg or Pro, while AAS is an oxidation product of Lys. When oxidative stress was induced in rats by treatments with t-butyl hydroperoxide or acrolein, rat plasma protein levels of GGS and AAS were found to be significantly higher compared with control rats. The AAS-content in serum albumin or in total plasma proteins collected from eight different mammalian species was found to be inversely proportional to their maximum lifespan potential. The content of AAS in plasma proteins of untreated adult rats showed a positive correlation with the age of the rat. In young rats a negative correlation with age was found for both GGS and AAS. We conclude that GGS or AAS may be useful novel biomarkers of oxidative damage to proteins in vivo.     

Studies on 125I-labeled proteins in rat plasma using an air-driven ultracentrifuge: protein-protein interactions and nonideality

The molecular weights of a number of ¹²⁵I-labeled plasma proteins have been determined from an analysis of their sedimentation equilibrium behavior in an air-driven ultracentrifuge. The values obtained agree well with results obtained by other methods. Molecular weights obtained for ¹²⁵I-labeled bovine serum albumin and the rat serum proteins albumin, α₁-acid glycoprotein, and major acute-phase α₁-protein were unaffected by the addition of 7% rat plasma. Direct evidence for protein-protein interactions was obtained for mixtures of ¹²⁵I-labeled rat α₁-acid glycoprotein and the plant lectin concanavalin A and for mixtures of ¹²⁵I-labeled protein A from Staphylococcus aureus and 7% rat plasma. Interactions of a different type were observed when the sedimentation equilibrium profiles of ¹²⁵I-labeled proteins were determined in concentrated solutions of other proteins. Under these conditions the effects of molecular exclusion or nonideality became significant and low estimates were obtained for the molecular weights of the labeled proteins. Analysis of the data obtained for ¹²⁵I-labeled bovine serum albumin in concentrated solutions of bovine serum albumin (20–80 mg/ ml) yielded nonideality coefficients in good agreement with literature values. Analysis of the behavior of ¹²⁵I-labeled rat serum albumin, transferrin, and α₁-acid glycoprotein yielded nonideality coefficients and hence activities of these proteins in undiluted rat plasma.     

Reversible inhibition of protein synthesis in lung by halothane

Alterations in the synthesis and degradation of proteins were investigated in intact lungs exposed to the volatile anaesthetic halothane. In rat lungs perfused in situ with Krebs-Henseleit bicarbonate buffer containing 4.5% (w/v) bovine serum albumin, 5.6 mM-glucose, plasma concentrations of 19 amino acids and 690 microM-[U-14C]-phenylalanine and equilibrated with O2/N2/CO2 (4:15:1), protein synthesis, calculated based on the specific radioactivity of aminoacyl-tRNA, was inhibited by halothane. The anaesthetic did not affect degradation of lung proteins. The inhibition of protein synthesis was rapid in onset, dose-dependent, and quickly reversible. It did not appear to be associated with overall energy depletion, with non-specific changes in cellular permeability, or with decreased availability of amino acids as substrates for protein synthesis.