Showing papers on "Serum albumin published in 1978"
TL;DR: The procedure appears to be a specific and sensitive technique for the localization of serotonin in the central nervous system of the rat and has the advantage that adjacent sections can be examined by the immunofluorescence method using antisera to a variety of antigens.
517 citations
TL;DR: A new automated dye-binding method for serum albumin determination with bromcresol purple (BCP) that has several advantages over an existing bromCresol green (BCG) method, which offers a solution to the poor accuracy of existing BCG methods while retaining many of their desirable features.
Abstract: We describe a new automated dye-binding method for serum albumin determination with bromcresol purple (BCP) that has several advantages over an existing bromcresol green (BCG) method. The continuous-flow method is sensitive, linear, and precise, with negligible sample interaction at an analytical rate of 60 samples per hour. Unlike BCG, BCP did not react with an albumin-free serum globulin preparation or pure human transferrin solutions. Reaction with serum was instantaneous; in contrast, BCG exhibits a slow nonspecific reaction with some specimens. The specificity of BCP was demonstrated by good agreement with results of "rocket" immunoelectrophoresis (EIA) where y(BCP) = 0.95X(EIA) + 1.72. The BCG method overestimated serum albumin concentration where y(BCG) = 1.01X(EIA) + 6.77. Precipitation, which affects the BCG method, was not observed with BCP. Blank corrections were negligible, salicylate did not interfere, and bilirubin affected the method only if present in very high concentration. The method offers a solution to the poor accuracy of existing BCG methods while retaining many of their desirable features.
270 citations
TL;DR: The carbodiimide-catalyzed conjugation of a 6700 molecular weight fragment of poly-L-lysine to radiolabeled human serum albumin or to horseradish peroxidase enhances the membrane transport of each protein into cultured mouse fibroblasts approximately 11- and 200-fold, respectively.
Abstract: The carbodiimide-catalyzed conjugation of a 6700 molecular weight fragment of poly-L-lysine to radiolabeled human serum albumin or to horseradish peroxidase enhances the membrane transport of each protein into cultured mouse fibroblasts approximately 11- and 200-fold, respectively. At least 50% of the peroxidase activity remained after conjugation. Trypsinization and carbamylation of the two conjugates demonstrates that the enhancement of their cellular uptake is related to their poly-L-lysine content. Simple addition to the medium of comparable amounts of free poly-L-lysine has no effect on the transport of either native protein. Addition of poly-L-ornithine (molecular weight 200,000) at 3-30 microgram/ml, a condition known to cause enhancement of 125I-labeled human serum albumin uptake by mouse sarcoma cells, has no visible effect on the cellular uptake of native horseradish peroxidase. The intracellular localization of the enzyme-poly-L-lysine conjugate can be demonstrated cytochemically by either light or transmission electron microscopy. A concentration of conjugate that increases the uptake more than 200-fold does not cause any detectable morphological change suggestive of cell toxicity. Furthermore, because poly-L-lysine is an excellent substrate for intracellular proteolytic enzymes, it can be expected to be broken down and reutilized in the cell.
212 citations
TL;DR: The carbohydrate moieties of rat liver transferrin or apoprotein B of chick liver VLDL do not appear to play an essential role in the secretion process, and despite the inhibitory effect of tunicamycin on glycosylation, secretion of all four proteins was virtually unimpaired.
177 citations
TL;DR: The level of albumin mRNA, whether assayed by cell-free translation or by hybridization to a specific complementary DNA probe, was markedly decreased in livers of diabetic animals and was restored to normal by insulin treatment, suggesting thatalbumin mRNA content is the primary factor responsible for altering rates of album in synthesis under these conditions.
Abstract: We have studied the effects of alloxan-induced diabetes and subsequent insulin replacement on albumin and total hepatic protein synthesis. Diabetes resulted in a reduction to approximately 20% of normal in albumin synthesis relative to the rate of total protein synthesis in vivo and a reduction to 10% in the absolute rate of albumin secretion by perfused livers. In contrast, the synthesis of total secretory protein and retained hepatic protein was affected to a lesser extent by diabetes. Treatment of diabetic rats with insulin restored rates of albumin and total hepatic protein synthesis to normal levels. The molecular basis of these alterations in albumin synthesis was investigated by examining albumin mRNA levels in livers of normal, diabetic, and insulin-treated diabetic animals. The level of albumin mRNA, whether assayed by cell-free translation or by hybridization to a specific complementary DNA probe, was markedly decreased in livers of diabetic animals and was restored to normal by insulin treatment. These changes occurred in parallel with changes in the rates of albumin secretion observed in perfused liver, suggesting that albumin mRNA content is the primary factor responsible for altering rates of albumin synthesis under these conditions.
134 citations
TL;DR: Changes in body composition associated with moderate degrees of nutritional compromise were related principally to decreases in body cell mass, and multiple regression equations were developed that allow prediction of muscle cellmass, fat-free weight, and body cellmass from simple anthropometry and serum albumin levels.
129 citations
TL;DR: Urea (7M) and heating (35 to 55 degrees C) caused a major increase in the viscosity of mucin and mucin-albumin mixtures, suggesting that rupture of hydrogen bonds, unfolding and partial denaturation of mucIn promotes greater intertangling (possibly hydrophobic interactions) between mucIn and albumin molecules.
Abstract: The interaction of serum albumin with a model epithelial mucin from pig stomach was explored by rotary viscometry. During 30 min of incubation of human serum albumin(20mg/ml) and pig gastric mucin (8mg/ml) in iso-osmotic buffers at 37 degrees C, the solution became markedly viscous. Viscosity enhancement was proportional to albumin concentration (2-40mg/ml), was most pronounced under conditions of low shear rate (less than 45S-1), and was considerably greater than the additive or multiplicative viscosity values calculated from albumin or mucin solutions measured separately. The viscous mucin-albumin complex was destroyed by high shear rates (greater than 90S-1), but slowly re-formed under zero shear conditions. Elevation of pH (7 to 9), ionic strength (0.1 to 1.0), and addition of disodium EDTA (5mM) did not cause marked or specific alterations in the viscosity of the mixture, suggesting that electrostatic interactions probably do not stabilize mucin-albumin complexes. Urea (7M) and heating (35 to 55 degrees C) caused a major increase in the viscosity of mucin and mucin-albumin mixtures, suggesting that rupture of hydrogen bonds, unfolding and partial denaturation of mucin promotes greater intertangling (possibly hydrophobic interactions) between mucin and albumin molecules. The implications of mucin-albumin interaction in diseases associated with mucus obstruction are briefly discussed.
112 citations
TL;DR: Of all the amino acids investigated in the CSF, only tryptophan was significantly increased in patients in hepatic coma compared to cirrhotic patients not in coma, and Associated with the elevated plasma free tryPTophan in coma patients was an increase in plasma free fatty acids and a marked decrease in serum albumin levels.
111 citations
TL;DR: It is concluded that the drug is bound by two groups of binding sites with the association constants K1=40.0 X 10(-3) and K2=0.39 X 10(3), and the number ofbinding sites n1=1.5 and n2=6.8.
Abstract: 1 Based on the Scatchard plot of the binding data of valproic acid (VPA) it is concluded that the drug is bound by two groups of binding sites with the association constants K1=40.0 X 10(-3) and K2=0.39 X 10(3), and the number of binding sites n1=1.5 and n2=6.8. 2 The binding is dependent on dialysis time, on temperature, on the drug concentration, and on the protein concentration in plasma. 3 At therapeutic plasma concentrations unbound VPA is 8.4 +/- 2.5%, but is increased to 20.3 +/- 4.7% in patients with significant impairment of renal function (P less than 0.001). 4 In patients with renal disease a good correlation is found between unbound VPA and serum creatinine, creatinine clearance, blood nitrogen and uric acid, respectively. A poor correlation is seen between unbound VPA and total protein or albumin concentration in plasma.
99 citations
TL;DR: The blood-brain barrier in adult rats was opened unilaterally by infusing 1.58 M L (+)-arabinose in 0.9% NaCl solution into the internal carotid artery, via a catheter in the externalCarotid, and barrier opening was not associated with edema as measured two days after infusion.
94 citations
Journal Article•
TL;DR: A simple technique using a small disc which is dipped into a 125I-labeled protein solution has been devised to study the adsorption of human albumin, fibrinogen, and IgG onto Cuprophane or PVC.
TL;DR: Evaluation of the requirement for replaceable functions of serum has improved greatly the specificity and sensitivity of the bioassay for the nonreplaceable functions and led to clonal growth of normal human and chicken cells with less than 500 μg per ml dialyzed serum protein.
Abstract: Multiplication of normal diploid cells in culture is controlled by a complex set of interacting extracellular variables. The amount of serum protein needed for colony formation by such cells is affected directly by many of the other variables, including the nature of the culture surface, the type of trypsinization procedure used, and the qualitative and quantitative composition of the culture medium. By a sequential process of adjusting all of these variables to optimum values for cellular multiplication with minimal amounts of serum protein, we have been able to obtain clonal growth of normal human and chicken cells with less than 500 μg per ml dialyzed serum protein. Precise quantitative adjustment of nutrient concentrations is particularly important. The multiplication-promoting functions of serum can be classified operationally as “replaceable” (those that can be replaced by modifying the medium or the culture conditions) and “nonreplaceable” (those that we have not yet been able to replace). Elimination of the requirement for replaceable functions of serum has improved greatly the specificity and sensitivity of the bioassay for the nonreplaceable functions. The nonreplaceable multiplication-promoting activity from fetal bovine serum for human diploid fibroblasts has been separated from fetuin and serum albumin and purified approximately 15-fold.
TL;DR: Results suggest that vesicle fusion is a requirement for conversion of proalbumin into albumin.
Abstract: 1 An enzyme from rat liver that converts proalbumin into albumin is described Partial purification, inhibitor studies and the conditions for maximum activity suggest that the enzyme is cathepsin B 2 A membrane-bound enzyme, located mainly in lysosomes, also converts proalbumin into albumin This appears to be a membrane-bound form of cathepsin B 3 Isolated Golgi vesicles, incubated under conditions suitable for cathepsin B, convert endogenous proalbumin into albumin 4 This conversion in Golgi vesicles has an absolute requirement for Ca2+ at micromolar concentrations Mg2+ does not affect or substitute for Ca2+ Both the proalbumin and the albumin formed from it are intravesicular 5 Converting activity is enhanced by pretreatment with the known chemical fusogen, poly(ethyleneglycol) 6 Vesicles preincubated at pH above 7 in the presence of dithiothreitol show a marked fall in converting activity This can be partially restored by incubation with native vesicles These results suggest that vesicle fusion is a requirement for conversion of proalbumin into albumin
TL;DR: It is suggested that the superior growth performance of the bulls is due, at least partially, to hormonally mediated differences in nitrogen metabolism that result in a greater deposition of lean tissue and hence increased weight gain.
Abstract: Eight British Friesian bulls and eight steers were compared in terms of performance and levels of metabolites and hormones in circulating blood. Under conditions of generous nutrition the bulls grew significantly more quickly, exhibited a superior feed conversion efficiency and had lower levels of serum albumin and plasma urea and higher levels of serum growth hormone and prolactin than the steers. Differences in levels of plasma glucose and free fatty acids and serum total protein and insulin were not significant. It is suggested that the superior growth performance of the bulls is due, at least partially, to hormonally mediated differences in nitrogen metabolism that result in a greater deposition of lean tissue and hence increased weight gain.
Journal Article•
TL;DR: It is evident, however, that the OLS-BSA conjugate elicited in rabbits O-antibodies with the same specificity as whole bacteria.
Abstract: The O-antigenic polysaccharide of phenol-water extracted Salmonella typhimurium (O antigens 4, 12) lipopolysaccharide was enzymatically cleaved by phage P22 endorhamnosidase. An octasaccharide with the (formula: see text) structure Gal-Man-Rha-Gal-Man-Rha was isolated and shown to retain the O-antigen 4 specificity of the native polysaccharide. After oxidation of the terminal reducing rhamnose residue to the corresponding aldonic acid, the octasaccharide was covalently linked to bovine serum albumin (OLS-BSA) by use of a water-soluble carbodimide. The resulting conjugate showed O-antigen 4 specificity in enzyme-linked immunosorbent assay (ELISA) ans passive hemagglutination inhibition tests. Immunization of rabbits with the OLS-BSA conjugate gave rise to antibodies directed toward both the octasaccharide and the carrier protein. ELISA titration with synthetic disaccharide-protein conjugates as antigens revealed that the antibody titer against the mannose-rhamnose structure was higher than against the abequose-mannose structure. In rabbits immunized with heat-killed whole bacteria the titers against the two disaccharides were equal. The reason for this difference is not obvious. It is evident, however, that the OLS-BSA conjugate elicited in rabbits O-antibodies with the same specificity as whole bacteria.
TL;DR: In vitro alkylation of melphalan at 37 degrees with human plasma containing 30 microgram/ml, calculated by equilibrium dialysis, methanol extraction, and high-pressure liquid chromatographic analysis, is 30% after 8 hr.
TL;DR: The results suggest that the steroid-resistant nephrotic syndrome can be treated symptomatically by indomethacin, and a harmful renal effect of long-term indomethin administration was found to be unlikely.
Abstract: In 25 patients with nephrotic syndromes of different origin, indomethacin caused an immediate decrease in glomerular filtration rate (GFR) and urinary protein excretion. This effect of indomethacin on GFR and proteinuria was more pronounced when the renin-angiotensin system was stimulated by a low-sodium diet and 50 mg hydrochlorothiazide daily, and resulted in a significant rise in serum albumin. Withdrawal of indomethacin after 1--3 years of administration was followed by an increase in proteinuria to pretreatment levels in 9 out of 15 patients. A harmful renal effect of long-term indomethacin administration was found to be unlikely. The results suggest that the steroid-resistant nephrotic syndrome can be treated symptomatically by indomethacin.
TL;DR: The conclusion is that the rabbit hepatic asialoglycoprotein receptor cannot discriminate between D-galactosyl and D-glucosyl-terminated glycoproteins and binds both.
TL;DR: It is postulated that an important function of bile salts in the intestinal lumen is to clear the interface of the dietary fat from proteins of exo- and endogeneous sources thus making it available for pancreatic lipolysis.
TL;DR: The seminal plasma in sperm suspensions from boar, bull, rabbit, ram and stallion was replaced with simple defined media as completely as possible by a combination of centrifugation through Ficoll and dilution, and sperm motility was preserved better in the presence of serum albumin.
Abstract: The seminal plasma in sperm suspensions from boar, bull, rabbit, ram and stallion was replaced with simple defined media as completely as possible by a combination of centrifugation through Ficoll and dilution. After this process, motility declined and the cells showed a tendency to agglutinate and/or stick to glass. Varying the ionic strength of the medium had little effect upon these parameters but sperm motility was preserved better in the presence of serum albumin. When a number of purified proteins and other macromolecules were tested individually in this way for their motility-preserving ability, bovine or human serum albumin was consistently the most effective. Defatting the albumin or altering its nature by mild reduction, oxidation or alkylation had little detectable effect on its motility-preserving ability; the protein did not appear to be acting as a chelator of metal ions, for it could not be replaced by EDTA. The response of the spermatozoa to replacemrnt of seminal plasma varied between species: bull spermatozoa were particularly sensitive and serum albumin had little effect upon their subsequent motility.
TL;DR: Use of optimized assay conditions that eliminate dependence on “replaceable” activities from serum reduces the number of crude fractions that affect multiplication and facilitates quantification and purification of the remaining "nonreplaceable" multiplication-promoting activities.
TL;DR: Treatment of rats with 0.5-25 mumol/100 g body weight of colchicine for 1 h or more caused an inhibition of hepatic protein synthesis and incorporation of radioactivity into two forms of intracellular albumin which were precipitable with antiserum to rat serum albumin but which were separable by diethylaminoethyl-cellulose chromatography.
Abstract: Treatment of rats with 0.5-25 mumol/100 g body weight of colchicine for 1 h or more caused an inhibition of hepatic protein synthesis. This effect was not seen if animals were exposed to colchicine for less than 1 h. The delayed inhibition of protein synthesis affected both secretory and nonsecretory proteins. Treatment with colchicine (15 mumol/100 g) for 1 h or more caused the RNA content of membrane-bound polysomes to fall but did not change the polysomal profile of this fraction. By contrast, the total RNA content in the free polysome cell fraction was increased, and this was due to the presence of more ribosomal monomers and dimers. Electron microscope examination of the livers from rats treated for 3 h with colchicine showed an accumulation of secretory vesicles within the hepatocytes and a general distention of the endoplasmic reticulum. Administration of radioactive L-leucine to the rats led to an incorporation of radioactivity into two forms of intracellular albumin which were precipitable with antiserum to rat serum albumin but which were separable by diethylaminoethyl-cellulose chromatography. One form has arginine at the amino-terminal position and is proalbumin, and the other form, which more closely resembles serum albumin chromatographically, has glutamic acid at its amino terminus. Only proalbumin was found in rough and smooth endoplasmic reticulum fractions and in a Golgi cell fraction wich corresponds morphologically to mostly empty and partially filled secretory vesicles. However, in other Golgi cell fractions which were filled with secretory products, both radioactive proalbumin and serum albumin were found. This indicates that proalbumin is converted to serum albumin in these secretory vesicles just before exocytosis. Colchicine delayed the discharge of radioactive albumin from these filled secretory vesicles and caused an accumulation of both proalbumin and serum albumin within these cell fractions.
TL;DR: It is concluded that correcting total serum calcium values for serum albumin concentration improves discrimination of borderline hyperparathyroid patients, but that measurement of ionized calcium in serum discriminates better.
Abstract: We studied 25 borderline-hyperparathyroidism patients whose total serum calcium concentration was within normal limits (reference range: 2.25--2.75 mmol/liter) but whose concentrations of serum ionized calcium were above normal (reference range: 1.03--1.23 mmol/liter). Their hyperparathyroidism was histopathologically verified. To compare the discriminating value of corrected serum calcium with ionized calcium, we studied the serum calcium and albumin concentrations in a reference group of 2098 patients. After patients from endocrine and dialysis departments were excluded from the reference group, we obtained the range (mean +/- 2 SD) 2.05--2.71 mmol/liter for uncorrected serum calcium and 2.11--2.63 mmol/liter for corrected serum calcium. The correction factor for calcium on albumin was 20 mumol/g. Even with this limit for corrected serum calcium, 13 of 25 borderline hyperparathyroidism patients had values that fell within the reference range. We conclude that correcting total serum calcium values for serum albumin concentration improves discrimination of borderline hyperparathyroid patients, but that measurement of ionized calcium in serum discriminates better.
TL;DR: Phenytoin appeared to bind to a single site on the albumin molecule and could be competitively displaced from this site by concentrations of valproic acid above 280 mumol l-1, although this was statistically significant only at a concentration of 480 mumolL-1 pheny toin.
Abstract: 1 Valproic acid or phenytoin were added to fresh human serum in varying concentrations and their binding characteristics determined by the method of Scatchard (1949). 2 Changes in serum albumin binding were investigated for phenytoin in the presence of 280, 560, 1050 and 2100 mumol l-1 valproic acid, and for valproic acid in the presence of 40, 120, 280 and 480 mumol l-1 phenytoin. 3 Phenytoin appeared to bind to a single site on the albumin molecule and could be competitively displaced from this site by concentrations of valproic acid above 280 mumol l-1. 4 At high concentrations of valproic acid, the affinity of phenytoin for albumin was greatly decreased but the number of available binding sites was increased from one to four. 5 Valproic acid was bound to two high affinity and five low affinity binding sites but the latter were not detectable at valproic acid concentrations below 2100 mumol l-1. 6 Phenytoin displaced valproic acid from its high affinity binding sites, although this was statistically significant only at a concentration of 480 mumol l-1 phenytoin.
TL;DR: Studies on binding of retinoic acid and its analogues to serum albumin indicate that no correlation exists between binding affinity for albumin and their biological potency.
Abstract: Binding affinities of retinoic acid and its synthetic analogues to intracellular retinoic acid-binding protein, which is a possible candidate for mediating their biological function, and to serum albumin, the plasma transport protein, were evaluated. A quantitative method involving elimination of interfering serum albumin by immunoprecipitation was developed to measure the binding efficiency of these retinoids, some of which are active in modifying epithelial differentiation and preventing tumorigenesis. Two cyclopentenyl analogues of retinoic acid and 13-cis-retinoic acid showed, like retinoic acid, a binding efficiency of 100% for the cellular binding protein. With the phenyl, dichlorophenyl and trimethylmethoxyphenyl analogues of retinoic acid, the binding efficiency increased as the substituents on the aromatic ring increased; thus the trimethylmethoxyphenyl analogue binds almost as efficiently as retinoic acid itself. However, the trimethylmethoxyphenyl analogue with a sulphur atom on the side chain has a much decreased binding affinity. The correlation noticed between the binding efficiency of these retinoids and their biological activity in differentiation and/or in the control of tumorigenesis particularly enhances the confidence in the present method of determining the relative binding efficiencies. None of the vitamins, hormones and cofactors tested, showed appreciable affinity for the retinoic acid-binding site. Studies on binding of retinoic acid and its analogues to serum albumin indicate that no correlation exists between binding affinity for albumin and their biological potency.
TL;DR: It is suggested that dietary protein supply affects selectively the synthesis and/or functional stability of albumin mRNA in rat liver.
Abstract: In rats fed on a protein-deficient diet, albumin synthesis as a percentage of total liver protein synthesis falls from the normal value of approx. 15% to about 8%. We have extracted total cytoplasmic RNA from individual rat livers and measured the concentration of active albumin mRNA by translation in a reticulocyte lysate system from which the endogenous mRNA had been removed [Pelham & Jackson (1976) Eur. J. Biochem. 67, 247-256]. In this messenger-dependent system it is possible to measure the synthesis of albumin as a proportion of the overall protein synthesis promoted by the addition of the hepatic RNA. The results show that the concentration of translatable albumin mRNA in samples of total cytoplasmic RNA from livers of protein-deficient rats is decreased markedly. These findings suggest that dietary protein supply affects selectively the synthesis and/or functional stability of albumin mRNA in rat liver.
TL;DR: The data from two lines of differentiated rat hepatoma cells found in culture suggest that retinol has a specific regulatory effect on RBP metabolism, and these cells thus resemble the normal rat liver cell in vivo in regard to the known regulation ofRBP metabolism.
Journal Article•
TL;DR: The immune response generated following curative local heating of the VX2 carcinoma is involved in regression of the primary tumor as well as in the destruction of metastases and the abrogation of such enhanced immunocompetence by total-body heating supports the concept that in this animal tumor system whole-body hyperthermia is hazardous for the host.
Abstract: Nonspecific immunocompetence in VX2 tumor-bearing rabbits was assessed by skin response to dinitrochlorobenzene and development of antibody titer to bovine serum albumin. Skin reactivity to a 3 m KCI extract of the VX2 and antitumor antibody titer were used to monitor host immunocompetence against the tumor. Rabbits bearing a 15- to 20-mi i.m. VX2 tumor in the hind limb were treated by local and total-body heating after established metastases were present in regional and aortic lymph nodes and lungs. Following local heating of the VX2 (intratumor temperature, 47–50°/30 min) achieved by radiofrequency current at 13.56 MHz, there was tumor regression and host cure in 9 of 13 (70%) rabbits. Tumor regression was accompanied by a marked and sustained increase in skin reactivity to both tumor extract and dinitrochlorobenzene, and there was a 100-fold increase in serum levels of antitumor and anti-bovine serum albumin antibody. The animals are alive 2 years after heating and are immune to inoculation of 30 × 106 VX2 cells; 1 × 106 tumor cells led to a 100% death rate in 72 ± 7 (S.D.) days in untreated rabbits. In the 4 rabbits that did not respond to heating, unrestrained tumor growth was accompanied by a progressive decrease in host response to skin tests and antibody titers of 1:10 or less, findings similar to those in untreated tumor-bearing hosts. Eight rabbits were subjected to total-body hyperthermia (42°/60 min on 3 successive days) 7 days after radiofrequency treatment. In 7 of the animals (88%), temporary restraint of tumor growth was followed by return to exponential increase in tumor volume and rapid death. This was accompanied by abrogation of the enhanced cellular and humoral immune responsiveness that followed local heating; in the single animal that was cured there was a sustained increase in skin response to dinitrochlorobenzene and tumor extract and in serum levels of antitumor and anti-bovine serum albumin antibody. Necrotic material removed from regressing VX2 carcinomas up to 17 days after radiofrequency heating produced tumors on inoculation into rabbits. It is concluded that the immune response generated following curative local heating of the VX2 carcinoma is involved in regression of the primary tumor as well as in the destruction of metastases. The abrogation of such enhanced immunocompetence by total-body heating supports the concept that in this animal tumor system whole-body hyperthermia is hazardous for the host.
TL;DR: The kinetics of bilirubin binding to human serum albumin at pH 7.40, 4 degrees C, was studied by monitoring changes in bilirubain absorbance and Curve-fitting procedures allowed the assignment of absorption coefficients to the intermediate species.
TL;DR: It is reported here that inhibition of opiate binding by phospholipase A can be reversed almost completely by incubation of the enzyme-treated membranes with bovine serum albumin (BSA).
Abstract: OPIATE receptors in animal and human brain have been shown to be tightly associated with cell membranes1–3. Our laboratory has reported the solubilisation of an etorphine–receptor complex4, but to date it has not been possible to obtain an active receptor in soluble form. Nevertheless, it has been possible to study many biochemical characteristics of the membrane-bound receptor. Its sensitivity to sulphhydryl reagents and a number of other protein reagents5,6 as well as to proteolytic enzymes1,7 suggests the participation of protein(s) in opiate binding. The evidence is less clear with respect to a function for phospholipids. Opiate binding activity of cell membrane preparations from rat brain has been shown to be exquisitely sensitive to phospholipase A of Vipera russelli venom (in the ng ml−1 range)8, but very insensitive to phospholipase A present in the venom of Crotalus adamenteus1 or that derived from pig pancreas (Lin & Simon, unpublished). Phospholipase C is inhibitory only in very high concentrations1,8. The great sensitivity of opiate receptors to the Russell's viper enzyme and to ionic and non-ionic detergents4,7 points to a possible role for phospholipids in the binding process. We report here that inhibition of opiate binding by phospholipase A can be reversed almost completely by incubation of the enzyme-treated membranes with bovine serum albumin (BSA).