Showing papers on "Bovine serum albumin published in 1989"
TL;DR: The pathobiological relevance of pyrraline may relate to its reported antiproteolytic and mutagenic properties and may play a role in diabetic neuropathy in analogy to pyrroles formed during hexane-induced neuropathy.
318 citations
TL;DR: The higher rate of fluorescence generation in nonenzymatically fructated BSA could be explained by a faster conversion of its Amadori groups, especially relevant in tissues where fructose levels increase in diabetes as a result of the operation of the sorbitol pathway.
230 citations
TL;DR: Observations indicate that early diabetes-induced hemodynamic changes and increased vascular albumin permeation and urinary albumin excretion are aldose reductase-linked phenomena, and increases in blood flow may reflect impaired contractile function of smooth muscle cells in resistance arterioles.
Abstract: This study investigated hemodynamic changes in diabetic rats and their relationship to changes in vascular albumin permeation and increased metabolism of glucose to sorbitol. The effects of 6 wk of streptozocin-induced diabetes and three structurally different inhibitors of aldose reductase were examined on 1) regional blood flow (assessed with 15-μm 85 Sr-labeled microspheres) and vascular permeation by 125 I-Iabeled bovine serum albumin (BSA) and 2) glomerular filtration rate (assessed by plasma clearance of 57 Co-labeled EDTA) and urinary albumin excretion (determined by radial immunodiffusion assay). In diabetic rats, blood flow was significantly increased in ocular tissues (anterior uvea, posterior uvea, retina, and optic nerve), sciatic nerve, kidney, new granulation tissue, cecum, and brain. 125 I-BSA permeation was increased in all of these tissues except brain. Glomerular filtration rate and 24-h urinary albumin excretion were increased 2- and 29-fold, respectively, in diabetic rats. All three aldose reductase inhibitors completely prevented or markedly reduced these hemodynamic and vascular filtration changes and increases in tissue sorbitol levels in the anterior uvea, posterior uvea, retina, sciatic nerve, and granulation tissue. These observations indicate that early diabetes-induced hemodynamic changes and increased vascular albumin permeation and urinary albumin excretion are aldose reductase-linked phenomena. Discordant effects of aldose reductase inhibitors on blood flow and vascular albumin permeation in some tissues suggest that increased vascular albumin permeation is not entirely attributable to hemodynamic changes. We hypothesize that 1) increases in blood flow may reflect impaired contractile function of smooth muscle cells in resistance arterioles and 2) increases in vascular 125 I-BSA permeation and urinary albumin excretion reflect impaired vascular barrier functional integrity in addition to increased hydraulic conductance secondary to microvascular hypertension associated with decreased vascular resistance.
218 citations
TL;DR: It was concluded that, although polyanionic proteins in solution may inhibit mineral induction and growth, very minute quantities of such molecules, when immobilized on a surface, induce mineral at physiological concentrations of calcium and phosphate ions.
Abstract: The purpose of this study was to investigate the mineral induction capacity in vitro of polyanionic proteins covalently bound to a surface. Rat dentin gamma-carboxyglutamate-containing protein of the osteocalcin type (Gla-protein), proteoglycan (PG), and phosphoprotein (PP-H), as well as phosvitin (PhV) and bovine serum albumin (BSA), were covalently linked to agarose beads. There were incubated at 37 degrees C in solutions with a Ca/P molar ratio of 1.67, [Ca][P] molar products in the range 1.0-1.8 mM2, and an ionic strength of 0.165. The incubations were performed at constant pH and composition conditions; no spontaneous precipitation occurred under these conditions. Mineral formation, as monitored by scanning electron microscopy (SEM), was induced by all immobilized polyanions, including enzymatically dephosphorylated PP-H and PhV. No mineral was induced by BSA. The mineral inductive capacity of immobilized polyanionic proteins, as judged by the SEM after identical incubations, was found to differ between the different ligands. The mineral induced by PP-H and PG was shown by X-ray diffraction to be apatitic. It was concluded that, although polyanionic proteins in solution may inhibit mineral induction and growth, very minute quantities of such molecules, when immobilized on a surface, induce mineral at physiological concentrations of calcium and phosphate ions. The data presented may be taken to suggest that PP-H and PG, and perhaps other polyanions, may possibly be responsible for mineral nucleation in dentin and bone. The results, however, also point to the rather limited specificity in this type of reaction.
205 citations
TL;DR: αs1-Casein and soybean globulins were polymerized and gelatinized by Ca2+-independent transglutaminase that was isolated from the culture filtrate of a microorganism thought to belong to Streptoverticillium sp.
Abstract: αs1-Casein and soybean globulins were polymerized and gelatinized by Ca2+-independent transglutaminase that was isolated from the culture filtrate of a microorganism thought to belong to Streptoverticillium sp. of actinomycetes. This enzyme polymerized such albumins as bovine serum albumin, human serum albumin and conalbumin in the presence of dithiothreitol. Rabbit myosin was polymerized by the present emzyme but actin was not. An RP-HPLC analysis after enzymic digestion of the polymerized asl -casein showed existence of the £-(y-Glu)Lys bond. Thus, it was confirmed that the polymerization was formed by a catalytic reaction of the transglutaminase.
205 citations
TL;DR: Results demonstrated that LPL enzymatic activity and protein were removed from endothelial cells by triglyceride-rich lipoproteins (chylomicrons and VLDL).
202 citations
TL;DR: The insulin gene co-introduced with HMG-1 was transported into the nuclei of liver cells much more efficiently than the gene Co- Introduced with BSA and the amount of transcript of the insulin gene was more than 10 times greater than that of the geneCo- introduced with B SA.
167 citations
TL;DR: The thermal denaturation of bovine serum albumin (BSA) was studied at pH 2.8 and 7.0 in the range of 2–65°C and the structural change was reversible in the temperature range below 45°C, but was partially reversible upon cooling to room temperature subsequent to heating at 65°C.
Abstract: The thermal denaturation of bovine serum albumin (BSA) was studied at pH 2.8 and 7.0 in the range of 2-65 degrees C. The relative proportions of alpha-helix, beta-structure, and disordered structure in the protein conformation were determined as a function of temperature, by the curve-fitting method of circular dichroism spectra. With the rise of temperature at pH 7.0, the proportion of alpha-helix decreased above 30 degrees C and those of beta-structure and disordered structure increased in the same temperature range. The structural change was reversible in the temperature range below 45 degrees C. However, the structural change was partially reversible upon cooling to room temperature subsequent to heating at 65 degrees C. On the other hand, the structural change of BSA at pH 2.8 was completely reversible in the temperature range of 2-65 degrees C, probably because the interactions between domains and between subdomains might disappear due to the acid expansion. The secondary structure of disulfide bridges-cleaved BSA remained unchanged during the heat treatment up to 65 degrees C at pH 2.8 and 7.0.
166 citations
TL;DR: Reactivated PAI-1, which was inactivated by incubation at physiological conditions could again be fully reactivated, in contrast to chloramine T-oxidized PAi-1 , which was irreversibly inactivated.
Abstract: The stability of PAI-activity has been studied at different conditions. The inactivation followed first order kinetics. Lowering the temperature and decreasing the pH both, increased the stability of PAI-1 dramatically. Addition of the PAI-1 binding protein, vitronectin, to reactivated PAI-1, about doubled the half-life of PAI-1 at all conditions studied. In the presence of chloramine T, the inactivation of reactivated PAI-1 was very rapid. In this case the protective effect of purified vitronectin, human plasma or fetal calf serum, but not of bovine serum albumin, was pronounced. The stability of the spontaneously active high Mr form of PAI-1 (partially purified or in plasma), constituting a complex between PAI-1 and vitronectin, was quite similar to reactivated PAI-1 in the presence of vitronectin. Addition of pure vitronectin, human plasma or fetal calf serum to such material had no further stabilizing effect. Reactivated PAI-1, which was inactivated by incubation at physiological conditions could again be fully reactivated, in contrast to chloramine T-oxidized PAI-1, which was irreversibly inactivated.
150 citations
TL;DR: Hapten inhibition of precipitate formation between amaranthin and asialo-ovine submaxillary indicated that the T-disaccharide and its alpha-linked glycosides were the best inhibitors and the C'-4 axial hydroxyl group of the galactosyl moiety are the most important loci for lectin interaction.
136 citations
TL;DR: Physical disruption of fecal bacteria released large quantities of proteases, indicating that the lysis of bacteria in the colon may contribute to the extracellular proteolytic activity in feces.
Abstract: Protease activities in human ileal effluent and feces were compared by using a variety of native and diazotized protein substrates. In many cases the diazotized proteins had altered susceptibilities to hydrolysis compared with the native proteins. Proteolytic activity was significantly greater than (P less than 0.001) in small intestinal effluent than in feces (319 +/- 45 and 11 +/- 6 mg of azocasein hydrolyzed per h per g, respectively). Moreover, fecal proteolysis was qualitatively different in that ileal effluent did not hydrolyze the highly globular protein bovine serum albumin, whereas all fecal samples tested degraded this substrate. Inhibition experiments provided further evidence that fecal protease activity differed from that in the small intestine. Physical disruption of fecal bacteria released large quantities of proteases, indicating that the lysis of bacteria in the colon may contribute to the extracellular proteolytic activity in feces. Protease inhibition studies with washed fecal bacteria showed that they produced serine, cystine, and metalloproteases, and experiments with synthetic p-nitroanilide substrates indicated that low levels of trypsin- and chymotrypsin-like activities were associated with whole cells. An elastase-like enzyme was bound to the outer membranes of some fecal bacteria.
TL;DR: Indirect ELISA and RIA revealed that MCYST-LR-ethylenediamine-bovine serum albumin was a better immunogen and antibodies against a microcystin (MCYST) leucine-arginine variant were demonstrated 4 weeks after immunization of rabbits.
Abstract: Antibodies against a microcystin (MCYST) leucine-arginine variant (MCYST-LR) were demonstrated 4 weeks after immunization of rabbits with either MCYST-LR-polylysine- or MCYST-LR-ethylenediamine-modified bovine serum albumin. A radioimmunoassay (RIA), a direct competitive enzyme-linked immunosorbent assay (ELISA), and an indirect competitive ELISA were developed for characterization of the antibodies. Indirect ELISA and RIA revealed that MCYST-LR-ethylenediamine-bovine serum albumin was a better immunogen. Competitive RIA and direct ELISA revealed that the antibodies had good cross-reactivities with an MCYST-arginine-arginine variant (MCYST-RR), MCYST-LR, an MCYST-tyrosine-arginine variant (MCYST-YR), and nodularin (NODLN); but they had lower reactivities with variants MCYST-leucine-tyrosine (MCYST-LY) and MCYST-leucine-alanine (MCYST-LA). The antibodies did not cross-react with ozonolyzed MCYST-LR. The concentrations causing 50% inhibition of binding of reduced MCYST-LR to the antibodies by MCYST-RR, MCYST-LR, MCYST-YR, NODLN, MCYST-LA, and MCYST-LY in the RIA were 43, 105, 112, 503, 671, and 1,920 ng/ml, respectively. The concentrations causing 50% inhibition of binding of MCYST-LR-horseradish peroxidase to the antibodies by MCYST-RR, MCYST-LR, MCYST-YR, NODLN, MCYST-LY, and MCYST-LA in the ELISA were 1.75, 2.2, 3.4, 4.6, 50, and 114 ng/ml, respectively.
TL;DR: The finding that the conjugate containing α-sialic acid alone was capable of being recognized by reovirus at a level comparable to that of the other sialoside conjugates was of particular significance.
TL;DR: The effects of these fatty acids on the secretion of very low density lipoprotein (VLDL) apolipoprotein B (apo B) were estimated from the incorporation of 3H-leucine into the medium apo B in comparison to cells incubated with fatty acid-poor albumin.
Abstract: Oleic acid (18:1n-9, OA), docosahexaenoic acid (22:6n-3, DHA), or eicosapentaenoic acid (20:5n-3, EPA) was added to HepG2 cells at a concentration of 1 mM in a 5:1 or 2:1 molar complex with bovine serum albumin (BSA), and this was incubated for 3 hours. The incorporation of 3H-glycerol into cellular and medium triglyceride (TG), and the mass of TG were measured. The effects of these fatty acids on the secretion of very low density lipoprotein (VLDL) apolipoprotein B (apo B) were estimated from the incorporation of 3H-leucine into the medium apo B in comparison to cells incubated with fatty acid-poor albumin. The secretion of human albumin by the cells was also estimated by immunochemical precipitation of the labeled albumin. In addition, the intracellular levels of apo B messenger ribonucleic acid (mRNA) were measured by the dot-blot hybridization technique. Relative to control cells incubated with BSA, OA (complexed to BSA at a 5:1 molar ratio) stimulated TG synthesis and secretion sevenfold. Compared to OA, EPA was 24% less effective for both processes, whereas DHA inhibited only the secretion of TG (-43%). The secretion of VLDL apo B was not affected by OA, but was decreased 31% by EPA and 54% by DHA. When the molar ratio of fatty acid complexed to albumin was changed to 2:1, similar results were obtained with respect to TG production. The levels of apo B mRNA relative to actin mRNA were not significantly altered by any of the fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: In this article, transverse water proton relaxation in solutions of native bovine serum albumin can be quantitatively interpreted in terms of fast chemical exchange between water and protein protons.
Abstract: The major features of N.M.R. transverse water proton relaxation in solutions of native bovine serum albumin can be quantitatively interpreted in terms of fast chemical exchange between water and protein protons. Transverse proton relaxation dispersions are observed as a function of CPMG pulse spacing and spectrometer frequency and are shown to be consistent with the fast exchange of water with NH and OH protons of the amino acid side chains in the protein. The mean first order exchange rate is about 5 × 103 s-1. Although there is evidence that proteins influence the state of the water around them (the so called ‘bound’ water concept) the results obtained suggest that this influences the proton relaxation in a minor way compared to the potent effect of the chemical exchange mechanism.
TL;DR: The effect of boswellic acids on bovine serum albumin (BSA)-induced arthritis in rabbits was studied and the leucocyte-inhibitory activity of bos wellic acids was not due to its cytotoxic effect.
Patent•
04 Aug 1989TL;DR: In this paper, a method for the preparation of human serum albumin and other heterologous (non-yeast) proteins by growing a yeast, especially of the genus Kluyveromyces, modified by the use of recombinant DNA techniques is described.
Abstract: of EP0361991Microbiological method for the preparation of human serum albumin and other heterologous (non-yeast) proteins by growing a yeast, especially of the genus Kluyveromyces, modified by the use of recombinant DNA techniques.
TL;DR: A series of highly sensitive and specific radioimmunoassays for peptides that are liberated with the activation of hemostatic system zymogens in vivo, which measure the cleavage of prothrombin by factor Xa” and the scission of protein C by the thrombin-thrombomodulin complex, respectively.
TL;DR: It is proposed that factor VII is autoactivated in vitro in the presence of a positively charged surface and is caused by contaminating bovine proteases.
Abstract: Single-chain human recombinant factor VII produced by transfected baby hamster kidney cells was purified to homogeneity in the presence of benzamidine. The amidolytic activity of single-chain recombinant factor VII with a peptidylnitroanilide substrate, methoxycarbonyl-D-cyclohexanylglycyl-L-arginine-p-nitroanilide, was less than 1% of that obtained with factor VIIa. Purified single-chain recombinant factor VII spontaneously activated in the absence of inhibitor. The activation reaction was enhanced by at least 2 orders of magnitude in the presence of a positively charged surface, provided either as an anion-exchange matrix or as poly(D-lysine). The progress curve for factor VIIa generation was sigmoidal. Benzamidine inhibits recombinant factor VIIa activity and factor VII activation with identical inhibition constants (Ki) of 11 mM. In contrast, benzamidine inhibition of bovine factor Xa and bovine factor IIa was observed at Ki values equal to 0.3 and 0.5 mM, respectively. Bovine factors Xa and IIa are known activators of factor VII and the most likely contaminants of our recombinant factor VII preparations. Single-chain recombinant factor VII purified from cells cultured in the absence of bovine serum activated at the same rate as factor VII from cells cultured in the presence of bovine serum. This also excluded the possibility that the activation reaction was caused by contaminating bovine proteases. On the basis of these observations, we propose that factor VII is autoactivated in vitro in the presence of a positively charged surface.
TL;DR: Ganglioside-protein conjugate binding reveals gangliosides-specific brain membrane receptors and inhibition of 125I-(GT1b)4BSA binding was competitive and reversible while that by phosphatidylinositol and phosphatodylglycerol was not.
TL;DR: In this paper, a series of ion exchange equilibrium experiments were completed and analyzed by a mass action model and the Z values estimated (and confirmed with an independent slope method) range from 0.8 to 3.6 indicating that most of the ionized sites on the prot Scatchard pots of the equilibrium data indicate that there is competition between at least two different binding forms of each protein studied.
TL;DR: The results indicate that the efficiency of adhesion to RGD- BSA-coated surfaces is highly dependent on the valency of the (RGD)n-BSA conjugates, and Interestingly, competition and blocking experiments with antibodies and with soluble competing proteins suggest that it is the vitronectin receptor rather than the fibronect in receptor which mediates adhesion.
01 Jan 1989
TL;DR: Surfaces which specifically enhance fibronectin (FN) adsorption from serum containing media were prepared and investigated and had a greater fraction of surface C-O functionalities than did low plating efficiency, low FN adsorptive substrates.
Abstract: Surfaces which specifically enhance fibronectin (FN) adsorption from serum containing media were prepared and investigated. Since FN adsorbed to a substrate from serum facilitates the spreading and subsequent replication of anchorage-dependent cells in culture, these new surfaces were of interest. The surfaces studied were prepared by treating either poly(ethyleneterephthalate) (PET) or polystyrene (PS) with a radiofrequency plasma discharge of ethylene oxide (C2H4O) or perfluoropropane (C3F8) vapor, a mixture of the two, or one of the following vapors: acetone, air, methanol, or water. The surfaces were analyzed by electron spectroscopy for chemical analysis (ESCA). Identification and quantitation of surface functional groups was done by high resolution ESCA. FN adsorption from a series of serum dilutions to modified plastic surfaces was measured using Iodine (125I)-labeled FN. Swiss mouse 3T3 fibroblasts and MM14 mouse skeletal myoblasts were each plated onto these surfaces, as well as on two different types of commercially available culture dishes. Plating efficiency was measured on each surface. 3T3 cell spreading after 2 h, spreading kinetics, and attachment kinetics were also studied on some surfaces. All PET and PS plasma-treated surfaces except those treated with C3F8 adsorbed more FN than did three commercially available culture surfaces. FN adsorption was maximal at intermediate serum concentration on all surfaces. The greatest enhancement in FN adsorption occurred on the acetone plasma-treated surface. Bovine serum albumin adsorption from serum to the acetone plasma-treated surface was less than that to the untreated surface. The plating efficiencies of both 3T3 and MM14 cell types correlated well with FN adsorption to the plasma-treated surfaces, but the cell behavior on the commercial tissue culture dishes did not always follow this trend. In general, surfaces exhibiting both high plating efficiencies and high FN adsorption had a greater fraction of surface C-O functionalities than did low plating efficiency, low FN adsorption substrates. The possible role of FN as well as other serum spreading factors in mediating enhanced cell growth is discussed.
TL;DR: The adsorption of bovine serum albumin from flowing solutions onto germanium and three polyetherurethanes varying in soft segment content was studied by a Fourier transform infrared/attenuated total reflectance technique and no distinction could be made between BSA adsorbed to the different PEUs.
Abstract: The adsorption of bovine serum albumin from flowing solutions onto germanium and three polyetherurethanes varying in soft segment content was studied by a Fourier transform infrared/attenuated total reflectance technique. Spectral differences observed in the amide I, II, and III regions upon adsorption to all four surfaces were consistent with a loss of helix and gain of beta-structure. There appeared to be a slight difference between BSA adsorbed to germanium and the PEUs, but no distinction could be made between BSA adsorbed to the different PEUs.
TL;DR: In contrast to BSA, the binding and transcellular transport of cBSA and gBSA appear to proceed by an adsorptive-phase endocytic mechanism.
Abstract: We have measured the permeability and binding characteristics of bovine serum albumin (BSA), cationized BSA (cBSA), and glycosylated BSA (gBSA) to primary cultures of bovine brain capillary endothelial cells (BBCEC). These endothelial cells serve as an in vitro model to study the binding, uptake, and transcellular transport of small and large molecule flux across the blood-brain barrier. The rate of [3H]BSA flux across the cultured BBCEC monolayers grown onto polycarbonate membranes (5-microns pore size) was linear with increasing BSA concentration and the flux could be inhibited by temperature reduction to 0-4 degrees C. The maximal binding of [3H]BSA was 0.04 fmol/mg total cell protein and could not be inhibited by nonradiolabeled BSA. The binding of cBSA and gBSA was rapid and could be inhibited by nonradiolabeled cBSA or gBSA, respectively. The maximal amount bound was 1.8 fmol/mg total cell protein for cBSA and 17.4 fmol/mg total cell protein for gBSA. The dissociation constants (Kd's) were 27 +/- 13 and 3.7 +/- 1.1 nM for cBSA and gBSA, respectively. The flux rates of cBSA and gBSA across the endothelial cell monolayers were linear with respect to concentration and they were approximately seven times greater than those observed for BSA. Each of the proteins appeared on the antiluminal side of the endothelial cell monolayers primarily (90%) as intact protein as determined by trichloroacetic acid (TCA) precipitations and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). The results for BSA are similar to those observed for lucifer yellow, a fluid-phase endocytic marker.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: Steady-state fluorescence polarization studies show that PA-DPH detects the phase transition of both neutral and anionic bilayers, and should be useful both as an anionic fluorescent membrane probe and a long-chain free fatty acid analogue.
TL;DR: This chapter discusses the purification and reconstitution of glucose transporter from human erythrocytes, and the identification has been achieved either through immunoblotting with polyclonal or monoclonal antibodies raised against the purified ERYthrocyte transporter or through photoaffinity labeling with the 3 H-labeled ligand cytochalasin B.
Abstract: Publisher Summary This chapter discusses the purification and reconstitution of glucose transporter from human erythrocytes. Purification and reconstitution of the erythrocyte transporter are achieved by the following steps: preparation of erythrocyte membranes by the osmotic lysis of erythrocytes; removal of the peripheral (cytoskeletal) proteins from the membranes by treatment with dilute base; partial solubilization of the protein-depleted membranes with the detergent octylglucoside; separation of the transporter and some membrane lipids from this detergent extract by chromatography on Diethylaminoethyl (DEAE)-cellulose; and reconstitution of the transporter into a membrane of these lipids through the removal of the detergent by dialysis. Protein is assayed by a modification of the Lowry procedure used for membrane proteins, with bovine serum albumin as the standard. The lack of success with these lipids in the octylglucoside dialysis method led to the testing of erythrocyte lipids, which allow the assay of the transport function. The identification has been achieved either through immunoblotting with polyclonal or monoclonal antibodies raised against the purified erythrocyte transporter or through photoaffinity labeling with the 3 H-labeled ligand cytochalasin B.
TL;DR: A new ELISA protocol was established which made it possible to test for low levels of IFN-gamma in human serum and plasma samples and was easy to apply with basic laboratory equipment.
TL;DR: Antibodies directed against advanced glycation products formed during Maillard reaction have been generated and characterized and may serve as a useful tool to elucidate pathophysiological roles of advanced Maillard Reaction in diabetic complications and aging processes.
TL;DR: It is suggested that isoproterenol can reduce the thrombin-induced increase in endothelial permeability in vitro by directly maintaining actin filaments and the shape of endothelial cells.
Abstract: The ability of the beta-adrenergic agonist, isoproterenol, to attenuate the thrombin-induced increase in endothelial permeability was examined by measuring 125I-labeled albumin clearance across endothelial cell monolayers Bovine pulmonary artery endothelial cells (CCL-209) were grown to confluence on gelatinized, polycarbonate micropore filters and mounted on modified Boyden chambers with Dulbecco's modified Eagle's medium (DMEM) and 05% bovine serum albumin alpha-Thrombin at 02 nM to 2 microM produced a dose-related increase (P less than 001) in 125I-labeled albumin clearance from the DMEM control value Light and electron microscopy revealed that the thrombin-induced increase in permeability correlated with changes in cell shape and rearrangement of filamentous actin Coincubation of 2 microM isoproterenol with 2 microM alpha-thrombin reduced (P less than 001) the thrombin-induced increase in albumin clearance and the observed morphological changes This attenuation was not caused by inhibition of thrombin's enzymatically active site, since isoproterenol did not impair thrombin's fibrinogen clotting activity nor its amidolytic cleavage of an artificial substrate (Spectrozyme-TH) Coincubation of 20 microM propranolol, a beta-adrenergic antagonist, with 2 microM isoproterenol and thrombin blocked the permeability-decreasing effect of isoproterenol Both 2 microM isoproterenol and 2 pM alpha-thrombin alone decreased (P less than 001) albumin clearance below the DMEM control value These results suggest that isoproterenol can reduce the thrombin-induced increase in endothelial permeability in vitro by directly maintaining actin filaments and the shape of endothelial cells