Showing papers on "Serum albumin published in 1992"
TL;DR: The three-dimensional structure of human serum albumin has been determined crystallographically to a resolution of 2.8 Å and should provide insight into future pharmacokinetic and genetically engineered therapeutic applications of serumalbumin.
Abstract: The three-dimensional structure of human serum albumin has been determined crystallographically to a resolution of 2.8 A. It comprises three homologous domains that assemble to form a heart-shaped molecule. Each domain is a product of two subdomains that possess common structural motifs. The principal regions of ligand binding to human serum albumin are located in hydrophobic cavities in subdomains IIA and IIIA, which exhibit similar chemistry. The structure explains numerous physical phenomena and should provide insight into future pharmacokinetic and genetically engineered therapeutic applications of serum albumin.
3,482 citations
TL;DR: It is found that naturally produced nitric oxide circulates in plasma primarily complexed in S-nitrosothiol species, principal among which is S-Nitroso-serum albumin, which likely serves as a reservoir with which plasma levels of highly reactive, short-lived free nitrics can be regulated for the maintenance of vascular tone.
Abstract: We have recently shown that nitric oxide or authentic endothelium-derived relaxing factor generated in a biologic system reacts in the presence of specific protein thiols to form S-nitrosoprotein derivatives that have endothelium-derived relaxing factor-like properties. The single free cysteine of serum albumin, Cys-34, is particularly reactive toward nitrogen oxides (most likely nitrosonium ion) under physiologic conditions, primarily because of its anomalously low pK; given its abundance in plasma, where it accounts for approximately 0.5 mM thiol, we hypothesized that this plasma protein serves as a reservoir for nitric oxide produced by the endothelial cell. To test this hypothesis, we developed a methodology, which involves UV photolytic cleavage of the S--NO bond before reaction with ozone for chemiluminescence detection, with which to measure free nitric oxide, S-nitrosothiols, and S-nitrosoproteins in biologic systems. We found that human plasma contains approximately 7 microM S-nitrosothiols, of which 96% are S-nitrosoproteins, 82% of which is accounted for by S-nitroso-serum albumin. By contrast, plasma levels of free nitric oxide are only in the 3-nM range. In rabbits, plasma S-nitrosothiols are present at approximately 1 microM; 60 min after administration of NG-monomethyl-L-arginine at 50 mg/ml, a selective and potent inhibitor of nitric oxide synthetases, S-nitrosothiols decreased by approximately 40% (greater than 95% of which were accounted for by S-nitrosoproteins, and approximately 80% of which was S-nitroso-serum albumin); this decrease was accompanied by a concomitant increase in mean arterial blood pressure of 22%. These data suggest that naturally produced nitric oxide circulates in plasma primarily complexed in S-nitrosothiol species, principal among which is S-nitroso-serum albumin. This abundant, relatively long-lived adduct likely serves as a reservoir with which plasma levels of highly reactive, short-lived free nitric oxide can be regulated for the maintenance of vascular tone.
1,175 citations
TL;DR: The objective of this study was to determine the probabilities of specific morbid events or death among patients with end-stage renal disease treated by hemodialysis, and older age and history of cardiovascular disease were independently associated with a greater probability of death.
529 citations
TL;DR: It is suggested that IL-6 can induce an increase in endothelial permeability in vitro by rearranging actin filaments and by changing the shape of endothelial cells.
Abstract: The effect of interleukin 6 (IL-6) on endothelial permeability was examined by measuring fluorescein isothiocyanate-labeled albumin flux across an endothelial cell monolayer. Bovine vascular endothelial cells (BVEC) were cultured up to confluency on collagen-coated polycarbonate micropore filters and then the filters were mounted on modified Boyden chambers. Treatment of the BVEC with IL-6 at 100 ng/ml for 21 h caused a remarkable increase in the permeability of fluorescein isothiocyanate-labeled albumin across the endothelial monolayer. This effect of IL-6 was concentration dependent, in the range from 10-200 ng/ml of IL-6. The effect of IL-6 was also time dependent, the maximal level being reached at 21 h from the beginning of the treatment. This stimulatory effect of IL-6 on albumin clearance was completely abolished by the addition of anti-IL-6 antibody. Light microscopic observation of a cross-section of a monolayer showed that the IL-6-induced increase in the permeability was correlated with changes in cell shape and rearrangement of intracellular actin fibers. IL-6 did not show any cytotoxicity toward or growth inhibition of endothelial cells, even at more than 200 ng/ml. The enhancing effect of IL-6 on the increase in the permeability was reversible; when IL-6 was removed by a medium change and the cells were incubated for a further 24 h without IL-6, the permeability was restored to the control level. These results suggest that IL-6 can induce an increase in endothelial permeability in vitro by rearranging actin filaments and by changing the shape of endothelial cells.
381 citations
TL;DR: Patients with insulin-dependent diabetes mellitus have immunity to cow's-milk albumin, with antibodies to an albumin peptide that are capable of reacting with a beta-cell--specific surface protein, and such antibodies could participate in the development of islet dysfunction.
Abstract: Background Cow's milk has been implicated as a possible trigger of the autoimmune response that destroys pancreatic beta cells in genetically susceptible hosts, thus causing diabetes mellitus. Studies in animals have suggested that bovine serum albumin (BSA) is the milk protein responsible, and an albumin peptide containing 17 amino acids (ABBOS) may be the reactive epitope. Antibodies to this peptide react with p69, a beta-cell surface protein that may represent the target antigen for milk-induced beta-cell--specific immunity. Methods We used immunoassays and Western blot analysis to analyze anti-BSA antibodies in the serum of 142 children with insulin-dependent diabetes mellitus, 79 healthy children, and 300 adult blood donors. Anti-ABBOS antibodies were measured in 44 diabetic patients at the time of diagnosis, three to four months later, and one to two years later. Results All the diabetic patients had elevated serum concentrations of IgG anti-BSA antibodies (but not of antibodies to other milk proteins), the bulk of which were specific for ABBOS: The mean (+/- SE) concentration was 8.5 +/- 0.2 kilofluorescence units (kfU) per microliter, as compared with 1.3 +/- 0.1 kfU per microliter in the healthy children. IgA antibodies were elevated as well, but not IgM antibodies. The antibody concentrations declined after diagnosis, reaching normal levels in most patients within one to two years. The initial decline involved anti-ABBOS--specific antibodies almost exclusively. Much lower serum concentrations of anti-BSA antibodies were found in all 379 control subjects, but only 2.5 percent of them had small amounts of ABBOS-specific IgG. Conclusions Patients with insulin-dependent diabetes mellitus have immunity to cow's-milk albumin, with antibodies to an albumin peptide that are capable of reacting with a beta-cell--specific surface protein. Such antibodies could participate in the development of islet dysfunction.
373 citations
TL;DR: It is proposed that lysophosphatidates may play an important role in linking platelet activation to receptor-mediated tissue regeneration and making the active factor nondialyzable against aqueous solvents and protecting against digestion by various lipases.
370 citations
Journal Article•
TL;DR: If pH, PCO2, and the concentrations of serum albumin and phosphate are measured, all independent variables, which physically determine "acid-base balance" in plasma, can be quantified and new ways to evaluate "unidentified anions" in metabolic acidosis can be explored.
353 citations
TL;DR: In patients with active MS, only those with detectable TNF-alpha showed signs of blood-brain barrier damage, and intrathecal levels of T NF-alpha in active MS correlated with albumin ratios and with the degree of barrier damage.
208 citations
TL;DR: The results indicate that administration of oral vitamin C may inhibit the glycosylation of proteins in vivo by a competitive mechanism.
Abstract: Twelve nondiabetic subjects consumed 1 g/day vitamin C for 3 mo. A fasting blood sample was taken at the start of the study and at the end of each month for the measurement of plasma and intraerythrocyte glucose, vitamin C, glycosylated hemoglobin (affinity chromatography and electrophoresis), and glycosylated albumin (affinity chromatography). Although there were no significant changes in fasting glycemia, glycosylated hemoglobin (affinity chromatography) decreased 18%, from 6.18 +/- 0.48% (mean +/- SD) at the start to 5.05 +/- 0.50% (P less than 0.0001) after 3 mo, whereas, HbA1 measured by electrophoresis increased 16%, from 6.17 +/- 0.61 to 7.16 +/- 0.59% (P less than 0.0001) in this period. Glycosylated albumin decreased 33%, from 1.56 +/- 0.24 to 1.04 +/- 1.01% (P less than 0.0001) after 3 mo. This discrepancy between glycosylated hemoglobin measured by electrophoresis and affinity chromatography was due to methodological differences between the two techniques, with affinity chromatography measuring "true" glycosylated hemoglobin. The greater decrease found with glycosylated albumin was probably due to the different distribution of vitamin C between plasma and within the erythrocyte, levels after 1 mo of supplementation being 109 +/- 19 and 59 +/- 9 microM, respectively (P less than 0.001). This indicates that administration of oral vitamin C may inhibit the glycosylation of proteins in vivo by a competitive mechanism.
204 citations
TL;DR: The albumin-early mortality association suggests that serum albumin levels are a predictor for subclinical disease in the healthy elderly, independent of health status.
198 citations
TL;DR: In this article, a genetically engineered HSA-CD4 hybrid was designed to specifically block the entry of the human immunodeficiency virus into CD4+ cells, which is correctly processed and efficiently secreted by Kluyveromyces yeasts.
Abstract: Due to its remarkably long half-life, together with its wide in vivo distribution and its lack of enzymatic or immunological functions, human serum albumin (HSA) represents an optimal carrier for therapeutic peptides/proteins aimed at interacting with cellular or molecular components of the vascular and interstitial compartments. As an example, we designed a genetically engineered HSA-CD4 hybrid aimed at specifically blocking the entry of the human immunodeficiency virus into CD4+ cells. In contrast with CD4, HSA-CD4 is correctly processed and efficiently secreted by Kluyveromyces yeasts. In addition, its CD4 moiety exhibits binding and antiviral in vitro properties similar to those of soluble CD4. Finally, the elimination half-life of HSA-CD4 in a rabbit experimental model is comparable to that of control HSA and 140-fold higher than that of soluble CD4. These results indicate that the genetic fusion of bioactive peptides to HSA is a plausible approach toward the design and recovery of secreted therapeutic HSA derivatives with appropriate pharmacokinetic properties.
TL;DR: Hypoalbuminemia and lower serum albumin were independently associated with anemia, recent diagnosis of cancer, two or more limitations in activities of daily living, residence in a nursing home, heavy cigarette smoking, and older age.
TL;DR: Data presented here suggest that TNF alpha is related to blood-brain barrier damage in bacterial meningitis and that its effect could be dissociated from that of IL-1 beta.
Abstract: Brain damage after meningeal infection could result from impairment of cerebral endothelial cell functions and disruption of blood-brain barriers Tumor necrosis factor-alpha (TNF alpha) and interleukin-1 beta (IL-1 beta) produce many of their effects by acting on endothelial cells This study correlates levels of TNF alpha and IL-1 beta in paired cerebrospinal fluid (CSF) and serum samples with the degree of blood-brain barrier damage, as manifested by CSF to serum albumin quotient, in 48 patients with bacterial meningitis and 66 controls CSF levels of TNF alpha and IL-1 beta in bacterial meningitis were significantly higher than in controls Intrathecal levels of TNF alpha, but not IL-1 beta, correlated with albumin quotient (P less than 001), with degree of blood-brain barrier disruption (P less than 001), and with disease severity and indices of meningeal inflammation Sequential CSF samples demonstrated that IL-1 beta and TNF alpha disappear from the CSF within 24 h of antibiotic treatment Data presented here suggest that TNF alpha is related to blood-brain barrier damage in bacterial meningitis and that its effect could be dissociated from that of IL-1 beta
TL;DR: A method for the determination of the (6R)- and (6S)-stereoisomers of leucovorin using electrokinetic chromatography (EKC) in the affinity mode has been developed and represents a new means of obtaining thermodynamic data for substrate binding interactions and for the general study of drug cross-reactions and interactions of drugs with serum and other proteins.
Abstract: A method for the determination of the (6R)- and (6S)-stereoisomers of leucovorin using electrokinetic chromatography (EKC) in the affinity mode has been developed. Bovine serum albumin (BSA) is used as a run buffer additive to incorporate enantiomeric selectivity into the system. Protein-wall interactions are minimized by using a poly(ethylene glycol) (PEG) coated capillary. Chiral resolution is obtained in 12.5 min with efficiencies greater than 200,000 theoretical plates using BSA as an additive, while no resolution is obtained in the absence of BSA. A general equation is derived to calculate the free energy of interaction between the leucovorin isomers and the BSA molecule. This method represents a new means of obtaining thermodynamic data for substrate binding interactions and for the general study of drug cross-reactions and interactions of drugs with serum and other proteins.
TL;DR: The enantioselective binding to HSA exhibited by warfarin, suprofen and ketoprofen was found to be due to differential binding of the enantiomers at Site I; the primary binding site for suprofe and ketofen was not enantiOSElective.
TL;DR: Albumin was readily released from these structures during activation of neutrophils with inflammatory mediators, indicating that secretory vesicles are unique endocytic vesicle that can be triggered to exocytose by inflammatory stimuli.
Abstract: In search for matrix proteins released from secretory vesicles of human neutrophils, a prominent 67-kD protein was identified in the extracellular medium of neutrophils stimulated by the chemotactic peptide, FMLP. The protein was purified to apparent homogeneity and partially sequenced. The sequence of the first 32 NH2-terminal amino acids was identical to the sequence of albumin. mRNA for human albumin could not be detected in bone marrow cells, nor could biosynthetic labeling of albumin be demonstrated in bone marrow cells during incubation with [14C]leucine. Immunofluorescence studies on single cells demonstrated the presence of intracellular albumin in fixed permeabilized neutrophils. Light microscopy of immunogold-silver-stained cryosections visualized albumin in cytoplasmic "granules." The morphology of these was determined by immunoelectron microscopy as vesicles of varying form and size. Subcellular fractionation studies on unstimulated neutrophils demonstrated the presence of albumin in the low density pre-gamma and gamma-regions that contain secretory vesicles, but are devoid of specific granules and azurophil granules. Albumin was readily released from these structures during activation of neutrophils with inflammatory mediators. Immunoblotting demonstrated the presence of immunoglobulin and transferrin along with albumin in exocytosed material from stimulated neutrophils. This indicates that secretory vesicles are unique endocytic vesicles that can be triggered to exocytose by inflammatory stimuli.
TL;DR: In this article, the concentration dependence of surface tension was evaluated with DuNouy ring tensiometry for solutions of α-lactalbumin (α-Lac), β-Lactoglobulin (β-Lg), and bovine serum albumin (BSA).
TL;DR: Results suggest that 2‐acyl‐lysophosphatidylcholine bound to albumin could be an efficient delivery form of unsaturated fatty acids to the developing rat brain and that the fatty acid delivery form could modulate their fate in the tissue.
Abstract: The aim of the present study was to investigate whether unsaturated 2-acyl-lysophosphatidylcholine bound to plasma albumin is a relevant delivery form of unsaturated fatty acids to the developing brain. Twenty-day-old rats were perfused for 30 s with labeled palmitic, oleic, linoleic, and arachidonic acids in either their unesterified form or esterified in 2-acyl-lysophosphatidylcholine labeled on the choline and fatty acid moieties. Both forms were bound to albumin. Incorporation in brain lipid classes was followed within 1 h. The brain uptake of the unesterified fatty acids reached a plateau at 5-15 min and was maximal for arachidonic acid (0.45% of the perfused dose). The brain uptake of palmitoyl-lysophosphatidylcholine was similar to that of palmitic acid, whereas that of other lysophosphatidylcholines increased with the degree of unsaturation (rate and maximal uptake) and was six- to 10-fold higher than that of the corresponding unesterified fatty acid. 2-Acyl-lysophosphatidylcholines were taken up without prior hydrolysis and reacylated into doubly labeled phosphatidylcholine, which was the most labeled lipid class, whereas lipid distribution of the unesterified fatty acid was more diversified. Partial hydrolysis of 2-acyl-lysophosphatidylcholine occurred in the brain tissue, and redistribution of the fatty acyl moiety into other phospholipid classes was also observed and was the highest for arachidonic acid. In this case, the percentage of esterification of this fatty acid in phosphatidylinositol (expressed as a percentage of the total lipid fraction) was relatively lower than that observed when the unesterified form was used.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: Frontal analysis, using R-warfarin and L-tryptophan as probes for these sites, demonstrated that the immobilized HSA had binding behavior equivalent to that observed for HSA in solution, and thyroxine was binding directly to both types of site.
TL;DR: In this article, the diffusion coefficient of bovine serum albumin (BSA) was measured in aqueous solutions of varying temperature, pH, BSA concentration, and ionic strength.
Abstract: The diffusion coefficient of bovine serum albumin (BSA) was measured in aqueous solutions of varying temperature, pH, BSA concentration, and ionic strength. The measurements were carried out using dynamic light scattering with the photon detector set at a 90 o angle. The measured diffusion coefficients were compared to calculated values using phenomenological models which account for the screened Coulomb interaction between the charged proteins, as well as hydrodynamic corrections to the friction factor. The dimensions of BSA were obtained from structural data, and the charge on the protein was estimated using titration data
TL;DR: Overall molecular charge does not appear to be an important feature of the species‐specific blood‐CSF albumin transport mechanism in neonatal rats, and it is unlikely that in situ synthesis of albumin contributes to the naturally high levels of album in CSF in the developing brain.
Abstract: 1. The transfer of albumin between the blood and the cerebrospinal fluid (CSF) has been investigated in neonatal (3 days old) and juvenile (20 days old) rats. At both stages of postnatal development, all of the albumin present in the CSF can be accounted for by transfer from the blood. Thus it is unlikely that in situ synthesis of albumin contributes to the naturally high levels of albumin in CSF in the developing brain. 2. The high concentration of albumin in CSF of the neonatal rat brain cannot be accounted for solely by diffusion from the blood. In the 3-day-old rat, only about one quarter of the albumin in CSF enters by diffusion from the blood, whilst the remainder appears to be transported into the CSF by a specific mechanism which can discriminate between different species of albumin. The specific transport component of albumin transfer between the blood and the CSF appears to be developmentally regulated and is not apparent in 20-day-old rats. 3. Chemical modification of albumin resulting in either an increase or a decrease in electrophoretic mobility (at pH 7.4), significantly reduces blood-CSF transfer of albumin in 3-day-old rats, but has little effect in the 20-day-old rat. Thus overall molecular charge does not appear to be an important feature of the species-specific blood-CSF albumin transport mechanism in neonatal rats.
TL;DR: The steady-state distribution of endogenous albumin in mouse diaphragm was determined by quantitative postembedding protein A-gold immunocytochemistry using a specific anti-mouse albumin antibody, and a linear relationship between blood radioactivity and vascular labeling density was found.
Abstract: The steady-state distribution of endogenous albumin in mouse diaphragm was determined by quantitative postembedding protein A-gold immunocytochemistry using a specific anti-mouse albumin antibody. Labeling density was recorded over vascular lumen, endothelium, junctions, and subendothelial space. At equilibrium, the volume density of interstitial albumin was 18% of that in circulation. Despite this large difference in albumin concentration between capillary lumen and interstitium, plasmalemmal vesicles labeling was uniformly distributed across the endothelial profile. 68% of the junctions displayed labeling for albumin, which was however low and confined to the luminal and abluminal sides. The scarce labeling of the endothelial cell surface did not confirm the fiber matrix theory. The kinetics of albumin transcytosis was evaluated by injecting radioiodinated and DNP-tagged BSA. At 3, 10, 30, and 60 min, and 3, 5, and 24 h circulation time, blood radioactivity was measured and diaphragms were fixed and embedded. Anti-DNP antibodies were used to map the tracer in aforementioned compartments. A linear relationship between blood radioactivity and vascular labeling density was found, with a detection sensitivity approaching 1 gold particle per DNP-BSA molecule. Tracer presence over endothelial vesicles reached rapidly (10 min) a saturation value; initially localized near the luminal front, it evolved towards a uniform distribution across endothelium during the first hour. An hour was also needed to reach the saturation limit within the subendothelial space. Labeling of the junctions increased slowly, out of phase with the inferred transendothelial albumin fluxes. This suggests that they play little, if any, role in albumin transcytosis, which rather seems to proceed through the vesicular way.
TL;DR: Poly-β-hydroxybutyrate, an amphiphilic lipid that has been found to be a ubiquitous component of the cellular membranes of bacteria, plants and animals, is investigated using chemical and immunological methods and suggests it may have important physiological effects.
TL;DR: The results suggest that rapid growth of human prostatic carcinoma metastases in spinal bone may result from a combination of conditions that include drainage of prostatics carcinoma cells into the paravertebral circulation, high concentrations of available transferrin in bone marrow, and increased sensitivity of prostatic cancer cells to the mitogenic activity of transferrin.
Abstract: Aggressive prostatic carcinomas most frequently metastasize to the skeletal system. We have previously shown that cultured human prostatic carcinoma cells are highly responsive to growth factors found in human bone marrow. To identify the factor(s) responsible for the increased prostatic carcinoma cell proliferation, we fractionated crude bone marrow preparations by using hydroxylapatite HPLC. The major activity peak contained two high molecular weight bands (M(r) = 80,000 and 69,000) that cross-reacted with antibodies to human transferrin and serum albumin, respectively. Bone marrow transferrin, purified to apparent homogeneity by using DEAE-Affi-Gel Blue chromatography, anti-transferrin affinity chromatography, and hydroxylapatite HPLC, markedly stimulated prostatic carcinoma cell proliferation, whereas human serum albumin showed no significant growth factor activity. Marrow preparations, depleted of transferrin by passage over an anti-transferrin affinity column, lost greater than 90% of their proliferative activity. In contrast to the response observed with the prostatic carcinoma cell lines, a variety of human malignant cell lines, derived from other primary sites and metastatic to sites other than bone marrow, showed a reduced response to purified marrow-derived transferrin. These results suggest that rapid growth of human prostatic carcinoma metastases in spinal bone may result from a combination of conditions that include (i) drainage of prostatic carcinoma cells into the paravertebral circulation, (ii) high concentrations of available transferrin in bone marrow, and (iii) increased sensitivity of prostatic carcinoma cells to the mitogenic activity of transferrin.
TL;DR: Results indicate that beta-lactoglobulin could participate in the digestion of milk lipids during the neonatal period by enhancing the activity of pregastric lipase through removal of the fatty acids that inhibit this enzyme.
TL;DR: Photon correlation spectroscopy and laser doppler anenometry showed that the coating reduced the adsorption of the protein to the polystyrene microspheres surface, which confirmed that the hydrophilic polyoxyethylene steric layer, created by coating with the block copolymers, reduced the advertisers of human serum albumin.
TL;DR: Feedback regulation of albumin gene expression by serum colloids may serve as a specific homeostatic mechanism to maintain the steady-state level of total protein in the circulation.
Abstract: A novel feedback regulatory mechanism operating on transcription of the albumin gene is described in the rat. In 1946, it was proposed that circulating colloids, including serum albumin, may affect the synthesis and/or secretion of albumin in the liver. The molecular basis for this proposed regulation has now been investigated by adding oncotically active macromolecules to the circulation of normal or genetically albumin-deficient Nagase analbuminemic rats (NAR) and analyzing the hepatic expression of genes, including albumin after 24 h. The transcription rate of the albumin gene was higher in NAR than in normal rats and was dramatically reduced by raising serum albumin to 1.6 g/dl. Intravenous infusion of albumin into normal rats also decreased transcriptional activity of the albumin gene by 50-60%, and this decrease correlated with changes in serum colloid osmotic pressure after albumin infusion. Inhibition of albumin gene transcription was also observed upon intravenous infusion of other protein or nonprotein macromolecules, such as gamma-globulin and dextran. This down-regulation appears to control the steady-state level of albumin mRNA in the liver. Aside from a concomitant decrease in apo E gene transcription after albumin or macromolecule infusion, there was no change in the transcription rate of other genes, including those exhibiting liver-preferred or -specific expression (e.g., tyrosine amino-transferase, cytochrome P-450, alpha 1-antitrypsin, apolipoproteins A-I and B, and transferrin) or general cellular expression (e.g., alpha-tubulin, pro alpha 2 collagen, and beta-actin). Feedback regulation of albumin gene expression by serum colloids may serve as a specific homeostatic mechanism to maintain the steady-state level of total protein in the circulation.
Journal Article•
TL;DR: Angiotensinogen (ANG) was localized using an affinity-purified antibody and paraffin sections of seven human eyes and was present selectively in the cytoplasm of the nonpigmented ciliary epithelium (NPCE).
Abstract: The circulating renin-angiotensin system (RAS) is an important determinant in maintaining adequate systemic blood pressure, and it also may modify organ-specific blood flow. All recognized RAS components have been identified in the eye. In this study, angiotensinogen (ANG) was localized using an affinity-purified antibody and paraffin sections of seven human eyes. An antibody for human serum albumin was used for comparison. The ANG was present selectively in the cytoplasm of the nonpigmented ciliary epithelium (NPCE), more prominently in the pars plana than in the pars plicata. Both ANG and albumin were present in the blood vessel lumina of the uvea and retina. Both antibodies also stained perivascular tissue in the uvea, but not in the retina, reflecting the relative tightness of blood-tissue barriers. The detection of ANG in the NPCE may be significant in view of previous descriptions localizing prorenin and angiotensin-converting enzyme in the same cell layer.
TL;DR: It is concluded that the disulfide-reduced state with partially folded variable conformation is involved in the reversible interconversion between the denatured reduced form and the native disulfides-bonded form of human serum albumin.
TL;DR: Both the hydraulic and macromolecular permeability of an individual layer of GBM are much greater than that reported for the intact glomerulus, suggesting a major contribution of cellular elements to glomerular permeability properties.
Abstract: The glomerular basement membrane (GBM) is an integral structural component of the glomerular filter, but its contribution to the hydraulic and macromolecular permeability properties of the glomerulus has been the subject of much controversy. We have modified previously reported methods to develop a technique with which to study filtration properties of microgram quantities of isolated GBM in vitro at physiological pressures. Rat glomeruli were sieved, and cells were removed with N-laurylsarcosine and DNase. GBM (150 micrograms; greater than 95% pure) were added to a mini-ultrafiltration cell and consolidated under pressure to form a continuous filter at the base of the cell. Water flux was identical to inulin clearance at applied pressures less than 150 mmHg and increased with progressive increments in the transmembrane pressure. Hydraulic conductivity of GBM was inversely related to the prevailing transmembrane pressure gradient. The hydraulic conductivity depended on albumin concentration in a manner that was not monotonic, with the conductivity being lower at 4 g/dl albumin than at 0 or 8 g/dl. When plasma was utilized as the retentate, the fractional clearance of albumin was over twice that of immunoglobulin G, and the fractional clearance of each protein was much higher than that in the intact glomerulus. On the basis of these results, both the hydraulic and macromolecular permeability of an individual layer of GBM are much greater than that reported for the intact glomerulus. The large quantitative differences between GBM permeability and that of intact glomeruli suggest a major contribution of cellular elements to glomerular permeability properties.