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PubMed1994

Influence of circulating D-dimer levels on assays of fibrinogen.

The influence of circulating D-dimer levels on two different assays for fibrinogen was studied in 31 normal female subjects, 18 late pregnant subjects, 8 male subjects with acute myocardial infarction (AMI) and 9 subjects with unstable angina (UA). Both functional and chemical methods for fibrinogen showed significant correlation (r = 0.8171; P < 0.001). However, values for fibrinogen were significantly lower using the functional method in normal females, AMI and UA patients with mean (SD) ratios of 0.88 (0.11), 0.78 (0.17) and 0.84 (0.09) respectively as compared to the chemical assay method. In late pregnancy this was not observed with a mean ratio of 1.09 (0.22) obtained between the two methods. The D-dimer level in normal subjects was mean 194 (95.3) ng/ml whilst in late pregnancy, in AMI and UA, the levels were significantly elevated at 1093 (1034), 382 (216) and 1056 (708) ng/ml respectively. Significant correlation between fibrinogen and D-dimer levels was observed only in AMI and UA patients but not in late pregnancy. In 3 patients with AMI undergoing thrombolysis, no functional fibrinogen was detectable for the first 12 h following intravenous streptokinase (SK) despite the presence of chemically detectable fibrinogen with values of 13% to 30% of pre-treatment levels and evidenced by lytic states evaluated by thromboelastography (TEG). Grossly elevated D-dimer levels of between 25 x 10(3) and over 100 x 10(3) ng/ml were present during this time. Functional fibrinogen was detectable by 24 h following SK therapy but its level in relation to fibrinogen detected chemically remained depressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1976

[A rapid and precise determination of fibrinogen and its cleavage products (author transl)].

A method is described for the quantitative determination of fibrinogen equivalents in citrated blood before and after removal of the fibrinogen by coagulation. The method employs an immunological reaction, which is measured by mechanized nephelometry. Thus the sum of all the fibrinogen equivalents can be compared with the concentration of "cleavage products". The difference between the two readings represents the concentration of coagulable fibrinogen. For the fibrinogen concentration of 11.15 mg/l, variation coefficients of 2.81% in series and 3.31% for day to day were obtained. The accuracy of a new method was tested under conditions of fibrinogenolysis, and in the presence of heparin, by comparison with simple radial immunodiffusion, and with the "coagulation physiological rapid method for the determination of fibrinogen" after Clauss ((1957), Acta-Haematol, 17, 237-246). In addition 180 citrated blood samples of different patients were compared with the simple radial immunodiffusion, the method of Clauss and the new method. Only the new rapid method appears to measure plausible fibrinogen values, and permits a clear differentiation between coagulable and non-coagulable fibrinogen equivalents. It can be recommended for clinical practice.

Autoanalysis↗
PubMed1980

Fibrinogen Houston: a dysfibrinogen exhibiting defective fibrin monomer aggregation and alpha-chain cross-linkages.

A 38-year-old male patient with a life-long history of easy bruising and mild bleeding had a prolonged activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT). Reptilase (Bathrops atrox) clotting time was normal. His undiluted and diluted plasma prolonged the APTT, PT, and TT of normal plasma. Fibrin produced from patient plasma was insoluble in 5 M urea. Plasma fibrinogen level was increased when measured as clottable protein and by Laurell electroimmunoassay. Specific assays of plasma factors II, V, VII, X, VIII, IX, XI, and XII were normal. A circulating antithrombin in patient plasma was excluded by demonstrating normal thrombin-induced platelet aggregation of gel-separated platelets in the presence of patient plasma. Purified patient fibrinogen reproduced the anticoagulant effect of patient plasma. Patient fibrinogen antigen was similar to normal fibrinogen antigen by immunodiffusion, immunoelectrophoresis (pH 5.2 and 8.6), and crossed immunoelectrophoresis. His unreduced purified fibrinogen had normal migration on polyacrylamide slab gels. Also, the migration in gel slabs of A alpha, B beta and gamma-polypeptide chains, produced by mercaptoethanol reduction of purified patient fibrinogen, was similar to reduced normal fibrinogen. Thrombin-induced total fibrinopeptide release was normal. However, fibrin monomers produced from patient fibrinogen by thrombin (devoid of fibrinopeptides A and B) reaggregated abnormally; fibrin monomers produced by reptilase (devoid of only fibrinopeptides A) reaggregated normally. Fibrin generated from patient plasma in the presence of factor XIII and calcium, was defective in the formation of covalently bonded alpha-alpha polymers and demonstrated an increased susceptibility to the lytic effects of plasmin (generated in vitro by the addition of streptokinase).

Adult↗
PubMed1995

Fibrinogen in obesity before and after weight reduction.

Several studies have shown that obesity is associated with atherosclerosis. The reason may be that there is often a gathering together of risk factors for cardiovascular disease in obesity. Recently plasma fibrinogen level has been identified as an important cardiovascular risk factor. The aim of the study was to investigate fibrinogen levels in obesity before and after weight reduction. Obese but otherwise healthy patients with overweight problems were studied. 448 female patients (39.1 +/- 13.2 years, body mass index 38.7 kg/m2) and 136 male patients (39.4 +/- 12.8 years, body mass index 40.7 kg/m2) were examined after overnight fasting. Sixty patients (44 female, 16 male) were studied after 9.5 +/- 6.2 month of dieting (1200 kcal/day: 20% protein, 30% fat and 50% carbohydrates). The weight loss was 16.7 +/- 11.0 kg in the female and 16.2 +/- 6.7 kg in the male patients, and blood pressure, triglycerides, blood glucose and uric acid had declined. The fibrinogen level correlated with the body mass index, the waist circumference, the hip circumference and the waist to hip ratio. The fibrinogen level also correlated with insulin. A partial correlation of fibrinogen and insulin continued to exist after removing the linear effects of the other variables measured. After weight reduction, the level of fibrinogen was lower. In patients with extreme overweight and high fibrinogen levels, who reduced their BMI by 7.4 +/- 1.24 kg/m2, the weight loss correlated with the decrease in fibrinogen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Transient adsorption of fibrinogen on foreign surfaces: similar behavior in plasma and whole blood.

The adsorption of fibrinogen from both human whole blood and plasma to a number of "foreign" surfaces is reported. Adsorption was measured as a function of plasma or blood dilution using radioiodine labeling. We showed previously that adsorption of fibrinogen from plasma exhibits a maximum at a plasma dilution of about 100:1, and have attributed this behavior to competition from other plasma proteins. (The same phenomenon is manifest as a time transient in fibrinogen adsorption.) In the present work we show that exactly the same trends are observed in whole blood. For each of the four surfaces, glass, siliconized glass, collagen-coated glass and polyethylene, the adsorption of fibrinogen as a function of dilution is the same in whole blood as in plasma. Each of these surfaces shows a unique dependence of fibrinogen adsorption on plasma or blood dilution. On cuprophane and a hydrophilic polyether urethane there is essentially no adsorption of fibrinogen from blood or plasma. For the hydrophilic polyurethane this result may be artifactual, but the absence of fibrinogen binding to cuprophane in blood or plasma is real since fibrinogen is found to be adsorbed in monolayer amounts from buffer.

Adsorption↗
PubMed2007

A novel poly(ethylene glycol)-fibrinogen hydrogel for tibial segmental defect repair in a rat model.

The aim of this study is to investigate regeneration in a segmental bone defect using a novel fibrinogen-based hydrogel material. The use of hydrogels made from poly(ethylene glycol) (PEG) conjugated to fibrinogen for this purpose may be better to conventional fibrin-based materials as it offers an additional degree of control over the structural characteristics and biodegradation of the material. At the same time, it maintains some of the inherent biofunctionality of the fibrinogen molecule. PEGylated fibrinogen hydrogels with various degrees of proteolytic resistance based on PEG and fibrinogen composition were designed for slow, intermediate, and fast biodegradation. The hydrogels were implanted into 7-mm segmental rat tibial defects without additional osteoinductive factors with the rationale that the ingrowth matrix will displace the normal fibrin clot while sustaining a similar healing effect for a longer duration. Histological and X-ray results confirmed that the extent and distribution of newly formed bone in the defect after 5 weeks strongly parallels the biodegradation pattern of the implanted material. When compared to nonunions in animals treated with the fast-degrading implants and untreated control animals, the rats implanted with the intermediate-degrading material exhibited osteoneogenesis. This data supports the hypothesis that the perseverance of the PEGylated fibrinogen material can be synchronized with the optimal healing characteristics of a segmental osseous defect and that the consequent sustained release of fibrinogen fragments facilitates the osteogenic response at the injury site. The PEGylated fibrinogen material may, therefore, be a highly efficacious material for promoting the healing of bone defects and especially nonunion fractures.

Absorbable Implants↗
PubMed2006

The acute phase reactant, fibrinogen, as a guide to plasma exchange therapy for acute Guillain-Barré syndrome.

The Guillian Barré syndrome is an acute inflammatory disorder for which plasma exchange is effective treatment. Up to 10% relapse after plasma exchange suggesting that treatment sometimes finishes before disease activity has resolved. We studied whether plasma fibrinogen, an inflammatory marker, might be used to determine when to discontinue plasma exchange in patients with acute Guillain-Barré syndrome. We conducted a post-hoc analysis of apheresis database and hospital records of patients treated with plasma exchange for acute Guillain-Barré syndrome during 1999-2004. Data were analyzed from 28 patients who underwent a total of 29 courses of plasma exchange for acute Guillain-Barré syndrome. The mean (+/-SD) plasma fibrinogen concentration was 422.5 (+/-96.4) mg/dl at the time of presentation and, in 17 of the 29, it was above 400 mg/dl (reference range 200-400). Twenty of the 21 patients whose fibrinogen fell by more than 30% from baseline by the time of the final plasma exchange treatment had neurological improvement. There was improvement in only 3 of the 8 instances where fibrinogen decreased by less than 30% by the end of plasma exchange therapy. A > or =30% decrease in fibrinogen by the conclusion of plasma exchange was significantly associated with sustained neurological improvement (P = 0.0025). The plasma fibrinogen level appears to reflect disease activity in acute Guillain-Barré syndrome. A <30% fall in fibrinogen level despite plasma exchange may indicate the need to continue plasma exchange to maximize the benefit of treatment or minimize the risk of relapse. Therapeutic plasma exchange need not be extended when plasma fibrinogen remains > or =30% below its level at presentation by the time of the final planned plasma exchange procedure.

Acute Disease↗
PubMed1995

A fluorescence quench and dequench assay of fibrinogen polymerization, fibrinogenolysis, or fibrinolysis.

We present a kinetic assay based on the use of fluorescein isothiocyanate (FITC)-labeled fibrinogen as a fluoroactive substrate. The multiple FITCs bound to fibrinogen experienced quenching due to their close proximity. The thrombin-induced polymerization of FITC-fibrinogen led to additional fluorescence quenching due to enhanced neighbor-neighbor interactions in protofibrils and protofibril aggregates. The initial rate of quenching was directly dependent on the thrombin concentration at either low or high ionic strength. The final extent of quenching during polymerization with thrombin could be modulated by prevailing ionic strength and thrombin concentration suggesting that the quenching was due to fibril extension as well as aggregation. The full extent of quenching was greatly reduced by addition to the reaction of unlabeled fibrinogen or Gly-Pro-Arg-Pro, as expected for quenching due to neighbor-neighbor interactions. In contrast to polymerization, cleavage of fibrinogen by plasmin released FITC-labeled fragments free of proximity-based quenching that resulted in a large intensity increase as lysis proceeded--a process termed dequenching. The majority of the dequenching signal during fibrinogenolysis occurred during the generation of fragment X which proceeded as a first-order process with respect to fibrinogen-bound plasmin with kcat = 0.479 s-1. The Kd of active plasmin to fibrinogen was calculated to be 0.42 microM. Addition of epsilon-aminocaproic acid (epsilon ACA)-plasmin complex to FITC-fibrinogen produced little dequenching, demonstrating a requirement for binding in order to initiate lysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibrinogen↗
PubMed1999

The degradation of nascent fibrinogen chains is mediated by the ubiquitin proteasome pathway.

Recent studies have shown that ubiquitin-dependent proteolysis by proteasomes plays an essential role in the degradation of ER-retained proteins. We investigated the degradation of individual fibrinogen chains in transfected COS cells which express but do not secrete single chains. In transfected COS cells, the degradation of fibrinogen Bbeta and gamma chain was markedly inhibited by the proteasome inhibitors lactacystin and MG132. These specific proteasome inhibitors also partially affected the degradation of Aalpha chain. In HepG2 cells, which synthesize and secrete fibrinogen, the degradation of intracellular free gamma chain was also inhibited by MG132. We also detected high molecular weight polyubiquitinated forms of fibrinogen chains in transfected COS cells and in HepG2 cells by sequential immunoprecipitation. These results implicate proteasomes in the degradation of fibrinogen chains. In COS cells, gamma chains have a longer half-life than Bbeta chains and Aalpha chains, suggesting that the presence of surplus gamma chains in fibrinogen-producing cells is due to the unequal degradation rate of fibrinogen chains. These results indicate that the ubiquitin-proteasome pathway may be a major system for the degradation of unassembled fibrinogen chains.

Acetylcysteine↗
PubMed1999

Characteristics of fibrinogen binding to the domain of CD11c, an alpha subunit of p150,95.

beta2 integrins on leukocytes play important roles on cell-cell or cell-matrix adhesion through their ability to bind multiple ligands. The alpha subunits of leukocyte CD11/CD18 integrins contain an approximately 200-amino-acid inserted domain (I-domain) which is implicated in ligand binding function. To understand the characteristics of ligand binding to the alpha subunit of beta2 integrin p150,95 (CD11c/CD18), a recombinant form of the I-domain of CD11c was generated and analyzed for the interaction with fibrinogen, one of the ligands of p150,95. It was found that the CD11c I-domain bound fibrinogen specifically. Fibrinogen binding to the CD11c I-domain was inhibited by a molar excess of fragment E, a central domain of fibrinogen, and not by that of fragment D, a distal domain of fibrinogen, suggesting that CD11c/CD18 recognizes a central domain of fibrinogen. Divalent cations such as Mg(2+) and Mn(2+) were required for fibrinogen binding to the CD11c I-domain. Also alanine substitutions on the putative metal binding sites of the CD11c I-domain such as Asp(242) and Tyr(209) reduced its ability to bind fibrinogen. These data reinforce the fact that the divalent cation is a prerequisite for ligand binding of the CD11c I-domain.

Amino Acid Substitution↗
PubMed1997

Involvement of fibrinogen in protamine-induced pulmonary hypertension.

Protamine reversal of heparin anticoagulation occasionally results in pulmonary hypertension as well as systemic hypotension. To examine the contribution of blood components to this induction of pulmonary hypertension, we developed an isolated rat lung perfusion model and perfused heparinized plasma, heparinized serum, and Hepes (4% bovine serum albumin, 20 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, 5 mM glucose, in warm physiological saline) buffer solution with or without fibrinogen. Perfusion with heparinized plasma and Hepes buffer solution with fibrinogen caused pulmonary hypertension; perfusion with heparinized serum or Hepes buffer solution without fibrinogen did not, suggesting that fibrinogen is involved in the induction of pulmonary hypertension. We also labeled protamine with 125I and compared the amounts of protamine accumulating in the lung with different concentrations of fibrinogen. The amount of protamine trapped in the lung increased according to the concentration of fibrinogen. Fibrinogen may accelerate the reaction between pulmonary endothelial cells and protamine or protamine-heparin complexes. In the mechanism of protamine-induced pulmonary hypertension, fibrinogen, as well as heparin and protamine, may be an essential component.

Animals↗
PubMed1992

Drugs affecting plasma fibrinogen levels.

Current knowledge indicates that high plasma levels of fibrinogen help predict stroke and myocardial infarction. It is known that plasma fibrinogen is synthesized in the liver, that interleukin-6 (IL-6) affects this synthesis, and that, when exposed to appropriate stimuli, monocytes generate a variety of monokines, including IL-6. It is also known that prolonged administration of N-3 fatty acids, ticlopidine, fibrates, pentoxifylline, or alcohol lower plasma fibrinogen levels. The mechanism(s) involved in this effect are poorly understood. However, in view of the role of IL-6 and monocytes in the regulation of plasma fibrinogen levels, it is conceivable that the lowering effect of these drugs involves effects on some steps of the regulatory machinery. In addition to fibrinogen, IL-6 regulates the synthesis of other acute-phase proteins. This raises the question of whether high plasma fibrinogen levels do reflect the response of an acute-phase reactant to the severity of the atherosclerotic vascular damage taking place. Current evidence is inconclusive with respect to this possibility. On the other hand, the epidemiological data available indicate that measurements of plasma fibrinogen should be included in the cardiovascular risk-factor profile. In view of this, we believe that information emerging from population-based studies in which plasma fibrinogen is measured is important to identify appropriate directions to be followed to address unsolved issues in the area.

Fibrinogen↗
PubMed1988

Positive imaging of venous thrombi and thromboemboli with Ga-67 DFO-DAS-fibrinogen.

A newly developed thrombus imaging agent, 67Ga-DFO-DAS-fibrinogen (67Ga-fibrinogen), was used for 22 studies in 20 cases of suspected deep venous thrombosis. Increased accumulation of 67Ga-fibrinogen in venous thrombi was depicted at 48 h after injection in 10 of the 15 cases (10 of 17 studies) who showed abnormal findings in radionuclide venography. A hot spot in the lung emboli was visualized in two cases. Seven of the eight cases having anticoagulant therapy showed increased 67Ga-fibrinogen uptake, while follow-up 67Ga-fibrinogen scintigraphy after the administration of heparin and urokinase did not reveal an abnormal hot spot in one case. 67Ga-fibrinogen can be made available simply by adding 67Ga solution to a vial containing fibrinogen-DAS-DFO conjugate. In conclusion, 67Ga-fibrinogen is considered to be a promising agent for detecting active venous thrombi and to assess the effect of anticoagulant therapy.

Adult↗
PubMed1991

Characterization of the immunochemical reactivity of fibrinogen fragments by competitive radioimmunoassay: an improved method of analysis.

Published results on the immunochemical reactivities of fibrinogen and fibrinogen fragments with fibrinogen-elicited antibodies that had been fractionated on the basis of preferential interaction with A alpha [Nagy, J. A., Meinwald, Y. C., and Scheraga, H. A. (1982), Biochemistry 21, 1794-1806] and B beta [Nagy, J. A., Meinwald, Y. C., and Scheraga, H. A. (1985) Biochemistry 24, 882-887] peptides of this bivalent antigen have been reinterpreted. First, the multivalent counterpart of the Scatchard analysis has been used to determine the intrinsic association constant for the interaction of antibody with [125I]fibrinogen, the radiolabeled ligand used in subsequent competitive binding studies. Second, the corresponding affinity constant for native fibrinogen has been evaluated from the relevant competitive radioimmunoassays by means of a quantitative analysis that takes into account the bivalency of both the radiolabeled and native fibrinogen molecules. Finally, affinity constants for the interactions of various fibrinogen fragments with antibody are also obtained by the procedure, and their magnitudes rationalized in terms of the equilibrium coexistence of unreactive (disordered) and native (functional) states of the fibrinogen peptides.

Binding, Competitive↗
PubMed2003

[Fibrinogen and atherothrombosis: vulnerable plaque or vulnerable patient?].

Fibrinogen is far more important as a risk factor for acute cardiovascular syndromes than generally recognized. Evidence from a recent metaanalysis (including 22 studies of 63,736 subjects and 5,717 events [1] suggests that the risk for myocardial infarction and stroke almost doubles if the fibrinogen level exceeds 3.03 g/l (measured according to Clauss) with an odds ratio of 1.99 and a 95% confidence interval of 1.85-2.13. The predictive value of fibrinogen levels equally applies to men and women, young and old, primary and secondary prevention. Repeated fibrinogen measurements are particularly helpful with emphasis on high risk patients: concentrations of the upper tertile indicate a 92% higher risk of impending acute cardiovascular syndromes, as evidenced by a metaanalysis evaluating five prospective studies with 9,639 participants and 671 events [1]. Together with other risk factors such as hypertension, hypercholesterolemia, or diabetes, the risk of fatal and nonfatal acute cardiovascular syndromes may further increase by 6-12- fold, while fibrinogen remains an independent risk factor for both cardiac and extracardiac atherothrombotic complications, as well as for iatrogenic complications like restenosis following PTCA or stenting. Fibrin(ogen) and his effector thrombin substantially determine the extent and outcome of atherothrombotic complications, because they are the molecules linking the mutually dependent events of atherogenesis, coagulation/fibrinolysis, rheology/vasotonus, and inflammation. Interventional studies on fibrinolytic and defibrinating substances, as well as GpIIb/IIIa-inhibitors for treatment of acute cardiovascular syndromes have confirmed the benefit of fibrinogen reduction and extended the experimental evidence for the relevance of fibrin(ogen) in the pathogenesis of these syndromes. Accordingly, the preventive use of fibrates leading to moderate reductions in plasma cholesterol and fibrinogen diminished significantly the rate of reinfarction. The emerging possibilities from a more than 50% fibrinogen reduction (by studies using H.E.L.P. apheresis) strengthened the therapeutic concept to free the blood from all risk factors-as effective as it can be-in order to achieve an optimal plaque regression, since changes in the blood composition strongly affect the fragility and stability of the atherosclerotic plaques.

Acute Disease↗
PubMed2006

Diabetic nephropathy is associated with increased albumin and fibrinogen production in patients with type 2 diabetes.

AIMS/HYPOTHESIS: Hyperfibrinogenaemia and albuminuria are cardiovascular risk factors, often coexisting in diabetic and non-diabetic people. Albuminuria in turn is associated with a compensatory albumin overproduction in non-diabetic patients. It is not known whether the presence of albuminuria in patients with type 2 diabetes mellitus is associated with greater albumin and fibrinogen production rates than in normoalbuminuric patients. SUBJECTS, MATERIALS, AND METHODS: Using leucine isotope methods, we measured fractional and absolute synthesis rates (FSR, ASR) of albumin and fibrinogen in post-absorptive type 2 diabetic patients with either normal (n=11) or increased (n=10) urinary albumin excretion. RESULTS: In albuminuric patients, albumin FSR (16.2+/-1.5%/day) and ASR (20.5+/-1.9 g/day) were greater (p<0.02 and p<0.05, respectively) than in normoalbuminuric patients (FSR=11.5+/-1.1%/day; ASR=15.7+/-1.2 g/day). Fibrinogen FSR was similar between patients with normal and increased albumin excretion, but concentration, the circulating pool and ASR of fibrinogen were 40 to 50% greater (p<0.035) in patients with albuminuria. Albuminuria was positively correlated with albumin ASR, with fibrinogen concentration, the fibrinogen pool and ASR, whereas albumin synthesis was inversely correlated with calculated oncotic pressure. CONCLUSIONS/INTERPRETATION: Synthesis of albumin and fibrinogen is upregulated in type 2 diabetic patients with increased urinary albumin excretion. Albuminuria is associated with enhanced fibrinogen and albumin synthesis.

Albuminuria↗
PubMed2004

Secretion of recombinant human fibrinogen by the murine mammary gland.

Transgenic animals secreting individual chains and assembled fibrinogen were produced to evaluate the capacity of the mammary gland for maximizing assembly, glycosylation and secretion of recombinant human fibrinogen (rhfib). Transgenes were constructed from the 4.1 kbp murine Whey Acidic Protein promoter (mWAP) and the three cDNAs coding for the Aalpha, Bbeta and gamma fibrinogen chains. Transgenic mice secreted fully assembled fibrinogen into milk at concentrations between 10 and 200 microg/ml, with total secretion of subunits approaching 700 microg/ml in milk. Partially purified fibrinogen was shown to form a visible and stable clot after treatment with human thrombin and factor XIII. The level of assembled fibrinogen was proportional to the lowest amount of subunit produced where both the Bbeta and gamma chains were rate limiting. Both the Bbeta and gamma chains were glycosylated when co-expressed and the degree of saccharide maturation was dependent on expression level, with processing preferred for gamma chains over Bbeta chains. Also, the subunit complexes gamma2, Aalphagamma2 and the individual subunits Aalpha, Bbeta and gamma were found as secretion products. When the Bbeta was secreted individually, the glycosylation profile of the molecule was of a mature complex saccharide indicating recognition of the molecule by the glycosylation pathway without association with other fibrinogen chains. To date secretion of Bbeta chain has been not observed in any cell type, suggesting that the secretion pathway in mammary epithelia is less restrictive than that occurring in hepatocytes and other cells previously used to study fibrinogen assembly.

Animals↗
PubMed1985

Phosphorylation in vitro of fibrinogen from three mammalian species with four different protein kinases.

Human, dog, and rabbit fibrinogen served as substrates for calcium-activated, phospholipid-dependent protein kinase, cAMP-dependent protein kinase, casein kinase TS, and casein kinase S. The chains of phosphorylated fibrinogen were separated by polyacrylamide gel electrophoresis and the phosphorylation patterns, obtained on autoradiography of the gels, were found to be characteristic for each of the four protein kinases. Dog, and even more so rabbit, fibrinogen was phosphorylated more rapidly than human fibrinogen by calcium-activated, phospholipid-dependent protein kinase and by casein kinase TS. Dog fibrinogen was not a good substrate for cAMP-dependent protein kinase. The rate of phosphorylation with casein kinase S did not differ very much between the fibrinogens of the three species. In most cases the A alpha-chain was most rapidly phosphorylated. However, in dog fibrinogen incubated with casein kinase TS the B beta-chain was most rapidly phosphorylated. A substantial part of this phosphate seemed to be incorporated as phosphorylthreonine into fibrinopeptide B. In human fibrinogen incubated with the casein kinase TS preparation the gamma-chain as well as the A alpha-chain appeared to be phosphorylated.

Animals↗