Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Prothrombin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed2006

A control switch for prothrombinase: characterization of a hirudin-like pentapeptide from the COOH terminus of factor Va heavy chain that regulates the rate and pathway for prothrombin activation.

Membrane-bound factor Xa alone catalyzes prothrombin activation following initial cleavage at Arg(271) and prethrombin 2 formation (pre2 pathway). Factor Va directs prothrombin activation by factor Xa through the meizothrombin pathway, characterized by initial cleavage at Arg(320) (meizo pathway). We have shown previously that a pentapeptide encompassing amino acid sequence 695-699 from the COOH terminus of the heavy chain of factor Va (Asp-Tyr-Asp-Tyr-Gln, DYDYQ) inhibits prothrombin activation by prothrombinase in a competitive manner with respect to substrate. To understand the mechanism of inhibition of thrombin formation by DYDYQ, we have studied prothrombin activation by gel electrophoresis. Titration of plasma-derived prothrombin activation by prothrombinase, with increasing concentrations of peptide, resulted in complete inhibition of the meizo pathway. However, thrombin formation still occurred through the pre2 pathway. These data demonstrate that the peptide preferentially inhibits initial cleavage of prothrombin by prothrombinase at Arg(320). These findings were corroborated by studying the activation of recombinant mutant prothrombin molecules rMZ-II (R155A/R284A/R271A) and rP2-II (R155A/R284A/R320A) which can be only cleaved at Arg(320) and Arg(271), respectively. Cleavage of rMZ-II by prothrombinase was completely inhibited by low concentrations of DYDYQ, whereas high concentrations of pentapeptide were required to inhibit cleavage of rP2-II. The pentapeptide also interfered with prothrombin cleavage by membrane-bound factor Xa alone in the absence of factor Va increasing the rate for cleavage at Arg(271) of plasma-derived prothrombin or rP2-II. Our data demonstrate that pentapeptide DYDYQ has opposing effects on membrane-bound factor Xa for prothrombin cleavage, depending on the incorporation of factor Va in prothrombinase.

Blood Coagulation↗
PubMed1985

Staphylocoagulase-binding region in human prothrombin.

A staphylocoagulase-binding region in human prothrombin was studied by utilizing several fragments prepared from prothrombin by limited proteolysis. Bovine prothrombin, prethrombin 1, prethrombin 2, and human diisopropylphosphorylated alpha-thrombin strongly inhibited formation of the complex ("staphylothrombin") between human prothrombin and staphylocoagulase, but bovine prothrombin fragment 1 and fragment 2 had no effect on the complex formation, indicating that the binding region of human prothrombin for staphylocoagulase is located in the prethrombin 2 molecule. To identify further the staphylocoagulase-binding region, human alpha-thrombin was cleaved into the NH2-terminal large fragment (Mr = 26,000) and the COOH-terminal fragment (Mr = 16,000) by porcine pancreatic elastase. Of these fragments, the COOH-terminal fragment, which includes Asn-200 to the COOH-terminal end of the alpha-thrombin molecule, partially inhibited the complex formation between staphylocoagulase and human prothrombin. In contrast, the NH2-terminal large fragment did not show any inhibitory effect on the staphylothrombin formation. These results suggest that the staphylocoagulase interacts with human prothrombin through the COOH-terminal region of alpha-thrombin B chain. Other plasma proteins, factor X, factor IX, protein C, protein S, protein Z, all of which are structurally similar to prothrombin, did not inhibit the staphylothrombin formation at all, indicating that a specific interaction site with staphylocoagulase is contained only in the prothrombin molecule.

Animals↗
PubMed1991

Comparison of the affinities to bovine and human prothrombin of the staphylocoagulases from Staphylococcus intermedius and Staphylococcus aureus of animal origin.

Staphylocoagulases of Staphylococcus aureus (40 strains originally isolated from horses, dogs, cats, cows, sheep, opossums, pigs, humans, and a goat) and Staphylococcus intermedius (19 isolates from dogs and 1 pigeon strain) were tested for their affinity to prothrombins of either bovine or human origin. The tests used were the coagulase tube test (using human, bovine, or equine fibrinogen with either bovine or human prothrombin as the source of coagulase-reacting factor) and a chromogenic assay which enabled quantification of the amidolytic activity of the staphylocoagulase-prothrombin complex. S. intermedius showed weak specificity for human prothrombin, with 15% of the coagulases clotting human fibrinogen, 25% clotting equine fibrinogen, and 40% clotting bovine fibrinogen. However, 65% of coagulases clotted equine fibrinogen, 75% of coagulases clotted human fibrinogen, and 100% of coagulases clotted bovine fibrinogen when bovine prothrombin was used. The animal isolates of S. aureus displayed more diverse specificity toward prothrombin than S. intermedius strains. While 85% of coagulase preparations clotted human fibrinogen when human prothrombin was used, only 45% of preparations clotted bovine fibrinogen when bovine prothrombin was used. However, 62.5% of coagulases clotted human fibrinogen when bovine prothrombin was used and 85% of coagulases clotted bovine fibrinogen when human prothrombin was used. This may be a reflection of the diversity of the animal origins of S. aureus isolates.

Animals↗
PubMed2002

Antibodies to factor XII are distinct from antibodies to prothrombin in patients with the anti-phospholipid syndrome.

Patients with the anti-phospholipid syndrome (APS) have antiphospholipid antibodies (aPA) which are often targeted towards phospholipid binding proteins such as beta2-glycoprotein I and prothrombin. Antibodies to factor XII (FXIIabs) have also been identified in some patients with APS. Factor XII (FXII) is a member of the kringle family of proteins which include plasminogen and prothrombin. Antibodies to prothrombin have been associated with myocardial infarction and have been shown to cross react with plasminogen. Sixteen patients with APS and FXIIabs were investigated for the presence of antibodies to prothrombin, by enzyme linked immunosorbent assay in a calcium (Ca++) independent assay. All sixteen showed different antibody binding patterns than those observed for antibodies to FXII. Eight patients were further investigated using surface plasmon resonance (SPR) for antibody binding to covalently bound FXII and to covalently bound prothrombin in both Ca++ dependent and independent systems. Of three patients demonstrating antibody binding to FXII by SPR, none demonstrated antibody binding to prothrombin in a Ca++ independent system with one demonstrating antibody binding to prothrombin that was Ca++ dependent. Of five patients who did not bind FXII by SPR, one demonstrated antibody binding to prothrombin in a Ca++ independent system while two demonstrated antibody binding to prothrombin in a Ca++ dependent system. Antibodies to FXII in patients with APS appear to be distinct from antibodies to prothrombin.

Antibody Affinity↗
PubMed1991

[Abnormal prothrombin in acute hepatic failure: the characterization and clinical evaluation].

Abnormal prothrombin was detected by latex agglutination method in the plasma of the patients with acute hepatic failure (AHF) at significantly higher rate (82% of fulminant hepatitis and 100% of subacute hepatitis) than in acute hepatitis (33%). The concentration of abnormal prothrombin was also significantly higher in acute hepatic failure. Since the concentration of abnormal prothrombin reversely correlated with that of hepaplastin test or prothrombin time, the measurement of plasma abnormal prothrombin seemed to be useful in monitoring the severity of acute hepatic injury. Interestingly, enzyme immunoassay which is specific for des-gamma-carboxy prothrombin (PIVKA-II) could not detect abnormal prothrombin in acute hepatic failure. Furthermore, in crossed immune-electrophoresis, the abnormal prothrombin in AHF and that in disseminated intravascular coagulation syndrome showed similar mobility differing from PIVKA-II. These results suggest that abnormal prothrombin can be a useful marker for AHF. Further characterization of the abnormal prothrombin may shed light on the mechanisms of severe coagulopathy in AHF.

Acute Disease↗
PubMed1985

The kinetics of activation of normal and gamma-carboxyglutamic acid-deficient prothrombins.

The kinetics of activation of normal and gamma-carboxyglutamic acid (Gla)-deficient prothrombins isolated from cattle maintained for extended periods on the vitamin K antagonist dicoumarol were studied. The catalyst was prothrombinase, comprising isolated Factor Xa, Factor Va, phospholipid vesicles, and calcium ion. The Km and kcat values for prothrombins with 0, 1, 2, 5, 7, and 10 Gla residues were determined both by initial rate analysis and by integrated Michaelis-Menten-Henri analysis. Each of the Gla-deficient prothrombins exhibited kcat values similar to that of normal 10-Gla prothrombin but Km values that were 8- to 20-fold greater than that of the normal molecule. The increased Km coincided with a loss of Ca2+- and phospholipid-binding properties of the Gla-deficient prothrombins. The magnitude of the defect in both the kinetics of activation and Ca2+ and phospholipid binding is not progressive with the loss of Gla residues but rather appears abruptly with the loss of as few as 3 of the 10 Gla residues present in the normal substrate. The theoretical relationship between Km(app) and the dissociation constant (Kd) of the prothrombin-phospholipid interactions was derived. According to the result, the increase in apparent Km observed with the Gla-deficient prothrombins corresponds to at least a 100- to 1000-fold decrease in affinity for phospholipid compared to the affinity of normal prothrombin. In addition, the products of the activation of 10-Gla prothrombin were found to inhibit the activation of the Gla-deficient prothrombins.

1-Carboxyglutamic Acid↗
PubMed1988

Early processing of prothrombin and factor X by the vitamin K-dependent carboxylase.

Binding interactions between the membrane-associated vitamin K-dependent carboxylase and its prothrombin and factor X substrates have been investigated in liver microsomes. Both substrates are firmly attached to microsomal membrane fragments which also harbor the carboxylase. In vitro 14CO2 gamma-carboxylation of these substrates, triggered by reduced vitamin K1H2, resulted in release of 14C-labeled prothrombin precursors from the membrane fragments, but no release of 14C-labeled factor X precursors could be demonstrated, which suggested a difference in early processing of these substrates by the carboxylase. Warfarin treatment of rats resulted in a 3-fold increase in the membrane concentration of factor X antigens and a 20-fold increase in 14C gamma-carboxylation of the membrane pool of factor X carboxylase substrates. There was a dose-response relationship between the amount of drug administered to the rats and 14C labeling of the membrane pool of factor X carboxylase substrates. On the other hand, the membrane concentration of prothrombin antigens did not increase in response to the drug, and 14CO2 gamma-carboxylation of the membrane pool of prothrombin carboxylase substrates was the same in warfarin and saline-treated rats. The results demonstrate significant differences in the interaction between the carboxylase and its prothrombin and factor X substrates. It appears that the different interactions result from binding of the prothrombin and the factor X precursors to separate microsomal membrane proteins that are involved in the gamma-carboxylation reaction. Warfarin appears to induce the factor X precursor-specific but not the prothrombin precursor-specific binding proteins, which suggests a new mechanism for the action of warfarin. These binding proteins may be under different genetic control. Treatment of the prothrombin and the factor X carboxylase substrates with endonuclease H showed that the rat prothrombin and the human factor X carboxylase substrates are high mannose glycoproteins. The human prothrombin and the rat factor X carboxylase substrates did not, on the other hand, change their migration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels after endonuclease H treatment. The data demonstrate differences in the glycoprotein nature of the rat and the human carboxylase substrates.

Animals↗
PubMed1979

The turnover in normal dogs of prothrombin and its fragments; effect of induced intravascular coagulation.

When 125I-labeled canine prothrombin was given to normal adult dogs intravenously, it was calculated that 240% of the plasma prothrombin crossed the capillary barrier per day, 410% of the interstitial prothrombin returned to the blood stream daily, and 79% of the plasmatic prothrombin was catabolized per day. These data are in close agreement with those observed for bovine prothrombin in calves by Takeda (1970). When derived from normal dog prothrombin, prethrombin-1 is a mixture of 2 polypeptides, one larger than the other, and both present in about equal amounts. The longer peptide, "prethrombin-1-long," was catabolized twice as fast as prothrombin, and the shorter, "prethrombin-1-short," 4 times faster. Prothrombin fragment-1 was catabolized by the normal dog still more rapidly. The catabolism of prothrombin was not accelerated in 3 dogs receiving continuous infusions of a thromboplastic emulsion of dog brain. Nor was the level of prothrombin in their plasma remarkably altered.

Afibrinogenemia↗
PubMed1982

Influence of metal ions on prothrombin self-association. Demonstration of dimer formation by intermolecular cross-linking with dithiobis(succinimidylpropionate).

Interaction of certain metal ions with prothrombin and prothrombin fragment 1 has been shown to result in conformational change(s). Self-association of prothrombin and prothrombin fragment 1 in the presence of divalent cations has been reported. The present study has made use of a covalent cross-linking reagent, dithiobis(succinimidylpropionate), to study the self-association of prothrombin in the presence of divalent cations. In the presence of certain divalent cations, prothrombin dimer is the product of such cross-linking. Optimal dimerization of bovine prothrombin requires preincubation with calcium ions prior to the addition of cross-linking reagent. Calcium ions are also required for dimerization after this preincubation period. A similar time dependence is not seen with human prothrombin. The dimerization of bovine prothrombin is also supported by strontium and gadolinium to an extent comparable to that of calcium and to a lesser extent by barium or manganese. Magnesium ions do not support dimerization. The results suggest that certain divalent cations either induce or stabilize a conformation of prothrombin which can self-associate to form dimers. The results further suggest that divalent cations are also necessary for the actual cross-linking process subsequent to this conformational change.

Amino Acid Sequence↗
PubMed1993

The importance of specific gamma-carboxyglutamic acid residues in prothrombin. Evaluation by site-specific mutagenesis.

Prothrombin has 10 gamma-carboxyglutamic acid residues which are essential for the metal ion binding properties and membrane binding function of the protein. To assess the importance of each gamma-carboxyglutamic acid residue we made, by site directed mutagenesis, a series of mutant human prothrombins each with a single glutamic acid to aspartic acid substitution at positions 6, 7, 14, 16, 19, 20, 25, 26, 29, or 32 which are gamma-carboxylated in native prothrombin. Along with wild-type prothrombin, the prothrombin mutants were expressed in Chinese hamster ovary cells, purified by immunoaffinity chromatography using polyclonal anti-prothrombin antibodies, and shown by amino acid analysis to contain the expected number of gamma-carboxyglutamic acid residues. Only substitution of gamma-carboxyglutamic acid 6 with aspartic acid yields a protein with procoagulant activity, affinity for phospholipid and KM(app) for prothrombinase indistinguishable from wild-type prothrombin. In contrast, the conservative gamma-carboxyglutamic acid to aspartic acid mutation at positions 16, 26, or 29 results in proteins with little or no procoagulant activity, Kd(app) for binding to phospholipid at least 200-fold higher than wild-type prothrombin and a KM(app) for interaction with the prothrombinase complex nearly 100-fold higher than wild-type prothrombin. The mutations at residues 7, 14, 19, 20, 25, or 32 yielded proteins with intermediate procoagulant activities, between 15 and 52% of wild-type prothrombin. These data have been interpreted to suggest that there are certain gamma-carboxyglutamic acid residues which are important to maintaining the basic structure of the calcium-liganded Gla domain while other gamma-carboxyglutamic acid residues subserve other functions including membrane binding and interdomain interactions.

1-Carboxyglutamic Acid↗
PubMed1995

Development of an ELISA for autoantibodies to prothrombin showing their prevalence in patients with lupus anticoagulants.

Some lupus anticoagulants (LA) have been shown to be directed against phospholipid-bound prothrombin. While developing an ELISA to detect anti-prothrombin autoantibodies in patient serum or plasma, no or very low signal was observed using human prothrombin immobilized on plain polystyrene plates. In contrast, the same LA-positive samples bound specifically to prothrombin coated on gamma-irradiated plates, depending on the radiation dose, in the absence of added calcium and phospholipid. Optimization of the assay required the addition of 0.1% Tween 20 to the buffers. Antibody specificity for immobilized prothrombin was ascertained by competition using liposome-bound prothrombin, since fluid-phase prothrombin competed poorly. Seventy-seven of 139 patients (55.4%) with LA related to a variety of underlying diseases possessed anti-prothrombin antibodies (27 IgG, 35 IgM and 15 both isotypes), either isolated or more often associated with anti-beta 2 glycoprotein I (beta 2GPI) antibodies. These included 67-71% of the patients with systemic lupus erythematosus and related disorders, primary antiphospholipid antibody syndrome or drug-induced LA (autoimmune groups), but only 19-20% of those with infection or malignancy (p < 0.001). As previously shown for anti-beta 2GPI antibodies, IgG2 was the predominant IgG subclass reactive with prothrombin. Thus, autoimmune patients with LA have a high incidence of antibodies to beta 2GPI and prothrombin, the binding of which could similarly require high antigen density and/or exposure of cryptic epitopes resulting from protein interaction with an irradiated (i.e. more anionic) polystyrene surface.

Autoantibodies↗
PubMed2001

Determination of prothrombin in feline plasma.

Determination of the major common pathway protein prothrombin, a vitamin K-dependent protein synthesized in the liver, may be useful for identifying coagulopathies in cats with liver disease or vitamin K antagonism. In people with liver disease, prothrombin is more commonly and more severely decreased than other procoagulant proteins. The purpose of this study was to evaluate a commercial chromogenic assay(DiaPharma Group, West Chester, Ohio, USA) for the determination of prothrombin activity in plasma from healthy cats. The method involves the cleavage of prothrombin by Ecarin, a nonphysiologic enzyme activator that cleaves prothrombin to meizothrombin, which then interacts with a chromogenic substrate. Citrated (n = 20) and EDTA (n = 37) plasma samples from clinically healthy cats were tested using 100-fold and on occasion 200-fold dilutions. The assay was run according to manufacturer's specifications and the relative percentage prothrombin activity was calculated using standard curves generated from a feline citrated plasma pool and human reference plasma. Slope and regression values (r =.998) were similar for feline and human samples, suggesting that Ecarin cleaves prothrombin in both feline and human plasma in an analogous manner. The correlation between results obtained using feline vs human reference plasma was high for both citrated (r =.910) and EDTA samples (r =.998). When prothrombin was determined using human reference plasma, results from citrated feline plasma samples were 75.7% +/- 9.0% of normal compared to 91.6% +/- 7.0% of normal when the feline standard curve was used. Similar results were obtained using EDTA plasma. Our results indicate that the prothrombin chromogenic assay may be useful for evaluating one component of the hemostatic pathway in feline plasma. The prothrombin chromogenic assay utilizes routine instrumentation, requires small sample volume (5 microliter/assay), and may be used on EDTA plasma. To optimize sensitivity, the assay should be run using a standard curve generated with a feline plasma pool.

Journal Article↗
PubMed1987

Platelet procoagulant properties studied with snake venom prothrombin activators.

Purified snake venom prothrombin activators were used to probe the procoagulant properties of platelet membranes. Human platelets were able to stimulate prothrombin activation by the venom activators from Oxyuranus scutellatus and Notechis scutatus, while the prothrombin activator from Echis carinatus was not affected by the presence of platelets. The prothrombin-converting activity of platelets was further studied with the venom activator from Oxyuranus scutellatus and with the factor Xa-Va complex as prothrombin activating enzymes. Stimulation of platelets with collagen, collagen plus thrombin or with the Ca-ionophore A23187 resulted in a considerable increase of platelet prothrombin converting activity probed with the factor Xa-Va complex as well as with the prothrombin activator from Oxyuranus scutellatus. The stimulatory effect of activated platelets on the rates of prothrombin activation by Oxyuranus scutellatus was similar to that determined for factor Xa-Va-catalyzed prothrombin activation. Compared to non-stimulated platelets, platelets stimulated with thrombin plus collagen exposed 20-times more procoagulant sites for as well the factor Xa-Va complex, as for the venom activator from Oxyuranus scutellatus. The actual number of procoagulant sites per platelet determined with the factor Xa-Va complex was in close agreement with the number of sites determined with the venom activator. Also the time course of appearance of procoagulant activity during platelet stimulation by collagen plus thrombin was comparable for both activator complexes. Phospholipase A2 treatment of stimulated platelets resulted in an almost complete loss of their ability to stimulate prothrombin activation by the enzyme from Oxyuranus scutellatus or by factor Xa-Va complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed2004

Prevalence and clinical associations of prolonged prothrombin time in adult untreated coeliac disease.

INTRODUCTION: Untreated coeliac disease may induce malabsorption of many nutrients. It may also induce vitamin K deficiency, which causes prolongation of the prothrombin time. The aim of the present study was to evaluate the prevalence and associations of prolonged prothrombin time in a series of coeliac adults. METHODS: We carried out a cross-sectional analysis of data collected on 390 adults with untreated coeliac disease diagnosed from January 1997 to December 2000. Prolonged prothrombin time was defined as INR > or = 1.4. RESULTS: A prolonged prothrombin time was found in 72 coeliac patients (18.5%). Parenteral vitamin K therapy was required in 5.6% of patients. Patients with prolonged prothrombin time had significant lower values of haemoglobin, iron, proteins, cholesterol and serum aspartate transaminase, and significantly higher prevalence of diarrhoea, weight loss, abdominal pain and low bone mineral density in comparison with patients with normal prothrombin time. However, low bone density was present in 11.6% of patients with normal INR. A prolonged prothrombin time was only found in a few patients with subclinical coeliac disease (0.9%). CONCLUSIONS: Data indicate that the prevalence of prolonged prothrombin time is about 20% in a large series of adult untreated coeliac patients. A prolonged prothrombin time was significantly related to all the markers of severe malabsorption, including low mineral density. Our suggestion is that vitamin K related proteins may also play a role in determining or worsening calcium homeostasis disorders in coeliac disease. The very low prevalence of coagulation disorders in subclinical coeliac disease indicates that there is no need to screen for coeliac disease in patients with isolated coagulation disorders.

Adult↗
PubMed1997

Plasma tissue factor antigen levels in capillary whole blood and venous blood: effect of tissue factor on prothrombin time.

To measure the amount of tissue factor released during specimen collection and its potential effect of shortening the prothrombin time, we measured tissue factor and prothrombin time in twenty-three paired venous and capillary blood samples from anticoagulated patients and in ten paired samples from controls. We also compared venous prothrombin time determined by a plasma-based assay with venous and capillary prothrombin time determined with a whole blood assay. Venous specimens were obtained using a two-syringe technique; capillary specimens were obtained by fingerstick after wiping the first drop of blood. Plasma tissue factor was determined by an enzyme-linked immunoabsorbant assay. The patients' mean venous tissue factor (235 +/- 101 pg/ml) and capillary tissue factor (268 +/- 106 pg/ml) were higher than those of the controls (161 +/- 42 pg/ml and 187 +/- 63 pg/ml, respectively, P < 0.05). These differences disappeared after adjusting for age. Capillary tissue factor levels were higher than venous tissue factor (244 +/- 102 pg/ml vs. 213 +/- 93 pg/ml), with a mean difference of 31 pg/ml (P = 0.0001). In addition, whole blood prothrombin time was lower in the capillary than in the venous samples (17.7 +/- 5 sec vs. 18.3 +/- 5.4 sec, P = 0.004). However, there was no correlation between capillary-venous differences in tissue factor and capillary-venous differences in the whole blood prothrombin time. Whole blood capillary and venous prothrombin times highly correlated with the plasma-based venous prothrombin time (r = 0.98, P < 0.0001). These results demonstrate that obtaining blood by fingerstick does not result in a clinically significant release of tissue factor. In addition, we did not observe any interference of plasma tissue factor with the whole blood prothrombin time assay. A direct relationship between tissue factor and age was observed.

Adult↗
PubMed1993

Comparison of the behavior of normal factor IX and the factor IX Bm variant Hilo in the prothrombin time test using tissue factors from bovine, human, and rabbit sources.

A subset of hemophilia B patients have a prolonged bovine-brain prothrombin time. These CRM+ patients are classified as having hemophilia Bm. The prolongation of the prothrombin time has been reported only with bovine brain (referred to as ox brain in some literature) as the source of thromboplastin; prothrombin times determined with thromboplastin from rabbit brain or human brain are not reported to be prolonged. Factor IX from a hemophilia Bm patient (factor IX Hilo) was isolated. The activity of factor IX Hilo was compared to that of normal factor IX in prothrombin time assays when the thromboplastin source was of bovine, rabbit, or human origin. Factor IX, either normal or Hilo, prolonged a prothrombin time regardless of the tissue factor source. However, unless thromboplastin was from a bovine source, this prolongation required high concentrations of factor IX. Further, factor IX normal was as effective as factor IX Hilo in prolonging the prothrombin time when rabbit or human thromboplastin was used. With bovine thromboplastin, factor IX Hilo was significantly better than factor IX normal at prolonging the prothrombin time. The amount of prolongation was dependent on the amount of factor IX Hilo added. In addition, the prolongation was dependent on the concentration of factor X present in the sample. The prothrombin time changed as much as 20 seconds when the factor X concentration was varied from 50% to 150% to normal (fixed concentration of factor IX Hilo). These results demonstrate the difficulty of classifying the severity of a hemophilia Bm patient based on the bovine brain prothrombin time unless both the factor IX and factor X concentrations are known.

Animals↗
PubMedDate not supplied

Adsorption and reactivity of human prothrombin to artificial surfaces.

Human prothrombin in Tyrode's solution, in mock plasma (albumin, fibrinogen, and IgG mixture), and in citrated plasma adsorbs to Cuprophane, polyvinylchloride, and polyacrylonitrile surfaces. The adsorption of prothrombin is maximal in Tyrode's solution and minimal in plasma. The surface concentrations of prothrombin are highest on polyacrylonitrile, second on polyvinylchloride, and lowest on Cuprophane at all prothrombin concentrations tested in the bulk solution. Qualitative tests show that prothrombin adsorbed to polyvinylchloride can be activated by Taipan snake venom to generate thrombin that clots fibrinogen. However, more quantitative tests indicate that only part of the adsorbed prothrombin on all three materials can be activated to form thrombin exhibiting amidolytic activity. The partial reactivity of adsorbed prothrombin is further confirmed by release of 125I-peptide from surface bound 125I-prothrombin after treatment with Australian Taipan snake venom. Prothrombin bound to Cuprophane seems to promote granulocyte adhesion, but has no effect on platelet adhesion.

Acrylic Resins↗
PubMed1995

Prothrombin cleavage by human vascular smooth muscle cells: a potential alternative pathway to the coagulation cascade.

Thrombin is a potent mitogen for human vascular smooth muscle cells (HVSMC) and its enzymatic activity is required for this function. The present study demonstrates that prothrombin is also mitogenic for HVSMC due to the generation of enzymatically active thrombin which occurs upon incubation of prothrombin with the cells. Analysis by SDS-PAGE, immunoblotting, and amino acid sequencing revealed that prothrombin incubated with HVSMC undergoes limited proteolysis. Prethrombin 1 was formed through cleavage at R155-S156. Cleavage at R271-T272 generated fragment 1.2 and prethrombin 2 whilst cleavage at R284-T285 yielded truncated prothrombin 2 (prethrombin 2'). However, cleavage at R320-I321 which, during prothrombin activation produces two-chain alpha-thrombin, was not detectable. Studies on HVSMC-conditioned medium revealed that a similar pattern of prothrombin cleavage occurred by a cell-secreted factor(s). Amidolytic activity analysis indicated that 1-3% catalytically active thrombin-like activity was generated upon incubation of prothrombin with HVSMC-conditioned medium. By treating conditioned medium with various classes of proteinase inhibitors or hirudin, it was determined that prothrombin is cleaved by a cell-derived serine proteinase-like factor(s) at R271-S272 and by alpha-thrombin at R155-S156 and R284-T285. Antibodies neutralising the activity of either urokinase, tissue plasminogen activator, or factor Xa failed to alter the prothrombin cleaving activity of conditioned medium. This activity which may catalyse an alternative pathway for the generation of thrombin, was eluted from a gel filtration column as a single peak with apparent molecular mass of 30-40 kDa.

Adolescent↗