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PubMed1979

The effect of prothrombin fragment 2 on the inhibition of thrombin by antithrombin III.

The effect of prothrombin fragment 2 on the inhibition of thrombin by antithrombin III has been studied. Fragment 2 was found to slow the rate of inhibition of thrombin by antithrombin III about 3-fold. The effect of prothrombin fragment 2 on antithrombin III inhibition was examined by comparing its action in the presence of either thrombin or meizothrombin (des fragment 1). The second order rate constants for antithrombin III inhibition of thrombin with saturating fragment 2 and antithrombin III inhibition of meizothrombin (des fragment 1) were the same. Prothrombin fragment 2 had no effect on either antithrombin III inhibition of meizothrombin (des fragment 1) or Factor Xa. The effect of the fragment on the reaction mechanism of thrombin inhibition was evaluated to see if the fragment altered binding of antithrombin III to thrombin or inhibited the formation of the covalent complex. The fragment was found to have no inhibitory effect on the rate of covalent complex formation, indicating that the protective effect of the fragment is by inhibiting binding of antithrombin III to thrombin. These data suggest that prothrombin fragment 2 may be an important factor in controlling the localization of clot formation by regulating the interaction between thrombin and antithrombin III.

Animals↗
PubMedDate not supplied

[Antithrombin III in 86 patients with venous thrombosis (author's transl)].

Antithrombin III concentration was studied in 86 patients with recurrent or extensive venous thrombosis. Two of them were found to have an hereditary antithrombin III deficiency. 25 patients receiving heparin therapy had low antithrombin III concentration. After stopping heparin treatment antithrombin rose to a normal level. Pathological antithrombin III modifications are recalled (synthesis decrease in liver diseases, intra vascular consumption during active venous thrombosis). Antithrombin III decreased activity induced by heparin treatment is pointed out.

Antithrombin III↗
PubMed1977

Metabolism of antithrombin III (heparin cofactor) in man: effects of venous thrombosis and of heparin administration.

The metabolism of human antithrombin III (heparin cofactor) was studied in four control subjects, in four subjects with peripheral obliterative arterial disease, in six patients with recent venous thrombosis and in one patient with clinically severe haemophilia A. The labelled antithrombin III has a high specific activity (5.75 units/mg) and displayed a single band on SDS-polyacrylamide gel electrophoresis. On Sephadex G-100 gel filtration the labelled material eluted in the same position as the antithrombin III activity in plasma. Crossed immunoelectrophoresis of a mixture of fresh plasma and labelled antithrombin III against a specific antiserum, revealed a single precipitin line in which radioactivity was concentrated. The changes in electrophoretic mobility of both the plasma antithrombin III and the labelled material following the addition of heparin to the mixture or following coagulation were identical. The purified antithrombin III behaved as a homogeneous protein in the turnover experiments. The plasma radioactivity data were approximated by a sum of two exponential terms and the metabolism of antithrombin III represented by a two compartment mammillary model. Results in the control subjects were as follows: plasma antithrombin III concentration 19.6 +/- 2.3 mg/100 ml; intravascular fraction 0.45 +/- 0.05; fractional catabolic rate 0.55 +/- 0.02 of the plasma pool per day; half-life of the plasma radioactivity 2.83 +/- 0.26 days. Circulating large molecular weight degradation products of labelled antithrombin III could not be detected by Sephadex G-100 gel filtration. No significant differences in these parameters were found in the patients with peripheral arterial insufficiency. The turnover rate of antithrombin III was normal in the patient with haemophilia A. In three patients with venous thrombosis not treated with heparin, the turnover of labelled antithrombin III was in the normal range. In three patients with venous thrombosis, treated with heparin, the plasma radioactivity half-life was significantly shortened (2.13 +/- 0.08 days) and the fractional catabolic rate increased (0.75 +/- 0.05) of the plasma pool per day). In one of these patients, the labelled antithrombin III had been incubated with an equimolar amount of heparin prior to injection. In this patient the plasma radioactivity half-life was in the same range as in the other two patients (2.15 days).

Adult↗
PubMed1978

Some immunological investigations on antithrombin III 'Budapest'.

Immunoelectrophoretic studies were carried out on plasma from a patient with an abnormal antithrombin III molecule (antithrombin III 'Budapest'). One-dimensional immunoelectrophoresis using a commercial antibody to antithrombin III (antibody to alpha2-AtIII) showed two precipitin peaks of alpha2-AtIII antigen. Two-dimensional immunoelectrophoresis showed two precipitin peaks, one with normal electrophoretic mobility, the other with increased electrophoretic mobility. It was shown that alpha2-AtIII antigen with normal mobility was identical to normal alpha2-AtIII, and that the alpha2-AtIII antigen with increased electrophoretic mobility was antigenically deficient, and appeared to be present in higher concentration than the normal alpha2-AtIII antigen. Although one-dimensional immunoelectrophoresis on plasma from the patient's son showed only one peak, two-dimensional immunoelectrophoresis revealed that the son also had two populations of alpha2-AtIII, one with normal mobility, the other with increased mobility. However, the alpha2-AtIII antigen with normal mobility appeared to be present in higher concentration than the alpha2-AtIII antigen with increased mobility. One- and two-dimensional immunoelectrophoresis using a different commercial antibody to alpha2-AtIII showed only one precipitin peak using the patient's plasma. The precipitin peak observed following two-deminsional immunoelectrophoresis was asymmetric and showed increased mobility.

Adult↗
PubMed1975

Antithrombin III: a backward glance o'er travel'd roads.

By devising and applying quantitative methods for the assay of thrombin and autoprothrombin C and by developing techniques for their purification, it was possible to obtain information about the function and properties of antithrombin. The inhibitor is a protein for which the initial purification steps consist of removing fibrinogen from plasma by heating to 56 degrees for 3 min, removing prothrombin complex by absorption on barium carbonate, absorbing the antithrombin on aluminum hydroxide, and eluting with phosphate buffer. Antithrombin is limited in its capacity to neutralize thrombin activity, and, under some conditions, the rate of inhibition was accelerated, but equivocal results were involved. Heparin cofactor was found to be essential for retarding the formation of thrombin, and, by inference, it is essential for retarding the formation of autoprothrombin C. Heparin cofactor and antithrombin III are the same. Thrombin absorbs on fibrin, and this has been referred to as the "antithrombin I effect." Interference with the thrombin-fibrinogen reaction by mixtures of antithrombin III and heparin is called the "antithrombin II henomenon." The acceleration of thrombin inactivation at the time thrombin forms is called the "antithrombin IV effect." It was discovered that antithrombin III neutralizes thrombin, as well as autoprothrombin C. The inhibitor and the enzyme form a mutual depletion system. To assay for antithrombin III, a standard quantity of thrombin (about 1,100U/ml) was reacted with antithrombin III for 2 hr. The percent thrombin inactivated was then measured. In random samples of human blood, a wide range of antithrombin III concentration was found. The inhibitor is relatively stable in plasma and serum. It is not changed in concentration when Dicumarol therapy is instituted. Ether extraction of plasma reduces antithrombin III activity. Seitz filtration of plasma did not remove activity. Under special conditions, antithrombin III enhances esterase activity of thrombin. Under special conditions, thrombin regenerates from the thrombin-antithrombin III complex. Antithrombin III neutralizes the activity of prethrombin-E and thrombin-E; consequently, an active histidine center found in the B1 chain of thrombin is not essential for the binding of antithrombin. Autoprothrombin II-A activity was neutralized by antithrombin III. Autoprothrombin C was found to be neutralized by antithrombin III; the amounts required varied with the molecular forms of autoprothrombin C. Thrombin and autoprothrombin C apparently occupy the same binding sites on antithrombin III. An equation was developed to account for all the known characteristics of antithrombin III functions. The kinetic aspects of thrombin neutralization were found to correspond exactly with those of autoprothrombin C. Antithrombin III is a high-capacity inhibitor of the two most powerful enzymes in blood coagulation.

Antithrombin III↗
PubMed1979

Isolation and characterization of antithrombin III from human, porcine and rabbit plasma, and rat serum.

1. Human, porcine, rabbit, and rat antithrombin III have been purified by affinity chromatography using heparin-agarose. The amino acid and carbohydrate compositions, amino-terminal sequences, immunological cross-reactivities, and inhibitions of human thrombin were studied. 2. Human, porcine, rabbit, and rat antithrombin III are single-chain glycoproteins containing hexose, glucosamine, and neuraminic acid. 3. The total carbohydrate contents were 17, 16, 14, and 15% for human, porcine, rabbit, and rat antithrombin III, respectively. 4. Molecular weights estimated from the migration in sodium dodecyl sulfate (SDS)-poly-acrylamide gel electrophoresis were 59,000, 58,000, 63,000, and 63,000 for human, porcine rabbit, and rat antithrombin III, respectively. 5. These four proteins have similar amino acid compositions, although some minor differences were noted. 6. Human, porcine, and rabbit antithrombin III have a histidine residue at the amino-terminus, while rat antithrombin III contains an amino-terminal asparagine residue. 7. The amino-terminal sequences up to the first 17 residues showed high homology among the four proteins. 8. Some immunological cross-reactivity was observed only between human and porcine antithrombin III. 9. The apparent dissociation constants (KI) for the complexes between human thrombin and human, porcine, rabbit, and rat antithrombin III were about 1.2 x 10(-10) M, 9.5 X 10 (-9) M, 1.4 X 10(-7) M, and 2.8 X 10(-9) M, respectively.

Amino Acid Sequence↗
PubMed1978

Inhibition of urokinase by complex formation with human antithrombin III in absence and presence of heparin.

Human antithrombin III was purified from fresh human plasma by affinity chromatography on heparin-Sepharose, affinity chromatography on concanavalin A Sepharose, gel filtration on Ultrogel AcA 34, ion exchange chromatography on DEAE A-50 Sephadex and preparative agarose gel electrophoresis. The hydrolytic activity of urokinase (plasminogen activator from urine) on acetyl-glycyl-L-lysine methylester acetate (Ac-gly-lys-OMeAc) was inhibited by antithrombin III in a slow time-dependent manner. Heparin accelerated the reaction between activator and inhibitor. Inhibition of catalytic activity was associated with the formation of an 1:1 molar complex between activator and inhibitor as revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The complex was also demonstrated by crossed immunoelectrophoresis against anti-antithrombin III.

Antigen-Antibody Complex↗
PubMed1976

Hereditary antithrombin III deficiency and thromboembolic disease.

Two teenage brothers with recurrent thromboembolic disease were found to have antithrombin III deficiency. A family study spanning four generations revealed a total of 10 members with antithrombin III deficiency. Five of the 10 affected family members have had thrombotic problems. Antithrombin III deficiency was documented by coagulation assays measuring heparin cofactor, anti-Factor Xa, and progressive antithrombin activity; the level of antithrombin III antigenic material measured by immunoelectrophoresis was low in subjects with abnormal coagulation assays. The clinical features which may lead one to suspect the hereditary hypercoagulable condition of antithrombin III deficiency are reviewed.

Antithrombins↗
PubMed1977

[Antithrombin III deficiency and tendency to thrombosis (author's transl)].

Antithrombin III (AT III) was determined in 290 patients with deep venous thrombosis and/or pulmonary embolism by immunological methods (radial immunodiffusion, Laurell technique) and by biological activity (heparin cofactor activity and anti-Xa activity). Patients with venous thrombosis had a significantly lower AT III concentration, as determined by the immunological methods or biological method (heparin cofactor activity), than normal persons without any history of venous thrombosis. A decreased level of AT III was found in 27 patients. In these patients the immunoreactive antithrombin III was decreased to the same degree as biological activity (heparin cofactor activity or anti-Xa activity). Thirteen out of these 27 patients belonged to 9 families and, hence, congenital AT III deficiency can be assumed in these cases. The aetiology was unknown in the other half. Patients with AT III deficiency are prone to spontaneous and/or recurrent venous thrombosis. A high incidence of pulmonary embolism and particularly, of fatal pulmonary embolism is remarkable. In more than half of the patients the first thrombotic event occurred before the age of 35. The treatment of choice in such patients is with oral anticoagulants of the coumarin group.

Adult↗
PubMed1977

Binding of heparin to human antithrombin III as studied by measurements of tryptophan fluorescence.

Corrected fluorescence excitation and emission spectra of human antithrombin III have been determined. The fluorescence observed originates almost entirely from tryptophan residues. Reduction of the disulfide bonds followed by carboxymethylation did not change the fluorometric properties of the protein. The binding of heparin to antithrombin III caused a marked fluorescence enhancement by about 30% of the intrinsic protein emission intensity. Various samples of heparin yielded different binding curves. Heparin fractionated by gel filtration seemed to be bound to two sites on antithrombin III with association constants of 0.6-10(6)m-1 and 0.2-10(6)M-1 respectively. Heparin, prepared by affinity chromatography on matrix-bound antithrombin III appeared to be bound to only one site with an association constant of 2.3-10(6)M-1. Under similar conditions heparin caused no increase of the intrinsic protein emission intensity when added to reduced and carboxymethylated antithrombin III. The implications of these findings are discussed.

Alpha-Globulins↗
PubMed1976

Alteration of plasma antithrombin III levels in ischemic heart disease.

The amount of antithrombin III in plasma was determined quantitatively in 218 males between 45-60 years of age. The mean antithrombin III value was found to be low in the group with low risk for ischemic heart disease, intermediate in the group with high risk for ischemic heart disease and highest in the group with acute myocardial infarction. Concomitant study of kaolin-activated partial thromboplastin time revealed a sharp decrease in its mean value in the group with acute myocardial infarction. The high correlation between antithrombin III and kaolin-activated partial thromboplastin time for the entire population suggests that the development of ischemic heart disease is a gradual process and that failure of the damping mechanism results as an acute event. These findings may be useful in the determination of the coagulation state of these patients.

Acute Disease↗
PubMed1979

Central retinal vein occlusion in a patient with familial antithrombin III deficiency: case report.

A 60-year old man with familial antithrombin III deficiency, a primary cause of hypercoagulation, developed central retinal vein occlusion. Familial antithrombin III deficiency is inherited as an autosomal dominant condition. It is characterized by recurrent episodes of thromboembolism. The occurrence of central retinal vein occlusion in a person with familial deficiency of antithrombin III suggests the possibility of a casual relationship.

Animals↗
PubMed1978

Effect of heparin on thrombin inactivation by antithrombin-III.

The inactivation of thrombin by heat and by its physiological inhibitor, antithrombin-III, shows quite different dependence on heparin concentration. Heparin at 250 microgram/ml protects thrombin against heat inactivation, and thrombin behaves heterogeneously in this reaction. In the absence of heparin, the thermodynamic activation parameters change with temperature (deltaH+ = 733 kJ/mol and 210 kJ/mol at 50 and 58 degrees C respectively). When heparin is present, heat inactivation of the protected thrombin species proceeds with deltaH+ = 88 kJ/mol and is independent of temperature in the same range. On the other hand, heparin at 0.125-2.5 microgram/ml accelerates the thrombin-antithrombin-III reaction. Thrombin does not show heterogeneity in this reaction and the time courses at any heparin concentration and any temperature between 0 and 37 degrees C appear to follow first-order kinetics. Activation enthalpy is independent of heparin concentration or temperature, deltaH+ = 82-101 kJ/mol, varying slightly with antithrombin-III concentration and thrombin specific activity. Heparin seems to exert its effect by increasing activation entropy. On the basis of these data we suggest a mechanism of action of heparin in the thrombin-antithrombin-III reaction which accounts for all the important features of the latter and seems to unify the different hypotheses that have been advanced.

Antithrombin III↗
PubMed1977

[Electrophoretic mobility of antithrombin III in an agarose gel with heparin. (author's transl)].

The electrophoretic mobility of several forms of antithrombin III in an agarose gel has been compared with the mobility in a gel containing heparin. When a serum was studied, three different compounds were observed. The inactige antithrombin III with higher molecular size, separated by gel filtration, was found to be homogenous even if there was heparin in the gel. A purified antithrombin III, prepared by affinity chromatography, contained an immunoreactive material of higher molecular size which has no activity and a higher mobility in agarose gel. When heparin is incorporated in the agarose plate, the electrophoretic mobility of this polymerized antithrombin III is not modified.

Antithrombins↗
PubMed1976

The effect of antithrombin III on the activity of the coagulation factors VII, IX and X.

Antithrombin III, purified to homogeneity according to polyacrylamide gel disc electrophoresis and immunoelectrophoresis, inhibited the activity of purified factor IXa and Xa, whereas factor VII was not inhibited either in the active or in the native form. Antithrombin III is the single most important inhibitor of factor Xa in plasma. Factor Xa does not, however, reduce the activity of antithrombin III against thrombin.

Antithrombins↗
PubMed1979

Evidence for a plasma inhibitor of the heparin accelerated inhibition of factor Xa by antithrombin III.

The ability of heparin fractions of different molecular weight to potentiate the action of antithrombin III against the coagulation factors thrombin and Xa has been examined in purified reaction mixtures and in plasma. Residual thrombin and Xa have been determined by their peptidase activities against the synthetic peptide substrates H-D-Phe-Pip-Arg-pNA and Bz-Ile-Gly-Arg-pNA. High molecular weight heparin fractions were found to have higher anticoagulant activities than low molecular weight heparin when studied with both thrombin and Xa incubation mixtures in purified mixtures and in plasma. The inhibition of thrombin by heparin fractions and antithrombin III was unaffected by other plasma components. However, normal human plasma contained a component that inhibited the heparin and antithrombin III inhibition of Xa particularly when the high molecular weight heparin fraction was used. Experiments using a purified preparation of platelet factor 4 suggested that the platelet-derived heparin-neutralizing protein was not responsible for the inhibition.

Animals↗
PubMed1976

Oral contraceptives, antithrombin- III activity, and postoperative deep-vein thrombosis.

Deep-vein thrombosis (D.V.T.) was detected by the fibrinogen-uptake test in six out of a total of thirty-one young women undergoing emergency abdominal surgery who gave a history of recent oral contraceptive intake. In contrast, no D.V.T. developed in nineteen similar patients who were not on oral contraceptives (P less than 0-01). Plasma-antithrombin-III activity was significantly lower preoperatively in patients taking oral contraceptives; postoperative D.V.T. subsequently developed in three out of five patients with preoperative antithrombin-III activity below 50%. In seventy-eight dental patients undergoing molar extraction, antithrombin-III activity was measured before, during, and after operation. Activity fell in all patients during operation, but the fall was significantly greater in women taking oral contraceptives (P less than 0-01). The intra-operative fall in antithrombin-III activity was prevented by a small preoperative dose of subcutaneous heparin.

Adolescent↗
PubMed1977

Inactivation of alpha- and beta-thrombin by antithrombin-III, alpha 2-macroglobulin and alpha 1-proteinase inhibitor.

Inactivation of alpha- and beta-thrombin by alpha 2-macroglobulin, by alpha 1-proteinase inhibitor and by antithrombin-III and heparin was studied. The amount of alpha- and beta-thrombin inactivated by antithrombin-III was proportional to the concentration of the inhibitor, but the inactivation rates of the two forms of thrombin were different. Heparin facilitated complex-formation between alpha-thrombin and antithrombin-III, whereas inactivation of beta-thrombin by antithrombin was only slightly influenced, even at a heparin concentration two orders of magnitude higher. alpha 2-Macroglobulin inhibited both alpha- and beta-thrombin activity similarly, i.e. the amount of alpha- and beta-thrombin inactivated as well as the rates of their inhibition were the same. alpha 1-Proteinase inhibitor also formed a complex with alpha- and beta-thrombin, similarly to antithrombin-III, although the inactivation of the enzyme needed high inhibitor concentration and long incubation time. These results suggest that the inactivation of beta-thrombin, if it occurs in the plasma, is also controlled by plasma inhibitors.

Antithrombins↗