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PubMed1981

Immunological evidence for a proteolytic cleavage at the active site of antithrombin in the mechanism of inhibition of coagulation serine proteases.

Previous studies have shown that a modified form of antithrombin, cleaved at a single Arg-Ser bond near the carboxy-terminal end of the chain, is formed during the reaction with thrombin concurrent with the formation of the inactive enzyme-inhibitor complex. A variety of evidence suggests that this cleavage site is the active site of antithrombin. In this work, antisera against intact antithrombin, the modified form of antithrombin and the antithrombin-thrombin complex were used in immunodiffusion analyses to probe the state of the inhibitor in its complexes with coagulation serine proteases. The results show that new antigenic determinants not present in intact antithrombin are created in modified antithrombin by the single peptide-bond cleavage. the same antigenic determinants are found also in complexes between antithrombin and thrombin or factor Xa. No evidence for the exposure of other new determinants in the complexes was obtained. The most likely conclusion from these results is that antithrombin exists in its complexes with the serine proteases as the modified, two-chain form of the inhibitor. This suggests that the mechanism of inhibition involves proteolytic cleavage of the active site of antithrombin by the protease.

Animals↗

PubMed1987

Probing the heparin-binding domain of human antithrombin III with V8 protease.

From structural analysis on genetically abnormal and chemically modified human antithrombin III [Koide, T., Odani, S., Takahashi, K., Ono, T. and Sakuragawa, N. (1984) Proc. Natl Acad. Sci. USA 81, 289-293; Chang, J.-Y. and Tran, T. H., (1986) J. Biol. Chem. 261, 1174-1176; Blackburn, M. N., Smith, R. L., Carson, J. and Sibley, C. C. (1984) J. Biol. Chem. 259, 939-941], the heparin-binding site of antithrombin III has been suggested to be in the region of Pro-41, Arg-47 and Trp-49. In this study the heparin-binding site was probed by preferential cleavage of V8 protease on heparin-treated and non-treated native antithrombin III. The study has been based on the presumption that the heparin-binding site of antithrombin III is situated at exposed surface domain and may be preferentially attacked during limited proteolytic digestion. Partially digested antithrombin III samples were monitored by quantitative amino-terminal analysis and amino acid sequencing to identify the preferential cleavage sites. 1-h-digested antithrombin III was separated on HPLC and peptide fragments were isolated and characterized both qualitatively and quantitatively. The results reveal that Glu-Gly (residues 34-35), Glu-Ala (residues 42-43) and Glu-Leu (residues 50-51) are three preferential cleavage sites for V8 protease and their cleavage, especially the Glu-Ala and the Glu-Leu sites, was drastically inhibited when antithrombin III was preincubated with heparin. Both high-affinity and low-affinity antithrombin-III-binding heparins were shown to inhibit the V8 protease digestion of native antithrombin III, but the high-affinity sample exhibited a higher inhibition activity than the low-affinity heparin. These findings (a) imply that the segment containing residues 34-51 is among the most exposed region of native antithrombin III and (b) support the previous conclusions that this region may play a pivotal role in the heparin binding.

Amino Acid Sequence↗

PubMed2003

Trend to efficacy and safety using antithrombin concentrate in prevention of thrombosis in children receiving l-asparaginase for acute lymphoblastic leukemia. Results of the PAARKA study.

An association has been reported between thrombotic events and the use of L-asparaginase (ASP) in children with acute lymphoblastic leukaemia (ALL). The mechanism for thrombosis is likely related to an acquired antithrombin deficiency. Since a primary prophylaxis using antithrombin concentrates may prevent thrombosis, the PARKAA (Prophylactic Antithrombin replacement in kids with ALL treated with L-asparaginase) study was performed. The objectives of PARKAA were to determine if there was a trend to efficacy and safety of antithrombin treatment as assessed by 1) incidence of thrombosis 2) incidence of bleeding and 3) plasma markers of endogenous thrombin generation as surrogate outcomes for thrombosis. The study was not powered to answer the question of efficacy and safety, but rather to detect a trend. PARKAA was an open, randomised, controlled study in children with ALL being treated with ASP. Children were randomised to receive antithrombin infusions or no antithrombin treatment. All thrombotic events were confirmed using bilateral venography, ultrasound, echocardiography and MRI. The incidence of thrombosis in patients treated with antithrombin was 28% (95% CI 10-46%), compared to 37% (95% CI 24-49%) in the non treated arm. Two minor bleeds occurred in patients in the treated arm, but were not considered to be related to antithrombin. No significant differences were seen in plasma markers by the treatment group. In conclusion, treatment with antithrombin concentrate shows a trend to efficacy and safety. In contrast, there was no difference in surrogate markers for thrombosis. Carefully designed clinical trials are needed to test the efficacy and safety of antithrombin in this population.

Adolescent↗

PubMed1996

Antithrombin and atherosclerosis in the Rotterdam Study.

Antithrombin is a potent inhibitor of thrombotic tendency. Whether atherosclerotic disease is associated with high or low antithrombin is unclear. Studies of the relation between antithrombin and presence of arterial disease have shown contrasting results. In the Rotterdam Study, a single-center, population-based cohort study of 7983 subjects aged 55 years and older, the association between atherosclerosis and antithrombin was evaluated. The ratio of ankle to arm blood pressure is a graded marker for atherosclerosis and provides the opportunity to investigate nonlinear associations. In the first 1427 participants of the Rotterdam Study who did not use anticoagulants, both antithrombin and the ratio of ankle to arm blood pressure were measured. In men the association between the two was quadratic: antithrombin activity was increased in men with moderate peripheral arterial atherosclerosis compared with those without, and in men with more severe atherosclerosis it was decreased. In women the association was linear: a decreased ratio of ankle to arm pressure was associated with increased antithrombin activity. These associations were independent of smoking, body mass index, serum lipids, fibrinogen, and factor VIIc. We propose that antithrombin activity rises in response to increased risk of cardiovascular disease and also in response to the presence of atherosclerosis, whereas antithrombin may decrease with increasing severity of the atherosclerotic process in men. This may explain the contrasting results found in previous studies. Changes in antithrombin over time might be useful in predicting the risk of cardiovascular disease and progression.

Aged↗

PubMed1999

Value of thrombin-antithrombin III complexes in major orthopedic surgery: relation to the onset of venous thromboembolism.

This study evaluated (a) the possible changes of plasma levels of thrombin-antithrombin III complexes during hospitalization to predict venous thromboembolism in patients undergoing elective total hip replacement and (b) the sensitivity and specificity of thrombin-antithrombin III complexes in the late incidence of deep vein thrombosis when these patients are discharged from the hospital. In 50 consecutive patients (18 men, mean age = 63 +/- 8 years) a venous blood sample was obtained from each patient before surgery and postsurgery on days 5 +/- 2, 9 +/- 2, and 45 to evaluate the thrombin-antithrombin III complexes by the enzyme-linked immunosorbent assay as a part of a larger surveillance program. Six of 50 patients developed deep vein thrombosis, diagnosed by phlebography on the 45th day postsurgery. From the day before until the ninth day after surgery, mean values of the thrombin-antithrombin III complexes increased to a greater extent in patients with deep vein thrombosis than in those without, although the differences were not significant (from 14.8 +/- 11.2 ng/mL to 36.2 +/- 19.1 ng/mL in the former group and from 13.6 +/- 3.3 ng/mL to 22.4 +/- 5.1 ng/mL in the latter, p = NS). On the 45th day after surgery the mean value of the thrombin-antithrombin III complexes reduced less in patients with deep vein thrombosis (up to 9.9 +/- 1.9 ng/mL and to 25.2 +/- 17.2 ng/mL, respectively, p = NS). In addition, thrombin-antithrombin III complexes remained over the level reached on the fifth day only in the patients who developed deep vein thrombosis. On the 45th day after surgery, thrombin-antithrombin III complexes exhibited a sensitivity of 17%, a specificity of 86%, and an accuracy of 78% in differentiating the presence and absence of deep vein thrombosis as compared with phlebography. We conclude that after total hip replacement (a) serial measurement of the thrombin-antithrombin III complexes does not appear helpful in predicting venous thromboembolism during hospitalization, and (b) measurement of thrombin-antithrombin III complexes has a low diagnostic accuracy in diagnosing delayed deep vein thrombosis. However, the greater and persistent increase of thrombin-antithrombin III complexes level in patients who developed deep vein thrombosis may deserve further investigations.

Adult↗

PubMed1981

Effect of human granulocytic elastase on isolated human antithrombin III.

The interaction of elastase isolated from human granulocytes with purified human antithrombin III was investigated. Antithrombin III did not display any inhibitory effect on granulocytic elastase. Dependent on enzyme concentration, however, granulocytic elastase induced progressive inactivation of antithrombin III leading to an almost complete loss of the thrombin inhibitory activity at a molar ratio of elastase: antithrombin III = 0.4:1 within 5 min at 25 degrees C. Antithrombin III is not drastically degraded by elastase as revealed by polyacrylamide gel electrophoretic and rocket immunoelectrophoretic investigations. However, characterization by two-dimensional immunoelectrophoresis with heparin in the first dimensional gel layer revealed a distinct change in the electrophoretic mobility of the inhibitor preincubated with elastase compared to native antithrombin III. This indicates that heparin binding sites of antithrombin III are occupied or affected by the elastase-induced peptide bond cleavage(s). Granulocytic proteinase inhibitors (eglin, Bowman-Birk inhibitor) proved to be highly effective in preventing the antithrombin III inactivation by degradation due to elastase. It is assumed that at least part of the antithrombin III consumption in diseases such as septicemia or endotoxemia is due to proteolysis by granulocytic proteinases. Application of specific inhibitors in the early phase of these ailments should be able to prevent this unspecific degradation of the endogenous antithrombin III.

Antithrombin III↗

PubMed1992

Role of tryptophan 49 in the heparin cofactor activity of human antithrombin III.

To probe the functional role of tryptophan 49 in human antithrombin III, a mutant antithrombin, W49K, has been expressed in baby hamster kidney cells. The mutation reduces the affinity for heparin pentasaccharide by 1.8 kcal mol-1 but does not alter the heparin enhancement of the rate of factor Xa inhibition. 1H NMR spectra of W49K antithrombin show that the structure of the protein and the mode of heparin binding appear to be unaltered by the mutation, although tryptophan 49 is perturbed by heparin binding. 19F NMR spectra of 6-fluorotryptophan-substituted antithrombin show that tryptophan 49 is in a solvent-exposed environment. The heparin-induced fluorescence enhancement of W49K antithrombin is significantly different from that of wild-type antithrombin. Pentasaccharide induces only a 24% enhancement of antithrombin fluorescence, while high affinity heparin induces an enhancement of 40%. The results indicate that tryptophan 49 is probably a heparin contact residue but can be mutated without altering the remaining heparin-antithrombin interactions or the heparin-induced conformational change and resultant activation toward Factor Xa. Hydrophobic as well as charge interactions are thus probably involved in the specificity of the antithrombin-heparin pentasaccharide interaction. The lower fluorescence enhancements suggest that the heparin-induced 40% fluorescence enhancement used as the hallmark of activating heparin species is not the best indicator of the structural change in antithrombin that results in enhancement of the rate of proteinase inhibition.

Animals↗

PubMed1992

Conversion of antithrombin from an inhibitor of thrombin to a substrate with reduced heparin affinity and enhanced conformational stability by binding of a tetradecapeptide corresponding to the P1 to P14 region of the putative reactive bond loop of the inhibitor.

A synthetic tetradecapeptide having the sequence of the region of the antithrombin chain amino-terminal to the reactive bond, i.e. comprising residues P1 to P14, was shown to form a tight equimolar complex with antithrombin. A similar complex has previously been demonstrated between alpha 1-proteinase inhibitor and the analogous peptide of this inhibitor (Schulze, A. J., Baumann, U., Knof, S., Jaeger, E., Huber, R. and Laurell, C.-B. (1990) Eur. J. Biochem. 194, 51-56). The antithrombin-peptide complex had a conformation similar to that of reactive bond-cleaved antithrombin and, like the cleaved inhibitor, also had a higher conformational stability and lower heparin affinity than intact antithrombin. These properties suggest that the peptide bound to intact antithrombin at the same site that the P1 to P14 segment of the inhibitor occupies in reactive-bond-cleaved antithrombin, i.e. was incorporated as a sixth strand in the middle of the major beta-sheet, the A sheet. The extent of complex formation was reduced in the presence of heparin with high affinity for antithrombin, which is consistent with heparin binding and peptide incorporation being linked. Antithrombin in the complex with the tetradecapeptide had lost its ability to inactivate thrombin, but the reactive bond of the inhibitor was cleaved as in a normal substrate. These observations suggest a model, analogous to that proposed for alpha 1-proteinase inhibitor (Engh, R.A., Wright, H.T., and Huber, R. (1990) Protein Eng. 3, 469-477) for the structure of intact antithrombin, in which the A sheet contains only five strands and the P1 to P14 segment of the chain forms part of an exposed loop of the protein. The results further support a reaction model for serpins in which partial insertion of this loop into the A sheet is required for trapping of a proteinase in a stable complex, and complete insertion is responsible for the conformational change accompanying cleavage of the reactive bond of the inhibitor.

Amino Acid Sequence↗

PubMed1988

Antithrombin Milano, single amino acid substitution at the reactive site, Arg393 to Cys.

Antithrombin Milano is an unusual antithrombin variant, exhibiting an abnormal, fast moving component on crossed immunoelectrophoresis (in the absence of heparin). Antithrombin isolated from the propositus could be resolved into two peaks on anion-exchange chromatography; antithrombin Milano peak 1 of Mr approximately 60,000 which could inhibit thrombin, and antithrombin Milano peak 2 of Mr approximately 120,000 which was inactive. The latter component also reacted with antisera to both antithrombin and albumin on immunoblotting. Under reducing conditions, the approximately 120,000 Mr component migrated on SDS-PAGE as two distinct bands with Mr approximately 60,000, one of which reacted with antiserum to antithrombin and the other (of slower mobility) of which reacted with antiserum to albumin only. These and other results established the approximately 120,000 Mr component to be an inactive, disulphide-linked variant antithrombin and albumin complex. The variant antithrombin was isolated, following reduction and S-carboxymethylation, by reverse-phase HPLC and then it was fragmented with CNBr. A major CNBr pool containing the sequence Gly339-Met423 was treated with trypsin, followed by V8 protease. The resulting peptides were analysed by fast atom bombardment mass spectrometry (Fab-MS) mapping. A peptide of molecular mass 1086, corresponding to the normal sequence Ala382-Arg393, was almost absent from the mass spectrum, but an additional peptide of mass number 1772 was present. These results are almost identical to those found in another variant antithrombin, Northwick Park (Erdjument et al., J Biol Chem, 262: 13381, 1987; Erdjument et al., J. Biol Chem, 263: 5589-5593, 1988), indicating the same single amino acid substitution of Arg393 to Cys.

Amino Acid Sequence↗

PubMed1987

[Alteration in coagulation and fibrinolysis after burn injury and significance of anticoagulation therapy using heparin and antithrombin III concentrate].

Burn injury causes dynamic alterations in the coagulation and fibrinolysis, and so-called DIC often occurs in burned patients. In this study the clinical significance of heparin therapy combined with antithrombin III concentrate in animal experiments and clinical experiences were discussed. The changes in blood coagulation, fibrinolysis and kidney function and the effect of anticoagulation therapy using heparin were investigated in rabbits with third degree burn covering 35% of the total body surface area. The animals were subjected to determinations for various kidney function tests, blood coagulation and fibrinolysis tests, blood viscosity and hematocrit value before induction of the burn and after 8 and 24 hours respectively. Thirty rabbits were divided into a non-therapy group, an intravenous infusion group, a heparin group, an antithrombin III group, and an antithrombin III plus heparin group and the results were compared among them. Oliguria and a disturbance of kidney function were noted even at hour 8 after burn in the non-therapy group. In the intravenous infusion group urine volume was maintained well although the early stage of non-oliguric renal insufficiency was noted. The changes noted in the intravenous infusion group were prevented almost completely in the heparin group at hour 8, but FENa and CH2O were elevated at hour 24 probably because antithrombin III activity was depressed markedly. In the antithrombin III group and the antithrombin III plus heparin group, however, creatinine clearance was moderately elevated while FENa and CH2O remained unchanged as compared with the values before the burn. The antithrombin III plus heparin group showed slightly better results than the antithrombin III group in Ucr/Pcr ratio, creatinine clearance and CH2O. The results of the present study indicate that it is extremely effective to initiate appropriate fluid infusion therapy immediately after a burn and administer antithrombin III concentrate in combination with or without heparin for the prevention of acute renal insufficiency in patient with a severe burn. The effects of antithrombin III concentrate when used clinically were also discussed.

Adult↗

PubMed1984

Elimination of intravenously administered radiolabelled antithrombin III and heparin in humans.

Antithrombin III was purified from normal plasma by DEAE-Sephadex chromatography and heparin affinity chromatography; the protein was subsequently radiolabelled with 125I. 125I-antithrombin III alone and 125I-antithrombin III in the presence of high affinity 35S-heparin fractions were injected into normal humans. 125I-radiolabel and protein bound 35S-radioactivity were followed separately. In semilogarithmic plots 125I-antithrombin III disappeared according to a double exponential curve with a half-life in the second phase of 56.8 hr in the absence of heparin and of 33.7 hr in the presence of heparin. Protein bound 35S-radioactivity disappeared much faster than the 125I-radiolabel. These data support the concept that heparin disappears as free heparin from the equilibrium heparin - antithrombin III in equilibrium heparin + antithrombin III. Immuno-reactive antithrombin III decreased from 100% to 85-90% immediately after injection of 125I-antithrombin III in the presence of heparin and returned to normal values within 30 min. This suggests that antithrombin III is transiently sequestered, possibly in trimolecular complexes consisting of antithrombin III, heparin and either lipases or other vascular bound proteins.

Adult↗

PubMed1982

The active site of antithrombin. Release of the same proteolytically cleaved form of the inhibitor from complexes with factor IXa, factor Xa, and thrombin.

Reactions between near equimolar amounts of antithrombin and Factors IXa or Xa resulted in the formation of a free proteolytically modified, two-chain form of the inhibitor, in addition to the inactive antithrombin-protease complexes. The modified inhibitor produced by either enzyme was electrophoretically identical with that formed in the reaction with thrombin. As in the latter reaction, the formation of the modified antithrombin by Factor Xa was increased in the presence of heparin, while only small amounts were produced by Factor IXa both in the absence and presence of the polysaccharide. NH2-terminal sequence analyses of the isolated modified inhibitor formed by Factor Xa showed that a single Arg-Ser bond in the COOH-terminal end of the inhibitor had been cleaved. This cleavage site is identical with that identified in free thrombin-modified antithrombin. The purified antithrombin-Factor IXa and antithrombin-Factor Xa complexes were dissociated by ammonia or hydroxylamine into free enzyme and a modified two-chain form of the inhibitor. Electrophoresis studies and NH2-terminal sequence analyses showed that the modified antithrombin obtained from either complex was identical with that produced in free form by the two enzymes and also with the modified inhibitor that is released from the antithrombin-thrombin complex. The fact that identical results were obtained for the reactions between antithrombin and three enzymes with different specificities strongly suggests that the observed Arg-Ser cleavage site is the active site of antithrombin.

Amino Acid Sequence↗

PubMed1998

Antithrombin prevents endotoxin-induced pulmonary vascular injury by inhibiting leukocyte activation.

Replacement of antithrombin has proved to be effective for treating disseminated intravascular coagulation. The administration of antithrombin is also useful for preventing organ failure in animals challenged with endotoxin or bacteria, and it increases the survival rate of such animals. Since inhibition of coagulation abnormalities by heparin failed to prevent organ failure in animals challenged with bacteria, antithrombin might exert therapeutic effects independently of its anticoagulant effect. These therapeutic mechanisms of antithrombin have been explored by using animal models of septicemia. Antithrombin prevents pulmonary vascular injury by inhibiting leukocyte activation in rats challenged with endotoxin. A higher dose of antithrombin was required to prevent pulmonary vascular injury than was required to inhibit disseminated intravascular coagulation. This preventive effect of antithrombin is mediated by the promotion of endothelial release of prostacyclin, an inhibitor of leukocyte activation. An interaction between antithrombin and heparin-like glycosaminoglycans on the endothelial cell surface appears to be important for this effect. Heparin inhibits such therapeutic effects of antithrombin by preventing it from interacting with the cell surface heparin-like glycosaminoglycans. Since activated leukocytes are of critical importance in patients with sepsis-associated organ failure, this anti-inflammatory activity of antithrombin may explain why it can prevent organ failure as well as coagulation abnormalities in patients with sepsis.

6-Ketoprostaglandin F1 alpha↗

PubMed2006

Antithrombin significantly influences platelet adhesion onto immobilized fibrinogen in an in-vitro system simulating low flow.

BACKGROUND: Adhesion of platelets onto immobilized fibrinogen is of importance in initiation and development of thrombosis. According to a recent increase in evidence of a multiple biological property of antithrombin, we evaluated the influence of antithrombin on platelet adhesion onto immobilized fibrinogen using an in-vitro flow system. METHODS: Platelets in anticoagulated whole blood (29 healthy blood donors) were labelled with fluorescence dye and perfused through a rectangular flow chamber (shear rates of 13 s-1 to 1500 s-1). Platelet adhesion onto fibrinogen-coated slips was assessed using a fluorescence laser-scan microscope and compared to the plasma antithrombin activity. Additionally the effect of supraphysiological AT supplementation on platelets adhesion rate was evaluated. RESULTS: Within a first minute of perfusion, an inverse correlation between platelet adhesion and plasma antithrombin were observed at 13 s-1 and 50 s-1 (r = -0.48 and r = -0.7, p < 0.05, respectively). Significant differences in platelet adhesion related to low (92 +/- 3.3%) and high (117 +/- 4.1%) antithrombin activity (1786 +/- 516 U vs. 823 +/- 331 U, p < 0.05) at low flow rate (13 s-1, within first minute) have been found. An in-vitro supplementation of whole blood with antithrombin increased the antithrombin activity up to 280% and platelet adhesion rate reached about 65% related to the adhesion rate in a non-supplemented blood (1.25 +/- 0.17 vs. 1.95 +/- 0.4 p = 0.008, respectively). CONCLUSION: It appears that antithrombin in a low flow system suppresses platelet adhesion onto immobilized fibrinogen independently from its antithrombin activity. A supraphysiological substitution of blood with antithrombin significantly reduces platelet adhesion rate. This inhibitory effect might be of clinical relevance.

Journal Article↗

PubMed2006

Antithrombin can modulate coagulation, cytokine production, and expression of adhesion molecules in abdominal aortic aneurysm repair surgery.

We investigated the effects of antithrombin on coagulation, fibrinolysis, and production of cytokines and adhesion molecules in abdominal aortic aneurysm repair surgery. Sixteen patients for Y-shaped graft replacement of abdominal aortic aneurysm were divided into an antithrombin group and a control group. In the antithrombin group, 3000 U antithrombin was infused over 30 min before heparin administration and 24 h later. White blood cell counts, platelet counts, prothrombin time ratio, and serum concentrations of antithrombin, polymorphonuclear leukocyte elastase, interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor-alpha, and adhesion molecules, and variables of coagulation and fibrinolysis were measured before surgery, at the end of surgery, and 1 and 2 days after surgery. The antithrombin concentration decreased in the control group, whereas it increased in the antithrombin group with significant differences between the groups. Prothrombin time ratio, concentrations of d-dimer, thrombin-antithrombin complex, and intercellular adhesion molecule-1 increased only in the control group and polymorphonuclear leukocyte elastase, IL-6, tumor necrosis factor-alpha, and vascular cell adhesion molecule-1 increased in both groups. They were significantly less in the antithrombin group except for intercellular adhesion molecule-1. In conclusion, antithrombin could decrease hypercoagulation and inflammatory activation during abdominal aortic aneurysm surgery, which may decrease adverse events.

Aged↗

PubMed1991

The incidence of dysfunctional antithrombin variants: four cases in 210 patients with thromboembolic disease.

210 patients, with a history of venous thrombosis, have undergone prothrombotic investigations. In nine cases a consistent deficiency of antithrombin was identified. In five there was a reduction in the plasma antigenic concentration of antithrombin and in a further four cases deficiency was due to the presence of a dysfunctional antithrombin variant. The variants have all been characterized by DNA analysis and in three the mutations have been confirmed by peptide sequencing (antithrombin Basel (41 Pro to Leu). Hamilton (382 Ala to Thr). Cambridge I (384 Ala to Pro) and Cambridge II (384 Ala to Ser). The incidence of antithrombin deficiency in patients with a history of venous thrombosis has previously been quoted at between 2% and 3%: there is no published data available on the incidence of antithrombin variants. In our series 5% of patients who presented before the age of 40 years had antithrombin deficiency, and 2% of the total number of patients investigated had a dysfunctional variant. Our figures indicate that a significant number of cases of antithrombin deficiency are due to dysfunctional variants and that the true incidence of antithrombin deficiency in patients with a history of venous thrombosis is in the order of 5%.

Adult↗

PubMed1980

Heterogeneity of the "classical" antithrombin III deficiency.

We investigated two thrombophilic families with the "classical" type of antithrombin III deficiency, i.e., with a low antithrombin III level measured both by immunochemical and functional methods. We obtained different antithrombin III patterns in the plasma of the affected members of the two families with the modified two dimensional immunoelectrophoresis method (heparin in agarose). In one family, the electrophoretic mobility of the antithrombin III is identical with that of normal antithrombin III. In the other, the antithrombin III displayed a decreased electrophoretic mobility in the heparinized agarose gel. The relatively low affinity of this antithrombin III to heparin could be directly proved by the heparin-agarose affinity chromatography, too. These two different antithrombin III patterns were observed by other investigators at different families as well. On the basis of our simultaneous observations of these two families we propose a classification of the inherited congenital antithrombin III deficiencies.

Adolescent↗

PubMedDate not supplied

Antithrombin III levels in pregnancy induced hypertension.

BACKGROUND: Antithrombin III deficiency is common as well as severe in both consumptive coagulopathy and conditions such as pregnancy induced hypertension. We determined antithrombin III levels in women suffering from pregnancy induced hypertension to determine its usefulness in assessing severity of the disease and outcome. METHODS: Forty-five pregnant women with mild and severe forms of pregnancy induced hypertension and 18 women with normal pregnancies matched for gestational age formed the study population. Fasting blood samples were collected and the plasma separated. Antithrombin III levels were estimated by the kinetic Berichrom antithrombin III method. RESULTS: The mean (SD) antithrombin III levels [0.76 (0.233) IU/ml] were significantly lower in pregnancy induced hypertension compared to the control group [0.97 (0.234) IU/ml]. Low antithrombin III and high diastolic blood pressure (> 110 mmHg) were related to poor pregnancy outcome in primigravidae. CONCLUSION: Mean antithrombin III levels were lower in pregnancy induced hypertension compared to a control group of women especially those who were primigravidae and had a diastolic blood pressure > 110 mmHg. Since low antithrombin III levels and a high diastolic blood pressure result in adverse pregnancy outcome monitoring of antithrombin III levels in pregnancy induced hypertension may help in assessing foetal jeopardy.

Adult↗