Normal Antithrombin III Research Articles

Predictive Utility of Antithrombin III in Acute Kidney Injury in Living-Donor Liver Transplantation: A Retrospective Observational Cohort Study

IntroductionThis study was performed to determine the association between the serum level of antithrombin III (ATIII) level and the risk of acute kidney injury (AKI) in patients undergoing living-donor liver transplantation (LDLT). Patients and methodsA total of 591 patients undergoing LDLT were retrospectively investigated and 14 patients were excluded because of a history of kidney dysfunction or missing data; 577 patients were finally enrolled in the study. The study population was divided into normal and low ATIII groups. Data on all laboratory variables, including ATIII, were collected on the day before surgery. ResultsAfter LDLT, 143 patients developed AKI (24.8%). A lower ATIII was independently associated with postoperative AKI along with preoperative (diabetes mellitus) and intraoperative (mean heart rate, hourly urine output) factors. Based on the standard cutoff for normal ATIII (<70%), the probability of AKI was 2.8-fold higher in the low ATIII group than in the normal ATIII group. In addition, patients with low ATIII received blood transfusion products during the operation and underwent longer duration mechanical ventilation. ConclusionsPreoperative ATIII measurement will help improve risk stratification for postoperative AKI development in patients undergoing LDLT.

Continuous Antithrombin III Administration in Pediatric Veno-Arterial Extracorporeal Membrane Oxygenation.

The purpose of this retrospective case-control study is to determine the effect of continuous antithrombin III (ATIII) infusion on extracorporeal membrane oxygenation (ECMO) coagulation. All ECMO patients within the pediatric intensive care unit from January 2012 to July 2014 were included. Comparison was made between those who received continuous infusion ATIII through a standardized replacement protocol with historic controls receiving intermittent ATIII doses. Patients receiving the continuous infusion ATIII protocol spent more time in goal ACT range (71.9% vs 52.2%, p < 0.0001). Mean daily ATIII activity was also increased in study group (77.3% versus 68.6%, p = 0.04). No statistical differences in number of heparin dose changes per day (3 versus 3.22, p = 0.90) were present between the 2 groups. Only 28% of the historic controls receiving intermittent ATIII doses achieved normal ATIII activity as compared with 80% of study patients (p = 0.24). Maximum heparin dose was also lower in continuous infusion protocol group (p < 0.01). Compared with nonprotocolized intermittent dosing, the use of a continuous infusion ATIII protocol demonstrated increased time within goal ACT range at a lower heparin dose, no increase in hemostatic complications, and trends toward fewer heparin changes and lower blood product usage.

The effect of immunodepletion of antithrombin III on the response of rabbits to Russell's viper venom-induced activation of factor X.

Many years ago it was shown that an infusion of tissue factor (TF) into rabbits causing only limited consumption of factor X and prothrombin resulted in extensive consumption of fibrinogen. More recently it was shown that an injection of a concentration of the factor X-activating fraction of Russell's viper venom (RVV-X) depleting rabbits of factor X resulted in only minimal consumption of both plasma prothrombin and fibrinogen. We report here experiments in which rabbits depleted of antithrombin III (ATIII) to different degrees were infused over 4 hours with a concentration of RVV-X, causing consumption of about 60% of plasma factor X. Similar minimal mean falls in plasma prothrombin and fibrinogen levels were observed in control rabbits given nonimmune goat IgG and in rabbits immunodepleted with goat anti-rabbit ATIII IgG to about 40% of normal plasma ATIII activity. However, if rabbits were immunodepleted to about 10% to 20% of normal plasma ATIII, then mean consumption of prothrombin was increased modestly and, more impressively, mean consumption of plasma fibrinogen was increased markedly. Whereas limited amounts of thrombin generated on the surface of phospholipid vesicles by factor VIIa/ TF can trigger extensive intravascular coagulation in rabbits with normal plasma ATIII levels, limited amounts of thrombin generated by reactions triggered by factor Xa formed in fluid phase did so only after plasma ATIII levels were markedly depleted. A possible reason for this difference is discussed.

CLINICAL STUDY OF HEPATOCELLULAR CARCINOMA (HCC) ACCOMPANIED BY LIVER CIRRHOSIS WITH LOW CONCENTRATION OF ANTITHROMBIN III (AT-III) IN THE VENOUS BLOOD AND SIGNIFICANCE OF AT-III TREATMENT AFTER HEPATECTOMY

We have investigated the clinical charachteristic of hepatocellular carcinoma (HCC) with liver cirrhosis showing preoperative low concentration of antithrombin III (AT-III) in the venous blood, and the significance of AT-III treatment after hepatectomy to protect disseminated intravascular coagulation (DIC). This study involved 13 patients with HCC with liver cirrhosis undergoing hepatectomy in our department between September 1992 and March 1995. Six out of 13 patients revealed less than 60% of AT-III level (low AT-III group), and another 7 out of 13 patients showed more than 70% of the level (normal AT-III group). Low AT-III group was treated by injecting AT-III intravenously during 3 days immediately after the operation. In the low AT-III group, preoperative ICG 15 minutes and serum total bilirubin levels increased, and K-ICG and serum platelet levels decreased more than those of normal AT-III group. AT-III regimen after hepatectomy was effective to maintain venous AT-III levels, however, it is advisable hereafter to investigate furthermore the indication for the AT-III treatment because there was one case of the mortality death due to portal thrombus.

Partial glycosylation of antithrombin III asparagine-135 is caused by the serine in the third position of its N-glycosylation consensus sequence and is responsible for production of the .beta.-antithrombin III isoform with enhanced heparin affinity

Two antithrombin III (ATIII) isoforms occur naturally in human plasma. The alpha-ATIII isoform has four N-linked oligosaccharides attached to asparagines 96, 135, 155, and 192. The beta-ATIII isoform lacks carbohydrate on asparagine-135 (N135), which is near the heparin binding site, and binds heparin with higher affinity than does alpha-ATIII. Two isoforms are also produced when the normal human ATIII cDNA sequence is expressed in baculovirus-infected insect cells, and the recombinant beta' isoform similarly binds heparin with higher affinity than the recombinant alpha' isoform. Consensus sequences (CSs) of the ATIII N-glycosylation sites are N-X-S for 135 and N-X-T for 96, 155, and 192. On the basis of database and in vitro glycosylation studies suggesting that N-X-S CSs are utilized less efficiently than N-X-T CSs, we hypothesized that the beta-ATIII isoform might result from inefficient core glycosylation of the N135 N-X-S CS due to the presence of a serine, rather than a threonine, in the third position. ATIIIs with N-X-S, N-X-T, and N-X-A consensus sequences were expressed in baculovirus-infected insect cells. In contrast to the N-X-S sequence, which expressed a mixture of alpha' and beta' molecules, the N-X-T variant produced alpha' exclusively, while the N-X-A variant produced beta' exclusively. Thus, serine in the third position of the N135 CS is responsible for its "partial" glycosylation and leads to production of beta-ATIII.(ABSTRACT TRUNCATED AT 250 WORDS)

The N-terminal domain of antithrombin-III is essential for heparin binding and complex-formation with, but not cleavage by, α-thrombin

Normal and mutant forms of human antithrombin-III (AT-III) were synthesized in a cell-free system in order to identify putative functional domains required for heparin binding and complex-formation with alpha-thrombin. Heparin-Sepharose chromatography resulted in the elution of approx. 70% of cell-free-derived normal AT-III-(1-432)-polypeptide as a peak between 0.2 M- and 0.7 M-NaCl. The cell-free-derived normal AT-III also reacted with alpha-thrombin. Approx. 15% of this AT-III formed covalent complexes with alpha-thrombin in 2 min. Unfractionated heparin accelerated the rate of formation of such complexes. Two truncated forms of AT-III (amino acid residues 219-432 and 251-432), containing only the putative thrombin-binding domain, were synthesized independently in this cell-free system. These truncated AT-III polypeptides did not bind heparin and were unable to form stable covalent complexes with alpha-thrombin. However, both of these AT-III polypeptides were cleaved by alpha-thrombin, presumably at the reactive centre Arg-393-Ser-394. The formation of the disulphide bond between Cys-247 and Cys-430 in AT-III-(219-432)-polypeptide had no effect on the results obtained. Mutations in full-length AT-III at Cys-430 had no effect on the ability of AT-III to bind heparin. There was, however, a slight decrease in the formation of stable inhibitory complexes with alpha-thrombin. A cell-free-derived AT-III mutant, devoid of amino acid residues 41-49, which comprise heparin-binding region 1 of AT-III, had slightly decreased heparin binding compared with cell-free-derived normal AT-III-(1-432)-polypeptide. This mutant AT-III polypeptide was unable, however, to form a stable complex with alpha-thrombin. We conclude therefore that the N-terminal domain of AT-III is essential for both heparin binding and complex-formation with alpha-thrombin, but not for the cleavage of AT-III at its reactive centre by alpha-thrombin.

Antithrombin-III-Hamilton, Ala 382 to Thr: an antithrombin-III variant that acts as a substrate but not an inhibitor of alpha-thrombin and factor Xa

Antithrombin-III-Hamilton has been shown to be a structural variant of antithrombin-III (AT-III) with normal heparin affinity but impaired protease inhibitory activity. The molecular defect of AT-III-Hamilton is the substitution of Thr for Ala at amino acid residue 382. The plasma of affected individuals contains approximately equal quantities of normal AT-III and AT-III-Hamilton. When AT-III was isolated from the plasma of the propositus by heparin-Sepharose chromatography, it had identical mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to normal plasma-derived AT-III, under both reducing and nonreducing conditions. However, the AT-III-Hamilton species, separated from the propositus' normal AT-III by a combination of heparin-Sepharose and thrombin-Sepharose chromatography, had increased mobility on reductive SDS-PAGE compared with AT-III from the propositus isolated by heparin-Sepharose chromatography alone. Under nonreducing conditions this AT-III-Hamilton species had decreased mobility compared with AT-III from the propositus (or normal AT-III) isolated only by heparin-Sepharose chromatography. When incubated with either human alpha-thrombin or human factor Xa, this AT-III-Hamilton species was unreactive. Approximately 50% of the AT-III from the propositus isolated by heparin-Sepharose chromatography, when incubated with either human alpha-thrombin or factor Xa, did not form complex but was cleaved, presumably at the reactive center Arg393-Ser394. To further substantiate the biological behavior of this variant, AT-III- Hamilton polypeptides were synthesized in a cell-free system. This recombinantly produced AT-III-Hamilton, when incubated with either human alpha-thrombin or factor Xa, was cleaved by both these proteases, but did not show any complex formation. The results indicate that AT- III-Hamilton does not form a stable covalent inhibitory complex with these serine proteases but can be cleaved at the reactive center. Thus, the inhibition of serine proteases by their natural inhibitors (the serpins) involves at least two separate, but interrelated events; hydrolysis at the reactive center followed by complex formation. AT-III- Hamilton is capable of only the first of these events.

Antithrombin-III-Hamilton, Ala 382 to Thr: An Antithrombin-III Variant That Acts as a Substrate But Not an Inhibitor of α-Thrombin and Factor Xa

Antithrombin-III-Hamilton has been shown to be a structural variant of antithrombin-III (AT-III) with normal heparin affinity but impaired protease inhibitory activity. The molecular defect of AT-III-Hamilton is the substitution of Thr for Ala at amino acid residue 382. The plasma of affected individuals contains approximately equal quantities of normal AT-III and AT-III-Hamilton. When AT-III was isolated from the plasma of the propositus by heparin-Sepharose chromatography, it had identical mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to normal plasma-derived AT-III, under both reducing and nonreducing conditions. However, the AT-III-Hamilton species, separated from the propositus’ normal AT-III by a combination of heparin-Sepharose and thrombin-Sepharose chromatography, had increased mobility on reductive SDS-PAGE compared with AT-III from the propositus isolated by heparin-Sepharose chromatography alone. Under nonreducing conditions this AT-III-Hamilton species had decreased mobility compared with AT-III from the propositus (or normal AT-III) isolated only by heparin-Sepharose chromatography. When incubated with either human α-thrombin or human factor Xa, this AT-III-Hamilton species was unreactive. Approximately 50% of the AT-III from the propositus isolated by heparin-Sepharose chromatography, when incubated with either human α-thrombin or factor Xa, did not form complex but was cleaved, presumably at the reactive center Arg393-Ser394. To further substantiate the biological behavior of this variant, AT-III-Hamilton polypeptides were synthesized in a cell-free system. This recombinantly produced AT-III-Hamilton, when incubated with either human α-thrombin or factor Xa, was cleaved by both these proteases, but did not show any complex formation. The results indicate that AT-III-Hamilton does not form a stable covalent inhibitory complex with these serine proteases but can be cleaved at the reactive center. Thus, the inhibition of serine proteases by their natural inhibitors (the serpins) involves at least two separate, but interrelated events; hydrolysis at the reactive center followed by complex formation. AT-III-Hamilton is capable of only the first of these events.

Site-directed mutagenesis of alanine-382 of human antithrombin III

Antithrombin III Hamilton is a structural variant of antithrombin III (AT-III) with normal heparin affinity but impaired scrine protcase inhibitory activity. The molecular defect of AT-III-Hamilton is a substitution of threonine for alanine at amino acid residue 382. Recently it has been shown that both plasma-derived and cell-free-derived AT-III-Hamilton polypeptides act as substrates rather than inhibitors of thrombin and factor Xa. In the present study, the cell-free expression phagemid vector pGEM-32f(+)-AT-III 1–433 was mutated at amino acid residue 382 of AT-III to generate 7 cell-free-derived variants. All these cell-free-derived AT-III variants were able to bind heparin as effectively as cell-free-derived normal AT-III. In terms of α-thrombin inhibitory activity each variant reacted differently. Variants could be grouped into 3 categories with respect to thrombin-AT-III complex formation: (1) near normal activity (glycine, isolcucine, leucine, valine): (2) low activity (threonine, glutamine): (3) no detectable activity (lysine). These data suggest that mutations at position 382 of AT-III may have a variable effect on protease inhibitory activity, depending on either the stability of the P 12-P 9 region of the exposed loop of AT-III, or the inability of the amino acid residue at position 382 to interact with a conserved hydrophobic pocket consisting of phenylalanine (at positions 77,221 and 422) and isolcucine (position 412) residues.

Antithrombin III in critically ill patients

To assess the role of antithrombin III (ATIII) in the thrombotic complications of acutely ill patients who suffered from septicemia or trauma, with or without evidence of acute lung injury, we measured the plasma concentration of ATIII-related antigen (ATIII:Ag) in 146 patients with acute lung injury and in 43 critically ill patients without lung injury. We found plasma ATIII:Ag levels of both groups of acutely ill patients to be significantly lower than those of normal subjects (n = 21). The plasma ATIII:Ag levels of patients with acute lung injury, however, were significantly higher than those without lung injury ( P < .01). By separating post-trauma acutely ill patients with lung injury from those with septicemia, we noted that their plasma ATIII:Ag levels were identical to those of normal subjects despite activation of blood coagulation. This finding led us to examine ATIII functional activity (ATIII:Fn) and search for ATIII-enzyme(s) complexes in 46 patients with acute lung injury (30 patients with sepsis and 16 post-trauma patients) and in 12 acutely ill patients without lung injury (eight patients with sepsis and four post-trauma patients). These 58 patients were representative of the groups studied and had no evidence of hepatic or renal dysfunction. We found significantly reduced ATIII:Ag and ATIII:Fn in septic patients, with or without lung injury, as compared with the normal levels ( P < .05). After trauma, patients with or without lung injury had normal ATIII:Ag, but the ATIII:Fn levels were disproportionately lower. Following trauma, the ATIII:Ag/ATIII:Fn ratio was significantly higher than in septicemia patients or in normal patients. Patients who died from septicemia and post-trauma had higher ATIII:Ag to ATIII:Fn ratios, while surviving patients had ATIII:Ag to ATIII:Fn ratios closer to normal. In addition, in all post-trauma or septicemia patients, there was evidence of ATIII-enzyme(s) complex formation by cross-immunoelectrophoresis despite ATIII levels and the presence or absence of acute lung injury. High ATIII:Ag to ATIII:Fn ratios and the presence of circulating ATIII:enzyme(s) complexes were associated with high mortality. The ATIII alterations, however, did not allow us to determine the presence of acute lung injury. The ATIII changes observed in our patients appeared to be primarily influenced by the differing pathways of blood activation that occurred in septicemia and trauma.

Identification and characterisation of an antithrombin III mutant (AT Dublin 2) with marginally decreased heparin reactivity

The antithrombin III (ATIII) isoform patterns of plasma and serum samples from cancer patients and controls were analysed by isoelectric focusing and immunoblotting. A novel ATIII banding pattern was identified in two individuals: a patient with breast carcinoma who developed deep venous thrombosis and a blood donor. Family studies in the patient showed the abnormal pattern to be due to a mutant form of ATIII (AT Dublin 2). The coagulation properties of AT Dublin 2 heterozygotes were normal. Immunologic and activity levels of ATIII, measured by standard techniques, were normal. Mutant plasma ATIII showed reduced thrombin reactivity at low concentrations of thrombin and demonstrated decreased reactivity with heparin over a range of heparin concentrations. This was confirmed using a modified ATIII heparin cofactor activity assay with varying heparin concentrations. The abnormal ATIII was also found to elute from heparin agarose at a lower ionic strength than normal ATIII. Two dimensional gel electrophoresis showed the abnormal ATIII to have similar molecular size distribution to normal ATIII. Neuraminidase treatment of normal and mutant plasma reduced the ATIII isoforms to one in both samples. The possible role of AT Dublin 2 in predisposing to hypercoagulation is discussed.

Quantitative and qualitative congenital deficiency of antithrombin III: A new molecular variant called at III - Barcelona 2

A Spanish family with a quantitative-qualitative antithrombin III(ATIII) deficiency and thrombotic tendency is reported. The qualitative defect was suggested by the crossed immunoelectrophoresis(CIE) in the presence of heparin in plasma of all those affected. However, the crossed immunoelectrofocusing(CIEF) showed the same AT-III pattern in controls and affected members. Two populations of ATIII were detected by affinity chromatography on heparin-sepharose from affected members'plasma. The ATIII unbound to sepharose beads was devoid of heparin cofactor activity and showed a lack of anodal migration in CIE in the presence of heparin. The ATIII eluted corresponded to normal ATIII. Our data supports the view that an abnormal ATIII molecule is present in all affected family members in the heterozygous state. This is the first reported ATIII variant in which a molecular abnormality produces a lack of affinity for heparin but no changes in its isoelectric point. This familial ATIII deficiency was named ATIII- Barcelona 2.

AT III Barcelona: A Familial Quantitative-Qualitative AT III Deficiency

A quantitative and qualitative deficiency of antithrombin III (ATIII) was found in four members of a Spanish family with thrombotic tendency. In all affected members, levels of ATIII antigen and activity (heparin cofactor activity) were reduced to 50% of the normal range. When crossed immunoelectrophoresis (CIE) was performed in the presence of heparin, an abnormal slow-moving peak was found. Crossed immunoelectrofocusing (CIEF) from normal and affected individuals showed that normal ATIII migrated between pH 4.9-5.3 while the ATIII under study was asymmetrically distributed between two pH ranges: 4.9-5.3 and 4.6-4.8. Affinity adsorption of affected members' plasma to heparin-sepharose beads revealed one population of ATIII in the supernatant corresponding to the abnormal ATIII, devoid of heparin cofactor activity and showing a peak between pH range: 4.6-4.8 in CIEF. Our data supports the view that a quantitative-qualitative deficiency was present in the heterozygous state in all the affected family members. Both normal and abnormal ATIII were present in plasma of the affected individuals. This abnormal ATIII was characterized by a lack of affinity for heparin. This familial ATIII deficiency was named ATIII Barcelona.

Antithrombin III (ATIII) activity in plasmas from normal and diseased horses, and in normal canine, bovine and human plasmas.

Plasma Antithrombin III (ATIII) activity was quantitated in 24 clinically normal Standardbred/Thoroughbred horses using a clotting time technique. ATIII activity ranged from 80 to 106% of the pooled reference standard plasma, with a mean of 94%. Horses presenting with impaction or spasmotic colic (n=17) had normal plasma ATIII activity, while 15 horses presenting with acute diarrhea/colitis had significantly lower plasma ATIII activity with a mean of only 74% of the reference plasma. Seven horses presenting with liver disease had significantly higher plasma ATIII activity with a range of 127 to 177% of the pooled reference plasma. Fifty-seven equine plasmas were retested using a rapid chromogenic substrate technique for quantitating plasma ATIII activity. A good correlation (r =+0.83) existed between clotting time and chromogenic determinations of ATIII. Pooled normal canine, human and bovine plasmas had only 65, 62 and 79%, respectively, of the ATIII activity of the equine reference plasma.

Antithrombin-III Denver, a reactive site variant.

Antithrombin-III Denver is a mutant protein which differs from the normal in being defective in serine protease binding (Sambrano, J. E., Jacobson, L. J., Reeve, E. B., Manco-Johnson, M. J., and Hathaway, W. E. (1986) J. Clin. Invest. 77, 887-893). It was isolated from the blood of an individual heterozygous for the abnormal gene by: affinity separation on heparin-Sepharose to obtain an antithrombin fraction, and gel filtration of the species present following complexing of the antithrombin fraction with a small excess of thrombin. The reduced, S-carboxymethylated protein formed a mixture of soluble tryptic peptides which was fractionated on Vydac C18. A single, unique peptide not present in a parallel experiment with normal antithrombin-III was isolated. This peptide was identified by sequence analysis and synthesis to correspond to residues 394-399 in the known sequence of the inhibitor, with leucine replacing reactive site P'1 residue Ser394. Although chromatograms of the tryptic peptides from the normal and mutant proteins were otherwise indistinguishable, the existence of additional residue replacements is not excluded. Measurements of the rate of thrombin binding by the mutant protein with p-aminobenzamidine as a fluorescent indicator showed that the second-order rate constant is reduced drastically. Meaningful measurements with the mutant protein could only be made in the presence of heparin and revealed a reduction of about 4000-fold in the rate constant.

Abnormal antithrombin III with defective serine protease binding (antithrombin III "Denver").

A hereditary (three family members) deficiency of antithrombin III (AT-III) in which AT-III antigen (AT-III ag) is normal in spite of low heparin cofactor and antithrombin activity is described. Plasma levels were: AT-III ag, 0.92-0.96 U/ml; AT-III heparin cofactor activity, 0.54-0.62 U/ml; progressive antithrombin activity index, 0.13-0.18; anti-Xa activity, 0.50-0.56 U/ml. Plasma crossed immunoelectrophoresis (CIE) patterns performed with and without added heparin were normal, but serum CIE revealed a decreased complex peak. Purification of the patient's plasma AT-III by heparin-sepharose affinity chromatography showed a normal protein recovery and elution profile, but the purified AT-III fraction showed only 50% of the normal progressive thrombin neutralization and anti-Xa activity. When thrombin-antithrombin (TAT) complexes were formed by incubating with excess thrombin, SDS-polyacrylamide gel electrophoresis (PAGE) analysis revealed that half the patient AT-III formed TAT complexes while the remainder migrated as free AT-III. All the control AT-III formed TAT complexes. The patient's nonreacting AT-III (AT-III "Denver"), isolated by affinity chromatography, showed CIE and SDS-PAGE migration patterns characteristic of normal AT-III but failed to bind thrombin or Xa. Calculations from turnover studies in one patient and normal subjects with autologous 131I-AT-III suggested that AT-III "Denver" is removed from the plasma slightly more rapidly than normal. These studies indicate that the patients' variant AT-III molecule was characterized by normal heparin interaction but defective binding and inhibition of thrombin and Xa. These characteristics allow isolation of the nonreactive variant molecule by heparin-sepharose affinity chromatography.

Intron structure of the human antithrombin III gene differs from that of other members of the serine protease inhibitor superfamily.

Antithrombin III (ATIII) plays an integral role in the coagulation system by inhibiting thrombin and several other activated clotting factors. Inherited deficiency of ATIII is quite common and can result in life-threatening thrombotic complications. In order to understand the basis of ATIII deficiency, we have isolated and characterized the normal human ATIII gene from a recombinant Charon 4A bacteriophage genomic library. The ATIII gene contains six exons and five introns distributed over approximately 19 kilobases of DNA. The positions of introns in the ATIII gene were compared with other members of the serine protease inhibitor family which share 17-31% amino acid homology. When aligned to achieve maximal protein homology, only one of the ATIII introns corresponded to the four introns of rat angiotensinogen or human alpha 1-antitrypsin. Similarly, only one ATIII intron was homologous to the seven introns of chicken ovalbumin. We present two testable models to explain the discrepancy in intron positions among members of the serine protease inhibitor superfamily of genes.

Antithrombin III Deficiency: Decreased Synthesis of a Biochemically Normal Molecule

A 29-yr-old white female has suffered from recurrent venous thromboses over the last 12 yr. Plasma antithrombin III (AT-III) levels were 48% of normal by immunoelectrophoresis and 56% by chromogenic assay. Three of four siblings and the father had similar AT-III levels without associated venous thromboses. Heparin-Sepharose chromatography demonstrated normal behavior of the patient's AT-III. Her purified AT-III could not be distinguished from AT-III purified from a normal control either by SDS polyacrylamide gel electrophoresis or by crossed immunoelectrophoresis, and the heparin cofactor activity and the progressive antithrombin activity of both AT-III samples were identical. Turnover studies were made in the patient using her own purified AT-III labeled with 131I, (*I). The results did not differ significantly from studies made with autologous *I-AT-III in two normal control women. Her fractional breakdown rate of 0.54 total plasma AT-III per day compared with 0.45 and 0.52 in the controls. These studies indicate that the patient synthesizes a normal AT-III molecule at half normal rates.

Antithrombin III deficiency: decreased synthesis of a biochemically normal molecule

A 29-yr-old white female has suffered from recurrent venous thromboses over the last 12 yr. Plasma antithrombin III (AT-III) levels were 48% of normal by immunoelectrophoresis and 56% by chromogenic assay. Three of four siblings and the father had similar AT-III levels without associated venous thromboses. Heparin-Sepharose chromatography demonstrated normal behavior of the patient's AT-III. Her purified AT- III could not be distinguished from AT-III purified from a normal control either by SDS polyacrylamide gel electrophoresis or by crossed immunoelectrophoresis, and the heparin cofactor activity and the progressive antithrombin activity of both AT-III samples were identical. Turnover studies were made in the patient using her own purified AT-III labeled with 131I, (*I). The results did not differ significantly from studies made with autologous *I-AT-III in two normal control women. Her fractional breakdown rate of 0.54 total plasma AT- III per day compared with 0.45 and 0.52 in the controls. These studies indicate that the patient synthesizes a normal AT-III molecule at half normal rates.

Metabolism of antithrombin III in cirrhosis and carcinoma of the liver.

1. The metabolism of human antithrombin III (ATIII) was studied by using 125I-labelled tracer. 2. The plasma half-life (t0.5) was 2.71 +/- 0.26 days in normal subjects and was similar in patients with cirrhosis or primary carcinoma of liver. 3. Patients with cirrhosis had low ATIII levels, decreased intravascular mass, total body mass and decreased absolute catabolic rate, suggesting decreased synthesis. The positive correlation of ATIII level with fractional catabolic rate (K10) indicated that the decreased catabolic might exert a positive inhibition on ATIII production. 4. These abnormalities were more exaggerated in patients with macronodular cirrhosis associated with hepatitis surface antigen or in those with ascites. 5. In cirrhotic patients with ascites an additional extravascular pool of ATIII was present which did not turn over at the same rate as the intravascular pool. 6. Patients with primary carcinoma of liver had moderately low ATIII, but normal intravascular mass and total body mass because of the increased plasma volume and normal absolute catabolic rate. 7. The negative correlation of ATIII levels with K10 suggested that the low levels could be due to increased catabolism or consumption. 8. One patient with disseminated malignancy and active superficial thrombophlebitis had normal ATIII metabolism.