An Assay of the Antithrombotic Action of Warfarin: Its Correlation with the Inhibition of Stasis Thrombosis in Rabbits

1978 ◽  
Vol 40 (02) ◽  
pp. 486-498 ◽  
Author(s):  
Stanford Wessler ◽  
Sanford N Gitel ◽  
Harry Bank ◽  
Uri Martinowitz ◽  
Ronald C Stephenson
Keyword(s):  
Venous Thrombosis ◽  
Vitamin K ◽  
Inhibitory Activity ◽  
Reaction Rate ◽  
Antithrombin Iii ◽  
Factor Ix ◽  
Factor X ◽  
Similar Increase ◽  
Antithrombotic Effect ◽  
And Control

SummaryNo assay of the antithrombotic action of warfarin has been available. Experiments were performed to determine whether Xa inhibitory activity - the reaction rate between activated factor X (Xa) and antithrombin III - could serve this function. 105 warfarin-treated patients demonstrated a significant 18% increase in Xa inhibitory activity compared to 51 controls, p <0.001, without any correlation between this activity and the prothrombin times in the treated patients. A similar increase in Xa inhibitory activity was obtained in rabbits treated with 2 mg of warfarin per day compared to control animals, p <0.001. Employing an assay which routinely produced venous thrombosis after clotting proteases were infused into warfarin-treated and control rabbits, three observations were made. 1. The extent of stasis thrombosis induced by injection of thrombin, Xa or activated factor IX, was significantly reduced in warfarin-treated rabbits compared to control animals, independent of alteration in the four established vitamin K-dependent zymogens. 2. In the rabbit, significant changes in prothrombin times and prothrombin and factor X activities preceded by 5 days both the increase in Xa inhibitory activity and the antithrombotic effect which became significant on the sixth day. 3. The correlation between Xa inhibitory activity of warfarin-treated rabbits and the extent of stasis thrombosis induced by Xa was significant, p<0.05. Xa inhibitory activity is one measure of the antithrombotic action of warfarin.

Factor X Levels, Polymorphisms in the Promoter Region of Factor X, and the Risk of Venous Thrombosis

2001 ◽  
Vol 85 (06) ◽  
pp. 1011-1017 ◽  
Author(s):  
Swibertus Poort ◽  
Hans Vos ◽  
Frits Rosendaal ◽  
Rogier Bertina ◽  
Marieke de Visser
Keyword(s):  
Risk Factor ◽  
Venous Thrombosis ◽  
Vitamin K ◽  
Promoter Region ◽  
Genotypic Variation ◽  
Coagulation Factor ◽  
Premenopausal Women ◽  
Factor Ix ◽  
Factor X ◽  
Increased Risk

SummaryElevated levels of procoagulant proteins factor II, factor VIII, factor IX, factor XI and fibrinogen are associated with an increased risk of venous thrombosis. In a population-based case-control study on venous thrombosis (Leiden Thrombophilia Study, LETS) we investigated whether elevated coagulation factor X (FX) levels are a risk factor for venous thrombosis and whether FX levels are determined by polymorphisms in the promoter region of the FX gene. We found that subjects with high FX levels (above the 90th percentile, ≥ 126 U/dl) had a 1.6-fold increased risk of venous thrombosis. The highest risk (OR = 4.3, 95% confidence interval: 1.5-12) was found in the subgroup of premenopausal women who are not using oral contraceptives. However, these estimated risks disappeared after adjustment for other vitamin K-dependent coagulation factors II, VII and IX. To study the influence of genotypic variation on plasma FX levels we assessed four polymorphisms in the promoter region of the FX gene: a TTGTGA insertion between position -343A and -342G, a C/T polymorphism at position -222, a C/A polymorphism at position -220 and a C/T polymorphism at position -40. No relationship between these investigated genotypes and FX levels was observed. We conclude that high FX levels predict risk of thrombosis, but are not a risk factor for venous thrombosis when the levels of other vitamin K-dependent proteins are taken into account.

scholarly journals Dose-dependent antithrombotic effect of warfarin in rabbits

Blood ◽  
1983 ◽  
Vol 61 (3) ◽  
pp. 435-438 ◽  
Author(s):  
SN Gitel ◽  
S Wessler
Keyword(s):  
Vitamin K ◽  
Coagulation Factors ◽  
Progressive Increase ◽  
Drug Dose ◽  
Mean Value ◽  
Factor X ◽  
Antithrombotic Effect ◽  
Tissue Thromboplastin ◽  
Dose Dependent Decrease ◽  
Dose Dependent

Abstract One-hundred and fifty-one rabbits, divided into controls and animals treated with varying daily doses of warfarin, were subjected to the stasis assay, and the amount of thrombosis quantitated after intravascular coagulation was initiated either by activated factor X or tissue thromboplastin. Following 8–10 days of warfarin administration, there was a significant dose-dependent decrease in the vitamin-K- dependent coagulation factors paralleled by an increase in the prothrombin time ratio. Whether thrombosis was initiated by activated factor X or tissue thromboplastin, there was, with increasing drug dose, a progressive increase in the inhibition of stasis thrombosis. This significant antithrombotic effect occurred even when the vitamin-K- dependent coagulation activities were at a mean value of 50%.

scholarly journals The anticoagulant mechanism of action of heparin in contact-activated plasma: inhibition of factor X activation

Blood ◽  
1985 ◽  
Vol 65 (5) ◽  
pp. 1226-1231 ◽  
Author(s):  
TB McNeely ◽  
MJ Griffith
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Coagulation Factors ◽  
Factor Ix ◽  
Factor X ◽  
Clotting Time ◽  
Intrinsic Pathway ◽  
Blood Coagulation Factors ◽  
Factor Ixa ◽  
Factor X Activation

Abstract The effects of heparin on the activation of blood coagulation factors IX and X in contact-activated plasma were determined in the present study. In the presence and absence of 0.5 U/mL heparin, the amounts of factor IX that were cleaved 30 minutes after the addition of calcium and phospholipid to plasma exposed to glass (ie, contact activated) were essentially identical. In the absence of heparin, however, the plasma clotting time was between three and four minutes, while in the presence of heparin, the clotting time was approximately 40 minutes. More factor IXa was inhibited by antithrombin III in the presence of heparin than in its absence, but factor IXa levels sufficient for factor X activation appeared to be present in the heparinized plasma. Neither an increase in factor Xa nor a decrease in factor X was detected, however, in heparinized plasma. We conclude that the step in the intrinsic pathway of coagulation that is inhibited in the presence of heparin is at the level of factor X activation.

scholarly journals Activated clotting factors in factor IX concentrates

Blood ◽  
1979 ◽  
Vol 54 (5) ◽  
pp. 1028-1038 ◽  
Author(s):  
MB Hultin
Keyword(s):  
Antithrombin Iii ◽  
Initial Rate ◽  
Factor Xa ◽  
Factor Ix ◽  
Clinical Settings ◽  
Factor X ◽  
Clotting Factors ◽  
Factor Ixa ◽  
Human Factor Ix ◽  
Factor X Activation

Abstract The precise quantitation of activated factors in human factor IX concentrates has been accomplished with the use of recently developed, specific assays for factors IXa, Xa, and thrombin. The assay for factor IXa, which measures the initial rate of 3H-factor-X activation, was shown to be specific for factor IXa in the concentrates. Activated factor IX concentrates contained 1.0–2.3 microgram/ml of factor IXa; whereas the assays of unactivated concentrates were negative (less than 0.2 microgram/ml). The assays of factor Xa and thrombin, which measure the initial rate of p-nitroaniline release from S-2222 and S-2238, respectively, showed similar small amounts of factor Xa (4–34 ng/ml) and thrombin (12–76 ng/ml) in the activated and unactivated concentrates. The nonactivated partial thromboplastin time of the concentrates correlated significantly with the factor IXa content, but not with factor Xa or thrombin. Antithrombin III antigen in 3 of 4 concentrates was several-fold higher than antithrombin III activity, suggesting the presence of antithrombin III complexed with activated factors. These results support the hypothesis that the degree of activation of factor IX concentrates is related primarily to the concentration of factor IXa, which may be responsible for the thrombogenicity of these concentrates in some clinical settings.

Genetic Polymorphism of Factor IX Gene in Greek Patients with Thrombophilia.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4121-4121
Author(s):  
Pantelis P.E. Makris ◽  
Michel M. Iskas ◽  
Rigini R. Papi ◽  
Dimitrios D.K. Kiriakidis
Keyword(s):  
Vitamin K ◽  
Polyacrylamide Gel Electrophoresis ◽  
Control Sample ◽  
Coagulation Factor ◽  
Factor Ix ◽  
University Hospital ◽  
Activate Factor ◽  
Factor X ◽  
Coagulation Factor Ix ◽  
Pcr Products

Abstract Introduction. Coagulation factor IX plays an important intermediate role in the activation of blood coagulation. It is located within the blood plasma as a zymogen, in its inactivated state. Factor IX is dependent on the presence of Vitamin K. The structure of factor IX closely resembles the structures of many other Vitamin K dependent plasma proteins, such as prothrombin, factor X and protein C. After being activated, Factor IX forms a complex with calcium ions, membrane phospholipids and coagulation factor VIIIa to activate factor X. The exact locus of the coagulation factor IX gene was found to exist in the Xq26-q27 region of the X chromosome. The FIX gene spans 34 kb and contains eight exons. Over 300 different mutations have been identified in the FIX gene, all of which result in the production of inactive FIX, causing hemophilia B. Aim. In this study we searched for mutations in the FIX gene which result in an increased activity of FIX thus being the cause of thrombophilia syndromes. Material: A total of 108 individuals from unrelated families were involved in this study, presenting thrombophilic syndromes. A control sample from a healthy non-thrombophilic individual was also used. Total DNA from the above individuals was supplied to us by the Haemostasis and Thrombosis Unit of AHEPA University Hospital, Thessaloniki, Greece. According to HAT (Heparin Antithrombin Test, Makris, Van Dreden 1998) method a mixture of human antithrombin and heparin is added in the plasma and partial thromboplastin time is estimated. 97% of normal individuals exhibit prolonged time values in this test, whereas in our patients the time was significantly reduced. However, after the addition of recombined human FIX (rhFIX) in the mixture, prolongation of PTT is noted. Methods: The promoter region and the eight exons of the FIX gene were amplified by PCR using seven labelled primer pairs specific for these regions, that were described previously in literature. The amplification reactions were performed in a MJ Research P200 thermal cycler while the Tm of each primer pair was optimised as shown in the table. PCR products were analyzed using LI-COR DNA analyzer which is based on fragment separation by polyacrylamide gel electrophoresis. With this method PCR products presenting up to a 1 bp difference in their molecular weight create distinct bands on the gel and thus an insertion, or deletion of a base can be detected. However, no such differentiation was present among the samples examined. Assuming that the potential mutations could involve point mutations and thus be undetectable by the above method, the samples were sequenced and compared with the control. Sequencing the promoter and the 8 exons sites of the FIX gene of the most high risk cases. A point mutation was detected in four of the samples. The mutation was a single base change (ACT →GCT) located at the 21975 bp of the FIX gene, in exon 6. This mutation causes a significant change, replacing the Thr194 residue with an Ala residue (T194A). The sequencing pattern of one of these patients and the control is shown in the figure. Figure Figure

scholarly journals Pharmacokinetic and antithrombotic properties of two pentasaccharides with high affinity to antithrombin III in the rabbit: comparison with CY216

Blood ◽  
1994 ◽  
Vol 84 (8) ◽  
pp. 2571-2577 ◽  
Author(s):  
D Carrie ◽  
C Caranobe ◽  
S Saivin ◽  
G Houin ◽  
M Petitou ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Antithrombin Iii ◽  
Subcutaneous Administration ◽  
Inhibitory Effect ◽  
Low Molecular Weight ◽  
Antithrombotic Effect ◽  
High Affinity ◽  
Antithrombotic Effects ◽  
Antifactor Xa ◽  
Inhibitory Agents

This study compares the pharmacokinetic and the antithrombotic properties of two pentasaccharides with high affinity to antithrombin III with those of a conventional low molecular weight heparin, CY216, in the rabbit. On a weight basis, SR 90107A/ORG 31540 (natural pentasaccharide [NPS]) and SR 80027A/ORG 31550 (sulfated pentasaccharide [SPS]) were, respectively, 4.7 and 26 times more potent antifactor Xa inhibitory agents than CY216. They were devoid of antithrombin activity, whereas the antifactor Xa/antithrombin ratio of CY216 was 3.8. After bolus intravenous administration, the clearance (mL/kg/h) of CY216 decreased from 91 +/- 27 for the dose of 12.5 U/kg to 49 +/- 14 for the dose of 50 U/kg and then remained constant up to the highest dose tested (500 U/kg). The clearance of NPS was unrelated to the dose and comparable to that of CY216 over 50 U/kg, whereas that of SPS was 10 times lower. Consistent results were observed after continuous intravenous infusions for 9 hours and subcutaneous administration. The duration of the antithrombotic effect was compared after a single subcutaneous injection of 250 U/kg of either compound in the stasis-Wessler model using human serum as thrombogenic stimulus. Two hours after the injection, the three compounds provided a thrombus prevention of greater than 95% and mean plasma activities of 0.8, 0.9, and 1.9 U/mL for CY216, NPS, and SPS, respectively. Twelve hours after injection, the antithrombotic effects of CY216 and NPS had totally vanished, whereas that of SPS was 68%. At that time, the plasma anti-Xa activities were less than 0.06 U/mL for CY216 and NPS, but 1.1 U/mL for SPS. For the latter compound, significant antithrombotic effects and detectable anti-Xa activities were still recorded 48 hours after the injection. The antithrombotic potency of the three compounds was also compared as their ability to inhibit the growth of a standardized venous thrombosis during 4 hours. The lowest total doses providing the maximum inhibitory effect were 3,125, 1,428, and 62 micrograms/kg for CY216, NPS, and SPS, respectively. These doses generated mean steady state antifactor Xa activities of 1.06, 1.5, and 1.2 anti-Xa U/mL, respectively. These observations indicate that the amplification mechanisms triggered by thrombin bound to fibrin and leading to the generation of new thrombin are essential to ensure venous thrombosis growth and that these mechanisms may be efficiently inhibited by pure antifactor Xa targeting agents.

The Inhibitor of Prothrombin Conversion in Plasma of Patients on Oral Anticoagulant Treatment

1981 ◽  
Vol 45 (03) ◽  
pp. 237-241 ◽  
Author(s):  
R M Bertina ◽  
M E J Westhoek-Kuipers ◽  
G H J Alderkamp
Keyword(s):  
Vitamin K ◽  
Spectrophotometric Assay ◽  
Factor Ix ◽  
Factor Vii ◽  
Factor X ◽  
Dilution Curve ◽  
Anticoagulant Treatment ◽  
Oral Anticoagulant Treatment ◽  
Coagulation Assays ◽  
Factor Ii

SummaryPooled plasma of patients under stable oral anticoagulation has been analysed with respect to the presence of the vitamin-K dependent factors (factors II, VII, IX and X). Of all factors 1.5-2 times more antigen than procoagulant activity was present. The concentration of factors II, X (measured spectrophotometrically) and VII is about 0.25 U/ml while factor IX is slightly higher. Coagulation assays of factor X always gave lower values than the spectrophotometric assay. This discrepancy was not influenced by the removal of either factor II-factor VII- or factor IX antigen. However, when the factor X antigen was replaced by normal factor X, all factor X assays gave identical results, indicating that PIVKA X is responsible for these discrepancies. Using the technic of the Thrombotest-dilution curve it was shown that PIVKA X is the factor that causes the abnormal prolongation of ox-brain prothrombin time in these plasmas.

scholarly journals Activation of human factor VII by activated factors IX and X

Blood ◽  
1982 ◽  
Vol 60 (5) ◽  
pp. 1143-1150 ◽  
Author(s):  
DR Masys ◽  
SP Bajaj ◽  
SI Rapaport
Keyword(s):  
Human Factors ◽  
Factor Viii ◽  
Active Site ◽  
Human Factor ◽  
Antithrombin Iii ◽  
Factor Ix ◽  
Factor Vii ◽  
Activate Factor ◽  
Factor X ◽  
Activated Factor Vii

Factor VII clotting activity increases about five-fold when blood is clotted in glass. Prior studies suggested that this results from activation induced by activated factor IX (IXa). However, in purified systems containing phospholipid and calcium, activated factor X (Xa) is known to activate factor VII rapidly. Therefore, we studied activation of factor VII by IXa and X, in systems using purified human factors. Concentrations of IXa and Xa were calculated from total activated protein concentrations rather than from active site concentrations. In the presence of phospolipid and calcium, both IXa and Xa activated factor VII 25-fold; however, Xa was roughly 800 times more efficient than IXa. Without added phospholipid, activation of factor VII by both Xa and IXa was markedly slowed, and Xa was roughly 20 times more efficient than IXa. When both phospholipid and calcium were omitted, activation of factor VII by either enzyme was negligible. Adding normal prothrombin, but not decarboxylated prothrombin, substantially slowed activation of factor VII by both Xa and IXa. Adding thrombin-activated factor VIII and antithrombin-III did not change rates of factor VII activation by either enzyme. These results from purified systems do not provide an explanation for the prior data from plasma systems.

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