The relationship between the hemorrhagic and antithrombotic properties of low molecular weight heparin in rabbits

Blood ◽  
1982 ◽  
Vol 59 (6) ◽  
pp. 1239-1245 ◽  
Author(s):  
CJ Carter ◽  
JG Kelton ◽  
J Hirsh ◽  
A Cerskus ◽  
AV Santos ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Blood Loss ◽  
Ex Vivo ◽  
Test System ◽  
Venous Stasis ◽  
Low Molecular Weight ◽  
Antithrombotic Effects ◽  
Induced Aggregation

We have compared the hemorrhagic and antithrombotic effects of a low molecular weight (LMW) heparin fraction and standard heparin in rabbits. Similar LMW heparin fractions have antithrombotic effects when tested in animals, but their hemorrhagic effects relative to standard heparin have not been established. Standard porcine mucosal heparin (mol wt 15,000 daltons) was depolymerized by nitrous acid to a low molecular weight fraction (mol wt 4600 daltons). Using equal USP units, the standard and Dep LMW heparin were compared in vitro, ex vivo, and in vivo. In vitro, when diluted in rabbit plasma, the Dep LMW heparin at equivalent anti-Xa activity showed less prolongation of thrombin clotting times or activated partial thromboplastin times. Ex vivo, platelets from rabbits treated with the Dep LMW heparin showed less inhibition of collagen-induced aggregation. The relative hemorrhagic properties of the two heparins were compared in vivo in rabbits using a sensitive blood loss assay, and the antithrombotic properties were compared in a thrombin-induced venous stasis model. By using an optimal threshold heparin dose in each test system, it was possible to demonstrate that equal USP units of Dep LMW heparin caused less blood loss but showed greater antithrombotic activity than standard heparin.

scholarly journals The relationship between the hemorrhagic and antithrombotic properties of low molecular weight heparin in rabbits

Blood ◽  
1982 ◽  
Vol 59 (6) ◽  
pp. 1239-1245 ◽  
Author(s):  
CJ Carter ◽  
JG Kelton ◽  
J Hirsh ◽  
A Cerskus ◽  
AV Santos ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Blood Loss ◽  
Ex Vivo ◽  
Test System ◽  
Venous Stasis ◽  
Low Molecular Weight ◽  
Antithrombotic Effects ◽  
Induced Aggregation

Abstract We have compared the hemorrhagic and antithrombotic effects of a low molecular weight (LMW) heparin fraction and standard heparin in rabbits. Similar LMW heparin fractions have antithrombotic effects when tested in animals, but their hemorrhagic effects relative to standard heparin have not been established. Standard porcine mucosal heparin (mol wt 15,000 daltons) was depolymerized by nitrous acid to a low molecular weight fraction (mol wt 4600 daltons). Using equal USP units, the standard and Dep LMW heparin were compared in vitro, ex vivo, and in vivo. In vitro, when diluted in rabbit plasma, the Dep LMW heparin at equivalent anti-Xa activity showed less prolongation of thrombin clotting times or activated partial thromboplastin times. Ex vivo, platelets from rabbits treated with the Dep LMW heparin showed less inhibition of collagen-induced aggregation. The relative hemorrhagic properties of the two heparins were compared in vivo in rabbits using a sensitive blood loss assay, and the antithrombotic properties were compared in a thrombin-induced venous stasis model. By using an optimal threshold heparin dose in each test system, it was possible to demonstrate that equal USP units of Dep LMW heparin caused less blood loss but showed greater antithrombotic activity than standard heparin.

Comparative Study of the Activity of High and Low Molecular Weight Urokinase in the Presence of Fibrin

1982 ◽  
Vol 47 (01) ◽  
pp. 036-040 ◽  
Author(s):  
M Samama ◽  
M Castel ◽  
O Matsuo ◽  
M Hoylaerts ◽  
H R Lijnen
Keyword(s):  
Molecular Weight ◽  
Human Plasma ◽  
Test System ◽  
Clot Lysis ◽  
Low Molecular Weight ◽  
Plate Method ◽  
Thrombolytic Activity ◽  
Fibrin Plate

SummaryThe fibrinolytic or thrombolytic activity of low molecular weight urokinase (LMW-UK) and high molecular weight urokinase (HMW-UK) is not significantly different when measured in a bovine fibrin plate method, in a circulating plasma system containing a 125I-labelled human fibrin clot, or on 125I-fibrin films in culture plates using normal or α2-antiplasmin depleted human plasma.In a human fibrin plate method however HMW-UK was found to be more active than LMW-UK. In a purified system on human 125I-fibrin films the activation of native or modified human plasminogen by HMW-UK was also found to be more effective than by LMW-UK.Using a clot lysis test system we did not observe a different inhibition of LMW-UK and HMW-UK upon incubation in human plasma. This is in contrast with previous reports that HMW-UK is inhibited more rapidly in human plasma than LMW-UK.In a purified system the inhibition rate of LMW-UK and HMW-UK by α2-antiplasmin is the same (rate constants at 25ΰC of 167 ± 9 M−1s−1 and 171 ± 5 M−1s−1 respectively).The clinical trials available at present used doses of urokinase which were in excess of those required to obtain a maximal fibrinolytic effect. This might explain why in these trials no difference was observed between the thrombolytic effect of LMW-UK and HMW-UK, while in vitro HMW-UK appeared to be more effective. However, one should always be careful to extrapolate in vitro observations as such to the in vivo situation encountered during thrombolytic therapy.

scholarly journals A Comparative Study of the Effects of Heparin and a Low Molecular Weight Semi-Synthetic Heparin Analogue Upon Platelet Function

1977 ◽  
Author(s):  
R. Michalski ◽  
D. A. Lane ◽  
V. V. Kakkar
Keyword(s):  
Molecular Weight ◽  
Intravenous Injection ◽  
Platelet Function ◽  
Factor Xa ◽  
In Vitro Tests ◽  
Low Molecular Weight ◽  
Clotting Time ◽  
Induced Aggregation

We have already reported O) some in vitro and in vivo properties of a low molecular weight glycosaminoglycan polysulphate. It was found that while this semi-synthetic heparin analogue (SSHA) was virtually inactive in a number of in vitro clotting assays, following intravenous or subcutaneous injection it has a more specific anti-Xa potentiating effect than heparin. In the present communication a comparison has been made of some effects of SSHA and heparin upon platelet function. In several of the in vitro tests performed, such as their potentiating effect on ADP and adrenaline induced aggregation and their effects on the aggregation of washed platelets by Factor Xa, heparin proved to be far more potent than SSHA. It was found that after intravenous injection of both drugs, PRP samples containing comparable anti-Factor Xa activities responded differently to the addition of thrombin as SSHA barely inhibited thrombin induced aggregation. Similarly, SSHA had little effect on the dilute thrombin clotting time of plasma, following intravenous injection. Heparin and analogue were neutralised to approximately the same degree by a crude PF4 preparation, and similar transient thrombocytopenia effects were observed with both drugs.

scholarly journals NOVEL NANOPARTICLES FOR THE ORAL DELIVERY OF LOW MOLECULAR WEIGHT HEPARIN: IN VITRO AND IN VIVO ASSESSMENT

2017 ◽  
Vol 10 (2) ◽  
pp. 254 ◽  
Author(s):  
Nallaguntla Lavanya ◽  
Indira Muzib ◽  
Aukunuru Jithan ◽  
Balekari Umamahesh
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Ex Vivo ◽  
In Vitro Release ◽  
Low Molecular Weight ◽  
Scanning Calorimetry ◽  
Ex Vivo Permeation ◽  
Permeation Studies

Objective: The objective of the present study was to prepare and evaluate a novel oral formulation of nanoparticles for the systemic delivery of low molecular weight heparin (LMWH). Methods: Nanoparticles were prepared by polyelectrolyte complexation (PEC) method using polymers sodium alginate and chitosan. Entrapment efficiency of LMWH in nanoparticles was found to be  ̴88%. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X‑ray diffraction (XRD), Scanning electron microscopy (SEM)  studies carried for nanoparticles. In vitro release studies were performed for the formulations. Ex vivo permeation studies were performed optimized formulation by using small intestine of rat and in vivo studies were conducted on rat model.Results: In vitro release studies demonstrated that the release of LMWH was negligible in the stomach and high in the small intestine. FTIR has indicated that there is no interaction between the ingredients in nanoparticle. DSC and XRD studies confirmed that the amino groups of chitosan interacted with the carboxylic groups of alginate. Invitro % drug release of 95% was shown by formulation AC5. Ex vivo permeation studies have elucidated that ̴ 73% of LMWH was transported across the epithelium. Nanoparticles have shown enhanced oral bioavailability of LMWH as revealed by 4.5 fold increase in AUC of plasma drug concentration time curve.Conclusion: The results suggest that the nanoparticles prepared can result in targeted delivery of LMWH into systemic circulation via intestinal and colon routes. Novel nanoparticles thus prepared in this study can be considered as a promising delivery system.Keywords: Antifactor Xa activity, Chitosan, Differential scanning calorimetry, Sodium alginate, Low-molecular-weight heparin, Oral bioavailability.

Studies in Man and Experimental Animals of a Low Molecular Weight Heparin Fraction

1981 ◽  
Vol 45 (03) ◽  
pp. 214-218 ◽  
Author(s):  
D P Thomas ◽  
R E Merton ◽  
W E Lewis ◽  
T W Barrowcliffe
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Specific Activity ◽  
Ex Vivo ◽  
High Specific Activity ◽  
Factor Xa ◽  
In Vivo Studies ◽  
Low Molecular Weight

SummaryIn vitro and in vivo studies were carried out on a commercially prepared low molecular weight heparin fraction. By APTT assay the fraction had a specific activity of half that of unfractionated mucosal heparin, yet retained full potency by anti-Xa assay (both clotting and chromogenic substrate). When administered intravenously to human volunteers, the anti-Xa/APTT ratio remained the same as it was in vitro. However, after subcutaneous injection, the ratio increased and anti-Xa activity could not be fully neutralized ex vivo by PF4. The fraction was as effective as unfractionated heparin in preventing experimental serum-induced thrombosis, suggesting that a heparin fraction with high specific activity by anti-Factor Xa assay compared to APTT activity may be an effective drug for the prophylaxis of venous thrombosis.

Antithrombin III-Independent Effect of Depolymerized Holothurian Glycosaminoglycan (DHG) on Acute Thromboembolism in Mice

1997 ◽  
Vol 77 (02) ◽  
pp. 399-402 ◽  
Author(s):  
Hideki Nagase ◽  
Keiko T Kitazato ◽  
Eiji Sasaki ◽  
Masahiko Hattori ◽  
Kenji Kitazato ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Antithrombin Iii ◽  
Dermatan Sulfate ◽  
Coagulation System ◽  
Independent Effect ◽  
Low Molecular Weight ◽  
Antithrombotic Effect ◽  
Antithrombotic Effects

SummaryA previous study in this laboratory showed that depolymerized holothurian glycosaminoglycan (DHG) has two different antithrombin III (ATIII)-independent inhibitory effects on the in vitro blood coagulation system: heparin cofactor II (HCII)-dependent inhibition of thrombin, and ATIII- and HCII-independent inhibition of factor X activation by factor IXa-factor Villa complex (Nagase et al. Blood 85, 1527-1534, 1995). In the present study, we compared the antithrombotic effects of DHG in normal and in ATIII-deficient mice with those of unfractionated heparin (UFH) and low molecular weight heparin (LMWH). DHG, unlike UFH and LMWH, exerted an in vivo antithrombotic effect even in mice with decreased plasma ATIII activity (about 30% of normal). We then compared the anticoagulant and antithrombotic effects of DHG in mice with those of high molecular weight (HMW)-DHG, low molecular weight (LMW)-DHG, and dermatan sulfate (DS). In terms of in vitro anticoagulant activity assessed by use of purified human components, DHGs (DHG, HMW-DHG, and LMW-DHG) had different anti-thrombin activity in the presence of HCII and anti-factor Xase activities, which differences were dependent on the molecular weight. With respect to in vivo antithrombotic activity, DHG, HMW-DHG, and LMW-DHG showed almost the same inhibitory effect on acute thromboembolism in mice (minimum effective dose [MED]: >0.3 mg/kg). Since the antithrombotic activities of DHGs were not correlated with the anticoagulant-specific activities, the contribution of the two anticoagulant activities to the in vivo antithrombotic effect of DHGs remains unknown. However, DHG was more effective against acute thromboembolism in mice than DS (MED >1 or >3 mg/kg), which showed no inhibitory activity toward factor Xase. Therefore, it seems that factor Xase inhibition contributes greatly to the antithrombotic effect of DHG and that DHG exerts this effect in mice mainly by inhibiting factor Xase.

Comparison of the Anticoagulant and Antithrombotic Effects of Synthetic Thrombin and Factor Xa Inhibitors

1990 ◽  
Vol 63 (02) ◽  
pp. 220-223 ◽  
Author(s):  
J Hauptmann ◽  
B Kaiser ◽  
G Nowak ◽  
J Stürzebecher ◽  
F Markwardt
Keyword(s):  
Factor Xa ◽  
Thrombin Inhibitors ◽  
Factor Xa Inhibitors ◽  
Venous Stasis ◽  
Clotting Time ◽  
Thrombosis Model ◽  
Activity Factor ◽  
Antithrombotic Effects

SummaryThe anticoagulant effect of selected synthetic inhibitors of thrombin and factor Xa was studied in vitro in commonly used clotting assays. The concentrations of the compounds doubling the clotting time in the various assays were mainly dependent on their thrombin inhibitory activity. Factor Xa inhibitors were somewhat more effective in prolonging the prothrombin time compared to the activated partial thromboplastin time, whereas the opposite was true of thrombin inhibitors.In vivo, in a venous stasis thrombosis model and a thromboplastin-induced microthrombosis model in rats the thrombin inhibitors were effective antithrombotically whereas factor Xa inhibitors of numerically similar IQ value for the respective enzyme were not effective at equimolar dosageThe results are discussed in the light of the different prelequisiles and conditions for inhibition of thrombin and factor Xa in the course of blood clotting.

Effects of Unfractionated and Low Molecular Weight Heparins on Platelet Thromboxane Biosynthesis “In Vivo”

1994 ◽  
Vol 72 (06) ◽  
pp. 942-946 ◽  
Author(s):  
Raffaele Landolfi ◽  
Erica De Candia ◽  
Bianca Rocca ◽  
Giovanni Ciabattoni ◽  
Armando Antinori ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Unfractionated Heparin ◽  
Low Molecular Weight Heparin ◽  
Primary Source ◽  
In Vivo Studies ◽  
Low Molecular Weight ◽  
Heparin Administration ◽  
To Receive

SummarySeveral “in vitro” and “in vivo” studies indicate that heparin administration may affect platelet function. In this study we investigated the effects of prophylactic heparin on thromboxane (Tx)A2 biosynthesis “in vivo”, as assessed by the urinary excretion of major enzymatic metabolites 11-dehydro-TxB2 and 2,3-dinor-TxB2. Twenty-four patients who were candidates for cholecystectomy because of uncomplicated lithiasis were randomly assigned to receive placebo, unfractionated heparin, low molecular weight heparin or unfractionaed heparin plus 100 mg aspirin. Measurements of daily excretion of Tx metabolites were performed before and during the treatment. In the groups assigned to placebo and to low molecular weight heparin there was no statistically significant modification of Tx metabolite excretion while patients receiving unfractionated heparin had a significant increase of both metabolites (11-dehydro-TxB2: 3844 ± 1388 vs 2092 ±777, p <0.05; 2,3-dinor-TxB2: 2737 ± 808 vs 1535 ± 771 pg/mg creatinine, p <0.05). In patients randomized to receive low-dose aspirin plus unfractionated heparin the excretion of the two metabolites was largely suppressed thus suggesting that platelets are the primary source of enhanced thromboxane biosynthesis associated with heparin administration. These data indicate that unfractionated heparin causes platelet activation “in vivo” and suggest that the use of low molecular weight heparin may avoid this complication.

Neutralization of a Low Molecular Weight Heparin (LHN-1) and Conventional Heparin by Protamine Sulfate in Rats

1986 ◽  
Vol 56 (03) ◽  
pp. 318-322 ◽  
Author(s):  
V Diness ◽  
P B Østergaard
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Thrombus Formation ◽  
Experimental Models ◽  
Protamine Sulfate ◽  
Low Molecular Weight ◽  
Antithrombotic Effect ◽  
Higher Doses

SummaryThe neutralization of a low molecular weight heparin (LHN-1) and conventional heparin (CH) by protamine sulfate has been studied in vitro and in vivo. In vitro, the APTT activity of CH was completely neutralized in parallel with the anti-Xa activity. The APTT activity of LHN-1 was almost completely neutralized in a way similar to the APTT activity of CH, whereas the anti-Xa activity of LHN-1 was only partially neutralized.In vivo, CH 3 mg/kg and LHN-1 7.2 mg/kg was given intravenously in rats. The APTT and anti-Xa activities, after neutralization by protamine sulfate in vivo, were similar to the results in vitro. In CH treated rats no haemorrhagic effect in the rat tail bleeding test and no antithrombotic effect in the rat stasis model was found at a protamine sulfate to heparin ratio of about 1, which neutralized APTT and anti-Xa activities. In LHN-1 treated rats the haemorrhagic effect was neutralized when APTT was close to normal whereas higher doses of protamine sulfate were required for neutralization of the antithrombotic effect. This probably reflects the fact that in most experimental models higher doses of heparin are needed to induce bleeding than to prevent thrombus formation. Our results demonstrate that even if complete neutralization of APTT and anti-Xa activities were not seen in LHN-1 treated rats, the in vivo effects of LHN-1 could be neutralized as efficiently as those of conventional heparin. The large fall in blood pressure caused by high doses of protamine sulfate alone was prevented by the prior injection of LHN-1.

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