Prevention and therapy of experimental venous thrombosis in rabbits by desmin 370.

Desmin 370 (D370), a low molecular weight dermatan sulfate, has been shown to reduce the size of preformed thrombi in rats, via a mechanism largely independent of its anticoagulant activity. In the present study we investigated the therapeutic efficacy of D370 in rabbits with experimental jugular vein thrombosis. Experiments performed to evaluate the antithrombotic dosages in rabbits indicated that D370 prevented the formation of venous thrombi (Wessler model) in a dose-dependent manner with complete inhibition at 20 mg/kg. When injected to rabbits bearing a 30 min aged thrombus, D370 caused a time- and dose-dependent reduction in thrombus weight. Thrombi harvested 2 h after injection of 50 mg/kg of D370 were 71% smaller than thrombi from saline-treated rabbits and 50% smaller than pretreatment thrombi, suggesting a double effect of the drug: inhibition of thrombus accretion and reduction of the existing thrombus. Interestingly, pretreatment with the fibrinolytic inhibitor EACA (1 g/kg), significantly attenuated the therapeutic efficacy of D370, suggesting a possible involvement of the fibrinolytic system. Heparin (50 and 200 U/kg) was less active as therapeutic agent, the maximal decrease in thrombus weight, as compared to untreated rabbits, amounting to 38%. Heparin, moreover, caused a more pronounced prolongation of APTT than comparable antithrombotic dosages of D370. Our present data extend previous results on the therapeutic efficacy of D370 and underscore its potential as an alternative antithrombotic drug.

Thrombolysis enhancing activity of a low molecular weight dermatan sulfate (Desmin 370) in experimental pulmonary embolism in rats.

The effect of Desmin 370 (D370), a low molecular weight dermatan sulfate, on the extent of lysis of radiolabelled pulmonary emboli in rats was evaluated. 125I-fibrin labelled blood clots were embolized into the lungs via a jugular vein, and the degree of lysis was calculated, at predetermined intervals, by the residual radioactivity in the lungs. A single i.v. injection of D370 (50 mg/kg) caused a significant increase in the rate of lysis, which was visible at 30 min and persisted for the whole experimental period (2 h). This effect was prevented by epsilon-aminocaproic acid (1 g/kg). At comparable antithrombotic dosages, heparin (2 mg/kg) also produced a significant enhancement of thrombolysis while hirudin (2 mg/kg) was totally ineffective. Heparin, however, produced a much more pronounced anticoagulant effect than D370. No changes in the plasma levels of plasminogen activator and plasminogen activator inhibitor activities were observed after treatment with D370. Moreover, the dermatan sulfate failed to enhance the blood fibrinolytic activity measured by a solid phase 125I-fibrin assay. These results extend previous data indicating that D370 may be efficient also in the therapy of thrombosis and provide direct evidence that this effect occurs, at least in part, via degradation of thrombus associated fibrin.

Bioavailability of Desmin, a low molecular weight dermatan sulfate, after subcutaneous administration to healthy volunteers.

The bioavailability of two different s.c. doses of Desmin (a new low molecular weight dermatan sulfate) was evaluated in 12 healthy volunteers (6 men, 6 women aged 22-45 years) who were injected, on 3 separate days and with a wash-out period of at least 21 days between each administration, with 200 and 300 mg of Desmin by the s.c. route and 200 mg by the i.v. route. Immediately before injection and at various times thereafter (after 15 min and 30 min for i.v. only and after 1, 2, 3, 4, 6, 8, 12, and 24 h for both s.c. and i.v. dosing), blood samples were drawn to investigate bioavailability by measuring several coagulation parameters: activated partial thromboplastin time, thrombin time, inhibition of factor Xa, Heptest, and heparin cofactor II. Furthermore the local tolerance of the s.c. and i.v. injections were investigated. The s.c. administration of the two Desmin doses had a negligible effect on the activated partial thromboplastin time and a very small effect on the thrombin time, measured with human thrombin; in contrast, Heptest, heparin cofactor II, and anti-Xa activities increased, with a good drug bioavailability (more than 100%). The plasma effects of Desmin were dose dependent only when measured by Heptest, which also gave a greater response after the s.c. administrations. There were no symptoms of intolerance or pain at the injection site after single i.v. and s.c. Desmin administration.

Desmin 370, a low molecular weight dermatan sulfate, reduces the weight of preformed thrombi in rats made afibrinogenemic by ancrod.

Desmin 370 (D370), a low molecular weight dermatan sulfate, has been shown to induce a marked reduction of the weight of preformed venous thrombi in rats and rabbits by mechanisms that appeared largely independent of inhibition of thrombus accretion. In order to provide further support for such a mechanism, we exploited the defibrinating capacity of ancrod to obtain a thrombosis model characterized by the lack of thrombus growth and thus sensitive only to agents promoting thrombus lysis. Thrombus formation in anesthetized rats was induced by vena cava ligature. Injection of ancrod (5 U/kg) 5 h after induction of venous stasis caused a more than 95% reduction in plasma fibrinogen and prevented thrombus accretion as indicated by the lack of thrombus weight increase during the 3 h experimental period (12.2 +/- 0.6 vs 14.5 +/- 1 as compared to 12.6 +/- 0.6 vs 19.6 +/- 0.8, p < 0.01, in control rats) and by the almost complete (> 90%) inhibition of 125I-fibrin(ogen) binding to thrombi. Moreover, when ancrod was given 1 h before vena cava ligature, no thrombi were formed within 2 h whereas at the same time interval visible thrombi were present in all control rats. Administration of D370 (10 mg/kg) to thrombus bearing rats, 1 h after induction of afibrinogenemia, resulted in a significant reduction in thrombus weight (43% after 2 h, p < 0.01) which was only slightly lower than that recorded in normofibrinogenemic rats (54%). Enhancement of plasma fibrinolytic activity by ancrod had no influence on thrombus lysis and was not all affected by administration of D370.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic effect of a low molecular weight dermatan sulphate (Desmin 370) in rat venous thrombosis--evidence for an anticoagulant-independent mechanism.

We evaluated the capacity of a low molecular weight dermatan sulphate (D370) to prevent thrombus formation and to induce a reduction of a stabilized thrombus in a rat venous thrombosis model. Injection of D370, 10 min before induction of venous stasis (prevention model), prevented thrombus formation in a dose-dependent way (ED50: 2.3 mg/kg). When given to rats 6 h after induction of venous stasis (therapeutic model), D370 caused a time- and dose-dependent reduction in thrombus size (60% to 70% reduction 2 h after injection of 10 mg/kg). At comparable antithrombotic dosages (i.e. minimum dose giving complete inhibition of thrombus formation), heparin (0.5 mg/kg) only caused 40% reduction of a preformed thrombus while hirudin (1 mg/kg) was virtually ineffective (less than 10% reduction in weight). All three compounds inhibited 125I-fibrin(ogen) deposition on 6-h aged thrombi by more than 85%, suggesting that D370 and, to a lesser extent, heparin reduce thrombus size via mechanisms other than inhibition of thrombus accretion. The involvement of a fibrinolysis-mediated mechanism in the D370-induced effect is suggested by the following. EACA (1 g/kg), when given to thrombus-bearing control animals, did not influence thrombus weight. However, when administered before D370 treatment, it prevented the expected reduction in thrombus weight by more than 80%, without influencing the effect of D370 on 125I-fibrin(ogen) accumulation onto preexisting thrombi. D370 injection caused neither an enhancement of fibrinolytic activity nor a reduction of PAI in plasma. In vitro, D370 (200 microns/ml) was unable to potentiate the spontaneous or PA-induced lysis of 125I-fibrinogen labelled blood, plasma, or purified fibrin clots.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombotic and thrombolytic activity of sulodexide in rats.

We evaluated the ability of sulodexide, an extracted glycosaminoglycan, to prevent thrombus formation and to reduce a stabilized thrombus in a rat venous thrombosis model (vena cava ligature). Injection of sulodexide 10 min before induction of venous stasis, prevented thrombus formation in a dose-dependent manner (median effective dose 0.55 mg/kg). When given to rats with 6-h-old thrombi, sulodexide caused a marked reduction in thrombus size which reached 70% after 2 h with the highest dose tested (2 mg/kg). The effect of sulodexide on established thrombi appears to be due, at least in part, to a fibrinolysis-mediated mechanism, since it was significantly inhibited by epsilon-aminocaproic acid, a well-known antifibrinolytic drug. Treatment with sulodexide did not noticeably affect plasma levels of plasminogen activator and its specific inhibitor. We also showed that fluorescein-labelled sulodexide, when given to animals with 6-h-old thrombi, was present within the thrombi harvested 2 h later, but was then absent from blood. The fluorescence was mainly located in areas filled with amorphous material, that was identified as fibrin by staining with phosphotungstic acid-hematoxylin. No fluorescein-labelled material could be detected in rats treated with fluorescein alone. These findings indicate that, besides preventing venous thrombus formation, sulodexide is able to promote thrombus dissolution by a mechanism that is partly related to local fibrinolysis stimulation.