The protective effect of acetylsalicylic acid on laser-induced venous thrombosis in the rat

Effect of aspirin-dipyridamole and heparin and their combination on venous thrombosis in hypercoagulable or thrombotic animals

Epsilon-amino-caproic acid (EACA) induces a clinically-useful anti-haemorrhagic, mildly thrombotic state while ellagic acid (EA) induces a severe hypercoagulable one. Reversal of these states may on occasion be necessary. The effectiveness of the antiplatelet drugs, aspirin and dipyridamole (ASA/D), in reducing thrombus weight was studied in normocoagulable animals and animals made hypercoagulable with EACA (333mg/kg) or EA (1.2mg/kg). Heparin (114iu/kg) was tested in the EACA group, both alone and in combination with ASA/D. Thrombogenicity was measured by weight formed on intravenous platinum wire in one hour. In normocoagulable animals, ASA/D reduced thrombus by 32%. Ellagic acid trebled mean thrombus weight and ASA/D reduced this by 49%, but did not restore normality. EACA increased mean thrombosis by one sixth. Treatment with heparin reduced this by 48% to a level well below that of untreated animals. Addition of a single dose of aspirin/dipyridamole to the heparin regime, reduced thrombosis by a further 31%, reaching to 21% of control thrombus. The results were statistically significant. Kaolin-activated blood clotting time was shortened by EA, but EACA had little effect on it, while ASA/D slightly and heparin markedly lengthened it.

Comparison of two experimental thrombosis models in rats effects of four glycosaminoglycans

Two experimental thrombosis models in rats have been compared with regard to the composition of the formed thrombi and the effects of various treatments on thrombus formation. In the first model thrombosis is induced in the vena cava by a combination of venous stasis and hypercoagulability; these thrombi consist merely of red cells and fibrin with only a few platelets. In the second model thrombosis is induced in an arterio-venous shunt in which the formed thrombi consist of red cells, fibrin and a large amount of platelet aggregates adhering to the foreign material. Antiplatelet serum and acetylsalicylic acid, which reduce blood platelet activity, inhibited thrombus formation only in the arteriovenous shunt model. Dicumoxane, an oral anticoagulant, was active in both models. The glycosaminoglycans heparin, Org 10172, Fragmin and the pentasaccharide, representing the AT-III binding sequence of heparin, were active in both models. However, there were qualitative and quantitative differences between the effects of the glycosaminoglycans suggesting differences in their modes of action.

Effect of acetylsalicylic acid on experimentally induced arterial thrombosis in rats

Acetylsalicylic acid (ASA) was tested for its antithrombotic activity in the arterial system after prophylactic administration to rats, using a new standardized method. Damage of the vessel wall was produced by chilling a small segment of the left carotid artery. Dose related, significant results were obtained after 3 mg/kg orally. If higher doses (10 and 30 mg/kg) are administered, the formation of non-occlusive thrombi is inhibited by 70--90% on the basis of thrombus weight. As the frequency distributions show, there are significantly more zero-values in the ASA treated groups (total 50%) than in the control groups. However, the incidence of occlusive thrombi was not changed by ASA. The long-lasting effect of ASA in inhibition of platelet aggregation was confirmed. The formation of arterial thrombi is significantly inhibited after prophylactic administration of 30 and 10 mg/kg up to 48 h before initiation of thrombosis. After administration of 3 mg/kg orally, only insignificant effects were observed. Thus the duration of action depends on the dose used.