Anticoagulant and antithrombotic effects of chemically modified heparins and pentosanpolysulfate

Pig mucosal heparin (GAG 98), in which the binding site for antithrombin had been inactivated by periodate oxidation (GAG 262), a supersulfated low-molecular-weight heparin (GAG 869), a low-molecular-weight heparin (Fragmin), and sodium pentosanpolysulfate have been investigated on their anticoagulant effects in vitro and ex vivo and in an animal thrombosis model in which rat mesenteric venules are damaged by defined laser energy. GAG 262 and pentosanpolysulfate had a markedly reduced anticoagulant effect compared to heparin, Fragmin, and the supersulfated low-molecular-weight heparin fragment. Similarily, the doses necessary to inhibit thrombus formation in the laser model were much higher for GAG 262 and for pentosanpolysulfate compared to heparin and the low-molecular-weight heparin Fragmin, but much lower for the supersulfated heparin fragment. The antithrombotic effect of the low-molecular-weight heparin Fragmin and the supersulfated heparin fragment after subcutaneous injection lasted much longer than the ex vivo detectable anticoagulant effect. Although some correlation between the antithrombotic and the anticoagulant effect in the laser model is evident, there seems to be no direct correlation between amount and duration of factor IIa or factor Xa inhibition and extent and duration of the inhibition of thrombus formation.