Dermatan sulphate (DS) has been shown to accelerate thrcmbin inhibition by its action on heparin cofactor II (HCII) but has no effect on anti thrombin III (Tollefson et al., 1983). In this study, we have examined the in vitro anticoagulant effect of a purified preparation of DS (free from heparin and heparan sulphate), m comparison with that of unfractionated heparin (UEH). We have also studied the effect of DS and UEH in preventing experimental venous thrombosis in rabbits and in inhibiting

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... ombin generation, both in vitro and in ex vivo plasma samples.Dermatan had low activity in vitro by APTT and anti-Xa assays (< 5 iu/ mg). When thrombin generation was measured in vitro, 1 μg/ml UEH was sufficient to inhibit thrombin formation. Although 1 μg/ml DS reduced thrombin generation to 40% of control values, there was no further reduction when the concentration of DS was increased to 8 μg/ml.When DS was injected into rabbits (n = 10), a dose of 150 μg/kg inpaired thrombogenesis m a Wessler stasis model. The mean thrombus score was reduced to 25% of the control values, although thrombosis could not be completely prevented, even after an eight-fold increase m dose (1250 μg/kg). When the duration of stasis was extended from 10 to 20 minutes, there was no impairment of thrombosis (mean thrombus score 100%) following 1250 μg/kg of DS. Thrombin generation measured in ex vivo plasma after 150 μg/kg of DS was 72% (s.e.m. 63-81) of that measured in pre-injection plasma. In contrast, 150 μg/kg of heparin prevented thrombosis after both 10 and 20 minutes stasis (mean score 0%) and thrombin generation was reduced to 17% (s.e.m. 12-23) of control values m ex vivo plasma samples.Unlike heparin, DS does not completely abolish thrcmbin generation in vitro and is not as potent as UEH in inhibiting thrombin generation m ex vivo plasma. While DS has demonstrable antithrombotic activity under defined conditions, it is less effective than heparin and increasing doses of DS do not improve antithrombotic effectiveness in this model.