The haemorrhagic and antithrombotic effects of dermatan sulphate

Heparin and dermatan sulphate are effective antithrombotic agents but the clinical use of heparin is complicated by haemorrhage. The haemorrhagic effect of dermatan sulphate is unknown. In this study we compared the antithrombotic, haemorrhagic and anticoagulant effects of heparin and dermatan sulphate in rabbits. The antithrombotic effect was measured as prevention of venous thrombus formation. The haemorrhagic effect was measured as 51Cr-blood loss from standardized cuts in rabbit ears. The anticoagulant effect was measured as changes in the APTT, TCT and circulating anti-factor Xa level, and the formation of 125I-thrombin/inhibitor complexes ex vivo. The effect of heparin and dermatan sulphate on collagen-induced platelet aggregation was measured ex vivo. Maximal antithrombotic effects of heparin and dermatan sulphate were achieved with 70 and 500 micrograms/kg respectively. A 20-fold increase in heparin dose caused an 8-fold increase in blood loss and higher doses (40- and 80-fold increases) caused further dose-related increases in blood loss (13- and 35-fold increases respectively). In contrast, a 20- to 40-fold increase in the antithrombotic dose of dermatan sulphate did not increase blood loss and an 80-fold dose increase caused only a 7-fold increase in blood loss. There was no relationship between the antithrombotic and haemorrhagic effects of either heparin or dermatan sulphate and their anticoagulant activities. In contrast, there was a relationship between the dose-related enhancement of blood loss by these glycosaminoglycans and the inhibition of collagen-induced platelet aggregation ex vivo. These results suggest that dermatan sulphate is less haemorrhagic than heparin at equivalent antithrombotic doses, and that the haemorrhagic effect is associated with a glycosaminoglycan-induced platelet defect.