Effect of polyanetholesulphonic acid and xylan sulphate on antithrombin III activity.

Both polyanetholesulphonic acid and xylan sulphate prolonged the partial thromboplastin clotting time of plasma. The anticoagulant effect of both compounds was reduced following pre-incubation of plasma with antiserum specific for antithrombin III. Polyanetholesulphonic acid was more effective than xylan sulphate in inhibiting thrombin-initiated clotting of plasma, and potentiated antithrombin III inhibition of both thrombin and Xa. Xylan sulphate was more effective in potentiating antithrombin III inhibition of Xa than of thrombin. These differential effects of xylan sulphate on different blood serine proteases are discussed in terms of the antithrombin III-mediated anticoagulant activity of heparin.