THE ROLE OF A 3-0 SULFO GROUP IN THE GLUCOSAMINE RESIDUE OF A SYNTHETIC OLIGOSACCHARIDE FOR THE DETERMINATION OF ANTITHROMBOTIC ACTIONS
We have previously reported on the antithromboticaction of a chemically synthesized heparin pentasaccharide which exhibits high affinity to anti thrombinIII and sole anti-factor Xa activity. In order to investigate the relative importance of the 3-0 sulfo group of this pentasaccharide, we evaluated the in vitro and in vivo antithrombotic activity of a synthetic pentasccharide devoid of the sulfo group at the third position of the glucosamine residue. In amidolytic and clot-based assays the 3-0 de- sulfated pentasaccharide (3-0-DP) failed to exhibit any antifactor Xa actions at concentrations <100 ug/ml in humanor rabbit plasmas, whereas pentasaccharide showed strong factor Xa inhibition at 1.0 ug/ml IK-=3.2x10 M)and at 10.0 ug/ml in rabbit plasma (K.=9.0×10™7 M). Using a rabbit stasis thrombosis model in which thrombosis was induce by human serum or an activated pro-thrombin complex concentrate, 3-0-DP failed to produce any antithrombotic action in acute intravenous regimens at dosages up to 200 ug/kg. In these two models, pentasaccharide produced >80% inhibition of induced thrombosis. These studies demonstrate the critical importance of the 3-0 sulfo group in this heparin pentasaccharide for the determination of antithrombotic activity, and that in this type of oligosaccharide, anti-factor Xa activity is responsible for producing the antithrombotic effect.