The effect of a sulfated polysaccharide on antithrombin III

A major naturally occurring inhibitor of blood is AT-III. We have investigated the potentiation of AT-III inhibition of factors Xa, IIa, and plasmin by the heparinoid substance SP-54. Both coagulation and amidolytic methods were used. SP-54 potentiated AT-III inhibition of factors Xa and IIa in the absence of heparin. When heparin was present, potentiation of inhibition of factor Xa usually occurred, but not of factor IIa. SP-54 also potentiated the AT-III inhibition of plasmin action. Laurell immunoelectrophoresis showed no changes in AT-III in the presence of SP-54. In view of the recent importance placed on the role of AT-III and factor Xa in thrombogenesis, an oral agent which potentiates AT-III activity can have important implications for thrombotic therapy.