Neutralization of Antithrombin VI (Fibrinogen Breakdown Products) with Platelet Antiheparin Factor (Platelet Factor 4)*

Summary It has been found that fibrinogen breakdown product – antithrombin VI – is neutralized by the purified preparation of platelet factor 4, obtained by means of zinc acetate precipitation and DEAE chromatography column. It has been suggested that antiheparin activity of platelet factor 4 and its ability to neutralize antithrombin VI may be related to the same protein. The purified preparation of platelet factor 4 does not influence the fibrinogen – fibrin conversion by thrombin. This means that platelet factor 2 and platelet factor 4 are not the same substance. Crude platelet extracts neutralize antithrombin III and V. However, the purified product did not interferes with the action of these antithrombins.