Studies on the Anticoagulant Properties of Chlorazol Fast Pink (Benzo Fast Pink 2BL) 1

Abstract

Chlorazol fast pink is representative of a group of azo dyes that are anticoagulant both in vitro and in vivo. At a concentration of 2.5 mg/ml, it completely inhibited the thrombin time, prothrombin time, and partial thromboplastin time of human plasma, and the thrombin time and Reptilase time of purified human fibrinogen. Among modes of action considered, it was found to inhibit the cleavage of fibrinopeptides A and B from fibrinogen, and the augmentation of the coagulant action of antihemophilic factor (factor VIII) by thrombin. It did not retard the aggregation of fibrin monomers, but the clots that formed were fragmentary. Clot formation returned to normal after removal of all but tightly bound dye from fibrinogen and thrombin. This and similar experiments suggested that the dye interfered reversibly with the interaction of thrombin and fibrinogen to a degree that accounted for much of its anticoagulant activity. The studies suggest that chlorazol fast pink may be an unusual tool for clarifying the steps involved in the formation of a fibrin clot.