Inactivation of Antihæmophilic Globulin by Thrombin

Abstract

NORMAL plasma defibrinated by addition of ‘Thrombin Topical’ (Parke Davis), 5 units per ml., loses its antihæmophilic activity¹. In the experiments described here, each of the reagents in the thromboplastin generation test² (platelets, serum, plasma adsorbed with barium sulphate and M/40 calcium chloride) in turn was incubated at 37° C., for periods of three minutes and longer, in the presence of thrombin, and then used in the thromboplastin-generating mixture. Initially ‘Thrombin Topical’ was used, generally in concentrations of the order of 0.15 unit per ml. In every case, the expected acceleration of thromboplastin generation was observed². However, while this treatment of the platelets, serum and calcium had no effect on the potency of the thromboplastin eventually generated, the ‘thrombinized’ and pre-incubated adsorbed plasma consistently yielded a much weaker thromboplastin than the control. Thus, pretreatment of the adsorbed plasma with ‘Thrombin Topical’ converted a normal thromboplastin generation curve into one resembling that found in hæmophilia. This effect was found to be irreversible and unaffected by dilution.