Summary. Coagulation of plasma fibrinogen in the presence of fibrin degradation products was studied in rabbits treated with ancrod (Arvin), Two techniques were employed: the first, based on trace-labelling of plasma samples with labelled fibrinogen in vitro, was to measure the degree to which solubilized fibrin inhibited coagulation; in the second, two differently labelled fibrinogens were used, one injected intravenously and the other added in vitro, by which estimation of fibrinogen in serum relative to the amount of circulating breakdown products was attempted.
The first technique is considered to provide reliable information about the extent of defective coagulation, and hence the proportion of masked fibrinogen present in serum. Because of the difficulty in obtaining resolution between fibrinogen and its breakdown products in clots, the second technique is thought to be more suitable for comparative studies rather than for measurements in absolute terms.
High doses of hydrocortisone administered to rabbits for several days prior to ancrod significantly reduced the speed of the dissolution of microclots. The data obtained are consistent with the hypothesis that the hormone interfered with fibrinolysis at the plasminogen activator level.