Factor X-activating activity from Guerin epithelioma.

The procoagulant activity (PCA) was examined in extracts from primary tumor and metastases of experimental Guerin epithelioma transplanted into Wistar rats. PCA was evaluated by measurement of the level of activation of coagulation factor X using specific chromogenic substrate S-2222. We observed that extracts from both primary tumor and metastases were able to activate factor X in vitro. This activity was not factor VII-dependent, it was inhibited by phenylmethylsulfonyl fluoride (PMSF) and mercuric chloride, and in a smaller degree by p-chloromercuric benzoate (p-CMB) and iodoacetic acid (IAA). No difference between procoagulant activity in extracts from primary tumor and from metastases was observed.