Aggregation of platelets and cell membrane vesiculation by rat cells transformed in vitro by Rous sarcoma virus

Primary rat embryo cells and established normal rat kidney cells transformed in vitro by Rous sarcoma virus induced the aggregation of rat platelets in vitro. The aggregating activity was shown to be specific for the transformed cells and was absent in the normal parent cells. The aggregation reaction is accompanied by the release of serotonin from the platelets. Further analysis and purification of this activity from the transformed cells demonstrated that the activity is shed from the cells growing in culture and is associated with membrane vesicles of heterogenous size. The normal cells also produced vesicles in culture; however, the level of vesicle productio was less than that from transformed cells, and the platelet aggregation and serotonin release activities were greatly reduced or absent in these vesicles.