An Activator of Plasminogen Produced by Cell Culture

Abstract

Summary

Previous investigators observed clot lysis by tissue grown in plasma clots(14, 15). Our results indicate that an “activator” of plasminogen is released from KB cell cultures. Supernatant from MK cell cultures activated plasminogen and was also proteolytic in the absence of plasminogen. These cell cultures had a third property, inhibition of proteolysis. The activator described here resembles “tissue activator” in that it is not proteolytic in the absence of serum and can be dissolved by KSCN. It also resembles activator from excised rat lung(16) in that it is the size of microsomes. The interpretation that release of activator from cell culture is a metabolic process and not from cell breakdown seems warranted since only a small fraction of the activity found in the supernatant can be extracted from the cells.