Release of both urokinase and tissue plasminogen activator from veins in vitro

Specimens of human veins were incubated in culture media, in which the concentrations of urokinase (UK) and tissue plasminogen activator (t-PA) were determined by radioimmunoassay and immunoradiometric assay. Both UK and t-PA were released to the media, in which the concentration of plasminogen activators was correlated to the weight of the specimens. The release of t-PA was maximal on the first day, after which it rapidly decreased, and t-PA was not demonstrable after the third day of incubation. By contrast, UK was continuously liberated to the media during the study period of 5 days. The present results indicate that both UK and t-PA are present in the vein wall and probably released by different cells.