Characterization of astrocyte plasminogen activator.

We have previously shown that astrocytes produce and secrete plasminogen activator (PA) and that this function is responsive to various modulating agents. When astrocyte conditioned medium (CM) is subjected to SDS-PAGE and PA activity localized by fibrin-agar gel overlay, the activity in the CM is found to comigrate with control t-PA. On affinity chromatography CM PA specifically binds to t-PA antibody. The latter also inhibits fibrinolytic activity of CM PA. When incubated with a fibrin clot, CM PA activity can be shown to bind to fibrin. These observations help identify the enzyme in astrocyte CM as t-PA. A possible role of astrocyte PA in myelin injury could provide an explanation for the previously observed correlation between fibrin deposition and demyelination as well as inhibition of demyelination by ancrod and heparin in experimental allergic encephalomyelitis.