Differences in pattern and level of plasminogen activator production between a cloned cell line from an ethylnitrosourea-induced glioma and one from normal adult rat brain.

The production of plasminogen activator (PA) by two cloned cell lines, one from an ethylnitrosourea-induced glioma (A15A5) and the other from normal adult rat brain (ARBO C9), has been investigated. Three assays were used to detect and measure PA in harvest fluids, cells and cell lysates. Similar levels were detected in harvest fluids from both cell lines. However, the cell and lysate assays indicated much higher levels in the tumor line. When actively growing cells were compared A15A5 cells had approximately 16X more fibrinolytic activity than the control cells with a limit of detection in the order of 10(3) cells or 1 microgram protein (cell lysate). In contrast for the control cells PA could only be detected when upwards of 10(4) cells or 5-10 micrograms protein were assayed. Plaminogen activator in as few as 10(3) tumor cells could be detected in the presence of 10(4) non-tumor cells. Plasminogen activator in 26 micrograms protein of A15A5 cell lysate could also be detected in the presence of 44 micrograms protein from ARBO C9 lysates indicating no inhibitory activity in the control cell lysates. Levels of PA in both harvest fluids and cell lysates were determined as cultures progressed through the growth cycle. For cell lysates this showed a build-up of PA in the normal cell line as the cells approached and attained confluence. A much higher level was measured in the tumor cells soon after seeding and maintained to confluence. No differences in growth cycle-associated changes in secreted PA could be determined in harvest fluids: both cell lines showing similar levels at confluence.