Immunological comparison between human and rat plasminogen activators in blood and the vessel wall

To evaluate the rat as an experimental model for plasminogen activator research, the ability of antibodies specific for human tissue type plasminogen activator and urokinase to suppress the plasminogen activator activity in whole plasma and in the vessel wall was studied in both rat and man. Plasminogen activator activity in plasma was assayed on fibrin plates containing plasminogen. Plasminogen activator in the vessel wall was shown by the fibrin side technique. Antibodies against human tissue type melanoma cell activator and urokinase were raised in goats and mixed into the fibrin film or the fibrin plates. In both species antibodies to melanoma cell activator were able to suppress the plasminogen activator activity completely in plasma and in the vessel wall. Anti-urokinase, however, had no suppressing effect. In rat plasma the inhibitory effect on the fibrinolytic activity was seen only with high concentrations of antibodies against melanoma cell activator, which suggests that rat plasminogen activator in plasma and vessel walls is similar to, but not identical with, human tissue type plasminogen activator.