Plasma urokinase levels measured by chromogenic assay after infusions of tissue culture or urinary source material

A standard curve of urokinase activity versus optical density was established for high molecular weight and low molecular weight urokinase molecules using the chromogenic substrate L-pyroglutamyl-glycyl-L-arginine-p-nitroanalide (KABI S-2444) and a World Health Organization urokinase preparation. Plasma urokinase levels were determined on samples collected during and after infusions of tissue culture or urinary source urokinase. The urinary source material achieved a significantly higher plasma blood level at the first sampling interval (2 hours) and disappeared more rapidly after termination of the infusion, than did tissue culture material. There was no correlation of the plasma chromogenic assay level with the plasma fibrinogen or plasminogen concentration nor with any other parameter associated with the “lytic state”. Both urokinase materials achieved plasma levels in excess of that required to produce a fibrinogenolytic state, and it is likely that a lower dose could be used to achieve the “lytic state”.