Determination of Plasma Urokinase Levels by Chromogenic Assay Levels: Comparison of Levels Attained During Infusion of Tissue Culture and Urinary Source Urokinase Preparations

Plasma urokinase levels were determined using the chromogenic substrate L-Pyroglutamyl-glycyl-L-arginine-p-nitroanalide (KABI S2444) on plasma samples collected before, during and after Infusions of tissue culture or urinary source urokinase (J, Lab. Clin. Med. 92:721, 1978). Each patient received a 2,000 IU/lb loading dose followed by an hourly rate of 2,000 IU/lb for 12 hours. There was no correlation between plasma urokinase level and critical concentration of drug or body weight and no difference in the effects of each preparation on laboratory reflections of a lytic state, such as the whole blood euglobulln lysis time, plasminogen or fibrinogen concentration. However, the chromogenic assay of urokinase activity showed that the urinary source material achieved a significantly higher plasma blood level at two hours and disappeared more rapidly after termination of the infusion than was observed with the tissue culture material. Although both urokinase infusions achieved plasma levels in excess of that required to produce a fibrinogenolytic state, it is likely that a significantly lower concentration is sufficient to produce a lytic state and that a larger dose of tissue culture material would be required to achieve this critical plasma urokinase level.