Characterization of commercially available plasminogen preparations in vitro: purity and reactivity

Three different commercially available plasminogen preparations (Immuno-, Kabi-, and Behring-plasminogens) were examined regarding purity and reactivity to different activators (high molecular weight [HMW] or low molecular weight [LMW] two-chain urokinase type plasminogen activator [tcu-PA], single chain urokinase type plasminogen activator [scu-PA], tissue type plasminogen activator [t-PA], and streptokinase [SK]). The Immuno-preparation was a Lys-plasminogen, commercially available for therapeutical use, whereas the research reagents for KabiVitrum and Behringwerke were Glu-plasminogen. Activity data provided by the manufacturers correlated well with our findings. Also a good correlation of reactivity to activators measured with a chromogenic substrate and on fibrin plates could be observed. The Immuno-plasminogen showed a minimum contamination with plasmin which has to be taken into consideration for the interpretation for its apparently higher activation by plasminogen activators compared to the plasmin-free plasminogens. Further in vitro and in vivo research has to be performed to find out criteria for a practicable scheme of administration of fibrinolytic agents for therapeutical thrombolysis.