Studies on the influence of reactants and buffer environment on clot lysis induced by human plasminogen activators

Clot lysis induced by tissue plasminogen activator and urokinase has been studied and the influences of pH, ionic environment and reactant concentrations have been determined. Both pH and ionic strength strongly affect the rate of clot lysis and distinctly different dependency profiles are obtained for tissue plasminogen activator and urokinase. Variations in concentration of plasminogen also profoundly affect the rate of clot lysis, maxima being obtained at different plasminogen concentrations depending on the concentration of fibrinogen. For urokinase, these maxima occurred at about a tenfold higher concentration of plasminogen than for the tissue plasminogen activator. The lysis times are directly dependent on the concentration of fibrinogen. Variation in thrombin concentration did not significantly affect the lysis times. Suitable conditions for the assays of tissue plasminogen activator and urokinase are suggested.