Fig. 8.

Two-chain urokinase with Ser¹⁹⁵Ala substitution (S195A-tcuPA; 0.5 mg/kg) does not affect the rate of intrapleural inactivation of urokinase (uPA). A: time dependence of the amidolytic activity of intrapleural, free uPA during intrapleural fibrinolytic therapy (IPFT) with 0.5 mg/kg of S195A-tcuPA with (●; n = 5) and without (■; n = 3) 0.25 mg/kg of scuPA. The amidolytic activity of free uPA was determined in samples of pleural fluid withdrawn at 10–40 min after IPFT. The amidolytic activity of free uPA was calculated as the difference between total uPA activity and activity attributed to α-macroglobulin (αM)/uPA complexes, as previously described (46). There was a statistically significant difference (P < 0.05) between free uPA activity in animals treated with (○) and without (□) scuPA (0.25 mg/kg). B: time dependence of the amidolytic activity of free uPA during IPFT with scuPA (0.25 mg/kg, ○; n = 5) and vehicle control (PBS, □; n = 3). The amidolytic activity of free uPA was the difference between total uPA activity and activity of αM/uPA complexes. There was a statistically significant difference (P < 0.05) between free uPA activity in animals treated with (○) and without (□) scuPA (0.25 mg/kg). C: observed first-order rate constants (k_obs) for the intrapleural inactivation of uPA with (●; n = 5) and without (○; n = 5) S195A-tcuPA (0.5 mg/kg). A single exponential equation was fit to the dependence of [free uPA] with respect to time to obtain the k_obs of PAI-1-independent inactivation of uPA as previously described (46). There was a statistically significant difference (P < 0.05) between k_obs in animals treated with (○) and without (□) scuPA (0.25 mg/kg). There was no statistically significant difference (P > 0.05) between the k_obs observed for IPFT with scuPA (0.25 mg/kg) with (●) or without (○) S195A-tcuPA (0.5 mg/kg).