The time course of resolution of adhesions during fibrinolytic therapy in tetracycline-induced pleural injury in rabbits

The time required for the effective clearance of pleural adhesions/organization after intrapleural fibrinolytic therapy (IPFT) is unknown. Chest ultrasonography and computed tomography (CT) were used to assess the efficacy of IPFT in a rabbit model of tetracycline-induced pleural injury, treated with single-chain (sc) urokinase plasminogen activators (scuPAs) or tissue PAs (sctPA). IPFT with sctPA (0.145 mg/kg; n = 10) and scuPA (0.5 mg/kg; n = 12) was monitored by serial ultrasonography alone ( n = 12) or alongside CT scanning ( n = 10). IPFT efficacy was assessed with gross lung injury scores (GLIS) and ultrasonography scores (USS). Pleural fluids withdrawn at 0–240 min and 24 h after IPFT were assayed for PA and fibrinolytic activities, α-macroglobulin/fibrinolysin complexes, and active PA inhibitor 1 (PAI-1). scuPA and sctPA generated comparable steady-state fibrinolytic activities by 20 min. PA activity in the scuPA group decreased slower than the sctPA group ( kobs = 0.016 and 0.042 min−1). Significant amounts of bioactive uPA/α-macroglobulin (but not tPA; P < 0.05) complexes accumulated at 0–40 min after IPFT. Despite the differences in intrapleural processing, IPFT with either fibrinolysin was effective (GLIS ≤ 10) in animals imaged with ultrasonography only. USS correlated well with postmortem GLIS ( r2 = 0.85) and confirmed relatively slow intrapleural fibrinolysis after IPFT, which coincided with effective clearance of adhesions/organization at 4–8 h. CT scanning was associated with less effective (GLIS > 10) IPFT and higher levels of active PAI-1 at 24 h following therapy. We concluded that intrapleural fibrinolysis in tetracycline-induced pleural injury in rabbits is relatively slow (4–8 h). In CT-scanned animals, elevated PAI-1 activity (possibly radiation induced) reduced the efficacy of IPFT, buttressing the major impact of active PAI-1 on IPFT outcomes.

The Nature of Synergy between Tissue-Type and Single Chain Urokinase-Type Plasminogen Activators

SummaryEnhancement of thrombolysis with combinations of tissue-type and single chain urokinase plasminogen activators (t-PA and scu-PA) has been demonstrated in vivo but has not been seen consistently in vitro. This study was designed to characterize interactions between t-PA and scu-PA with respect to rate of and extent of thrombolysis in vitro and to delineate mechanisms responsible. Combinations of t-PA and scu-PA at selected concentrations synergistically enhanced thrombolysis in vitro compared with thrombolysis induced by either activator alone. Enhanced thrombolysis did not occur at the expense of fibrin specificity since the extent of fibrinogenolysis and consumption of α2-antiplasmin were significantly less with synergistic combinations of t-PA and scu-PA compared with equi-effective concentrations of either activator alone. Attenuation of complex formation of t-PA and two chain u-PA (tcu-PA), formed from scu-PA, with plasma proteins did not appear to contribute to enhancement of thrombolysis as assessed by fibrin autography. Binding of 125I-t-PA to thrombi was increased by 27% at 1 hr and by 21% at 2 hr in the presence of scu-PA (p <0,001 for both). Conversion of scu-PA to tcu-PA was enhanced when thrombi were exposed to scu-PA in the presence of t-PA. Results of this study indicate that t-PA and scu-PA at selected concentrations enhance thrombolysis in vitro synergistically without compromising fibrin specificity. Enhanced binding of t-PA to thrombi in the presence of scu-PA and enhanced conversion of scu-PA to tcu-PA appear to contribute to synergy between t-PA and scu-PA for thrombolysis.

Separation of Plasminogen Activators from Human Plasma and a Comparison with Activators from Human Uterine Tissue and Urine

SummaryNormal human plasma contains acid-stable as well as labile plasminogen activators. The activity of activators in plasma euglobulins was inhibited by EACA in an uniform pattern, similar to that obtained with the major activators in human uterine tissue or with the purified porcine tissue activator, but different from the patterns obtained with plasmin or with urokinase.Gel filtration at high ionic strength separated activators corresponding to particle sizes of 60,000 dalton and about 10,000 dalton, corresponding to two activators similarly obtained from human tissue. The 60,000 dalton activator was precipitated in the euglobulin fraction. Its concentration increased in plasma after exercise. The 10,000 dalton activator was found mainly in the supernatant. Gel filtration in 0.15 M solutions yielded activators in fractions of molecular sizes of 100-140,000 dalton and 200,000 dalton or larger.The activity of normal and exercise euglobulins was inhibited by antiserum to a plasminogen activator prepared from porcine tissue, but it was not inhibited by antiserum to urokinase. Plasminogen activators in human plasma euglobulins resembled immunochemi- cally the activators in human uterine tissue.