Proteins of the fibrinolytic system in human thrombi
Robbie, L.A.; Bennett, B.; Croll, A.M.; Brown, P.A.; Booth, N.A.
Thrombosis and Haemostasis 75(1): 127-133
1996
ISSN/ISBN: 0340-6245 PMID: 8713791 Document Number: 463364
The proteins of fibrinolysis have been quantified in human thrombi, to assess the balance between plasminogen activators and their major inhibitor PAI-1. The relative roles of PAI-1 and alpha-2-AP were also examined since we have previously shown that both platelet PAI-1 and plasma alpha-2-AP are important determinants of clot lysis in vitro. Extracts and sections were prepared from human thrombi for quantitative immunoassay and immunohistochemical staining respectively. PAI-1 and alpha-2-AP were present at high concentrations. Levels of t-PA and t-PA-PAI-1 complex were relatively low. Staining confirmed the presence of abundant PAI-1, associated primarily with platelet material within the thrombus and also with fibrin. Staining for alpha-2-AP was also intense and demonstrated strong association with fibrin. The alpha-2-AP concentration was similar to its high plasma concentration, whereas PAI-1 levels were up to 30 times greater than that in circulating blood, suggesting that active recruitment of platelets contributes to the high PAI-1 concentration in thrombi.