Complexing of tissue plasminogen activator with PAI-1, alpha 2-macroglobulin, and C1-inhibitor: studies in patients with defibrination and a fibrinolytic state after electroshock or complicated labor.

Release of tissue plasminogen activator (t-PA) and its interaction with plasma protease inhibitors were studied in two patients with massive defibrination, one after electroshock and soft tissue injury and the other after complicated labor; both had very severe hemorrhage. Large quantities of free t-PA were present in the circulation for several hours. Complexes of t-PA with plasminogen activator inhibitor 1 (PAI-1), alpha 2-macroglobulin and C1-inhibitor were also observed. PAI-1 antigen rose dramatically in both patients, and complexes of t-PA with PAI-1 rose rapidly during the period of observation. In contrast, the complexes of t-PA with alpha 2-macroglobulin and C1-inhibitor, present initially, persisted for short periods only and disappeared when free t-PA disappeared from the circulation. Plasmin was generated initially, as indicated by the presence of plasmin-alpha 2-antiplasmin complexes. Plasma concentrations of alpha 2-macroglobulin, C1-inhibitor, antithrombin III, and alpha 2-antiplasmin were severely depleted initially, but rapidly returned to normal. The observations demonstrate that there is a major release of t-PA in such defibrinating patients, that there is a role for protease inhibitors other than PAI-1 in the regulation of endogenous t-PA, and indicate the great rapidity with which such free t-PA is complexed and cleared.