Plasmin inhibitors and fibrinogen breakdown during the initial phase of thrombolytic treatment--the problem of the alpha 2-antiplasmin determination.

During the first 3 hr of thrombolytic treatment with porcine plasmin (p-PL) or streptokinase (SK) a rapid decrease of clottable fibrinogen with generation of large amounts of fibrin(-ogen) degradation products (FDP) are found. alpha 2-antiplasmin (alpha 2AP) is rapidly neutralized. Whereas in patients treated with SK more than half of the original plasminogen was consumed, its level remained unchanged during p-PL infusion. When alpha 2AP reaches values below some 20%, spontaneous amidolytic activity towards S-2251 representing either PL-alpha 2-macroglobulin- or SK-plasminogen-complex activity appears. This activity has to be considered in the alpha 2AP assay in order to avoid underestimation of this inhibitor.