Plasminogen activators in QPD platelets.

Plasminogen activators were analyzed on casein substrate gels containing plasminogen. (A, D) Samples tested after 10% nonreduced SDS-PAGE. (B, C) Samples spotted directly onto substrate gels. (A) QPD releasate (QR, 6 μL; QR*, 10 μL) contained plasminogen activators that comigrated with tcu-PA (tcuPA, 8.8 ng) and LMW u-PA (LMWuPA, 3.2 ng), but not with purified plasmin (10 ng) or t-PA (tPA, 1 IU). (B) Unlike t-PA (0.5 IU), tcu-PA (5 ng) and the plasminogen activators in 1 μL QR and QL (QPD lysate) were inhibited on gels with added (+) 1 mM amiloride. (C) Large amounts of recombinant PAI-1 (final concentrations shown) were required to fully neutralize the plasminogen activators in pooled QR. (D) Zymograms indicated that the 100-, 50-, and 33-kd proteases in QR (5 μL/lane) were removed by rabbit antibodies to human u-PA (depl), but not by normal rabbit IgG (sham). The 33-kd protease in lanes sham and QR was evident on the original gel.