Plasminogen in control and QPD platelets.

Proteins were analyzed by Western blotting with rabbit anti–human plasminogen after 10% reduced SDS-PAGE. Lanes compare 12 μL control (C) and QPD (Q) lysates (L) and ionophore releasates (R) and control ionophore releasate, incubated overnight with 0 to 400 ng/mL tcu-PA (CR + tcuPA), as indicated. As references, Glu-plasminogen (plg; 20 ng/lane) and the plasmin generated by digesting Glu-plasminogen (60 ng) with 100 ng/mL tcu-PA (plg + tcuPA) are shown. QPD platelets contained proteolyzed plasminogen that comigrated with the heavy chain of plasmin (arrow; the light chain of plasmin was not visualized by the antisera). They also contained correspondingly reduced proportions of intact plasminogen and some smaller proteolyzed components, not evident in normal platelets. When control platelet releasate was incubated with exogenous tcu-PA, there was a similar loss of intact plasminogen, but the extent of plasminogen proteolysis was not as complete as in QPD platelets.