PLASMINOGEN-ACTIVATOR IN ACUTE MYELOID LEUKEMIC MARROWS - U-PA IN CONTRAST TO T-PA IN NORMAL MARROW

Leukaemic and normal bone marrow samples were compared in terms of the ir content of the fibrinolytic agents, tissue plasminogen activator (t -PA) and urokinase-type plasminogen activator (u-PA) and their inhibit ors, plasminogen activator inhibitors 1 and 2 (PAI-1 and PAI-2). Norma l marrow contained t-PA as the principal plasminogen activator, wherea s in leukaemic marrow samples u-PA was the predominant activator Both normal and leukaemic marrows contained PAI-1 in similar amounts, but w hereas normal marrow contained significant amounts of PAI-2 the leukae mic marrows contained very little. Plasminogen activators were present in uncomplexed, active forms and plasmin-alpha(2)-antiplasmin complex es were generated locally more prominently in leukaemic marrows. u-PA associated with blast cells may contribute to the severe forms of haem orrhage sometimes occurring in myeloid types of leukaemia.