THE MECHANISM OF CLOT DISSOLUTION BY PLASMIN*

Abstract

The respective roles of plasminogen activators and plasmin in human thrombolytic mechanisms have been investigated. Quantitation of thrombolysis was accomplished by the use of I131 labelled human plasma clots. Test systems using labelled clots containing varying concentrations of plasminogen permitted differentiation between the actions of plasminogen activators and plasmin itself. Studies on streptokinase-treated patients confirmed that the conclusions drawn from in vitro test systems were applicable to the in vivo state. It was demonstrated that the chief and primary mechanism of plasma thrombolysis involved the activation of intrinsic clot plasminogen with resulting autodigestion of the thrombus. The secondary mechanism of thrombolysis by exogenous plasmin action appeared to be relatively unimportant.