CONTACT ACTIVATION OF BLOOD-COAGULATION - TRIGGER PROPERTIES AND HYSTERESIS - KINETIC RECOGNITION OF FOREIGN SURFACES UPON CONTACT ACTIVATION OF BLOOD-COAGULATION - A HYPOTHESIS

A mathematical model of contact activation of blood coagulation was de veloped and analysed. The model variables are concentrations of factor XIIa, kallikrein and activated high-molecular-weight kininogen. Conce ntrations of active factors were shown to depend on the activating sig nal value in a hysteretic manner. Within a range of relatively small s ignals, two (activated and non-activated) stable states coexist (bista bility). Signals of the natural environment (surfaces of endothelial a nd blood cells) seem to be in the range of bistability; therefore, con tact activation that persists for a short time can induce a transition of the system to the activated state, and, correspondingly, the forma tion of a clot. The system cannot return to the initial state, which i s characterized by low activation levels, until the activating signals decrease significantly below those present in the circulation. (C) 19 98 Academic Press Limited.