PLATELET-ADHESION TO FIBRINOGEN, FIBRIN MONOMER, AND FIBRIN PROTOFIBRILS IN FLOWING BLOOD - THE EFFECT OF FIBRINOGEN IMMOBILIZATION AND FIBRIN FORMATION

Platelet fibrin(ogen) adhesive interactions were investigated in whole citrated blood using the rectangular perfusion chamber at wall shear rates of 300 and 1600s(-1) with regard to the amount and structure of immobilized protein. Only single platelets adhered to adsorbed fibrino gen at both low and high surface fibrinogen concentrations and at 1600 s(-1) almost no adhesion was observed. When using spray-immobilized pr otein, platelet adhesion was significantly higher than to adsorbed pro tein. Conversion of adsorbed fibrinogen to fibrin monomer resulted in the formation of pronounced platelets aggregates and with the elevatio n of wall shear rate 50% decrease of adhesion took place. Degree of pl atelet adhesion to fibrin monomer was significantly influenced by immo bilized protein concentration at both shear rates. However, the morpho logy (small and dense platelet aggregates) and extent of platelets adh ered to fibrin pentamer was nearly the same at both shear rates. Start ing with surface-bound fibrinogen and alternating addition of thrombin and fibrinogen fibrin pentamer was prepared using the stepwise synthe sis. This methodology is based on the observation that at low concentr ation immobilized fibrin monomer binds fibrinogen in 1:1 molar ratio. The gradually formed fibrin of a defined size and composition can be a useful tool in the further understanding of the role of fibrin archit ecture in the pathophysiology of thrombosis.