PLATELETS, COAGULATION AND IN VITRO THROMBUS FORMATION

¹ Department of Pharmacology, Medical Research Laboratories, Pfizer Inc., Groton, Connecticut

The relative contribution of platelet aggregation and fibrin formation to thrombus formation time in the Chandler loop has been investigated. Ellagic acid or collagen suspension accelerated silicone clotting time and thrombus formation time when added to dog blood in vitro. Collagen suspension caused aggregation of platelets in platelet-rich plasma, whereas ellagic acid had no effect. Intravenous administration of ellagic acid to dogs caused hypercoagulability: silicone clotting time and thrombus formation time were shortened and clots formed in isolated segments of vein; the platelet count was not affected. Injection of collagen suspension, however, prolonged thrombus formation time and caused thrombocytopenia; there was no effect on silicone clotting time, nor did clots form in isolated segments of vein. The results suggest that 1) thrombus formation in the Chandler loop is more sensitive to gross activation of the coagulation system than to formation of platelet aggregates and 2) blood motion may determine whether platelet-fibrin thrombi or clots form in vitro or in vivo.