PLATELET INTERACTION WITH COLLAGEN FIBRILS IN FLOWING BLOOD .2. IMPAIRED ADHESION-AGGREGATION IN BLEEDING DISORDERS - COMPARISON WITH SUBENDOTHELIUM

Abstract

Anticoagulated whole blood from patients and control subjects was circulated through an annular perfusion chamber in which the fibrillar collagen of .alpha. chymotrypsin-digested subendothelium and intact subendothelium were exposed. The blood flow conditions corresponded to those in arteries (830 s-1 wall shear rate). Platelet surface interaction was measured morphometrically. Decreased adhesion to fibrillar collagen associated with normal spreading and normal adhesion-induced formation of platelet thrombi was found with blood of patients with von Willebrand''s disease and the Bernard Soulier Syndrome, indicating a defect in the initial attachment reaction of platelets with collagen. Platelets of patients with thrombasthenia did normally adhere to the collagen fibrils and also lost their subcellular organelles during this reaction, but they totally failed to adhere to each other. In storage pool disease, platelet thrombus formation was consistently inhibited, but adhesion and spreading was inhibited in some patients and normal in others. In contrast, adhesion was always normal after ingestion of aspirin which consistently caused a marked inhibition of platelet thrombi. These findings correspond to those previously described on intact subendothelium. The observed defects are more pronounced on the fibrillar collagen than on intact subendothelium.