Comparison of fibrinogen association with normal and thrombasthenic platelets on exposure to ADP or chymotrypsin

Although 125I-fibrinogen becomes associated with washed platelets from normal human subjects during ADP-induced shape change and aggregation, 125I-fibrinogen did not become associated with washed plateletes from a thrombasthenic subject during ADP-induced shape change and the platelets did not aggregate. Platelets from control and thrombasthenic subjects were treated with chymotrypsin, which is known to degrade platelet membrane glycoproteins. More 125I-fibrinogen became associated with chymotrypsin-pretreated platelets from normal subejcts than with untreated platelets, and fibrinogen caused the enzyme-treated platelets to aggregate. 125I-fibrinogen did not become associated with chymotrypsin-pretreated thromobasthenic platelets, and fibrinogen did not aggregate them. Thus, there appears to be a defect in thrombasthenic platelets that prevents the association of fibrinogen with them.