Summary
ADP causes human, aspirin-treated, gel-filtered platelets to change from their native
discoid shape to spiny spheres with pseudopods, bind 125I-labeled fibrinogen, and aggregate if shaken with sufficient fibrinogen. After destruction
of the added ADP with the enzyme apyrase, the platelets revert to a disc shape and
lose much of their bound fibrinogen. Colchicine (208 μM or 83 μg/ml) added to ADP-treated
platelets before apyrase prevented restoration of the discoid shape but not the loss
of bound fibrinogen. It did not inhibit ADP-induced shape change, aggregation, or
fibrinogen binding. Cytochalasin B (0.02–0.2 μM or 0.01–0.10 μg/ml) prevented ADP-induced
shape change but not ADP-induced fibrinogen binding or aggregation. Thus, these findings
support earlier studies with thrombasthenic and EDTA-treated platelets and with normal
platelets at low pH, or in the presence of EDTA to indicate that fibrinogen binding
is associated with aggregability but not with platelet shape.
Keywords
Platelet aggregation - Fibrinogen binding (to platelets) - Colchicine - Cytochalasin
B - ADP
