Relationship of ADP-induced fibrinogen binding to platelet shape change and aggregation elucidated by use of colchicine and cytochalasin B.
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 muM or 83 microgram/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 muM or 0.01--0.10 microgram/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.
D000244:Adenosine Diphosphate / Q000502:physiology*; D001081:Apyrase / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects*; D003078:Colchicine / Q000494:pharmacology*; D003571:Cytochalasin B / Q000494:pharmacology*; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D010974:Platelet Aggregation / Q000187:drug effects*
D003571:Cytochalasin B; D000244:Adenosine Diphosphate; D005340:Fibrinogen; D001081:Apyrase; D003078:Colchicine