title: Characteristics of collagen-induced fibrinogen binding to human platelets.
abstract: Polymerized type I calf skin collagen induced a time-dependent specific binding of 125I-fibrinogen to washed human platelets. Binding occurred more rapidly in a shaken rather than in an unstirred system. It was linear in the range 0.05-0.3 microM added fibrinogen and was saturated at higher fibrinogen concentrations (more than 0.8 microM). Scatchard analysis showed a single population of binding sites (16530 +/- 5410 per platelet) with a Kd = 0.53 +/- 0.23 microM. Collagen-induced 125I-fibrinogen binding to platelets was completely inhibited by ADP antagonists such as creatine phosphate/creatine phosphokinase and AMP, and partially inhibited by pretreatment of the platelets with aspirin. With both normal and aspirin-treated platelets a close correlation was observed between the amount of 125I-fibrinogen bound and the extent of dense granule secretion. Our results confirm that fibrinogen becomes bound to platelet surface receptors during collagen-induced platelet aggregation and suggest that secreted ADP is an essential cofactor in this process.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism*; D003094:Collagen / Q000494:pharmacology*; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D010974:Platelet Aggregation / Q000187:drug effects; D012701:Serotonin / Q000378:metabolism; D013997:Time Factors
chemical_list: D012701:Serotonin; D000244:Adenosine Diphosphate; D005340:Fibrinogen; D003094:Collagen