title: Characterization and significance of collagen induced biphasic aggregation of human platelets.
abstract: Biphasic collagen-induced platelet aggregation, resembling that induced by epinephrine, was noted in platelet-rich plasma (PRP) of 11 stroke and 1 coronary disease patients. Similar pattern of aggregation was not observed in normal PRP. The occurrence of the biphasic collagen aggregation does not appear to relate to platelet count, smoking habit, medication, or other abnormalities such as hypertension, diabetes, and elevated serum lipid levels. However, platelets of these patients were very sensitive to aggregating agents including epinephrine and adenosine diphosphate. The concentration of collagen that elicited biphasic aggregation in these platelets was too weak to aggregate platelets of normal subjects. We believe that the release threshold of these platelets is reduced to such an extent that minute amounts of collagen, which would be insufficient to induce release from normal platelets, are capable of inducing release from these platelets. Both phases of collagen induced aggregation are probably resulted from the activation of the release mechanism.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D000368:Aged; D001772:Blood Cell Count; D001792:Blood Platelets / Q000648:ultrastructure; D002561:Cerebrovascular Disorders / Q000097:blood; D003094:Collagen / Q000494:pharmacology*; D003327:Coronary Disease / Q000097:blood; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D013268:Stimulation, Chemical
chemical_list: D000244:Adenosine Diphosphate; D003094:Collagen; D004837:Epinephrine