STUDIES ON THE MECHANISM OF RISTOCETIN-INDUCED PLATELET AGGLUTINATION - BINDING OF RISTOCETIN TO PLATELETS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 93  (2) , 220-231
Abstract
Ristocetin was trace-labeled with [3H] by the reductive methylation method. It agglutinated human platelets in the presence of VIIIR:WF [von Wille brand factor as measured in a ristocetin assay] in a manner indistinguishable from unlabeled ristocetin. The binding of the labeled ristocetin to normal and enzyme-modified human platelets was studied in the presence and absence of VIIIR:WF and at nonagglutinating and agglutinating concentrations of ristocetin. Virtually no difference in [3H]ristocetin binding was seen whether VIIIR:WF was present or not. Platelets treated with chymotrypsin, which destroys their ability to agglutinate to VIIIR:WF and ristocetin, did not bind less ristocetin than did control platelets. A pronounced, direct relationship was found between [3H]ristocetin bound by normal platelets and total ristocetin concentration. This implies that at the higher (agglutinating) concentrations of ristocetin more binding sites are exposed or, more probably, aggregation of ristocetin occurs.

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