Incorporation of Labelled Nucleotides and Aggregation of Human Blood Platelets

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Abstract
Addition of ADP-8-C14 to platelet-rich plasma results in platelet radioactivity through a series of temperature-dependent reactions involving stepwise dephosphorylation of the nucleotide in plasma and then incorporation of the adenosine residue by the platelet, where it participates as a precursor in synthesis of platelet adenine nucleotides. This sequence of events, which requires a heat-labile nondialysable plasma factor, is blocked by 0.01 M KCN, by EDTA, by arginine methyl ester, by adenosine, and by AMP. ADP-induced platelet aggregation does not require the reactions outlined above and proceeds without ADP - breakdown and without binding of the ADP- molecule to the platelet. A possible mechanism of this phenomenon is suggested. *) Presented in part before the American Physiological Society, April, 1965, and published in abstract form [Fed. Proc. 24: 260 (1965)]. Supported by grants from the National Heart Institute of the U.S. Public Health Service and the American Heart Association. **) Fellow of the Medical Foundation, Inc.