title: Abundant amounts of diadenosine 5',5"'-P1,P4-tetraphosphate are present and releasable, but metabolically inactive, in human platelets.
abstract: Diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) may be formed in the back reaction of the amino acid-activation reaction [Zamecnik, Stephenson, Janeway & Randerath (1966) Biochem. Biophys. Res. Commun. 24, 91-98]. On the basis of a number of observations of the properties of Ap4A it has been suggested that it may have a signal function for the initiation of DNA replication in eukaryotic cells] Grummt (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 371-375]. In the present paper human platelets have been shown to contain relatively large amounts of Ap4A. The compound is apparently metabolic inactive in platelets, but it is almost quantitatively released when platelets are activated to aggregate by treatment with thrombin. The results are discussed in connection with the known growth-stimulating activity of platelets.
mesh_terms: D000227:Adenine Nucleotides / Q000097:blood*; D000255:Adenosine Triphosphate / Q000097:blood; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D015226:Dinucleoside Phosphates; D006801:Humans; D066298:In Vitro Techniques; D043264:Phosphodiesterase I; D010727:Phosphoric Diester Hydrolases / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D012265:Ribonucleotides / Q000097:blood; D013917:Thrombin / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D015226:Dinucleoside Phosphates; D012265:Ribonucleotides; C020733:diadenosine tetraphosphate; D000255:Adenosine Triphosphate; D010727:Phosphoric Diester Hydrolases; D043264:Phosphodiesterase I; D013917:Thrombin