title: Characteristics of protein kinase C-independent exocytosis in human platelets.
abstract: We evaluated the characteristics of the protein kinase C (PKC)-independent mechanism for ATP release in platelet-rich plasma. When ADP (10 microM) and U46619 (1 microM) were both added as agonists, a significant release was observed immediately after stimulation. The PKC inhibitor, Ro-31-7549 (10 microM), or a cyclooxygenase inhibitor, aspirin (400 microM) or indomethacin (20 microM), partially inhibited ATP release with little effect on platelet aggregation. The ATP release observed in the presence of Ro-31-7549 was abolished by a cyclooxygenase inhibitor or by preventing aggregation without stirring. In the nonstirred condition, thromboxane B2 formation was reduced by 93%. When sodium arachidonate (1 mM) rather than U46619 was used with ADP, ATP release in the presence of Ro-31-7549 was abolished by stopping the stirring with no effect on thromboxane B2 formation. In contrast, ADP/U46619-induced ATP release observed in the presence of aspirin was only partially inhibited when the stirring was stopped. This release was also inhibited dose-dependently by Ro-31-7549 at concentrations between 1 and 10 microM. These results suggest that PKC-independent ATP-release in this system requires aggregation and is inhibited by a cyclooxygenase inhibitor, while PKC-dependent exocytosis is insensitive to aggregation and a cyclooxygenase inhibitor.
authors.affiliation: Department of Clinical Laboratory Medicine, Faculty of Medicine, University of Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: M
authors.initials: M
authors.lastname: Togo
authors.forename: H
authors.initials: H
authors.lastname: Sato
authors.forename: N
authors.initials: N
authors.lastname: Hashimoto
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
authors.forename: K
authors.initials: K
authors.lastname: Kurokawa
authors.forename: K
authors.initials: K
authors.lastname: Nakahara
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000166:cytology / Q000201:enzymology*; D005089:Exocytosis; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D008970:Molecular Weight; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013929:Thromboxane B2 / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D007211:Indoles; D008301:Maleimides; D010975:Platelet Aggregation Inhibitors; D014662:Vasoconstrictor Agents; D013929:Thromboxane B2; D000244:Adenosine Diphosphate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D001241:Aspirin; C064755:Ro 31-7549