title: Kinetics of platelet P-selectin mobilization: concurrent surface expression and release induced by thrombin or PMA, and inhibition by the NO donor SNAP.
abstract: Activated platelets and endothelium surface express the cell adhesion molecule P-selectin (CD62P), which plays an important role in mediating interactions with leukocytes. Increased levels of a functional soluble form of P-selectin (sP-selectin) have been reported in several pathological states but it is not clear whether this circulating sP-selectin originates from platelets and/or endothelial cells. Here we describe the concurrent kinetics of intracellular storage, surface expression and release of platelet P-selectin induced by thrombin or the protein kinase C activator PMA. Platelet activation with submaximal concentrations of thrombin (0.1 U/ml) resulted in a rapid decrease of intracellular P-selectin. This decrease of intracellular P-selectin concurred with a gradual increase of surface expression and an initial increase of sP-selectin. Our results indicate that intracellular stores of P-selectin were only partly mobilized upon activation with submaximal concentrations of thrombin. A high concentration of thrombin (1.0 U/ml) induced a rapid and nearly total decrease of intracellular stores and a more pronounced, but transient, increase of surface expression. The release of P-selectin was fast and occurred during the initial activation phase. The NO donor SNAP inhibited both surface expression and release of platelet P-selectin in a similar manner. PMA (0.1-1.0 microM) mediated a more slow, gradual and sustained surface expression and release of P-selectin than thrombin. Thus, surface expression and release of platelet P-selectin show different kinetics depending on the mode of activation.
authors.affiliation: Per.Whiss@hul.liu.se
authors.forename: P A
authors.initials: PA
authors.lastname: Whiss
authors.forename: R G
authors.initials: RG
authors.lastname: Andersson
authors.forename: U
authors.initials: U
authors.lastname: Srinivas
mesh_terms: D001792:Blood Platelets / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008297:Male; D019007:P-Selectin / Q000187:drug effects* / Q000378:metabolism; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015539:Platelet Activation; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013917:Thrombin / Q000494:pharmacology*
chemical_list: D019007:P-Selectin; C110881:S-nitro-N-acetylpenicillamine; D013917:Thrombin; D010396:Penicillamine; D013755:Tetradecanoylphorbol Acetate