title: Selective inhibition of protein kinase C. Effect on platelet-activating-factor-induced platelet functional responses.
abstract: The role of protein kinase C (PKC) in platelet-activating-factor (PAF)-induced platelet activation was examined by using two selective inhibitors of PKC, namely Ro 31-7549/001 and Ro 31-8220/002. Both inhibitors dose-dependently inhibited PAF-induced phosphorylation of the major 40-47 kDa protein substrate of PKC, with 50% inhibition at 4.5 microM-Ro 31-7549/001 and 0.7 microM-Ro 31-8220/002. Inhibition of PKC had no effect on maximal elevation of intracellular Ca2+ [Ca2+]i produced by either a high or a low dose of PAF, but significantly increased the duration of the Ca2+ signal and the thromboxane B2 (TxB2) generation in high-dose PAF-stimulated platelets. The inhibitors also abrogated the effect of the PKC activator phorbol 12-myristate 13-acetate on PAF-induced [Ca2+]i elevation. Sub-maximal PAF-induced dense-granule release and platelet aggregation were dose-dependently inhibited by Ro 31-7549/001 and Ro 31-8220/002. The findings suggest that endogenously activated PKC holds a bifurcating role in PAF-activated platelets, negatively affecting duration of both [Ca2+]i and TxB2 generation, and positively influencing dense-granule release and aggregation.
authors.affiliation: School of Pharmacy, University of Bath, U.K.
authors.forename: C T
authors.initials: CT
authors.lastname: Murphy
authors.forename: J
authors.initials: J
authors.lastname: Westwick
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D008301:Maleimides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010972:Platelet Activating Factor / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000097:blood / Q000494:pharmacology; D011817:Rabbits; D012701:Serotonin / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013929:Thromboxane B2 / Q000096:biosynthesis
chemical_list: D007211:Indoles; D008301:Maleimides; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D012701:Serotonin; D013929:Thromboxane B2; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; C064758:Ro 31-8220; C064755:Ro 31-7549