title: Relationship of arachidonic acid concentration to cyclooxygenase-dependent human platelet aggregation.
abstract: Inhibition of ex vivo arachidonic acid (AA)-induced aggregation is a biomarker for the isotype selectivity of cyclooxygenase (COX) inhibitors since platelets express COX-1 but not COX-2. At low concentrations, there is broad inter- and intrasubject variability in AA-induced aggregation of platelets ex vivo. This study defined a concentration that reliably induces aggregation without overcoming inhibition by therapeutic aspirin therapy (ASA, 81-mg) treatment. Logistic regression analysis of ex vivo aggregation, induced with increasing concentrations of AA in platelet-rich plasma (PRP), estimated that platelets from > or = 90% of subjects would aggregate at > or = 1.5 mM AA (95% confidence interval [CI], 1.1, 2.1). A concentration of 1.6 mM AA failed to aggregate platelets from 26 healthy volunteers, who had previously aggregated at this concentration, following six daily oral doses of 81 mg of ASA. These data demonstrate that 1.6 mM AA reproducibly induces platelet aggregation in PRP from healthy volunteers without overcoming the antiplatelet effect of daily low-dose aspirin therapy.
authors.affiliation: Division of Clinical Pharmacology, Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors.forename: Joanne
authors.initials: J
authors.lastname: Burke
authors.forename: Walter K
authors.initials: WK
authors.lastname: Kraft
authors.forename: Howard E
authors.initials: HE
authors.lastname: Greenberg
authors.forename: Melanie
authors.initials: M
authors.lastname: Gleave
authors.forename: Giovanni M
authors.initials: GM
authors.lastname: Pitari
authors.forename: Sandi
authors.initials: S
authors.lastname: VanBuren
authors.forename: John A
authors.initials: JA
authors.lastname: Wagner
authors.forename: Scott A
authors.initials: SA
authors.lastname: Waldman
mesh_terms: D000293:Adolescent; D000328:Adult; D016718:Arachidonic Acid / Q000097:blood / Q000494:pharmacology*; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D004334:Drug Administration Schedule; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D011451:Prostaglandin-Endoperoxide Synthases / Q000097:blood*; D015203:Reproducibility of Results
chemical_list: D016861:Cyclooxygenase Inhibitors; D016718:Arachidonic Acid; D011451:Prostaglandin-Endoperoxide Synthases; D001241:Aspirin