title: Platelet aggregation in human whole blood after chronic administration of aspirin.
abstract: We have used the impedance aggregometer to study the "ex vivo" effect of acetylsalicylic acid (ASA) in whole blood (WB) versus platelet-rich plasma (PRP) in 35 male healthy volunteers after 10 days of treatment with 25, 50, 125, 250, and 500 mg/day of ASA. Percent of inhibition of platelet aggregation was determinated at the end of treatment. A greater inhibition of platelet aggregation was observed in WB than in PRP when ASA was administrated at almost all doses. Maximal differences were at 25, 50, and 125 mg/day of ASA on adrenaline, collagen and arachidonic acid induced aggregation, and with 250 and 500 mg/day of ASA when ADP was used as aggregating agent. In the "in vitro" trials, IC-50 values of ASA on ADP and collagen induced aggregation were determined in platelet aggregation by the impedance method in both WB and PRP. ASA shows a lower IC-50 in WB than in PRP. When leucocytes were incubated in PRP samples, it effect was similar to the percent of inhibition in WB.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology*; D001773:Blood Cells / Q000502:physiology; D002469:Cell Separation; D003094:Collagen / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects*; D012107:Research Design
chemical_list: D001095:Arachidonic Acids; D016718:Arachidonic Acid; D000244:Adenosine Diphosphate; D003094:Collagen; D001241:Aspirin; D004837:Epinephrine