Salicylates impair platelet activation, implying that a prostanoid is involved in the activation process. However, the effect of vasoprine on platelet PGs is an exceptional example of the general aspirin-PG relationship. One small dose of oral aspirin
“permanently” Impairs the function of all available platelets, with the effect lasting several days. The gradual recovery of platelet function after a dose of aspirin is the converse of aspirins initial “cumulative” effect and reflects the appearance in the circulation of new, unaffected platelets that were formed in the marrow after the ingestion of the drug. The relationship between the salicylates and platelets consists of three features. An “anucleate target” “exquisite sensitivity” and a “permanent, limited” effect.
Anucleate Target in platelet
As fragments of the cytoplasm of bone marrow megakaryocytes, blood platelets lack a nucleus and are unable to synthesize new mRNA. Although retaining/translating some megakaryocytes mRNA, platelets are generally in capable of protein synthesis. And those exposed to aspirin do not appear to replace their complement of inactive cyclo-oxygenase. The “enucleate” nature of platelets and the covalent nature of aspirin-dependent acetylation combine to produce the “permanence” of the aspirin effect on platelet PG synthesis. In contrast, nucleated cells such as endothelium can replenish their supply of cyclo-oxygenase after aspirin treatment by synthesizing new enzyme, and this ability to recover from aspirin treatment contributes to the reduced aspirin sensitivity of these cells as compared with platelets.
Small,infrequent doses. Platelet prostaglandin synthesis is almost completely inhibited by small, infrequent dose of oral aspirin. As gauged by several parameters (Enzyme acetylation, urinary prostaglandin metabolites, ex-vivo prostaglandin synthesis), oral aspirin inhibits platelet prostaglandin synthesis nearly completely when administered either as one “large/single” dose (>100mg) or as daily “small/cumulative” doses (5 to 95mg).