Platelet aggregation in laminar flow. II. Shear rate and ADP-dependent effects of acetylsalicylic acid and indomethacin
Yung, W.; Frojmovic, M.M.
Thrombosis Research 28(3): 379-387
1982
ISSN/ISBN: 0049-3848 PMID: 7179223 Document Number: 190601
The relative contributions of physiologic activators and shear rates (G) on the formation and stability of platelet aggregates arising from platelets treated with widely clinically used non-steroidal antiinflammatory drugs such as acetylsalicylic acid (ASA) need to be characterized for conditions of low G believed to be important in vivo. Platelets in human citrated platelet-rich plasma (PRP) undergo ADP-induced aggregation in laminar flow by apparently 2 distinct processes: a low ADP-dependent process, generating large visible aggregates stable only at low shear rates, and a higher ADP-threshold-dependent process yielding more complete and shear-resistant large aggregate formation. Similar studies of both macroaggregation (TA) and actual percent aggregation (%PA) were made with ADP injections into PRP in the cone-in-plate device as a function of G and pretreatments with ASA (200 .mu.M) and indomethacin (10 .mu.M). These drugs reduced %PA in part and yielded only reversible macro-aggregation for studies conducted at the higher [ADP] (4-6 .mu.M) and at high G (.gtorsim. 120-150 s-1), with no significant effects at low G (.ltorsim. 30 s-1). The results are discussed in terms of a platelet stickiness factor, s, ascribed to changes in fibrinogen binding sites reported for these drug actions, and related to in vivo flow and variable platelet activation conditions.