Further evidence against the validity of using an ADP-removing enzyme system (CP/CPK) for demonstrating the role of secreted ADP in platelet activation.
The ADP-removing enzyme system creatine phosphate-creatine phosphokinase (CP/CPK) selectively inhibited primary aggregation in response to the thromboxane receptor agonist, U46619, in mouse aspirin-treated platelet-rich plasma. Inhibition by CP/CPK has become accepted as evidence for mediation by secreted ADP, yet primary aggregation is not usually attributed to secreted ADP. Hence these results throw doubt on the assumed mechanism by which CP/CPK inhibits aggregation. The possibility that such inhibition was due to removal of extracellular ADP released prior to platelet stimulation and exerting a potentiating influence was investigated. Ths explanation appeared unlikely as further additions of creatine phosphokinase to platelet-rich plasma preincubated with CP/CPK caused further inhibition of primary aggregation. Moreover, low concentrations of CP/CPK that reduced responsiveness to U46619 had no effect on collagen-induced aggregation, which ADP is known to potentiate. The evidence presented is consistent with CP/CPK exerting a direct inhibitory effect on platelet membranes and so inhibiting a facet of platelet aggregation not mediated by secreted ADP. These data support the conclusion of a previous study (Huang, E.M. and Detwiler, T.C., J. Lab. Clin. Med.,95, 59-68, 1980) that inhibition by CP/CPK cannot be taken as evidence for the involvement of secreted ADP.
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000244:Adenosine Diphosphate / Q000502:physiology*; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D003402:Creatine Kinase / Q000494:pharmacology*; D066298:In Vitro Techniques; D051379:Mice; D010725:Phosphocreatine / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology
D011450:Prostaglandin Endoperoxides, Synthetic; D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D003402:Creatine Kinase