Effect of clopidogrel treatment on ADP-induced phosphorylations in rat platelets.
Phosphorylations induced by 2-MeS-ADP, a potent agonist of platelet ADP receptors, have been studied in rat platelets, and the effect of clopidogrel, a compound which inhibits platelet aggregation by selectively reducing the binding of ADP to its low affinity receptors on platelets, has been determined. 2-MeS-ADP induced platelet activation (shape change and aggregation) simultaneously with the phosphorylation of myosin light chain (P20) and plekstrin (P47). Phosphorylation of P20 and P47 was transient, a maximum being observed 10 s after addition of the agonist when shape change reached its maximum. P20 and P47 phosphorylations were not strongly affected by clopidogrel treatment. Following stimulation of platelets with 2-MeS-ADP, several proteins were phosphorylated at tyrosine residues. Clopidogrel treatment inhibited the increase in phosphorylation of P140, P100, P80/85, P66 and P55 concomitantly with the inhibition of platelet aggregation. However, clopidogrel did not interfere with the early phosphorylation of the P80/85 kD doublet which occurs at the time of the shape change. P80/85, identified by immunodetection as cortactin, could be involved in the reorganization of the cytoskeleton necessary for morphological changes. Thus, by using clopidogrel-treated rat platelets, we were able to determine some of the phosphorylations coupled either to clopidogrel-resistant high-affinity ADP receptors leading to shape change or to clopidogrel sensitive low-affinity ADP receptors coupled to the aggregation process.
Savi
P
P
Haemobiology Research Department, Sanofi Recherche, Toulouse, France.
Artçanuthurry
V
V
Bornia
J
J
Grelac
F
F
Maclouf
J
J
Levy-Toledano
S
S
Herbert
J M
JM
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D000077144:Clopidogrel; D005260:Female; D010766:Phosphorylation; D015539:Platelet Activation; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013873:Thionucleotides / Q000378:metabolism; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000494:pharmacology
D010975:Platelet Aggregation Inhibitors; D013873:Thionucleotides; C002480:methylthio-ADP; D000244:Adenosine Diphosphate; D000077144:Clopidogrel; D013988:Ticlopidine