Role of P2Y1 purinoceptor in ADP-induced platelet activation.
ADP acts as an agonist of platelet aggregation via specific receptors which are still to be characterised. Amplification by PCR of a human platelet cDNA library confirmed the presence of mRNA of the P2Y1 receptor in platelets. In order to determine if these P2Y1 receptors were involved in ADP-induced platelet activation, we determined the effects of A3P5PS, an antagonist of the P2Y1 receptor, on the binding of [33P]2-MeS-ADP, a potent analogue of ADP. We found that A3P5PS displaced about 27% of [33P]2-MeS-ADP binding, a receptor population which has been shown to be resistant to treatment with clopidogrel, a selective anti-ADP agent. A3P5PS specifically inhibited 2-MeS-ADP-induced shape change and calcium increase but did not affect adenylyl cyclase down-regulation. 2-MeS-ADP-induced platelet aggregation was also inhibited by A3P5PS but was restored when platelets were further activated by serotonin, a non-aggregating compound, therefore suggesting that P2Y1-mediated stimulation is an absolute prerequisite for ADP to induce platelet aggregation and a key event for platelet activation and aggregation to occur. These results therefore show that ADP-induced aggregation cannot be attributed to activation of P2Y1 alone, but must be attributed to the simultaneous activation of the high affinity receptor (P2Y1) and a low affinity receptor of ADP (still to be discovered), each of them essential, but neither able to trigger aggregation alone.
Savi
P
P
Haemobiology Research Department, Sanofi Recherche, Toulouse, France.
Beauverger
P
P
Labouret
C
C
Delfaud
M
M
Salel
V
V
Kaghad
M
M
Herbert
J M
JM
D000244:Adenosine Diphosphate / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000077144:Clopidogrel; D006801:Humans; D066298:In Vitro Techniques; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000502:physiology*; D058472:Receptors, Purinergic P2Y1; D013988:Ticlopidine / Q000031:analogs & derivatives / Q000494:pharmacology
C546382:P2RY1 protein, human; D010975:Platelet Aggregation Inhibitors; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D000244:Adenosine Diphosphate; D000077144:Clopidogrel; D013988:Ticlopidine; D002118:Calcium