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Keywords:

  • P2TAC receptor;
  • P2T receptor;
  • P2YAC receptor;
  • P2Y12 receptor, platelets;
  • C6-2B glioma cells
  • P2Y receptor activation in many cell types leads to phospholipase C activation and accumulation of inositol phosphates, while in blood platelets, C6-2B glioma cells, and in B10 microvascular endothelial cells a P2Y receptor subtype, which couples to inhibition of adenylyl cyclase, historically termed P2YAC, (P2TAC or P2T in platelets) has been identified. Recently, this receptor has been cloned and designated P2Y12 in keeping with current P2 receptor nomenclature.

  • Three selective P2T receptor antagonists, with a range of affinities, inhibited ADP-induced aggregation of washed human or rat platelets, in a concentration-dependent manner, with a rank order of antagonist potency (pIC50, human: rat) of AR-C78511 (8.5 : 9.1)>AR-C69581 (6.2 : 6.0)>AR-C70300 (5.4 : 5.1). However, these compounds had no effect on ADP-induced platelet shape change.

  • All three antagonists had no significant effect on the ADP-induced inositol phosphate formation in 1321N1 astrocytoma cells stably expressing the P2Y1 receptor, when used at concentrations that inhibit platelet aggregation.

  • These antagonists also blocked ADP-induced inhibition of adenylyl cyclase in rat platelets and C6-2B cells with identical rank orders of potency and overlapping concentration – response curves.

  • RT – PCR and nucleotide sequence analyses revealed that the C6-2B cells express the P2Y12 mRNA.

  • These data demonstrate that the P2YAC receptor in C6-2B cells is pharmacologically identical to the P2TAC receptor in rat platelets.

British Journal of Pharmacology (2001) 133, 521–528; doi:10.1038/sj.bjp.0704114