Identification of contractile P2Y1, P2Y6 and P2Y12 receptors in rat intrapulmonary artery using selective ligands

Mitchell, Callum and Syed, Nawazish-I-Husain and Tengah, Asrin and Gurney, Alison and Kennedy, Charles (2012) Identification of contractile P2Y1, P2Y6 and P2Y12 receptors in rat intrapulmonary artery using selective ligands. Journal of Pharmacology and Experimental Therapeutics, 343 (3). pp. 755-762. ISSN 0022-3565 (

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ATP and UDP constrict rat intrapulmonary arteries, but which receptors mediate these actions is unclear. Here we used selective agonists and antagonists, along with measurements of P2Y receptor expression, to characterise the receptor subtypes involved. Isometric tension was recorded from endothelium-denuded rat intrapulmonary artery rings (i.d. 200-500 μm) mounted on a wire myograph. Expression of P2Y receptor subtype expression was determined using RT-PCR with receptor-specific oligonucleotide primers. The selective P2Y(1) agonist MRS2365 induced small, concentration-dependent contractions that were inhibited by the P2Y(1) antagonist MRS2179. Contractions evoked by ATP were unaffected by MRS2179, but inhibited by about one third by the P2Y(12) antagonist AR-C69931MX. Combined blockade of P2X1 and P2Y(12) receptors virtually abolished the response to ATP. ADP also evoked contractions that were abolished by AR-C69931MX. The selective P2Y(6) receptor agonist, PSB 0474, evoked concentration-dependent contractions and was approximately 3-times more potent than UDP, but the P2Y(14) agonist, UDP-glucose, had no effect. Contractions evoked by UDP were inhibited by the P2Y(6) receptor antagonist, MRS2578, but not the CysLT(1) antagonist, MK571. Higher concentrations of MRS2578 inhibited contractions to KCl and so were not studied further. mRNA for P2Y(1), P2Y(6) and P2Y(12) receptors was identified, but this could not be correlated with protein expression. Our working model is that P2Y(12) and P2X1 receptors are present in rat intrapulmonary arteries and together mediate ATP-induced vasoconstriction. Contractile P2Y(6), but not P2Y(14) or CysLT(1) receptors are also present and are a major site through which UDP evokes constriction.