title: Characterization of the P2 receptors in rabbit pulmonary artery.
abstract: 1. We have identified the P2 receptors mediating vasomotor responses in the rabbit pulmonary artery. 2. Neither ATP nor UTP contracted intact or endothelium-denuded rings. However, both relaxed intact rings of rabbit pulmonary artery that had been preconstricted with phenylephrine (pD2 5.2 and 5.6, respectively). 3. The vasodilator effect of UTP was endothelium-dependent and abolished by the nitric oxide synthase inhibitor NG-nitro-L-arginine (L-NOARG). 4. The vasodilator effect of ATP was only partially inhibited by removal of endothelium or addition of L-NOARG, suggesting an additional direct effect on vascular smooth muscle. 5. The endothelium-dependent vasodilator responses to UTP and ATP were competitively antagonized by suramin. 6. Preconstricted, endothelium-denuded rings were also relaxed by 2-methylthio ATP (pD2 6.6), a P2Y receptor agonist. 7. Ca(2+)-mobilizing P2U receptors were identified on smooth muscle cells on the basis of single cell responses to ATP (pD2 7.8) and UTP (pD2 7.9; 6.7 in the presence of 100 microM suramin). 8. There was no evidence of a Ca(2+)-mobilizing P2Y receptor in these cultured cells. 9. The data suggest the presence of (i) a suramin-sensitive P2U receptor on endothelial cells that induces vasorelaxation through NO release, (ii) a suramin-sensitive P2U receptor on cultured smooth muscle cells that mobilizes Ca2+ but is not coupled to vasomotor responses and (iii) a putative P2Y receptor on vascular smooth muscle cells that induces relaxation via a Ca(2+)-independent signal transduction pathway.
authors.affiliation: Centre for Immunology, St Vincent's Hospital, Darlinghurst, NSW, Australia.
authors.forename: R A
authors.initials: RA
authors.lastname: Qasabian
authors.forename: C
authors.initials: C
authors.lastname: Schyvens
authors.forename: R
authors.initials: R
authors.lastname: Owe-Young
authors.forename: J P
authors.initials: JP
authors.lastname: Killen
authors.forename: P S
authors.initials: PS
authors.lastname: Macdonald
authors.forename: A D
authors.initials: AD
authors.lastname: Conigrave
authors.forename: D J
authors.initials: DJ
authors.lastname: Williamson
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D018047:Receptors, Purinergic P1 / Q000187:drug effects / Q000502:physiology*; D013498:Suramin / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology*; D014664:Vasodilation / Q000502:physiology
chemical_list: D018047:Receptors, Purinergic P1; D019335:Nitroarginine; D009569:Nitric Oxide; D013498:Suramin; D000255:Adenosine Triphosphate; D002118:Calcium; D014544:Uridine Triphosphate