Evidence for the expression of multiple uracil nucleotide-stimulated P2 receptors coupled to smooth muscle contraction in porcine isolated arteries.
OBJECTIVE
The uracil nucleotides UDP and UTP have been reported to activate P2Y2, P2Y4 and P2Y6 receptors to cause vasoconstriction. We have performed a comparative analysis of these receptors in endothelium-denuded smooth muscle from porcine isolated coronary and ear arteries, using pharmacological and molecular tools.


METHODS
Tissue segments were used to construct non-cumulative concentration response curves for UTP and UDP, in the absence and presence of the P2 receptor antagonists PPADS or suramin. RT-PCR and immunoblot analyses were employed to define gene expression and immunoreactivity for P2Y2, P2Y4 and P2Y6 receptors.


RESULTS
In the coronary artery, UTP-evoked contractile responses were reduced in the presence of suramin, but not PPADS, while the smaller responses to UDP were unaffected by either antagonist. In the ear artery, contractile responses to UDP were much smaller than those to UTP; responses to UTP were inhibited by both PPADS and suramin. RT-PCR suggested predominant expression of P2Y2 receptors in the coronary artery, while P2Y4 and P2Y6 receptor gene expression appeared equivalent in both tissues. Immunoblot analyses provided evidence for P2Y6 receptors in both tissues, with equivocal evidence of P2Y2 and P2Y4 receptor immunoreactivities.


CONCLUSIONS
We conclude that UTP-evoked contraction of porcine coronary artery smooth muscle appears to be predominantly P2Y2-mediated, while the ear artery appears to express a uracil nucleotide-sensitive P2 receptor(s) which fails to fit readily into the current classification.
Rayment
S J
SJ
School of Biomedical Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, UK.
Latif
M L
ML
Ralevic
V
V
Alexander
S P H
SP
D000818:Animals; D015153:Blotting, Western; D003331:Coronary Vessels / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004423:Ear / Q000098:blood supply; D015870:Gene Expression; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D058910:Purinergic P2 Receptor Agonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058473:Receptors, Purinergic P2Y2; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013498:Suramin / Q000494:pharmacology; D013552:Swine; D014500:Uracil Nucleotides / Q000378:metabolism* / Q000494:pharmacology; D014530:Uridine Diphosphate / Q000378:metabolism; D014544:Uridine Triphosphate / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects
D058910:Purinergic P2 Receptor Agonists; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D014500:Uracil Nucleotides; C104749:purinoceptor P2Y4; C099845:purinoceptor P2Y6; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D014530:Uridine Diphosphate; D011732:Pyridoxal Phosphate; D013498:Suramin; D014544:Uridine Triphosphate