Characterization of Contractile P2 Receptors in Human Coronary Arteries by Use of the Stable Pyrimidines Uridine

The present study was designed to evaluate the relative con-tribution of the different contractile P2 receptors in endotheli-um-denuded human coronary arteries by use of extracellular nucleotides, including the stable pyrimidines uridine 59-O-3-thiotriphosphate (UTPgS) and uridine 59-O-thiodiphosphate (UDPbS). The isometric tension of isolated vessel segments was recorded in vitro, and P2 receptor mRNA expression was examined by reverse transcription-polymerase chain reaction. ab-Methylene-adenosine triphosphate (ab-MeATP) elicited contractions at a low concentration (pEC50 5 5.2), indicating the presence of contractile P2X receptors. The P2Y responses were analyzed after P2X receptor desensitization with 10 mM ab-MeATP. The stable nucleotides UTPgS and adenosine 59-O-3-thiotriphosphate (ATPgS), which are agonists of P2Y2 o