EVIDENCE FOR A NOVEL P-2X PURINOCEPTOR IN HUMAN PLACENTAL CHORIONIC SURFACE ARTERIES

To characterize the P-2X purinoceptor of arteries of human term placen ta, a non-innervated organ, actions of ATP, alpha,beta-methylene-ATP a nd UTP on de-endothelialized chorionic surface artery segments were co mpared. ATP and alpha,beta-methylene-ATP caused reversible concentrati on-dependent contractions, but UTP elicited little or no contraction u p to 517 mu M Concentration-effect curves to ATP and alpha,beta-methyl ene-ATP were parallel, and alpha,beta-methylene-ATP, EC(50) 4.2 +/- 1. 2 mu M, was 28-times as potent as ATP. At a saturating concentration, 103 mu M, alpha,beta-methylene-ATP did not desensitize the ATP recepto r. Contractions to ATP and alpha,beta-methylene-ATP were antagonized b y 300 mu M suramin. These findings indicate that P-2X purinoceptors ar e present in placental chorionic surface arteries and that they differ from P-2X purinoceptors in arteries of other tissues.