Evidence for a novel P2X purinoceptor in human placental chorionic surface arteries

To characterize the P2x purinoceptor of arteries of human term placenta, a non-innervated organ, actions of ATP, alpha, beta-methylene-ATP and UTP on de-endothelialized chorionic surface artery segments were compared. ATP and alpha,beta-methylene-ATP caused reversible concentration-dependent contractions, but UTP elicited little or no contraction up to 517 microM. Concentration-effect curves to ATP and alpha,beta-methylene-ATP were parallel, and alpha,beta-methylene-ATP, EC50 4.2 +/- 1.2 microM, was 28-times as potent as ATP. At a saturating concentration, 103 microM, alpha,beta-methylene-ATP did not desensitize the ATP receptor. Contractions to ATP and alpha,beta-methylene-ATP were antagonized by 300 microM suramin. These findings indicate that P2X purinoceptors are present in placental chorionic surface arteries and that they differ from P2X purinoceptors in arteries of other tissues.