title: The effects of P2 purinoceptor agonists on the isolated portal vein of the guinea pig.
abstract: UTP, ATP and several of its analogues enhanced contractions of the longitudinal smooth muscle layer of the guinea-pig portal vein. The rank order of potency was 2-methylthioATP > alpha, beta-methyleneATP > adenosine tetraphosphate > or = beta, gamma-methyleneATP > or = ATP = UTP > > adenosine. Suramin (100 microM) blocked the contractile effects of 2-methylthioATP and alpha,beta-methyleneATP, but not those of ATP and adenosine tetraphosphate. The P1 purinoceptor antagonist, 8-phenyltheophylline (10 microM), was without effect on the response to ATP. Field stimulation (5 s trains every 100 s, 1 ms, 55 V) caused frequency-dependent contractions that were partially reduced by the noradrenergic neurone blocking drug; BW 172C58 (4-benzoyl-xylocholine, 10 microM), but not by suramin. alpha,beta-MethyleneATP was more potent than beta,gamma-methyleneATP, UTP and adenosine tetraphosphate in partially inhibiting field stimulation-induced contractions of the portal vein; its effects, but not those of adenosine tetraphosphate, were reduced by suramin. These results indicate that the guinea-pig portal vein contains P2 purinoceptors; these include a P2x subtype, mediating contraction.
authors.affiliation: Department of Pharmacology, Monash University, Clayton, Victoria, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Orre
authors.forename: J N
authors.initials: JN
authors.lastname: Pennefather
authors.forename: M E
authors.initials: ME
authors.lastname: Story
authors.forename: J M
authors.initials: JM
authors.lastname: Haynes
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D011169:Portal Vein / Q000187:drug effects*; D011983:Receptors, Purinergic / Q000187:drug effects*; D014544:Uridine Triphosphate / Q000494:pharmacology*
chemical_list: D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D000241:Adenosine; D014544:Uridine Triphosphate