title: P2-purinoceptors of two subtypes in the rabbit mesenteric artery: reactive blue 2 selectively inhibits responses mediated via the P2y-but not the P2x-purinoceptor.
abstract: alpha,beta-Methylene ATP and ATP both produced concentration-dependent contractions of the isolated mesenteric artery of the rabbit that were not inhibited by reactive blue 2. In preparations where the tone had been raised with noradrenaline, ATP and 2-methylthio ATP, but not alpha,beta-methylene ATP, produced relaxations of the vessel. These relaxations were inhibited in the presence of reactive blue 2. Reactive blue 2 did not inhibit the contractions to noradrenaline, and only slightly inhibited relaxations to adenosine and acetylcholine. The rank order of potency of purine nucleotide analogues in contracting the vessel was: alpha,beta-methylene ATP greater than beta,gamma-methylene ATP = 2-methylthio ATP greater than ATP, and in relaxing the vessel at raised tone was: 2-methylthio ATP greater than ATP greater than beta,gamma-methylene ATP greater than alpha,beta-methylene ATP. It is concluded from this study that in the isolated mesenteric artery of the rabbit, purine nucleotides act via P2y-purinoceptors to cause the muscle to relax and via P2x-purinoceptors to cause the muscle to contract. The results also suggest that reactive blue 2 selectively inhibits responses mediated via the P2y-purinoceptor, at least within a limited concentration range.
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D011817:Rabbits; D011983:Receptors, Purinergic / Q000145:classification* / Q000187:drug effects; D014227:Triazines / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D011983:Receptors, Purinergic; D014227:Triazines; C012842:Cibacron Blue F 3GA; D000255:Adenosine Triphosphate