title: Analysis of P2-purinoceptor subtypes on the smooth muscle and endothelium of rabbit coronary artery.
abstract: We studied purinoceptor subtypes mediating constriction and dilatation in isolated rabbit coronary arteries with and without endothelium by comparing the effects of adenosine, ATP and the ATP analogues, alpha, beta-methylene ATP and 2-methylthio ATP. For contraction, the rank order of agonist potency was alpha, beta-methylene ATP > 2-methylthio ATP >> ATP; adenosine did not produce contraction. Removal of the endothelium did not affect these responses, but they were abolished by previous desensitisation with alpha, beta-methylene ATP. For relaxation, adenosine, ATP, and 2-methylthio ATP were equipotent, but alpha, beta-methylene ATP had no vasodilator effect and caused further contraction of the preparations. A transient contraction often preceded the relaxations to ATP at higher concentrations. The dilator responses to adenosine, ATP, and 2-methylthio ATP were significantly reduced but not abolished in preparations denuded of endothelium; previous desensitisation with alpha, beta-methylene ATP had no effect on the relaxant responses but abolished the initial transient contractions to ATP and 2-methylthio ATP. These results indicate the presence of vasodilator P1- and P2Y-purinoceptors on smooth muscle and, to a lesser extent, on endothelium and P2X-purinoceptors, mediating transient vasoconstriction on smooth muscle alone. The presence of smooth muscle P2Y-purinoceptors is unusual and has functional implications regarding the nature of the response of the coronary artery to ATP.
authors.affiliation: Department of Anatomy and Developmental Biology, University College, London, England.
authors.forename: L
authors.initials: L
authors.lastname: Corr
authors.forename: G
authors.initials: G
authors.lastname: Burnstock
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D003331:Coronary Vessels / Q000737:chemistry; D004730:Endothelium, Vascular / Q000737:chemistry* / Q000187:drug effects; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000737:chemistry* / Q000187:drug effects; D011817:Rabbits; D011983:Receptors, Purinergic / Q000032:analysis* / Q000187:drug effects; D013873:Thionucleotides / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
chemical_list: D011983:Receptors, Purinergic; D013873:Thionucleotides; D000255:Adenosine Triphosphate; D000241:Adenosine; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; C008501:2-methylthio-ATP