title: Comparison of the potency of 8-phenyltheophylline as an antagonist at A1 and A2 adenosine receptors in atria and aorta from the guinea-pig.
abstract: The potency of 8-phenyltheophylline as an antagonist at A1 adenosine receptors in guinea-pig atria and at A2 adenosine receptors in the guinea-pig aorta has been investigated. 8-Phenyltheophylline was an apparently competitive antagonist of the negative chronotropic effect of adenosine, 2-chloroadenosine, L-N6-phenyl-isopropyl adenosine (L-PIA) and 5'-N-ethylcarboxamide adenosine (NECA) on atria and of the relaxant effect of adenosine, 2-chloroadenosine and NECA on the aorta. The pA2 values for 8-phenyltheophylline ranged from 6.4 to 6.6 and were not significantly different, irrespective of the agonist or tissue used. These results indicate that 8-phenyltheophylline is a relatively potent antagonist at adenosine receptors but does not exhibit selectivity for either of the putative sub-types in isolated tissues.
authors.forename: M G
authors.initials: MG
authors.lastname: Collis
authors.forename: D B
authors.initials: DB
authors.lastname: Palmer
authors.forename: V L
authors.initials: VL
authors.lastname: Saville
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000378:metabolism; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000187:drug effects* / Q000378:metabolism; D011983:Receptors, Purinergic; D013806:Theophylline / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D013806:Theophylline; C028322:8-phenyltheophylline; D009638:Norepinephrine