title: 8-phenyltheophylline: a potent P1-purinoceptor antagonist.
abstract: 8-Phenyltheophylline was more potent than theophylline in antagonizing the inhibitory effects of adenosine in guinea-pig driven left atrium, rabbit basilar artery and electrically stimulated guinea-pig ileum preparations. In guinea-pig atrium and ileum, the antagonism of adenosine responses by the methylxanthines is of a competitive nature, but in rabbit basilar artery it does not appear to be so. In all three preparations, the effects of theophylline and 8-phenyltheophylline could be reversed by washing. It is concluded that 8-phenyltheophylline is a more potent P1-purinoceptor antagonist than theophylline.
mesh_terms: D000241:Adenosine / Q000037:antagonists & inhibitors*; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D011817:Rabbits; D011955:Receptors, Drug / Q000187:drug effects*; D011983:Receptors, Purinergic; D013806:Theophylline / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D011955:Receptors, Drug; D011983:Receptors, Purinergic; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine