title: Interaction of the antihypertensive drug urapidil with cardiac beta-adrenoceptors in vitro.
abstract: A possible interaction of the antihypertensive drug, urapidil with beta-adrenoceptors was investigated in a guinea-pig ventricular membrane preparation. Urapidil at concentrations above 1 microM antagonized the isoproterenol-induced stimulation of adenylate cyclase activity. Urapidil 10 microM shifted the concentration-response curve for isoproterenol in a parallel manner to the right by a factor of 16. Urapidil competed with specific beta-adrenoceptor binding of [125I]iodocyanopindolol with an IC50 of 12 microM. Since the affinity of urapidil to beta-adrenoceptors appeared rather low, any beta-adrenoceptor blocking property may be of relevance in vivo at high dosages only.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000959:Antihypertensive Agents / Q000378:metabolism / Q000494:pharmacology*; D001667:Binding, Competitive; D004789:Enzyme Activation / Q000187:drug effects; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D010879:Piperazines / Q000378:metabolism / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000959:Antihypertensive Agents; D010879:Piperazines; D011943:Receptors, Adrenergic, beta; D020120:Iodocyanopindolol; C015568:urapidil; D010869:Pindolol; D000262:Adenylyl Cyclases; D007545:Isoproterenol