title: [Atenolol, its cardioselective property for adrenergic beta-receptor blocking action and effect on the cardiac function (author's transl)].
abstract: Cardioselective property of the beta-adrenoceptor blocking action of atenolol and its effect on the AV conduction, the atrial muscle refractory period and the cardiac contractility were studied in comparison with these of propranolol. A ratio of pA2 values obtained in the isolated right-atrial preparations and the isolated tracheal preparations of guinea pigs demonstrated that atenolol was highly cardioselective, while propranolol was non-selective. This cardioselective property of atenolol was confirmed in in vivo experiments using guinea pigs. Atenolol increased the AV conduction time and decreased the cardiac contractility dose-dependently in anesthetized dogs of which the heart was electrically driven at fixed rates. At 140 beats/min, AV block was observed at 10 mg/kg, i.v. in 3 of 8 dogs, and further increase in a dose  ti 30 mg/kg resulted in acute heart failure in one of remaining 5 dogs, while propranolol, though showing a tendency to be less potent in depressing AV conduction in a dose range less than 0.3 mg/kg, produced a state of heart failure in 2 of 5 dogs at 3 mg/kg, i.v. and AV block in all of the remainder at 10 mg/kg, i.v. Functional refractory period of AV node as well as functional and effective refractory period the the atrial muscle were increased dose-dependently by atenolol and propranolol. There were no significant differences between both drugs regarding these effects. Further increase in a pacing rate to 160 and 180 beats/min augmented the depressing effect of both drugs on the AV conduction.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001262:Atenolol / Q000097:blood / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006329:Heart Conduction System / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D011412:Propanolamines / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D013268:Stimulation, Chemical; D014132:Trachea / Q000187:drug effects
chemical_list: D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D001262:Atenolol; D011433:Propranolol