TY - JOUR T1 - BLOCKADE OF CARDIAC EFFECTS OF ISOPROTERENOL BY 4-(2-HYDROXY-3-ISOPROPYLAMINOPROPOXY)-ACETANILIDE (ICI 50,172) JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 72 LP - 78 VL - 170 IS - 1 AU - PITAMBAR SOMANI AU - ATUL R. LADDU Y1 - 1969/11/01 UR - http://jpet.aspetjournals.org/content/170/1/72.abstract N2 - The beta adrenergic blocking activity of 4-(2-hydroxy-3-isopropyl-aminopropoxy)-acetanilide (ICI 50,172) was investigated in the isolated turtle heart preparation and the blood-perfused supported dog heart preparation (ISHP). The pA2 value for ICI 50,172 in the turtle heart was found to be 7.0. Intracoronary administration of isoproterenol produced a dose-dependent increase in heart rate, left ventricular contractile force, left ventricular systolic pressure and myocardial oxygen consumption and a decrease in coronary artery perfusion pressure in the ISHP. Pretreatment with 0.25 mg/kg of ICI 50,172 effectively blocked the myocardial effects of isoproterenol in a competitive manner. ICI 50,172 reduced the myocardial oxygen consumption of the ISHP with little or no effect on myocardial contractility or heart rate, suggesting an improved myocardial efficiency. © 1969, by The Williams & Wilkins Company ER -