INOTROPIC AND ELECTROPHYSIOLOGIC EFFECTS OF AMRINONE IN UNTREATED AND DIGITALIZED VENTRICULAR TISSUES

  • 1 January 1982
    • journal article
    • research article
    • Vol. 221  (1) , 188-196
Abstract
Amrinone may induce oscillatory afterpotentials (OAP) or aftercontractions (AC) in Purkinje tissue or myocardium. A relationship may exist between the production of OAP or AC and the inotropic effects of amrinone. Possible effects of amrinone on the oscillations and the positive inotropic effect produced by digitalis were studied. Isolated canine papillary and trabecular muscles, as well as false tendons, were exposed to 5.3 .times. 10-4 M amrinone. Some of the preparations were pretreated with acetylstrophanthidin (AS) in a dose just sufficient to induce OAP or AC. Standard electrophysiologic techniques were used to record transmembrane action potentials. Developed tension also was recorded. Amrinone by itself did not induce OAP or AC in myocardium or false tendons. This was true even when the resting membrane potential of the false tendons was reduced by means of focal current application. Amrinone increased the amplitude of AS-induced oscillations in both myocardium and false tendons. Amrinone increased strength of contraction of untreated myocardium at all basic cycle lengths and of AS-treated myocardium, especially at shorter basic cycle lengths. Amrinone decreased strength of contraction both of untreated and AS-treated false tendons at all basic cycle lengths. There may be important differences in the mechanisms of action of amrinone and digitalis.