INDUCTION OF DELAYED AFTERDEPOLARIZATIONS AND TRIGGERED ARRHYTHMIAS IN ISOLATED PURKINJE-FIBERS - COMPARISON OF RESIBUFOGENIN AND ACETYLSTROPHANTHIDIN

The purpose of this study was to compare the electrotoxicological effe cts of resibufogenin (RBG) (n=14) with acetylstrophanthidin (AS) (n=14 ) to induce delayed afterdepolarization (DAD) and triggered activity ( TA), an their alteration of the electrophysiological properties in she ep cardiac Purkinje fibers using the extracellular electrograms, signa l averaging, and standard microelectrode techniques simultaneously. Th e results indicated: 1) Lower toxic dose of RBG (0.52) mu mol.L(-1)) a nd AS (0.25) mu mol.L(-1)) induced intracellular and extracellular DAD (DAD)-I and DAD-E) at pacing cycle length of 990 and 690 ms. 2) Highe r toxic dose of RBG (2.6 mu mol.L(-1)) and AS (5.0 mu mol.L(-1)) induc ed DAD and TA, nonsustained or sustained premature action potential an d oscillatory potentials; 3) At the beginning period of superfusing th e drugs, both RBG and AS caused changes of the electrophysiological ch aracteristics. This study demonstrates that the electro-toxicological characteristics, and electrophysiological properties of RBG and simila r to that of AS and suggests that RBG belongs to the family of digital is-like drugs.