Electrophysiological effects of tiracizin and its metabolites in dog cardiac Purkinje fibers.
1. Conventional microelectrode technique was used to study the effects of tiracizin and its two main metabolites on the action potential parameters in dog cardiac Purkinje fibers. 2. Tiracizin induced a use-dependent depression of the maximal rate of depolarization during the upstroke of the action potential (EC50 = 0.323 +/- 0.059 microM, n = 5) and decreased the action potential duration (EC50 = 0.230 +/- 0.024 microM, n = 5). 3. The two main metabolites exerted similar effects, but only at concentrations about one order of magnitude higher than tiracizin. 4. It was concluded that the electrophysiological effects of tiracizin in dog Purkinje fibers correspond to those of Class I antiarrhythmic drugs also in cardiac Purkinje fibers. The main metabolites are less potent than the parent compound, therefore it is likely that their effects play a less important role in the beneficial effect of tiracizin in cardiac arrhythmias.
Németh
M
M
Department of Pharmacology, Albert Szent-Györgyi Medical University, Szeged, Hungary.
Varró
A
A
Papp
J G
JG
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D003984:Dibenzazepines / Q000494:pharmacology*; D004285:Dogs; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000187:drug effects* / Q000294:innervation*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008839:Microelectrodes; D011690:Purkinje Fibers / Q000187:drug effects*
D000889:Anti-Arrhythmia Agents; D003984:Dibenzazepines; C048166:tiracizine