THE INFLUENCE OF IMIDAZOLE ADMINISTRATION ON ARRHYTHMIAS INDUCED BY POTASSIUM-CHLORIDE, CALCIUM-CHLORIDE, AND OUABAIN IN ISOLATED GUINEA-PIG HEARTS

In isolated Langendorff-perfused guinea pig hearts, an aqueous 1% pota ssium chloride solution, injected into the cannula, induced cardiac ar rhythmias characterized by cardiac arrest alternating with ventricular extrasystoles. When imidazole was administered intraperitoneally in a dose of 5.87 mmol/kg, four hours prior to the experiment, an enhancem ent of the cardiac arrest was seen. In the same preparations, perfusio n with a Krebs-Henseleit solution enriched with an aqueous 3% calcium chloride solution brought about arrhythmias that consisted of ventricu lar extrasystoles followed by a transient cardiac stop and then by the alternation of tachyarrhythmias with bradyarrhythmias. The heart stop ped in cardiac arrest. Pretreatment with imidazole resulted in an obvi ous enhancement of the cardiotoxicity of calcium chloride. In ouabain- evoked (1.64 mu mol/kg) cardiac arrhythmias, imidazole also had a proa rrhythmogenic effect, accelerating the onset of arrhythmic events, inc luding ventricular fibrillation. It also raised the percentage of vent ricular fibrillations. These results are in contrast to our previous f indings, which have shown that in anesthetized rats, the intracerebrov entricular injection of imidazole had an antiarrhythmic activity. The causes of these discrepancies are discussed herein.