Effect of E4031, a class III antiarrhythmic drug, on ischemia- and reperfusion-induced arrhythmias in isolated rat hearts.
The delayed outward rectifier K+ channel has a role in the increase in automaticity of myocytes under pathophysiological conditions. The purpose of the present study was to clarify the effect of blockade of outward rectifier K+ channels by a class III antiarrhythmic drug, E4031, on ischemia- and reperfusion-induced arrhythmias. Ion fluxes, energy metabolites and cardiac function were measured and the epicardial electrocardiograms of Langendorff-perfused rat hearts were recorded during initial perfusion, global or regional ischemia and reperfusion. 10(-7) M of E4031 administered during the initial perfusion did not prolong the QT interval, but slowed the heart rate (


METHODS
222, E4031: 183 bpm, p < 0.05), increased myocardial 45Ca2+ uptake (


METHODS
2.1, E4031: 2.9 mumol/g dwt, p < 0.05) and attenuated the loss of intracellular K+ during ischemia (


METHODS
238, E4031: 248 mumol/g dwt, p < 0.05). E4031 tended to reduce ischemia-induced ventricular tachyarrhythmias (


METHODS
60, E4031: 30%, n.s.), but reperfusion-induced ventricular tachyarrhythmias were sustained longer by the administration of E4031 (CONTROL: 255, E4031: 623 sec, p < 0.05). Prior exposure to E4031 decreased the depletion of high energy phosphates during ischemia, but suppressed their recovery during reperfusion. These results suggest that the attenuated loss of K+ from the ischemic myocardium and the decrease in heart rate by E4031 contributed to the reduction of ischemia-induced arrhythmias. However, the increase in myocardial Ca2+ uptake and altered energy metabolism may be responsible for the increase in reperfusion-induced arrhythmias.
Department of Geriatric Medicine, Keio University School of Medicine, Tokyo, Japan.
K
K
Shinmura
M
M
Tani
H
H
Hasegawa
Y
Y
Ebihara
Y
Y
Nakamura
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001145:Arrhythmias, Cardiac / Q000188:drug therapy* / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism; D004734:Energy Metabolism / Q000187:drug effects; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy* / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology / Q000627:therapeutic use*; D015221:Potassium Channels / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016277:Ventricular Function, Left / Q000187:drug effects
D000889:Anti-Arrhythmia Agents; D010880:Piperidines; D015221:Potassium Channels; D011725:Pyridines; C063968:E 4031; D002118:Calcium