FERROUS ION DIMINISHED THE ANTIARRHYTHMIC EFFECT OF NALOXONE IN MYOCARDIAL-ISCHEMIA OF ISOLATED RAT HEARTS

This investigation was to examine the effect of ferrous ion (a prooxid ant) on the antiarrhythmic effect of naloxone (an endogenous opioid re ceptor antagonist) in isolated rat hearts, Isolated Sprague-Dawley rat hearts were perfused in the Langendorff mode and myocardial ischemia was performed by ligating the left descending coronary artery. Cardiac rhythm was recorded, Heart alpha-tocopherol concentrations were analy zed. Naloxone (1.2 mu mol/heart) was effective in reducing the severit y of arrhythmia (arrhythmia score; mean+/-S.E.M: 2.82+/-0.69 for nalox one v.s. 5.18+/-0.38 for control, p<0,01), Fe2+ (100 nmol/heart) alone did not significantly affect the arrhythmia score (5.63+/-0.32) when compared with the control, however, Fe2+ administration did cause sign ificant early onset of ventricular premature contraction and ventricul ar tachycardia, Additionally, Fe2+ administration diminished the nalox one's antiarrhythmic effect (arrhythmia score 4.12 +/- 0.40), alpha-To copherol, a major free radical scavenger that exerts protective functi ons on heart tissues during myocardial ischemia/reperfusion, was signi ficantly higher in the naloxone-treated group (59.05+/-3.00 nmol/g wet wt) than in the control group (43.84+/-4.17 nmol/g wet wt, p<0.05). T hese results suggest that endogenous opioid peptides and reactive oxyg en species might be related to ischemia-induced arrhythmia.