Acute inhibition of monoamine oxidase with pargyline does not modify the severity of ischemia and reperfusion-induced ventricular arrhythmias in dogs

INTRODUCTION: Monoamine oxidase inhibitors are proposed to provide cardioprotection by reducing the formation of H2O2 resulting from enzymatic deamination of biogenic amines following ischemia and reperfusion. OBJECTIVES: To examine whether pargyline, an irreversible and nonselective inhibitor of monoamine oxidase, modifies the severity of ventricular arrhythmias occurring during coronary artery occlusion and reperfusion in dogs. METHODS: In chloralose-urethane anesthetized dogs either saline (control, n=7) or pargyline (10 mg/kg; n=7) was administered intravenously 15 min before a 25 min occlusion of the left anterior descending coronary artery. Ventricular arrhythmias, plasma adrenaline/noradrenaline concentrations, and tissue and blood superoxide/H(2)O(2)levels were assessed. RESULTS: Compared with the control group, pargyline did not modify the severity of arrhythmias during occlusion (ventricular premature beats: 319 +/- 123 versus 305 +/- 128; episodes of ventricular tachycardia: 5.6 +/- 2.4 versus 5.0 +/- 2.2; incidences of ventricular tachycardia: 86% versus 100%; incidence of ventricular fibrillation: 29% versus 14%) and survival (0% versus 14%) on reperfusion. There were also no significant differences between the two groups in superoxide and H2O2 production, as well as in plasma adrenaline and noradrenaline concentrations. CONCLUSIONS: The inhibition of monoamine oxidases by pargyline does not influence the ischemia and reperfusion-induced ventricular arrhythmias and the generation of H2O2 in anesthetized dogs. These results suggest that, in this species, monoamine oxidase may not be the primary source of reactive oxygen species.