effects of pretreatment with non hypotensive dose of ramiprilat and losartan on myocardial ischemia-reperfusion induced arrhythmias and infarct size in rats

introduction: inhibition of renin angiotensin system represents an important approach in the management of cardiovascular diseases. the aim of this study was to explore the effects of pretreatment with non-hypotensive dose of angiotensin converting enzyme (ace) inhibitor, ramiprilat and angiotensin type 1 (at1) receptor blocker, losartan on myocardial infarct size and arrhythmias in a rat model of ischemia-reperfusion injury. methods: seventy male wistar rats were divided into five groups. one group received saline as control. other groups were given 10 mg/kg/day of losartan for one (l-1w) or ten weeks (l-10w) as well as 50 μg/kg/day of ramiprilat for one (r-1w) or ten weeks (r-10w) using a feeding needle. the rats were subjected to 30 minutes occlusion and 120 minutes reperfusion of the left coronary artery. infarct size was determined using triphenyl tetrazolium chloride staining. ischemia-induced ventricular arrhythmias were analyzed in accordance with the lambeth conventions. results: myocardial infarct size and the number of ventricular beats were significantly reduced in r-1w group, but the reduction was not significant in l-1w. after increasing the duration of pretreatment to 10 weeks in l-10w group, the infarct size, the number of ventricular beats and the episodes of ventricular tachycardia were significantly decreased. however in r-10w group the reduction of ventricular arrhythmias was not significant conclusion: based on the above mentioned results it could be concluded that losartan and ramiprilat, at a nonhypotensive dose, can reduce the induction of arrhythmias and infarct size following myocardial ischemia reperfusion. these drugs appear to act in a time-dependent manner. therefore, we expected an increased cardiac effect by long-term administration of losartan. however prolonged treatment with ramiprilat reduced its protective effect.