Effects of LDL and oxidized LDL on cardiac function in isoproterenol-induced myocardial infarction in rat

Notable discussions have been developed over the distinctive effects of LDL and oxidized LDL (OxLDL) on myocardial functions. The aim of the present study was to investigate the effects of OxLDL on electrocardiogram and hemodynamic parameters of rat's heart in isoproterenol (ISO)-induced myocardial infarction (MI) model.Male Wistar rats were allocated in to 6 groups and receive one of the 3 formulated diets (standard, cholesterol-rich and oxidized cholesterol-rich diets). After 14 weeks to induce MI, rats in 3 groups were received ISO (100 mg/kg) for 2 consecutive days subcutaneously. Lipid profiles, electrocardiogram patterns and hemodynamic parameters of all groups were investigated.Serum levels of LDL, cholesterol and triglycerides were significantly higher in the fat-rich diet fed groups compared to control group (P<0.001). The ISO-treated rats showed a marked reduction in the R-amplitude, R-R interval, LVSP, left ventricular contractility (LVdP/dtmax) and relaxation (LVdP/dtmin) as well as severe elevation in ST-segment and LVEDP value compared to the respective normal rats. High serum level of OxLDL resulted in significant exacerbation in the destructive effects of ISO on R-amplitude, R-R interval, LVSP, left ventricular contractility (LVdP/dtmax), relaxation (LVdP/dtmin), ST-segment and LVEDP values. Additionally, heart to body weight ratio as an index of myocardial edematous was also increased significantly. However, changes in these parameters in rats fed with cholesterol-rich diet were not significant.Generally, results indicated that the effects of high OxLDL level on electrocardiogram and hemodynamic parameter after MI was more reliable than effects of high LDL level.