Effects of High Fat-, Cholesterolenriched Diet on the Antioxidant Defence Mechanisms in the Rabbit Heart

In 7 rabbits fed on hyperlipidic diet (0.5% cholesterol, 5% peanut oil and 5% lard) for 4 weeks, the ventricular myocardium was tested for antioxidant defences and thiobarbituric acid reactive substances. Seven age-matched rabbits served as controls. The hearts were previously subjected to 45 min Langendorff perfusion to study coronary flow, developed tension and resting tension; coronary effluent values of CPK activity, pH and UV absorbance at 250 nm (i.e., low molecular weight ATP catabolites) were also investigated. After 4 weeks of diet, a significant rise of plasma cholesterol (P > 0.0001) and tryglycerides (P > 0.0001) was observed. Total superoxide dismutase, catalase and glutathione transferase activities underwent a significant increase (P > 0.05) in the hyperlipidemic animals. On the contrary, a depression of glutathione reductase (P > 0.01) and selenium-dependent glutathione peroxidase (P > 0.01) activities, associated with decreased levels of non proteic thiol compounds (P > 0.01), was assessed. The selenium-independent glutathione peroxidase activity was not detectable in both groups. Thiobarbituric acid reactive substances levels were significantly increased in the hyperlipidemic rabbit myocardium (P > 0.01). Even though heart hemodynamics, CPK release and perfusate pH did not differ in control and experimental animals, higher 250 nm absorbance values (P > 0.05) were detected in the myocardial effluent of hyperlipidemic rabbits. In conclusion, high fat-, cholesterol-enriched diet induces an imbalance in the rabbit heart antioxidant defences, some of which are increased, whereas others are depressed, eventually resulting in enhanced myocardial lipid peroxidation. These biochemical changes are associated with higher perfusate values of UV absorbance at 250 nm, but not with significant CPK leakage or myocardial hemodynamics derangement.