Abstract
Diets supplemented with fish oil have been shown to protect against the complications of coronary heart disease with reduced atherogenesis, smaller infarcts, fewer arrhythmias, and a lower mortality rate. This has been attributed to the effect of fish oil on blood cells and plasma components, including an inhibition of platelets, a decrease in plasma fibrinogen, reduction in release of free radicals from neutrophils and myocytes, and enhancement of the endothelium-derived relaxing factor. The current study was designed to compare the effects of a diet enriched with fish oil on myocardial ischemia and reperfusion, independent of blood cells and plasma components, using an isolated rat-heart preparation. Rats were fed either a fish-oil-enriched or a butter-enriched diet for 5 days, after which their hearts were removed and perfused according to the modified Langendorff procedure. The hearts were perfused with a bloodless (Krebs-Henseleit buffer), oxygenated perfusate. Ischemia was induced by stopping perfusion for 15 minutes followed by 10 minutes of reperfusion. Cardiac contraction and coronary perfusion pressure were measured before and after ischemia/reperfusion. The hearts were analyzed for myocardial phospholipid content. Plasma from each rat was collected for lipid analysis, platelet aggregation studies, and malondialdehyde measurement. The coronary effluent was analyzed for creatine kinase and immunoreactive thromboxane B2 release. The myocardial and plasma phospholipid content revealed lower n-6 essential fatty acids and higher n-3 fatty acids in both myocardia and plasma in the fish-oil-fed rats when compared with the control animals. Platelet aggregation was markedly diminished in the fish-oil group, whereas plasma malondialdehyde levels, reflecting lipid peroxidation, were significantly greater in the fish-oil-fed group. Ischemia/reperfusion caused a decrease in the force of cardiac contraction and an increase in coronary perfusion pressure in all hearts studied; however, these changes were less prominent in the fish-oil-fed hearts. Additionally, ventricular arrhythmias occurred in fewer of the fish-oil hearts (three of eight hearts) compared with the control group (seven of nine hearts). Myocardial creatine kinase, which is a reflection of myocardial injury, increased five to seven times basal levels in the control hearts but only three to four times in the fish-oil-fed hearts (p < .05). Immunoreactive thromboxane B2 release was also lower in the fish-oil-fed group.
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