Ischaemic preconditioning is a powerful cardioprotective phenomenon. Cardioprotection afforded by (n-3) polyunsaturated fatty acids (PUFA) also suggests preconditioning-like effects. This study examined the effects of dietary fish oil on heart function and injury during myocardial ischemia and reperfusion and interactions between diet and ischemic preconditioning (IP). Male Wistar rats were fed diets containing 10% fat by weight including either 7% fish oil + 3% olive oil (n-3) PUFA); 5% sunflower seed oil + 5% olive oil ((n-6) PUFA); or 7% saturated fat-rich beef tallow + 3% olive oil (SF) for 6 weeks. Isolated perfused hearts subjected to 30min regional ischemia were reperfused for 120min, with or without prior IP as three cycles of 5min global ischemia. Spontaneous resting heart rate, coronary flow, and end diastolic pressure were significantly lower in (n-3) PUFA hearts than (n-6) PUFA or SF. In reperfusion (n-3) PUFA hearts had significantly less arrhythmia, and better recovery of developed pressure and maximum rate of relaxation. Infarct size was significantly smaller in (n-3) PUFA hearts (10.9±0.6% ischemic zone, n=6) than (n-6) PUFA (47.4±0.3%, n=6) or SF (50.3±0.3%, n=6). IP significantly reduced arrhythmias and improved heart function similar to but significantly less than (n-3) PUFA diet alone. Infarct size was equally reduced by IP or (n-3) PUFA diet. IP did not further improve heart function or ischemic recovery in (n-3) PUFA hearts. Dietary fish oil provides nutritional preconditioning to the heart, providing as powerful or better cardioprotection than ischaemic preconditioning in facilitating post-ischemic recovery and limiting cardiac injury and myocardial infarction.
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