The effects of dietary mackerel oil on plasma and cell membrane lipids, on hemodynamics and cardiac arrhythmias during recurrent acute ischemia in the pig.

Fish-oil nutrition leads to a change in fatty acid composition of cellular membranes. To investigate whether this affects cardiac responses to acute myocardial ischemia, pigs were fed a 9.1% (w/w) mackerel-oil (n = 8) or 9.1% (w/w) lard-fat diet (n = 8). Eight weeks mackerel-oil feeding reduced plasmacholesterol (51%) and triglyceride (48%), while the n-6 fatty acids of cardiac and platelet membrane phospholipids were partially replaced by n-3 fatty acids. After 8 weeks the animals were anesthetized and the left anterior descending coronary artery was occluded 6 times for a period of 5 min at 15 min intervals. Recovery of cardiac function and the incidence of cardiac arrhythmias were similar for both dietary groups. However, during the last reperfusions, hyperemic responses were less in magnitude and shorter lasting in the lard-fat (81 +/- 17 ml/min) than in the mackerel-oil group (129 +/- 18 ml/min). This may be caused by a difference in thromboxane synthesis, as coronary venous blood thromboxane B2 levels were higher in the lard-fat (77 +/- 6 pg/ml) than in the mackerel-oil group (19 +/- 7 pg/ml, P less than 0.05) during peak hyperemia. The low baseline levels of both thromboxane B2 and 6-keto prostaglandin F1alpha in fish-oil fed animals originate from the reduced content of precursor fatty acid in the membrane phospholipids. In conclusion, despite marked changes in membrane fatty acid composition induced by prolonged feeding with fish oil, no modification of recovery of cardiac function and of incidence of cardiac arrhythmias was found during acute recurrent ischemia.