THE N-3 AND N-6 FATTY-ACIDS OF RED MEAT, CANOLA OIL AND FISH OIL AND THEIR EFFECT ON MYOCARDIAL LIPID AND EICOSANOID PRODUCTION

The degree of incorporation of the long-chain 20- and 22-carbon n-3 fa tty acids in cardiac phospholipid was determined in rats after they we re fed in two experiments diets of chow supplemented with red meat and various fats or oils. In the first experiment rats received diets sup plemented with fish oil, sheep fat, red meat or red meat from animals fed fish oil. The proportion of eicosapentenoic acid 20:5 (EPA) incorp orated into rat myocardial phospholipid fed meat from fish oil fed ani mals (0.6%) was significantly greater than that in rats fed normal mea t or sheep fat (0.3%), but significantly less than those fed fish oil as the sole supplement (3.4%). There were siginificant positive correl ations between dietary 20:5 and myocardial 20:5 and 22:6 (n-3) and sig nificant negative correlations between dietary 20:5 and myocardial 18: 2 and 20:4 (n-6). Regression analysis demonstrated that 98% of the var iation in myocardial 20:5 was controlled by dietary 20:5. In a second experiment rats received diets supplemented with red meat alone or red meat plus fish oil, canola oil or sheep fat. The fatty acid compositi on of myocardial phospholipid when meat was fed with fish oil was very similar to that of the first experiment when fish oil was fed alone. When canola oil was fed, there were significant increases in 18:1 (n-9 ) and 18:3 (n-3), but not in the 20:5 or 22:6 (n-3) fatty acids. Suppl ements of meat with fish oil or canola oil markedly reduced the produc tion of myocardial prostacyclin and thromboxane relative to that when sheep fat was fed. The concentration of both eicosanoids was significa ntly related to the ratio of n-6/n-3 fatty acids in the diet.