Fatty Acid Composition of Four Lipid Classes in Plasma of Rats and Chicks Receiving Linoleic and α-Linolenic Acids in their Diets

Weanling rats and one-day-old chicks were fed diets containing 10% of either safflower or linseed oil. Blood was obtained at different times and plasma lipids were separated into triglycerides, nonesterified fatty acids, phospholipids and cholesteryl esters. Feeding linseed oil (53.1% 18:3 and 17.3% 18:2) instead of safflower oil (1.3% 18:3 and 70.0% 18:2) caused extensive replacement of arachidonic acid by 20:5ω3 in all lipid fractions in both species. The cholesteryl ester fraction was species-specific in that its polyunsaturated fatty acids were almost exclusively of the C18 type in chicks, whereas rats contained both C18and C20polyunsaturated fatty acids. Modification of the fatty acid profiles of plasma lipids by dietary means could be important in thrombocyte function and thrombogenesis, as well as in cholesterol transport and atherogenesis. It is suggested that in studies in humans, consideration of the relative intakes of ω3 and ω6-polyunsaturated fatty acids would be useful, in addition to the generally used P/S ratio.