High fat diets varying in ratios of polyunsaturated to saturated fatty acid and linoleic to linolenic acid: a comparison of rat neural and red cell membrane phospholipids.

The polyunsaturated-saturated (P/S) fatty acid, and linoleic-linolenic (18:2n6/18:3n3) acid ratios of diets fed to rats were varied independently during pregnancy, lactation and, in the young, for 8 d after premature weaning. The intent was to alter the proportion of membrane phospholipid fatty acids derived from 18:2n6 and 18:3n3 in the developing rat, and to compare changes in very-long-chain polyunsaturated fatty acids in membranes from the central nervous system with those of the red blood cell. All experimental diets contained 40% of energy from fat. Similar relative changes in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) fatty acid pattern occurred in both neural and red blood cell membranes when dietary 18:2n6/18:3n3 was increased from 7 to 240. Docosapentaenoate (22:5n6) from 18:2n6 increased, and docosapentaenoate (22:5n3) and docosahexaenoate (22:6n3) from 18:3n3 decreased in both types of membranes. On the other hand, P/S ratios of 0.3 and 1.6 at a constant ratio of 18:2n6/18:3n3 produced identical membrane phospholipid fatty acid patterns. Both red blood cell and neural membranes show the same relative effects of modification of dietary lipids on the composition of very-long-chain polyunsaturated fatty acids.