DIETARY MENHADEN AND CORN OILS AND THE RED-BLOOD-CELL MEMBRANE LIPID-COMPOSITION AND FLUIDITY IN HYPERCHOLESTEROLEMIC AND NORMOCHOLESTEROLEMIC MINIATURE SWINE

Fatty acids in the diet are readily incorporated into lipids in variou s tissues. However, it is not clear whether all tissues have the same level of incorporation. Second, (n-6) unsaturated fatty acids increase the fluidity of membranes, but this has not been shown for (n-3) fatt y acids. in this study, we measured the incorporation of (n-6) and (n- 3) fatty acids into erythrocyte membrane lipids and studied their effe cts on the fluidity of erythrocyte membranes. One group of female mini ature swine was made hypercholesterolemic by feeding the swine cholest erol and lard for 2 mo; the other group served as controls and was fed a stock diet. Both groups were then fed either corn oil or menhaden o il or a mixture of the two for 23 additional weeks. Blood was collecte d at 0, 2, 4, 12 and 23 wk after initialization of the experimental di ets, and fatty acid composition of phospholipids was assessed. Membran e phospholipids of pigs fed menhaden oil had elevated (n-3) fatty acid s (20:5 and 22:6), and lower 18:2 than those fed corn oil. There was n o difference in 20:4 content. The fatty acid changes occurred as early as 2 wk after consumption of the corn oil or menhaden oil in pigs pre viously fed a stock diet, but it took longer in pigs previously fed la rd + cholesterol, indicating residual effects of pretreatment. Menhade n oil increased anisotropy (indicating decreased fluidity) more than c orn oil for the nonpolar probe diphenylhexatriene (DPH) at earlier tim e points, but not at 23 wk. Erythrocyte membrane fluidity was signific antly related to membrane polyunsaturate content, with (n-6) fatty aci ds having a greater influence than (n-3) fatty acids. A comparison of the present red blood cell fatty acid compositions with brain synaptos ome fatty acid compositions for the same animals showed poor correlati ons for some of the fatty acids. There was no significant direct relat ionship between docosahexaenoate (DHA) concentrations in erythrocyte m embranes with DHA concentrations in brain synaptosomes from cerebellum , forebrain and caudate nucleus.