The incorporation into tissue phospholipids and the effects on eicosanoid production of trans-fatty acid were studied in rats fed different proteins, casein or soybean protein. After feeding partially hydrogenated corn oil containing 32% t-18:1 at the 10% level for 3 weeks, the incorporation of trans-fatty acid into liver phospholipids was species-specific. More trans-acid was incorporated into phosphatidylinositol than into phosphatidylcholine (PC) and phosphatidylethanolamine (PE), and there was apparently no incorporation into cardiolipin. The incorporation of trans-acid tended to be higher in the rats fed soybean protein than in those fed casein. In general the proportion of linoleic acid increased, but that of arachidonic acid tended to be decreased by trans-fat as compared with cis-fat, suggesting an interference with linoleic acid desaturation, but this was not the case for the spleen of rats fed vegetable protein. The concentration of plasma prostaglanidin E2 was not influenced by the type of dietary fat, but trans-fat reduced the production of leukotriene C4 by the spleen on the basis of unit weight when the dietary protein source was casein, but not soybean protein. Thus, the influence of the trans-monoene fatty acid was quite diverse, and there was an interaction between dietary protein and trans-fatty acid. © 1994 Taylor &
Francis Group LLC.