Tissue-specific incorporation of positional isomers of dietary cis- and trans-octadecenoic acids in the rat.

The total lipids of liver, heart, blood serum, adipose tissue, testes and adrenals of rats fed a partially hydrogenated fat were found to contain each of the dietary delta 5- to delta 15- cis- and delta 3- to delta 16- trans-octadecenoic acids. The pattern of incorporation of individual isomeric octadecenoic acids was found to be specific for the different tissues. trans-Isomers were preferentially incorporated into liver and heart, whereas cis-isomers were enriched in the testes. The composition of positional isomers of both cis- and trans-octadecenoic acids in adipose tissue, testes and adrenals was similar to that of the dietary lipids, whereas the corresponding compositions in liver, heart and serum were distinctly different. Thus, within the series of cis-octadecenoic acids, less oleic acid (delta 9-isomer) and correspondingly higher proportions of vaccenic acid (delta 11-isomer) were found in liver and heart than in the dietary lipids. Within the series of trans-octadecenoic acids, the isomers ranging from delta 12 to delta 16, especially the delta 14-isomer, were preferentially incorporated into liver, heart and serum, whereas the delta 10- and delta 11-isomers, were distinctly excluded from these tissues.