INCORPORATION OF DIETARY CIS AND TRANS OCTADECENOATE ISOMERS IN THE LIPID CLASSES OF VARIOUS RAT-TISSUES

The percentage distribution of the geometrical and positional isomers in the hexadecenoates and octadecenoates isolated from triglycerides, phosphatidylcholines, and phosphatidylethanolamines of brain, heart, kidney, liver, lung, muscle, spleen, and adipose tissues from rats maintained four weeks on a semipurified diet supplemented with 15% partially hydrogenated safflower fatty acids, has been determined. Except for brain, octadecenoate percentages were increased in each of the lipid classes of all the tissues by the dietary fat. Although the diet did not contain detectable hexadecenoates, the 16:1 fraction from the lipid classes of all the tissues was composed of 10-70% of the trans isomers, indicating chain shortening of the dietary octadecenotes. Distribution of cis and trans positional isomers in triglyceride hexadecenoates was approximately the same in all tissues. Relatively high percentages of the Δ9, Δ10, and Δ11 isomers were observed, but the Δ8 was the predominating trans hexadecenoate isomer, indicating preferential chain shortening of the trans δ10 octadecenoate. Trans octadecenoates were found in all tissues, but concentrations were dependent on tissue and lipid class. The distribution of the cis and trans octadecenoate isomers was similar in all the tissue triglycerides, with the distribution of the trans isomers resembling the diet. In contrast, the percentage distribution of the trans octadecenoates in the phospholipid classes differed dramatically from the diet, and the distribution was dependent on both the tissue and lipid class. The Δ12, Δ13, and Δ14 trans octadiet, suggesting an accumulation of these isomers. Although the cis Δ10 octadecenoate was a significant dietary component, this isomer was not incorporated significantly into any lipid class of any tissue. The metabolic fate of this isomer remains unknown. © 1979 American Oil Chemists' Society.