Metabolism of labeled isomeric octadecenoates by the laying hen
1971
Mounts, T.L. | Emken, E.A. | Rohwedder, W.K. | Dutton, H.J.
Discrimination between octadecenoic acid isomers by the laying hen has been studied using tritium (3H), carbon-14 (14C) and deuterium (d) labeled oleate and elaidate esters. Hydrogen isotopes were positioned at the double bond, whereas14C was located in the 1-, carboxyl carbon. The egg acted as a biological trap, providing an automatic daily biopsy with which to study the metabolism of the fed isomers. Monitoring the incorporation of isomers was facilitated by dual label feeding experiments, and3H/14C, d2/do and d2/d1 ratios were determined on the isomeric mixtures fed, on the total egg lipids extracted and on the isolated neutral lipid and phospholipid fractions. Comparison of isotopic ratios of the fed mixture and of the lipid fractions provided an evaluation of discrimination by the hen during the transport of isomeric octadecenoates into the egg lipids. Radioactive and stabl isotope ratios determined for the neutral lipid indicated a preferential incorporation of the cis isomer. Stable isotope ratios determined for the phospholipid showed that the trans isomer is preferentially incorporated. The3H/14C ratios for the phospholipid recovered in each experiment increased greatly whichever isomer was labeled with3H, indicating an elimination of the 1-14C-label. Gas liquid radiochromatographic separation of the methyl esters from the neutral lipids and phospholipids showed that the isotopic labels were present almost exclusively in the octadecenoic acid constituent.
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