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Journal of Lipid Research, Vol. 46, 1974-1982, September 2005
Copyright © 2005 by American Society for Biochemistry and Molecular Biology

Simultaneous quantitative determination of deuterium- and carbon-13-labeled essential fatty acids in rat plasma

Yu Hong Lin, Robert J. Pawlosky and Norman Salem, Jr.¹

Section of Nutritional Neuroscience, Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-9410

Published, JLR Papers in Press, June 1, 2005. DOI 10.1194/jlr.M500128-JLR200

¹ To whom correspondence should be addressed. e-mail: nsalem{at}niaaa.nih.gov

This study reports methods for the quantitative determination of stable isotope-labeled essential fatty acids (EFAs) as well as an experiment in which deuterium-labeled linoleic acid (18:2n-6) and -linolenic acid (18:3n-3) were compared with those labeled with carbon-13 in rat plasma in vivo. Standard curves were constructed to compensate for concentration and plasma matrix effects. It was observed that endogenous pools of fatty acids had a greater suppressing effect on the measurements of ¹³C-U-labeled EFAs relative to those labeled with ²H₅. Using these methods, the in vivo metabolism of orally administered deuterated-linolenate, ¹³C-U-labeled linolenate, deuterated-linoleate, and ¹³C-U-labeled linoleate was compared in adult rats (n = 11). There were no significant differences in the concentrations of the ²H versus ¹³C isotopomers of 18:2n-6, 18:3n-3, arachidonic acid (20:4n-6), and docosahexaenoic acid (22:6n-3) in rat plasma samples at 24 h after dosing.

Thus, there appears to be little isotope effect for ²H₅- versus ¹³C-U-labeled EFAs when the data are calculated using the conventional standard curves and corrected for endogenous fatty acid pool size and matrix effects.

Abbreviations: 18:2n-6, linoleic acid; 18:3n-3, -linolenic acid; 20:4n-6, arachidonic acid; 20:3n-6, dihomo--linolenic acid; 22:6n-3, docosahexaenoic acid; 20:5n-3, eicosapentaenoic acid; EFA, essential fatty acid; FID, flame ionization detector; ISTD, internal standard; NCI, negative chemical ionization; PFB, pentafluorobenzyl

Supplementary key words deuterated linolenate • deuterated linoleate • carbon-13-labeled linolenate • carbon-13-labeled linoleate • standard curves • concentration effect curves • gas chromatography-mass spectrometry negative chemical ionization analysis

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				S. Gagne, S. Crane, Z. Huang, C. S. Li, K. P. Bateman, and J.-F. Levesque Rapid measurement of deuterium-labeled long-chain fatty acids in plasma by HPLC-ESI-MS J. Lipid Res., January 1, 2007; 48(1): 252 - 259. [Abstract] [Full Text] [PDF]

				Y. H. Lin and N. Salem Jr. In vivo conversion of 18- and 20-C essential fatty acids in rats using the multiple simultaneous stable isotope method J. Lipid Res., September 1, 2005; 46(9): 1962 - 1973. [Abstract] [Full Text] [PDF]