Submitted on April 4, 2005
Revised on May 18, 2005
Accepted on May 19, 2005
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
LMBB, NIAAA, NIH, Bethesda, MD 20892-9410
Corresponding Author: nsalem{at}niaaa.nih.gov
This study reports methods for the quantitative determination of stable isotope labeled essential fatty acids (EFA) as well as an experiment where deuterium labeled linoleic and a-linolenic acids were compared to those labeled with carbon-13 in rat plasma in vivo. Standard curves were constructed in order 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 vs. 13C isotopomers of 18:2n-6, 18:3n-3, 20:4n-6 and 22:6n-3 in rat plasma samples at 24 h after dosing. jlr Thus, there appears to be little isotope effect for 2H5 vs. 13C-U-labeled EFA when the data are calculated using the conventional standard curves and corrected for endogenous fatty acid pool size and matrix effects.
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