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[3‐ 13 C] γ‐linolenic acid: A new probe for 13 C nuclear magnetic resonance studies of arachidonic acid synthesis in the suckling rat
Author(s) -
Cunnane S. C.,
Moine G.,
Likhodii S. S.,
Vogt J.,
Corso T. N.,
Brenna J. T.,
Demmelmair H.,
Koletzko B.,
Tovar K. H.,
Kohn G.,
Sawatzki G.,
Muggli R.
Publication year - 1997
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-997-0027-y
Subject(s) - arachidonic acid , linolenic acid , polyunsaturated fatty acid , fatty acid , chemistry , biochemistry , carbon 13 nmr , chromatography , linoleic acid , stereochemistry , enzyme
Our objective was to develop a suitable probe to study metabolism of polyunsaturated fatty acids by 13 C nuclear magnetic resonance (NMR) in the suckling rat pup. [3‐ 13 C] γ‐Linolenic acid was chemically synthesized, and a 20 mg (Experiment 1) or 5 mg (Experiment 2) dose was injected into the stomachs of 6–10‐day‐old suckling rat pups that were then killed over a 192 h (8 d) time course. 13 C NMR showed that 13 C in γ‐linolenate peaked in liver total lipids by 12‐h post‐dosing and that [5‐ 13 C]‐arachidonic acid peaked in both brain and liver total lipids 48–96 h post‐dosing. 13 C enrichment in brain γ‐linolenic acid was not detected by NMR, but gas chromatography‐combustion‐isotope ratio mass spectrometry showed that its mass enrichment in brain phospholipids at 48–96 h post‐dosing was 1–2% of that in brain arachidonic acid. 13 C was present in liver and brain cholesterol and in perchloric acid‐extractable water‐soluble metabolites in the brain, liver and carcass. We conclude that low but measurable amounts of exogenous γ‐linolenic acid do access the suckling rat brain in vivo . The slow time course of [5‐ 13 C] arachidonic acid appearance in the brain suggests most of it was probably transported there after synthesis elsewhere, probably in the liver. Some carbon from γ‐linolenic acid is also incorporated into lipid products other than n−6 long‐chain polyunsaturated fatty acids.