[3-13C] gamma-linolenic acid: a new probe for 13C nuclear magnetic resonance studies of arachidonic acid synthesis in the suckling rat.
Our objective was to develop a suitable probe to study metabolism of polyunsaturated fatty acids by 13C nuclear magnetic resonance (NMR) in the suckling rat pup. [3-13C] gamma-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. 13C NMR showed that 13C in gamma-linolenate peaked in liver total lipids by 12-h post-dosing and that [5-13C]-arachidonic acid peaked in both brain and liver total lipids 48-96 h post-dosing. 13C enrichment in brain gamma-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. 13C 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 gamma-linolenic acid do access the suckling rat brain in vivo. The slow time course of [5-13C] arachidonic acid appearance in the brain suggests most of it was probably transported there after synthesis elsewhere, probably in the liver. Some carbon from gamma-linolenic acid is also incorporated into lipid products other than n-6 long-chain polyunsaturated fatty acids.
Cunnane
S C
SC
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Canada.
Moine
G
G
Likhodii
S S
SS
Vogt
J
J
Corso
T N
TN
Brenna
J T
JT
Demmelmair
H
H
Koletzko
B
B
Tovar
K H
KH
Kohn
G
G
Sawatzki
G
G
Muggli
R
R
D000818:Animals; D000831:Animals, Newborn; D016718:Arachidonic Acid / Q000096:biosynthesis*; D001921:Brain / Q000378:metabolism; D002250:Carbon Radioisotopes; D008099:Liver / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D051381:Rats; D013997:Time Factors; D017962:alpha-Linolenic Acid
D002250:Carbon Radioisotopes; D017962:alpha-Linolenic Acid; D016718:Arachidonic Acid