AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 4 846-R854, Copyright © 1996 by American Physiological Society

ARTICLES

Metabolic fate of an oral tracer dose of [13C]docosahexaenoic acid triglycerides in the rat

N. Brossard, M. Croset, J. Lecerf, C. Pachiaudi, S. Normand, V. Chirouze, O. Macovschi, J. P. Riou, J. L. Tayot and M. Lagarde
Institut National de la Sante et de la Recherche Medicale (INSERM) U 352, Chimie Biologique, Institut National des Sciences Appliquees-Lyon, Villeurbanne, France.

The appearance of 13C in rat lipoprotein, blood cells, and brain lipids was followed as a function of time after the ingestion of triglycerides (TG) containing [13C]22:6n-3. The time course of 13C abundance in 22:6n-3 of various lipid pools, measured by gas chromatography combustion-isotope mass spectrometry, established precursor-product relationships within lipids. The [13C]22:6n-3 was rapidly incorporated into very low density lipoprotein-chylomicron-TG and unesterified fatty acids bound to albumin, with a concomitant maximal appearance at 3 h and further decline. Lysophosphatidylcholines (lysoPC) bound to albumin were also enriched in [13C]22:6n-3, and their labeling appeared to be mainly due to hepatic secretion at the earliest time points. From 12 h postingestion, the synthesis of [13C]22:6n-3-lysoPC was twice as high as that of unesterified [13C]22:6n-3, making lysoPC a potential source of 22:6n-3 supply for tissues. The labeling of platelets, red blood cells, and brain phospholipids presented different kinetics, presumably involving the two lipid forms of [13C]22:6n-3 bound to albumin, to different extents. We conclude that [13C]22:6n-3 esterified in TG is rapidly redistributed within blood lipoproteins and the albumin fraction and that its incorporation in lipid species bound to albumin influences its uptake by target tissues.

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