Evidence for brain docosahexaenoate recycling in the free-moving adult rat: implications for measurement of phospholipid synthesis.
The specific activity (SA) of unesterified docosahexaenoic acid (22:6 n-3) in the brain and arterial plasma was measured after constant intravenous infusion of [3H] 22:6 n-3 in the free-moving rat. Within 40-105 min, an apparent steady state of labeled unesterified 22:6 n-3 in plasma and in brain was reached. However, the values of the brain to plasma 22:6 n-3 SA ratios ranged from 0.03 to 0.05, indicating that an isotopic equilibrium between brain and plasma was not attained. This suggests that a considerable endogenous source of unesterified 22:6 n-3 (95-97%) (likely derived from lipid metabolism) dilutes the SA of the tracer coming from plasma. Using the SA of 22:6 in plasma instead of brain would thus lead to a gross underestimation of the rate of phospholipid synthesis.
Gazzah
N
N
INSERM U 352, Laboratoire de Chimie Biologique, INSA-Lyon, Villeurbanne, France.
Gharib
A
A
Bobillier
P
P
Lagarde
M
M
Sarda
N
N
D000818:Animals; D016477:Artifacts; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D004281:Docosahexaenoic Acids / Q000032:analysis* / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D004951:Esterification; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism; D010743:Phospholipids / Q000096:biosynthesis*; D011849:Radioactive Tracers; D051381:Rats; D017208:Rats, Wistar; D014280:Triglycerides / Q000378:metabolism*; D014316:Tritium / Q000032:analysis
D008563:Membrane Lipids; D010743:Phospholipids; D011849:Radioactive Tracers; D014280:Triglycerides; D014316:Tritium; D004281:Docosahexaenoic Acids