title: Brain elongation of linoleic acid is a negligible source of the arachidonate in brain phospholipids of adult rats.
abstract: The extent to which the adult brain can derive some of its arachidonic acid (AA) through internalized synthesis from linoleic acid (LA) is uncertain. Thus, we determined for plasma-derived LA in vivo rates for brain incorporation, beta-oxidation, and conversion to AA. Adult male unanesthetized rats, reared on a diet enriched in LA but low in AA, were infused intravenously for 5 min with [1-(14)C]LA. Timed arterial samples were collected until the animals were killed at 5 min and the brain was removed after microwaving. Within plasma lipids, >96% of radioactivity was in the form of unchanged [1-(14)C]LA, but [(14)C]AA was insignificant (<0.2%). Eighty-six percent of brain radioactivity at 5 min was present as beta-oxidation products, whereas the remainder was mainly in 'stable' phospholipid or triglyceride as LA or AA (11 and <1%, respectively). Unesterified unlabeled LA rapidly enters brain from plasma, but its incorporation into brain total phospholipid and triglyceride, in the form of synthesized AA, is <1% of the amount that enters the brain. Thus, in rats fed even a diet containing low amounts of AA, the LA that enters brain is largely beta-oxidized, and is not a major source of AA in brain.
authors.affiliation: Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Building 9, Room 1S 126, Bethesda, MD 20892-1582, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: DeMar
authors.forename: Ho-Joo
authors.initials: HJ
authors.lastname: Lee
authors.forename: Kaizong
authors.initials: K
authors.lastname: Ma
authors.forename: Lisa
authors.initials: L
authors.lastname: Chang
authors.forename: Jane M
authors.initials: JM
authors.lastname: Bell
authors.forename: Stanley I
authors.initials: SI
authors.lastname: Rapoport
authors.forename: Richard P
authors.initials: RP
authors.lastname: Bazinet
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000097:blood / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000737:chemistry; D004032:Diet; D019787:Linoleic Acid / Q000097:blood / Q000378:metabolism*; D008297:Male; D010743:Phospholipids / Q000097:blood / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D002250:Carbon Radioisotopes; D010743:Phospholipids; D016718:Arachidonic Acid; D019787:Linoleic Acid