title: Identification of two molecular species of rat brain phosphatidylcholine that rapidly incorporate and turn over arachidonic acid in vivo.
abstract: In vivo rates of arachidonic acid incorporation and turnover were determined for molecular species of rat brain phosphatidylcholine (PtdCho) and phosphatidylinositol (PtdIns). [3H]Arachidonic acid was infused intravenously in pentobarbital-anesthetized rats at a programmed rate to maintain constant plasma specific activity for 2-10 min. At the end of infusion, animals were killed by microwave irradiation, and brain phospholipids were isolated, converted to diacylglycerobenzoates, and resolved as molecular species by reversed-phase HPLC. Most [3H] arachidonate (> 87%) was incorporated into PtdCho and PtdIns, with arachidonic acid at the sn-2 position and with oleic acid (18:1), palmitic acid (16:0), or stearic acid (18:0) at the sn-1 position. However, 10-15% of labeled brain PtdCho eluted in a small peak containing two molecular species with arachidonic acid at the sn-2 position and palmitoleic acid (16:1) or linoleic acid (18:2) at the sn-1 position. Analysis demonstrated that tracer was present in both the 16:1-20:4 and 18:2-20:4 PtdCho species at specific activities 10-40 times that of the other phospholipids. Based on the measured mass of arachidonate in each phospholipid molecular species, half-lives were calculated for arachidonate of < 10 min in 16:1-20:4 and 18:2-20:4 PtdCho and 1-3 h in 16:0-20:4, 18:1-20:4 PtdCho and PtdIns. The very short half-lives for arachidonate in the 16:1-20:4 and 18:2-20:4 PtdCho molecular species suggest important roles for these molecules in brain phospholipid metabolism and signal transduction.
authors.affiliation: Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892-1582, USA.
authors.forename: H U
authors.initials: HU
authors.lastname: Shetty
authors.forename: Q R
authors.initials: QR
authors.lastname: Smith
authors.forename: K
authors.initials: K
authors.lastname: Washizaki
authors.forename: S I
authors.initials: SI
authors.lastname: Rapoport
authors.forename: A D
authors.initials: AD
authors.lastname: Purdon
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D008297:Male; D015394:Molecular Structure; D019301:Oleic Acid / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000737:chemistry / Q000378:metabolism*; D010741:Phospholipases A; D011865:Radioisotope Dilution Technique; D051381:Rats; D017207:Rats, Sprague-Dawley; D018629:Spectrometry, Mass, Secondary Ion; D013229:Stearic Acids / Q000378:metabolism; D014316:Tritium; D010738:Type C Phospholipases
chemical_list: D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D013229:Stearic Acids; D014316:Tritium; D016718:Arachidonic Acid; D019301:Oleic Acid; D019308:Palmitic Acid; C031183:stearic acid; D010741:Phospholipases A; D010738:Type C Phospholipases