title: Effect of phospholipid oxidation products on transbilayer movement of phospholipids in single lamellar vesicles.
abstract: Single lamellar phosphatidyl[methyl-2H]choline vesicles were incubated with an excess of unlabeled phosphatidylcholine vesicles or phosphatidylcholine-cholesterol vesicles containing 8 mol % glucuronosyldiglyceride. Incubation of the two vesicle populations was performed in the presence or absence of a purified phosphatidylcholine exchange protein. The negatively charged glycolipid donor vesicles could be completely removed by column chromatography on DEAE-Sephacel. Following incubation with exchange protein and subsequent fractionation, the -N(CD3)3 phosphatidylcholine acceptor vesicles exhibited a 61-73% enrichment of the unlabeled phosphatidylcholine in the outer monolayer. Upon incubation in an air atmosphere, no appreciable transbilayer movement of the outer monolayer -N(CH3)3 phosphatidylcholine was observed for at least 5 days. Between days 5 and 7, however, extensive transbilayer movement occurred, leading to an outer monolayer/inner monolayer phosphatidylcholine ratio of 2.1 on day 7. In phosphatidylcholine-6 mol % cholesterol vesicles treated similarly, the outside/inside ratio of the unlabeled phospholipid was 6.7, suggesting a much smaller percentage of transbilayer movement. The loss of transbilayer asymmetry which occurred during a 36-h period after day 5 could be estimated at the upper limit, t 1/2 approximately 7.3 h for phosphatidylcholine vesicles and t 1/2 approximately 53 h for phosphatidylcholine-cholesterol vesicles. The actual rates for transbilayer movement, however, were likely more rapid. Transbilayer movement occurred at a time period when oxidized phospholipid breakdown products had reached critical levels.
mesh_terms: D000727:Androgen-Binding Protein; D002352:Carrier Proteins / Q000378:metabolism; D002474:Cell-Free System; D002784:Cholesterol; D006017:Glycolipids; D008051:Lipid Bilayers; D008244:Lysophosphatidylcholines; D009038:Motion; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids
chemical_list: D000727:Androgen-Binding Protein; D002352:Carrier Proteins; D006017:Glycolipids; D008051:Lipid Bilayers; D008244:Lysophosphatidylcholines; D010713:Phosphatidylcholines; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D002784:Cholesterol