Hydrolysis of exogenous [3H]phosphatidylcholine by brain membranes and cytosol |
| |
Authors: | Ling Song M Shane Baird Richard S Jope |
| |
Institution: | (1) Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 35294 Birmingham, AL |
| |
Abstract: | Phosphatidylcholine, in addition to the widely studied inositol phospholipids, is cleaved to produce second messengers in neuronal signal transduction processes. Because of the difficulty in labelling and measuring the metabolism of endogenous phosphatidylcholine in brain tissue, we investigated the utility of measuring the hydrolysis of exogenous labelled substrate incubated with rat cerebral cortical cytosol and membrane fractions as has been successful in studies of phosphoinositide hydrolysis. In the cytosol 3H]phosphatidylcholine was hydrolyzed at a linear rate for 60 min of incubation and GTPS stimulated hydrolysis by 63%. The products of phospholipase C and phospholipase D, phosphorylcholine and choline, contributed only 44% of the 3H]phosphatidylcholine hydrolytic products in the cytosol, with phospholipase D activity slightly predominating. GTPS stimulated cytosolic phospholipase C and reduced phospholipase D activity. 3H]Phosphatidylcholine was hydrolyzed much more slowly by membranes than by cytosol. In membranes the production of 3H]phosphorylcholine and 3H]choline were approximately equal, contributing 27% of the total 3H]phosphatidylcholine hydrolysis, and GTPS only caused a slight stimulation of phospholipase C activity. Chronic lithium treatment (4 weeks) appeared to slightly reduce 3H]phosphatidylcholine metabolism in the cytosol and in membranes, but no statistically significant reductions were achieved. Cytosol and membrane fractions from postmortem human brain metabolized 3H]phosphatidylcholine slowly, and GTPS had no effects. In summary, exogenous 3H]phosphatidylcholine was hydrolyzed by brain cytosol and membranes, and this was stimulated by GTPS, but the complex contributions of multiple metabolic pathways complicates the application of this method for studying individual pathways, such as phospholipase D which contributes only a fraction of the total processes hydrolyzing exogenous 3H]phosphatidylcholine. |
| |
Keywords: | Phosphatidylcholine hydrolysis phospholipase D phospholipase C choline metabolism lithium |
本文献已被 SpringerLink 等数据库收录! |
|