Hydrolysis of exogenous [3H]phosphatidylcholine by brain membranes and cytosol

Ling Song, M. Shane Baird, Richard S Jope

Research output: Contribution to journalArticle

4 Citations (Scopus)

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 GTPγS 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. GTPγS 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 GTPγS 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 GTPγS had no effects. In summary, exogenous [3H]phosphatidylcholine was hydrolyzed by brain cytosol and membranes, and this was stimulated by GTPγS, 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.

Original languageEnglish
Pages (from-to)1305-1311
Number of pages7
JournalNeurochemical Research
Volume18
Issue number12
DOIs
StatePublished - Dec 1 1993
Externally publishedYes

Fingerprint

Phosphatidylcholines
Cytosol
Hydrolysis
Brain
Membranes
Phospholipase D
Type C Phospholipases
Phosphorylcholine
Phosphatidylinositols
Choline
Metabolism
Signal transduction
Second Messenger Systems
Metabolic Networks and Pathways
Lithium
Labeling
Rats
Signal Transduction
Tissue
Substrates

Keywords

  • choline metabolism
  • lithium
  • Phosphatidylcholine hydrolysis
  • phospholipase C
  • phospholipase D

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry

Cite this

Hydrolysis of exogenous [3H]phosphatidylcholine by brain membranes and cytosol. / Song, Ling; Baird, M. Shane; Jope, Richard S.

In: Neurochemical Research, Vol. 18, No. 12, 01.12.1993, p. 1305-1311.

Research output: Contribution to journalArticle

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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 GTPγS 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. GTPγS 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 GTPγS 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 GTPγS had no effects. In summary, exogenous [3H]phosphatidylcholine was hydrolyzed by brain cytosol and membranes, and this was stimulated by GTPγS, 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.",
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