The metabolism of [<i>Me</i>−14C]choline in the brain of the rat <i>in vivo</i>

Ansell, G. B.; Spanner, Sheila

doi:10.1042/bj1100201

Cited by 107 publications

(35 citation statements)

References 24 publications

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“…3 3 s choline (Table). This substrate level of choline is perhaps nearer to that which might be expected in mammalian tissues in vivo [14]. DISCUSSION The incorporation of choline into phosphatidylcholine by the cytidine nucleotide mediated pathway is a complex process which requires the direct participation of at least three enzymes and a number of substrates, cofactors and energy sources.…”

Section: Resultsmentioning

confidence: 99%

The Origin of Mitochondrial Phosphatidylcholine within the Liver Cell

Jungalwala

Dawson

1970

Eur J Biochem

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The incorporation of choline into the phosphatidylcholine of subcellular fractions of rat liver has been examined. The mitochondrial fraction shows a minimal phosphatidylcholine synthesis compared with that produced by adding microsomes providing an incubation medium which allows adequate phospholipid synthesis is used. The small mitochondrial incorporation can be partly if not wholly explained by microsomal contamination or a non-energy dependent exchange process. It is concluded that the appreciable turnover of mitochondrial phosphatidylcholine observed in vivo can be explained most satisfactorily by assuming a transfer of newly synthesized phospholipid molecules from the endoplasmic reticulum.Although phospholipids play an essential role in many reactions of the mitochondrial electron transport system [l] their site of synthesis within the cell is a subject of some controversy. The phospholipid present in highest concentration in liver mitochondria is phosphatidylcholine and from experiments in vivo this appears to be turned over a t a rate which is only slightly slower than the microsomal phosphatidylcholine [2]. Early experiments suggested that liver mitochondria are devoid of the phosphatidylcholine synthesizing enzyme CDP-choline : 1,2 diglyceride cholinephosphotransferase which was found mainly in the microsomes [3,4]. Later studies of Stoffel and Schiefer [5] indicated that some of the enzyme was present in the outer mitochondrial membranes of rat liver, but these studies have been criticised on the grounds that no recovery of total activity or degree of microsomal contamination was provided [2,6,7 ]. Recently experiments were performed in this laboratory which indicated that the limited phosphatidylcholine synthesis from [32P]phosphate or CDP-[W]choline carried out by isolated liver mitochondria was largely due to microsomal contamination of these organelles [2]. An exchange of phosphatidylcholine between isolated microsomes and mitochondria was demonstrated and it was suggested that this was the process by which the dynamic turnover of phosphatidylcholine in the mitochondria is maintained. Contrasting markedly with these conclusions, Bygrave and Kaiser [8] chondria by an energy-dependent process with little or no contribution from contaminating or added microsomes. The experiments reported in this paper were performed in an attempt to resolve these differences. EXPERIMENTAL PROCEDUREIsolation of Mitochondria, Microsomes and Cell Supernatant The procedure followed was essentially the same as described by McMurray and Dawson [2]. Female rats of the Wistar albino strain, 200-250 gin weight were decapitated and the livers rapidly excised and chilled. All subsequent operations were performed a t 0"-4". The livers, usually pooled from two animals, were minced with scissors and homogenized in a motor-driven homogenizer with 0.008 in clearance [ l l ] for 1 min in 10 volumes of cold 0.25 M sucrose-0.1 mM EDTA, pH 7.4. The homogenate was centrifuged a t 2500 rev./min (800 xg) for 10 min in a Servall RC-2 centr...

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Section: Resultsmentioning

confidence: 99%

The Origin of Mitochondrial Phosphatidylcholine within the Liver Cell

Jungalwala

Dawson

1970

Eur J Biochem

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“…One-half of this extract was combined with one aliquot of the formic acid-acetone extract and neutralized with 0.1 M potassium phosphate buffer, pH 7.4. The KC104 precipitate was removed by centrifugation (10 minutes at 0°C and 10,000 g), and the supernatant containing all of the water-soluble, Ch-containing compounds was applied to a 1X 1 1.5 cm AG50W-X8 (hydrogen form, 100-200 mesh; Bio-Rad Laboratories, Richmond, CA) [Ansell and Spanner, 1968;Illingworth and Portman, 19721.33. GPCh was eluted with a small volume of H,O (approximately 10 ml), CDP-Ch was eluted with more H2 0 (approximately 30 ml) ,and PCh was eluted with 0.2 M HCl (approximately 20 nil).…”

Section: Methodsmentioning

confidence: 99%

Choline and phospholipid metabolism and the synthesis of acetylcholine in rat brain

Jope

Jenden

1979

J of Neuroscience Research

107

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The metabolism of choline by rat brain, plasma, and liver was investigated using combined gas chromatography mass spectrometry following microwave irradiation and treatment with deuterium-labeled choline. Methods were established to measure simultaneously the concentrations of six choline-containing compounds and the incorporation of labeled choline into each of them. Intravenous injection of [2H4]-choline led to initial labeling of choline, acetylcholine, and phosphocholine in rat brain, with all of the label eventually entering the phosphocholine pool. When labeled choline was administered in the diet its rate of incorporation into choline, phosphatidylcholine, and combined choline plasmalogen and lysophosphatidylcholine in the plasma and liver and into choline, acetylcholine, phosphocholine, glycerophosphorylcholine, phosphatidylcholine, and combined choline plasmalogen and lysophosphatidylcholine in the brain were determined. Choline, phosphatidylcholine, and combined choline plasmalogen and lysophosphatidylcholine in the plasma had similar specific activities. In the cortex and the striatum, choline and combined choline plasmalogen and lysophosphatidylcholine fraction generally had the highest specific activities. The time course of the post-mortem release of choline by the brain was measured, and the sources of this choline were, sequentially, acetylcholine, glycerophosphoryl-choline, and phospholipids.

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“…Cholinergic and non-cholinergic neurones take up choline (Diamond & Milfay, 1972), and much of the ganglion's endogenous choline is located outside cholinergic nerve endings (Friesen, Ling & Nagai, 1967). If recaptured choline selectively entered cholinergic nerve terminals, it might be used mainly for ACh synthesis, but if recaptured choline entered non-cholinergic structures, it would be converted to other metabolites such as phosphorylcholine or phosphatidylcholine (Ansell & Spanner, 1968;Collier & Lang, 1969;Abdel-Latif & Smith, 1972).…”

Section: Introductionmentioning

confidence: 99%

Acetylcholine synthesis from recaptured choline by a sympathetic ganglion

Collier¹,

Katz²

1974

The Journal of Physiology

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SUMMARY1. The recapture and re-use of choline formed by the hydrolysis of released acetylcholine (ACh) nerve terminals appear selectively to accumulate choline. 4. However, chronically decentralized ganglia accumulated as much choline as did acutely decentralized ganglia, and this was interpreted as indicating that at rest preganglionic nerve terminals do not selectively accumulate choline.5. Increased exogenous choline concentration increased the amount of radioactivity collected during nerve stimulation in the absence, but not the presence, of an anticholinesterase agent. The spontaneous efflux of radioactivity was little affected by changes in external choline levels. It is concluded that exogenous choline and choline made available from released transmitter compete for uptake into nerve terminals.

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The metabolism of [Me−14C]choline in the brain of the rat in vivo

Cited by 107 publications

References 24 publications

The Origin of Mitochondrial Phosphatidylcholine within the Liver Cell

The Origin of Mitochondrial Phosphatidylcholine within the Liver Cell

Choline and phospholipid metabolism and the synthesis of acetylcholine in rat brain

Acetylcholine synthesis from recaptured choline by a sympathetic ganglion

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