Choline in brain tissue

Shahed AR, Werchan PM, Stavinoha WB. 1996. Differences in acetylcholine but not choline in brain tissue fixed by freeze fixation or microwave heating. Methods Find Exp Clin... 

The enzymatic radioassay method for the analysis of acetylcholine and choline in brain tissue has been reported by Reid et al. [210]. The method describes the determination of nanogram amounts of acetylcholine and choline in as little as 10 mg of brain tissue, involves isolation of acetylcholine by high-voltage paper electrophoresis, alkaline hydrolysis of acetylcholine to choline, and conversion of this into [32P]-phosphoryl choline in the presence of choline kinase and [y32P] ATP. The labeled derivative is isolated by column chromatography on Bio-Rad AG1-X8 resin, using Tris buffer solution as the eluent. Cerenkov radiation from 32P is counted (at 33% efficiency) in a liquid scintillation spectrometer. The amount of phosphorylcholine is proportional to the amount of choline over the range of 0.08-8.25 nmol. 

The authors modified the method for sub-microgram amounts [111] and demonstrated its application to the determination of choline in brain tissue [110]. 

Maruyama et al. reported the use of a simple pyrolysis gas chromatographic method for the determination of choline and acetylcholine in brain tissue [136]. Schmidt and Speth reported a simultaneous analysis of choline and acetylcholine levels in rat brain tissue by a pyrolysis gas chromatographic method [137], Kosh et al. reported an improved gas chromatographic method for the analysis of acetylcholine and choline in rat brain tissue [138], Mikes et al. used a syringe micro-pyrolyzer for the gas chromatographic determination of acetylcholine, choline and other quaternary ammonium salts [139],... 

A derivative of choline important because it acts as the chemical transmitter of nerve impulses in the autonomic system. It has been isolated and identified in brain tissue. The enzyme cholinesterase hydrolyzes acetylcholine into choline and acetic acid, and is necessary in the body to prevent acetylcholine poisoning. Use Medicine (as bromide and chloride) biochemical research. 

It is interesting that peripheral cholinergic nerve endings cannot take up ACh (only choline) however, they can in brain tissue. 

Magnetic resonance spectroscopy (MRS) measures the levels of different metabolites in body tissues, usually in the evaluation of nervous system disorders. Concentrations of metabolites such as N-acetyl aspartate, choline, creatine, and lactate in brain tissue can be examined. Information on levels of metabolites is usefiil in determining and dis nosing specific metabolic disorders such as Ganavan s disease, creatine deficiency, and untreated bacterial brain abscess. MRS has also been usefiil in the differentiation of high-grade from low-grade brain tumors. 

The production of free inositol from phosphatidylinositol suggests the possibility that a phospholipase D type of activity might be involved in this system. The occurrence of phospholipase D in animal tissues was not reported until recently, when an enzyme which cleaves phosphatidylcholine to give choline and phosphatidic acid was found in brain tissue (Saito Kanfer, 1975). It is not known whether phosphatidylinositol can act as its substrate in an analogous reaction. 

This reaction is analogous to that previously described for the biosynthesis of choline plasmalogen (Reaction 17). It also occurs in brain tissue (McMurray 1964b). 

In 1945 Lipmann found that a novel coenz3mae—coenzyme A— is required for the enzymic acetylation of sulfanilamide in pigeon liver preparations. Soon afterwards Nachmannsohn and Berman (see also ) found that a coenzyme is also required for the synthe of acetyl choline from choline and acetate in brain tissue, and this was found to be identical with the coenzyme of the acetylation of sulfanilamide, i Subsequently, three other reactions of acetate were found to involve coenzyme A the formation of acetoacetic acid from acetate, the s3mthesis of citrate from oxalacetate and acetate, - and the exchange reaction between acetyl phosphate and inorganic phosphate in bacterial extracts. " Thus, coenzyme A was shown to be a general coenzyme of acetylations, and... 

The synthesis of phosphatidylcholine (Ptd-choline) in animal tissues is carried out chiefly by the cytidine nucleotide pathway, although base-exchange reaction and stepwise methylation of preexisting phosphatidylethanolamine (Ptd-ethanolamine) also contribute to its formation "7 The N-methylation pathway, first demonstrated in liver by Bremer and Greenberg and successively described in this tissue by several authors, has not been however unequivocally demonstrated in brain, and conflicting data have been produced in this c onnection, ... 

Pinally, the methylation pathway could represent an enzymic system linked to the source of choline in brain. It is known that the choline moiety as such cannot pass into the brain from the blood stream, but rather a lipid-choline moiety, probably lysophosphati-dylcholine, might be involved in the transport of the base. The methylation pathway, however, can be visualized as another means of producing choline in brain, provided Ptd-ethanolamine is transported into the brain. Conversely, due to the noticeable presence in the brain tissue of free serine, a possible pathway for choline production in brain may be represented by an exchange reaction between free serine and endogenous brain phospholipids, 9 20 cessive decarboxylation of phosphatidyl serine to Ptd-ethanolamine in the same tissue, finally followed by the described methylation reactions to produce a definite pool of active Ptd-choline,... 

Flentge, F, Venema, K, Koch, T and Korf, J (1997) An enz5mie-reactor for electrochemical monitoring of choline and acetylcholine. Applications in high-performance liquid chromatography, brain tissue, microdialysis and cerebral fluid. Annal. Biochem. 204 305-311. 

The transport of amino acids at the BBB differs depending on their chemical class and the dual function of some amino acids as nutrients and neurotransmitters. Essential large neutral amino acids are shuttled into the brain by facilitated transport via the large neutral amino acid transporter (LAT) system [29] and display rapid equilibration between plasma and brain concentrations on a minute time scale. The LAT-system at the BBB shows a much lower Km for its substrates compared to the analogous L-system of peripheral tissues and its mRNA is highly expressed in brain endothelial cells (100-fold abundance compared to other tissues). Cationic amino acids are taken up into the brain by a different facilitative transporter, designated as the y system, which is present on the luminal and abluminal endothelial membrane. In contrast, active Na -dependent transporters for small neutral amino acids (A-system ASC-system) and cationic amino acids (B° system), appear to be confined to the abluminal surface and may be involved in removal of amino acids from brain extracellular fluid [30]. Carrier-mediated BBB transport includes monocarboxylic acids (pyruvate), amines (choline), nucleosides (adenosine), purine bases (adenine), panthotenate, thiamine, and thyroid hormones (T3), with a representative substrate given in parentheses [31]. 

In addition to their functions as presynaptic autoreceptors, 0C2AR can also modulate release of other neurotransmitters (Figure 3). In the CNS, 0C2A and 0C2C receptors inhibit dopamine release in basal ganglia (Bucheler et al. 2002) as well as serotonin secretion in mouse hippocampus and brain cortex (Scheibner et al. 2001a). In the enteric nervous system, the release of acetylcholine as determined by [3H] -choline overflow from tissue slices was selectively inhibited by (X2aAR (Scheibner et al. 2002). 

Fan and Zhang determined acetylcholine and choline in rat brain tissue by a fluorescence immunoassay method, making use of immobilized enzymes and chemiluminescence detection [50]. Tissue was homogenized with a 10 fold volume of 0.6 M HC104, the homogenates were kept on ice for 30 min, and then centrifuged at 2000 G for 20 min. The pellets were... 

Duan et al. reported the use of a rapid and simple method for the determination of acetylcholine and choline in mouse brain by high performance liquid chromatography, making use of an enzyme-loaded post column and an electrochemical detector [144]. Perchloric acid extracts of small brain tissue were injected onto the HPLC system with no prior clean-up procedure. Detection limits for both compounds were 1 pmol, and this method was successfully applied to the measurement of acetylcholine in discrete brain areas of the mouse. 

Polak and Molenaar described a method for the determination of acetylcholine from brain tissue by pyrolysis-gas chromatography-mass spectrometry [200]. The deuterium-labeled acetyl-choline is pyrolytically demethylated with sodium benzenethiolate, followed by quantitative GC-MS analysis. In this method, care must be taken so that the samples do not contain appreciable amounts of choline since exchange of deuterium-labeled groups between acetylcholine and choline during pyrolysis may yield erroneous results. The same authors have also reported a method for the determination of acetylcholine by slow pyrolysis combined with mass fragment analysis on a packed capillary column [201]. 

The method is essentially specific for alcohol esters of choline and measures the total acetylcholine (free plus bound) content of the brain tissue. There is no interference from other substances which might have acetylcholine-like effects in biological assay. The results are expressed as micrograms of acetylcholine per gram of wet tissue. 

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