A radiometric study of cholinesterase and its inhibition

Winteringham, F. P. W.; Disney, R. W.

doi:10.1042/bj0910506

Cited by 43 publications

(19 citation statements)

References 14 publications

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“…With few exceptions (16,17), the methods currently in use employ considerable dilution. Dilution of the enzyme, however, is followed by considerable recovery from inhibition caused by reversible inhibitors.…”

Section: Discussionmentioning

confidence: 99%

Estimation of Cholinesterase Activity (EC 3.1.1.7; 3.1.1.8) in Undiluted Plasma and Erythrocytes as a Tool for Measuring In Vivo Effects of Reversible Inhibitors

Thomsen¹,

Kewitz²,

Pleul³

1988

Clinical Chemistry and Laboratory Medicine

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Summary:In vivo effects of reversible inhibitors of cholinesterase activity were determined radiometrically in undiluted samples of erythrocytes and plasma. [ 14 C]acetylcholine at substrate saturation, 25 °C and pH 7.4 permitted rapid and precise determination of butyrylcholinesterase (EC 3.1.1.8) and acetylcholinesterase (EC 3.1.1.7) activities. Reference values for acetylcholinesterase and butyrylcholinesterase were estimated in the plasma and erythrocyte haemolysate of 102 healthy volunteers.The time course of in vitro inhibition was monitored, starting immediately after addition of 9-amino-l,2,3,4-tetrahydroacridine (tacrine), eserine or pyridostigmine to undiluted human plasma. Maximal inhibition (in vitro) was seen within 60 min with tacrine and eserine, in contrast to 180min with pyridostigmine. The inhibition remained constant for more than 10 h except with eserine, from which enzyme activity showed an early recovery. Concentration response experiments were performed in undiluted human plasma and undiluted human erythrocyte haemolysate. /^-values of tacrine, eserine and pyridostigmine were estimated. In contrast to pyridostigmine and eserine, tacrine was found to have a higher affinity for butyrylcholinesterase than for acetylcholinesterase. Tacrine at 2.5 μηιοΐ/ΐ resulted in complete inhibition of butyrylcholinesterase and 70% inhibition of acetylcholinesterase activity. Dilution of these samples up to 100-fold was accompanied by almost complete recovery of acetylcholinesterase and by 50% recovery of butyrylcholinesterase. Introduction,

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Section: Discussionmentioning

confidence: 99%

Estimation of Cholinesterase Activity (EC 3.1.1.7; 3.1.1.8) in Undiluted Plasma and Erythrocytes as a Tool for Measuring In Vivo Effects of Reversible Inhibitors

Thomsen¹,

Kewitz²,

Pleul³

1988

Clinical Chemistry and Laboratory Medicine

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“…This compound has become an important tool in studies on the uptake and release of ACh by tissues, slices (Schuberth & Sundwall, 1967) or synaptosome preparations (Marchbanks, 1968), and in radiochemical assays of choline acetyltransferase (Fonnum, 1966) or cholinesterases (Winteringham & Disney, 1964). Radioactively labelled compounds are measured with the highest efficiencies by liquid-scintillation counting.…”

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confidence: 99%

Isolation of choline esters from aqueous solutions by extraction with sodium tetraphenylboron in organic solvents

Fonnum

1969

Biochemical Journal

213

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1. The method is based on the observation that choline esters and sodium tetraphenylboron (Kalignost) form complexes that are insoluble in water but soluble in organic solvents such as nitriles, higher ketones and benzyl alcohol. 2. The extraction procedure is an example of liquid cation exchange where tetraphenylboron is the cation-exchange group. 3. The proportion of choline esters extracted depends on the type and total amount of cation in the aqueous phase and the amount of sodium tetraphenylboron in the organic solvent. 4. The proportion of choline esters extracted is independent of the choline ester concentration, the pH (between 8 and 3) and the relative volumes of the two phases. 5. The affinity of sodium tetraphenylboron for choline esters increases with an increase in the size of the acyl group. 6. The choline ester extracted can be released into an aqueous solution by treatment with strong acids, silver salts and anion-exchange resins.

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“…Acetyl-C14-choline is very rapidly hydrolyzed by cholinesterase to yield acetate-C14; since acetate-C14 but not acetyl-C14-choline is acid volatile, radio analysis for acid-volatile product gives a quantitative measure of acetyl-C14choline hydrolysis and, therefore, of cholinesterase activity. This method of analysis is particularly useful in considering the kinetics of carbamate inhibition of cholinesterases (WINTERINGHAM and DISNEY 1964). 3,5-Diisopropylphenyl-H3 methylcarbamate has been used in kinetic studies on the release of 3,5-diisopropylphenol-H3 on reaction with cholinesterase, a reaction which is biphasic as expected for the initial carbamoylation phase followed by subsequent turnover of the enzyme, and which is blocked by organophosphate inhibitors .…”

Section: Active Sites Of Enzymes and Reaction Kineticsmentioning

confidence: 99%

Residues of Pesticides and Other Foreign Chemicals in Foods and Feeds / Rückstände von Pesticiden und anderen Fremdstoffen in Nahrungs- und Futtermitteln

1969

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A radiometric study of cholinesterase and its inhibition

Cited by 43 publications

References 14 publications

Estimation of Cholinesterase Activity (EC 3.1.1.7; 3.1.1.8) in Undiluted Plasma and Erythrocytes as a Tool for Measuring In Vivo Effects of Reversible Inhibitors

Estimation of Cholinesterase Activity (EC 3.1.1.7; 3.1.1.8) in Undiluted Plasma and Erythrocytes as a Tool for Measuring In Vivo Effects of Reversible Inhibitors

Isolation of choline esters from aqueous solutions by extraction with sodium tetraphenylboron in organic solvents

Residues of Pesticides and Other Foreign Chemicals in Foods and Feeds / Rückstände von Pesticiden und anderen Fremdstoffen in Nahrungs- und Futtermitteln

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