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PubMed1979

[Properties of cholinesterase and carboxylesterase from locust ganglia].

The activity of locust ganglia cholinesterase is found to depend on concentrations of acetylthiocholine (ATC), propionylthiocholine (PTC) and butyrylthiocholine (BTC); that of carboxylesterase--on concentration of p-nitrophenylacetate (25 degrees, pH 7,5). The activity of cholinesterase is inhibited by an excess of ATC and BTC, but is unaffected by an excess of PTC. At concentrations greater than 0.01 M PTC is hydrolyzed faster than ATC at optimal (1.10(-3) M) concentration. The cholinesterase hydrolysis of BTC proceeds slower than that of ATC and PTC. The bimolecular constants (kII) of the rate of cholinesterase and carboxylesterase interaction with structurally different organophosphorus inhibitors (OPI) were determined. It was found that methylsulfomethylates of O-alkyl-S (beta-ethylmercaptoethyl) methylthiophosphonates are stronger inhibitors of cholinesterase than carboxylesterase; on the contrast, their uncharged analogs are stronger inhibitors of carboxylesterase, since the substitution of the sulfide sulphur for the sulphonic one strongly decreases the anticholinesterase activity and slightly increases the anticarboxylesterase activity of these OPI. O-alkyl-S (carbomethoxymethylmercaptomethyl) methylthiophosphonates inhibit carboxylesterase stronger than cholinesterase. The inhibitory activity of diisopropylthiophosphates towards cholinesterase is much lower than that of the corresponding diethylthiophosphates, while the activity of the former towards carboxylesterase is approximately the same as the activity of diethylthiophosphates or more strongly pronounced. Diisopropylfluorophosphate is a potent inhibitor of carboxylesterase. The data obtained provide evidence for differences in the structure of the active sites of cholinesterase and carboxylesterase. The carboxylesterase has no anionic sites. Moreover, the active surface of this enzyme interacting with the leaving part of OPI possesses, a site which prevents the absorption of cationic OPI and favours the interaction with the OPI containing the carboxyether group. The esterastic site of carboxylesterase is larger than that of cholinesterase and can predominantly interact with OPI having a bulky phosphoryl part.

Animals↗
PubMed1992

An automated method for the determination of acetyl and pseudo cholinesterase in hemolyzed whole blood.

The aim of the present study was to develop a method which allows determination of pseudo (PsChE) and acetyl cholinesterase (AChE) activities in single hemolyzed blood samples of workers exposed to cholinesterase-inhibiting compounds, avoiding the time-consuming and laborious separation of plasma and erythrocytes. Two methods based on Ellman's colorimetric determination of cholinesterase activity were compared, and three different substrates were tested. The best results were obtained with the substrates butyrylthiocholine and acetyl(beta-methyl)thiocholine, both showing a substrate specificity of more than 97% with respect to PsChE and AChE, respectively. The method showed sensitivity to detect low levels of inhibition of AChE and PsChE in blood. The between-day precision was less than 4% for both cholinesterase activities. It was demonstrated with this method that hemolyzed blood can be stored at -20 degrees C at least 18 months without loss of cholinesterase activity. The method has been used for 18 months in a monitoring program for laboratory employees working with various cholinesterase-inhibiting compounds. The average co-efficients of intraindividual variation amounted to 6.8% (range 2.2-9.6%; 90 percentile, 8%) and 6.6% (range 2.9-9.9%; 90 percentile, 7.9%) for PsChE and AChE, respectively. In a group of non-exposed workers the average intraindividual variations were 4.0% (range 1.5-7.7%; 90 percentile, 7.6%) and 3.6% (range 0.6-6.6%; 90 percentile, 5.3%), respectively. Using the value of 4.0%, it appears possible to detect an individual decrease in cholinesterase activity of more than 8% below a baseline based on three determinations. The method can thus be used to detect relatively low levels of cholinesterase inhibition.

Cholinesterase Inhibitors↗
PubMed1997

Cholinesterases from the common oyster (Crassostrea gigas). Evidence for the presence of a soluble acetylcholinesterase insensitive to organophosphate and carbamate inhibitors.

Marine bivalves such as oysters and mussels are widely used as bioindicators of contamination in the monitoring of pollutant effects. As filter feeders, these species are known to be good general indicators of chemical contamination. However, the efficient use of decreased acetylcholinesterase activity in the oyster as a biomarker of exposure to neurotoxic compounds requires a definition of the different types of cholinesterases coexisting in this mollusk. This study reports the partial purification, separation and characterization of two cholinesterases extracted from the oyster Crassostrea gigas. Differences in apparent molecular weight, type of glycosylation and hydrophobicity, and sensitivity to inhibitors suggest that they are encoded by two different genes. 'A' cholinesterase (apparent molecular weight 200 kDa) is anchored to the membrane via a glycolipid, is not glycosylated but sensitive to organophosphate and carbamate inhibitors. 'B' cholinesterase (molecular weight 330 kDa) is hydrophilic, glycosylated and highly resistant to organophosphate and carbamate inhibitors. The kinetic properties of these two cholinesterases were compared with those of other invertebrate cholinesterases. The presence of a cholinesterase insensitive to insecticides suggests that a significant improvement in the use of oyster cholinesterases as biomarkers of pollutant effects could be achieved by simple separation of the two forms.

Acetylcholinesterase↗
PubMed2001

Correlation of blood cholinesterase levels with toxicity of sarin in rats.

The dose-mortality response curve for sarin when administered to pregnant rats is extremely steep. The pregnant animal either died during the treatment or survived with no observable fetal toxicity. Animals that died displayed many symptoms characteristic of anticholinesterase toxicity. The present study was conducted to determine whether the maternal deaths, clinical observations, and/or weight loss could be correlated with baseline blood cholinesterase levels in individual animals. Cholinesterase levels (plasma and erythrocyte) were obtained prior to, during, and following treatment of nonpregnant rats by gavage with 380 microg/kg/d sarin for 10 d. After the first dose, there was a drop in the plasma cholinesterase levels, which then remained low throughout the dosing period. There was a statistically significant correlation between body weight loss and plasma cholinesterase levels of the sarin dosed animals. The surviving animals also had lower plasma cholinesterase levels and lower body weights, both of which recovered on the cessation of dosing. The erythrocyte cholinesterase levels were not different between treated and nontreated rats. Neither plasma or erythrocyte baseline cholinesterase levels nor relative or absolute cholinesterase decline values could be used as predictors of mortality from sarin administration in rats.

Animals↗
PubMed1972

Effect of metrifonate on blood cholinesterases in children during the treatment of schistosomiasis.

In a controlled clinical trial, Tanzanian schoolchildren with urinary schistosomiasis, many of whom had coexisting hookworm infection, were randomly allocated to one of three groups that were treated with doses of 7.5, 10.0, and 12.5 mg per kg of body weight, respectively, of metrifonate, orally, up to 3 times at 14-day intervals. No serious side effects were observed during or after the administration of single or repeated doses. A few hours after medication, plasma cholinesterase was almost completely inhibited, regardless of the dose given, while erythrocyte cholinesterase was almost completely inhibited, regardless of the dose given, while erythrocyte cholinesterase was inhibited down to 40-60% of the pretreatment level, depending on the dose. Plasma cholinesterase was inhibited to a greater extent than erythrocyte cholinesterase but showed a more rapid recovery of activity. A moderate accumulation of unreactivated erythrocyte cholinesterase occurred at all dose levels with this regime. Four weeks after the last dose of drug, plasma cholinesterase activity was nearly normal in all the treated children. Erythrocyte cholinesterase activity returned to normal 8-15 weeks after the last dose. The therapeutic results confirmed the efficacy of metrifonate against Schistosoma haematobium. There was an additional though less striking effect against hookworm.

Adolescent↗
PubMed1980

Hydrolysis of diacetylmorphine (heroin) by human serum cholinesterase.

The enzyme in human serum that rapidly hydrolyzes diacetylmorphine (heroin) to 6-acetylmorphine is identified in this report as serum cholinesterase (EC 3.1.1.8, acylcholine acylhydrolase; also called pseudocholinesterase or butyrylcholine esterase). The rate of heroin hydrolysis was measured spectrophotometrically at 245 nm using highly purified serum cholinesterase. The turnover number was 500 mumol of heroin hydrolyzed per min per mumol active site. The product was identified spectrophotometrically and by thin-layer chromatography to be 6-acetylmorphine. There appeared to be marked product inhibition of heroin hydrolysis, as 6-acetylmorphine (Ki = 0.015 mM) bound 7 times more tightly than heroin (Ki = 0.11 mM). Purified human serum arylesterase did not hydrolyze heroin. Purified serum cholinesterase accounted for all the observed heroin hydrolysis by whole serum. The genetic variants of human serum cholinesterase, silent and atypical cholinesterase, were also tested. Serum from a person identified as having silent cholinesterase did not hydrolyze heroin. Purified atypical cholinestearase hydrolyzed heroin, but the binding was less tight (Km = 0.45 mM) than with usual cholinesterase (Km = 0.11 mM). The possibility that heroin potency may be influenced by serum cholinesterase genotype or activity level remains to be investigated.

Cholinesterase Inhibitors↗
PubMed2005

A prescribing cascade involving cholinesterase inhibitors and anticholinergic drugs.

BACKGROUND: The prescribing cascade model involves the misinterpretation of an adverse reaction to 1 drug and the subsequent, potentially inappropriate prescription of a second drug. We present a new example of the prescribing cascade involving cholinesterase inhibitors and anticholinergic drugs used to manage urinary incontinence. METHODS: A population-based retrospective cohort study was carried out in Ontario, Canada. Participants included 44,884 older adults with dementia (20,491 were dispensed a cholinesterase inhibitor and 24,393 were not), enrolled between June 1, 1999, and March 31, 2002. Subjects were observed until they received an anticholinergic drug, stopped the cholinesterase inhibitor treatment, died, or the study period ended (March 31, 2003). The main outcome measure was receipt of an anticholinergic drug to manage urinary incontinence. RESULTS: After adjusting for potential confounding factors, we observed that older adults with dementia who were dispensed cholinesterase inhibitors had an increased risk of subsequently receiving an anticholinergic drug (4.5% vs 3.1%; P<.001; adjusted hazard ratio, 1.55; 95% confidence interval, 1.39-1.72), relative to those not receiving cholinesterase inhibitors. This finding was consistent in a series of subgroup analyses. CONCLUSIONS: Use of cholinesterase inhibitors is associated with an increased risk of receiving an anticholinergic drug to manage urinary incontinence. The use of an anticholinergic drug in this setting may represent a clinically important prescribing cascade. Clinicians should consider the possible contributing role of cholinesterase inhibitors in new-onset or worsening urinary incontinence and the potential risk of coprescribing cholinesterase inhibitors and anticholinergic drugs to patients with dementia.

Aged↗
PubMed2003

Efficacy of cholinesterase inhibitors in the treatment of neuropsychiatric symptoms and functional impairment in Alzheimer disease: a meta-analysis.

CONTEXT: Cholinesterase inhibitors are the primary treatment for the cognitive symptoms of Alzheimer disease (AD). Cholinergic dysfunction is also associated with neuropsychiatric and functional deficits, but results from randomized controlled trials of cholinesterase inhibitors are conflicting. OBJECTIVE: To conduct a systematic review and meta-analysis to quantify the efficacy of cholinesterase inhibitors for neuropsychiatric and functional outcomes in patients with mild to moderate AD. DATA SOURCES: We performed a literature search of trials using MEDLINE (January 1966-December 2001), Dissertations Abstracts On-line, PSYCHINFO, BIOSIS, PubMed, and the Cochrane Controlled Trials Register. We retrieved English- and non-English-language articles for review and collected references from bibliographies of reviews, original research articles, and other articles of interest. We searched for both published and unpublished trials, contacting researchers and pharmaceutical companies. STUDY SELECTION: We included 29 parallel-group or crossover randomized, double-blind, placebo-controlled trials of outpatients who were diagnosed as having mild to moderate probable AD and were treated for at least 1 month with a cholinesterase inhibitor. Sixteen trials included neuropsychiatric and 18 included functional measures. DATA EXTRACTION: Two investigators (N.H.T. and J.H.) independently extracted study methods, sources of bias, and outcomes. Neuropsychiatric outcomes were measured with the Neuropsychiatric Inventory (NPI, 0-120 points) and the Alzheimer Disease Assessment Scale, noncognitive (ADAS-noncog, 0-50 points) and were analyzed with the weighted mean difference method. Functional outcomes were measured with several activities of daily living (ADL) and instrumental activities of daily living (IADL) scales and analyzed with the standardized mean difference method. DATA SYNTHESIS: For neuropsychiatric outcomes, 10 trials included the ADAS-noncog and 6 included the NPI. Compared with placebo, patients randomized to cholinesterase inhibitors improved 1.72 points on the NPI (95% confidence interval [CI], 0.87-2.57 points), and 0.03 points on the ADAS-noncog (95% CI, 0.00-0.05 points). For functional outcomes, 14 trials used ADL and 13 trials used IADL scales. Compared with placebo, patients randomized to cholinesterase inhibitors improved 0.1 SDs on ADL scales (95% CI, 0.00-0.19 SDs), and 0.09 SDs on IADL scales (95% CI, 0.01 to 0.17 SDs). There was no difference in efficacy among various cholinesterase inhibitors. CONCLUSIONS: These results indicate that cholinesterase inhibitors have a modest beneficial impact on neuropsychiatric and functional outcomes for patients with AD. Future research should focus on how such improvements translate into long-term outcomes such as patient quality of life, institutionalization, and caregiver burden.

Activities of Daily Living↗
PubMed1987

Anatomy of cholinesterase inhibition in Alzheimer's disease: effect of physostigmine and tetrahydroaminoacridine on plaques and tangles.

The histochemical distribution of cholinesterases in the cerebral cortex and their response to cholinesterase inhibitors such as physostigmine and tetrahydroaminoacridine (THA) were investigated in brains from patients with Alzheimer's disease and control subjects. In the temporal neocortex of the control subjects, most of the cholinesterase activity was located within axons and cell bodies belonging to cholinergic pathways. In keeping with their well-known cholinomimetic effects, physostigmine and THA effectively inhibited this cholinesterase activity. Cholinesterase-containing normal axons (and in some cases cells) were severely depleted in the cerebral cortex of patients with Alzheimer's disease. Although the cerebral cortex of these patients continued to display abundant cholinesterase activity, the location of this enzyme was largely shifted to the neuritic plaques and neurofibrillary tangles. In fact, the majority of these pathological structures demonstrated intense acetylcholinesterase and butyrylcholinesterase activities. Physostigmine and THA were potent inhibitors of these plaque- and tangle-bound cholinesterases as well. In patients with Alzheimer's disease, cholinesterase inhibitors would therefore appear to have a major and widespread effect directly upon the enzymatic activity of plaques and tangles. Consequently, the clinical effects of anticholinesterases in Alzheimer's disease may be based on mechanisms that are different from those that apply to the normal brain.

Acetylcholinesterase↗
PubMed1993

A modified spectrophotometric method appropriate for measuring cholinesterase activity in tissue from carbaryl-treated animals.

Inhibited cholinesterase in tissues of animals exposed to carbamate pesticides is known to reactivate readily, presenting considerable problems in the accurate assessment of cholinesterase activity in these tissues. Decarbamylation of cholinesterase is favored when the tissue samples are diluted and/or are incubated for an extended time. The present study was performed to identify modifications of the commonly used spectrophotometric assay for cholinesterase activity that would minimize spontaneous reactivation of enzyme activity. Those modifications included preincubation of concentrated tissue with concentrated chromogen (i.e., DTNB), dilution to final reaction volume immediately before measurement, and measurement of cholinesterase over a short period of time (5-10 min). The Ellman assay with and without modifications was performed using a microtiter plate reader on tissues from carbaryl-treated rats:undiluted plasma, diluted erythrocytes (1:25), minimally diluted erythrocytes (1:2), diluted brain (1:100), or minimally diluted brain (1:2). The results were compared to cholinesterase activities obtained using a radiometric method which employs minimally diluted tissue and short incubation times. The degree of cholinesterase inhibition for undiluted or minimally diluted tissue assayed by the modified method agreed with those obtained using the radiometric method. Even if the tissues were diluted immediately before assay, however, significant reactivation occurred by the time the first measurements were made by the conventional method. Furthermore, significant spontaneous reactivation may still occur using the modified method if the assay is run for more than 10 min. Use of this modified Ellman method will enable more accurate estimation of in vivo cholinesterase activity in animals treated with carbamates.

Animals↗
PubMed1980

Characterization of embryonic cholinesterase in chick limb bud by colorimetry and disk electrophoresis.

In the chondrogenic blastema of the chick limb bud an histochemical cholinesterase activity related to aggregation of the chondroblasts was described by Drews and Drews (1972). This cholinesterase activity was termed "embryonic cholinesterase" (Drews 1975). In the present study embryonic cholinesterase from the limb bud has been characterized by colorimetry and disk electrophoresis and compared to cholinesterase from the myotomes of the same embryos. Embryonic cholinesterase comprises both acetylcholinesterase and butyrylcholinesterase activity. The banding patterns of embryonic cholinesterase from limb bud and of cholinesterase from myotomes are identical. These findings support the hypothesis that the cholinergic system is involved in the regulation of embryonic development.

Acetylcholinesterase↗
PubMed1990

Genetic variants of human serum cholinesterase influence metabolism of the muscle relaxant succinylcholine.

People with genetic variants of cholinesterase respond abnormally to succinylcholine, experiencing substantial prolongation of muscle paralysis with apnea rather than the usual 2-6 min. The structure of usual cholinesterase has been determined including the complete amino acid and nucleotide sequence. This has allowed identification of altered amino acids and nucleotides. The variant most frequently found in patients who respond abnormally to succinylcholine is atypical cholinesterase, which occurs in homozygous form in 1 out of 3500 Caucasians. Atypical cholinesterase has a single substitution at nucleotide 209 which changes aspartic acid 70 to glycine. This suggests that Asp 70 is part of the anionic site, and that the absence of this negatively charged amino acid explains the reduced affinity of atypical cholinesterase for positively charged substrates and inhibitors. The clinical consequence of reduced affinity for succinylcholine is that none of the succinylcholine is hydrolyzed in blood and a large overdose reaches the nerve-muscle junction where it causes prolonged muscle paralysis. Silent cholinesterase has a frame shift mutation at glycine 117 which prematurely terminates protein synthesis and yields no active enzyme. The K variant, named in honor of W. Kalow, has threonine in place of alanine 539. The K variant is associated with 33% lower activity. All variants arise from a single locus as there is only one gene for human cholinesterase (EC 3.1.1.8). Comparison of amino acid sequences of esterases and proteases shows that cholinesterase belongs to a new family of serine esterases which is different from the serine proteases.

Amino Acid Sequence↗
PubMed2000

Inhibitory effect of orally administered donepezil hydrochloride (E2020), a novel treatment for Alzheimer's disease, on cholinesterase activity in rats.

Donepezil hydrochloride ((+/-)-2-[(1-benzylpiperidin-4-yl)methyl]-5, 6-dimethoxy-indan-1-one monohydrochloride: E2020: donepezil) is a potent and selective acetylcholinesterase inhibitor developed for the treatment of Alzheimer's disease. The present experiments were designed to compare the inhibitory effects of orally administered donepezil and other cholinesterase inhibitors, tacrine (9-amino-1,2, 3,4-tetrahydroacridine hydrochloride), (S)-N-ethyl-3-[(1-dimethyl-amino)ethyl]-N-methyl-phenylcarbamate hydrogentartrate (ENA-713, rivastigmine) and 3-[1-(phenylmethyl)-4-piperidinyl]-1-(2,3,4, 5-tetrahydro-1H-1-benzazepin-8-yl)-1-propanone fumarate (TAK-147), on the cholinesterase activity in the brain and plasma of rats. Moreover, in order to validate the cholinesterase inhibition data, we measured the brain and plasma concentrations of these drugs. Oral administration of donepezil, tacrine, ENA-713 or TAK-147, caused a dose-dependent inhibition of brain and plasma cholinesterase activities. The ID(50) values of these compounds for brain cholinesterase activity were 6.3, 40.5, 7.2 and 26.8 micromol/kg, respectively. On the other hand, the ID(50)170, 9.7 and 51.2 micromol/kg, respectively. Thus, the ratios of the ID(50)4.2, 1.3 and 1.9, respectively. Brain and plasma concentrations of donepezil, tacrine and TAK-147 increased dose-dependently. The ratios of the concentrations (brain/plasma) of these compounds were 6.1-8.4 for donepezil, 14.5-54.6 for tacrine and 7.0-20.6 for TAK-147. The values of 50% inhibitory concentration of these drugs in the brain were 0.42, 3.5 and 1.1 nmol/g, respectively. In contrast, the brain and plasma concentrations of ENA-713 at all doses, except the two highest doses, were below the quantification limit. These results suggest that orally administered donepezil satisfactorily penetrates into the brain and inhibits cholinesterase there, and that donepezil is a potent and selective inhibitor of brain cholinesterase in comparison with plasma cholinesterase in vivo.

Administration, Oral↗
PubMed2003

Inactivation of cholinesterase induced by chlorpromazine cation radicals.

To clarify the mechanism of the side effect of chlorpromazine, we examined the inactivation of cholinesterase induced by chlorpromazine. Cholinesterase was inactivated and its activity was lost in rat serum during interaction of chlorpromazine with horseradish peroxidase and H2O2. When chlorpromazine was oxidized by horseradish peroxidase and H2O2, the reaction solution colored pink and the visible absorption spectrum was consistent with the absorption spectrum of the chlorpromazine cation radical (CPZ*+). Adding cholinesterase immediately decreased the pink color of CPZ*+, indicating that CPZ*+ directly attacked cholinesterase to cause loss of the enzyme activity. Tryptophan residues in cholinesterase sharply decreased during the interaction of cholinesterase with horseradish peroxidase and H2O2. Presumably, loss of tryptophan residues changed the conformation of the cholinesterase protein and then the activity of the enzyme was lost. Other phenothiazine derivatives, including promethazine, triflupromazine, trifluoperazine, trimeprazine, thioridazine and perphenazine, also inactivated cholinesterase during the oxidation by horseradish peroxidase and H2O2. These results suggest that phenothiazine cation radicals participate in toxicological signs caused by the drugs.

Animals↗
PubMed1998

Pharmacokinetics of bambuterol in subjects homozygous for the atypical gene for plasma cholinesterase.

AIMS: It has been assumed that both plasma cholinesterase (EC 3.1.1.8) and oxidative enzymes are needed for optimum formation of the bronchodilator terbutaline from its biscarbamate prodrug bambuterol. The present study aimed at investigating the fate of bambuterol in subjects with deficient plasma cholinesterase but with normal oxidative (CYP2D6) capability. METHODS: The pharmacokinetics of bambuterol and terbutaline were studied in four healthy subjects (two men and two women) being homozygous for the atypical gene for plasma cholinesterase. Their oxidative metabolism was apparently good as they were all rapid metabolizers of debrisoquine. Bambuterol hydrochloride 20 mg was given orally once daily for 10 days, and plasma and urine samples were taken for 1.5 days (plasma) and 4.5 days (urine) after administration of the last dose. RESULTS: The pharmacokinetic parameters in the present study were grossly similar to those found in a study of bambuterol in subjects with normal plasma cholinesterase activity (N). However, subjects with atypical cholinesterase had a shorter terminal half-life of bambuterol (a measure of uptake rate), 4.8-12.6 h vs 8.3-22.3 h in N, and slightly higher plasma concentrations of bambuterol (average concentrations 1.9-3.7 nmol l(-1) vs 1.5-3.1 nmol l(-1) in N). Peak/trough terbutaline plasma concentrations ratios (2.1-3.2) were somewhat increased, but average plasma concentrations (8.3-14.5 nmol l(-1)) and terminal half-life (16.5-21.8 h) of terbutaline did not differ. CONCLUSIONS: In Caucasian populations, one subject out of 2500 is homozygous for the atypical gene for plasma cholinesterase. The atypical enzyme has a much lower affinity for bambuterol than the normal enzyme. Nevertheless, the subjects with atypical cholinesterase were able to produce terbutaline as efficiently as normal subjects. This might be explained by an altered uptake and metabolism in the absence of plasma cholinesterase, or the importance of this enzyme for the formation of terbutaline from bambuterol in vivo may have been overestimated.

Adult↗
PubMed1970

Silent cholinesterase gene: variations in the properties of serum enzyme in apparent homozygotes.

The cholinesterase activity of the sera of 25 subjects diagnosed as homozygotes for the silent cholinesterase gene was studied by a sensitive enzymatic method employing several thiocholine esters and various inhibitors, and by disc electrophoretic, immunochemical, and chromatographic methods.(a) With one exception, the sera fell into two classes by all criteria. One class (type I, 16 cases) had no normal serum cholinesterase. The other class (type II, eight cases) had about 2% of apparently normal serum cholinesterase. The remaining serum was intermediate between the two classes in several respects. One explanation for these results is that there are several "silent" genes concerned; possibly these are allelic.(b) Normal sera and all silent sera contain small amounts of a cholinesterase activity labeled the residual cholinesterase. The enzyme(s) responsible has properties similar to those of acetylcholinesterase rather than serum cholinesterase. It is estimated that about 1% of the activity of normal serum against acetylthiocholine is due to this enzyme. The source of the residual cholinesterase is not yet known.

Cholinesterases↗
PubMed1994

Effect of time and storage temperature on cholinesterase activity in blood from normal and organophosphorus insecticide-treated horses.

Delays between time of sampling and time of testing are common; therefore, the length of time that blood can be stored at various temperatures was evaluated for effects on cholinesterase activity. Six horses were treated with 16 g of trichlorfon per os, 6 horses were treated with 15 g of dichlorvos per os, and 10 horses were untreated controls. The cholinesterase activity in whole blood from each horse was measured using an adaptation of the Ellman colorimetric method. The blood from each horse was then divided into 3 groups and stored at 5 C (refrigerated), 20 C (room temperature), or 38 C (incubated). Subsequent cholinesterase activities were measured daily and then at weekly intervals. The cholinesterase activities did not significantly increase or were measured daily and then at weekly intervals. The cholinesterase activities did not significantly increase or decrease (P > 0.05) in the blood from the untreated horses until after 1 week for any of the 3 temperature groups. The cholinesterase activities did not significantly increase or decrease (P > 0.05) in the stored blood from the trichlorfon-treated horses for 4 weeks in all 3 temperature groups. The cholinesterase activities significantly increased (P < 0.05) in the stored blood from the dichlorvos-treated horses after 1 week when the blood was refrigerated and by 24 hours when the blood was stored at room temperature or incubated. Therefore, blood from normal or organophosphate-treated horses can be used for cholinesterase evaluation for up to 1 week when stored at 5 C.

Animals↗
PubMed1996

Pleural fluid to serum cholinesterase ratio for the separation of transudates and exudates.

STUDY OBJECTIVE: To evaluate the usefulness of two new parameters for separating pleural transudates and exudates: pleural fluid cholinesterase level and pleural fluid to serum cholinesterase ratio, and to compare the results with the other well-established criteria. DESIGN: Prospective evaluation of the patients referred for diagnostic thoracentesis. SETTING: Pulmonary sections of a community hospital and a university hospital. PATIENTS: One hundred ninety-three consecutive patients. Forty were excluded for different reasons. MEASUREMENTS: The following criteria for separating the pleural effusions in transudates and exudates were analyzed: Light's criteria, the pleural fluid cholesterol level, the pleural fluid to serum cholesterol ratio, the pleural fluid cholinesterase level, and the pleural fluid to serum cholinesterase ratio. RESULTS: One hundred fifty-three patients had conditions diagnosed. Thirty-five were classified as having transudates and 118 as exudates. The percentage of effusions misclassified by each parameter was as follows: Light's criteria, 7.8%; pleural fluid cholesterol, 7.8%; pleural fluid to serum cholesterol ratio, 6.5%; pleural fluid cholinesterase, 8.5%; and pleural fluid to serum cholinesterase ratio, 1.3%. CONCLUSIONS: The pleural fluid to serum cholinesterase ratio is the most accurate criterion for separating pleural transudates and exudates. If further studies confirm our results, the cholinesterase ratio could be used as the first step in the diagnosis of pleural effusions.

Cholesterol↗