The plasma cholinesteerases: a new perspective

Plasma cholinesterase activity: A benchmark for rapid detection of pesticide poisoning in an avian scavenger

Poisoning due to exposure to organophosphate and carbamate pesticides is a common threat for many wildlife species, especially for scavengers such as vultures. The Griffon vulture population (Gyps fulvus), for instance, is deteriorating in the Eastern Mediterranean, and is considered to be critically endangered in Israel, where 48 out of 107 (45 %) known injury/mortality cases in 2010-2021 were caused by poisoning. Lack of specific clinical indications, together with levels of organophosphate or carbamate pesticides too low to detect, challenge the ability to diagnose and treat such poisoning events. The activity of cholinesterase (ChE) in plasma has the potential to serve as an effective biomarker for monitoring exposure to anticholinesterase pesticides in live vultures. Yet, the applicability of this approach has been limited by intra- and inter-species variations in ChE basal levels. The present study aims to provide a benchmark for ChE activity levels in healthy Griffons and their intra-species variation. Blood samples from free-roaming (n = 231) and captive (n = 63) Griffons were collected during routine monitoring, and ChE levels were determined using a colorimetric method. We established that the ChE in the plasma of Griffons reflects mostly acetylcholinesterase as the dominant form. ChE levels in healthy Griffons are 0.601 ± 0.011 U/ml (mean ± SE), while Griffons with suspected or confirmed pesticide poisoning display much lower levels of ChE activity (typically <0.3 U/ml). We also characterized the age dependence of ChE activity, as well as differences among groups from different locations or origins. Our study provides a rapid diagnostic tool for the detection of exposure to organophosphate and carbamate pesticides that should facilitate the lifesaving treatment and the conservation of this species. Moreover, our protocols can be adapted to other species and geographical areas, addressing pesticide poisoning worldwide and contributing to the protection of endangered species and their ecological functions (e.g. sanitation by scavengers).

Long-Chain Acylcholines Link Butyrylcholinesterase to Regulation of Non-neuronal Cholinergic Signaling

Acylcholines are comprised of an acyl chain esterified to a choline moiety; acetylcholine is the best-characterized member of this class, functioning as a neurotransmitter in the central and peripheral nervous systems as well as an inhibitor of cytokine production by macrophages and other innate immune cells. Acylcholines are metabolized by a class of cholinesterases, including acetylcholinesterase (a specific regulator of acetylcholine levels) and butyrylcholinesterase (BChE, an enigmatic enzyme whose function has not been resolved by genetic knockout models). BChE provides reserve capacity to hydrolyze acetylcholine, but its importance is arguable given acetylcholinesterase is the most catalytically efficient enzyme characterized to date. While known to be substrates of BChE in vitro, endogenous production of long-chain acylcholines is a recent discovery enabled by untargeted metabolomics. Compared to acetylcholine, long-chain acylcholines show greater stability in circulation with homeostatic levels-dictated by synthesis and clearance-suggested to impact cholinergic receptor sensitivity of acetylcholine with varying levels of antagonism. Acylcholines then provide a link between BChE and non-neuronal acetylcholine signaling, filling a gap in understanding around how imbalances between acylcholines and BChE could modulate inflammatory disease, such as the "cytokine storm" identified in severe COVID-19. Areas for further research, development, and clinical testing are outlined.

Nanoparticles of zinc oxide defeat chlorpyrifos-induced immunotoxic effects and histopathological alterations

Background and Aim:

Chlorpyrifos (CPF) is a widely used organophosphate insecticide. Nanoparticles of zinc oxide (ZnO NPs) physically showed effective adsorbing property for some insecticides. The study was conducted to estimate the potential effect of ZnO NPs against CPF toxicity.

Materials and Methods:

Four groups of male rats were used; control group and three groups received drinking water contained 75 mg/L CPF, combined 75 mg/L CPF and 200 mg/L ZnO NPs, and 200 mg/L ZnO NPs, respectively.

Results:

CPF significantly decreased macrophage activity, serum lysozyme activity, and levels of interleukin-2 (IL-2) and IL-6; increased the percentage of DNA degeneration on comet assay of lymphocytes and significantly elevated hepatic and splenic malondialdehyde contents; and decreased their glutathione contents. The liver and spleen showed marked histological alterations after exposure to CPF with decreased expression of acetylcholinesterase. The coadministration of ZnO NPs ameliorated most of the undesirable effects of CPF, through elevation of macrophage and serum lysozyme activities, increased the levels of IL-2 and IL-6, corrected the oxidative stress markers, and alleviated most of the adverse effect exerted by CPF in liver and spleen tissues.

Conclusion:

The addition of ZnO NPs to CPF-contaminated drinking water may be useful as a powerful antioxidant agent against toxic damage induced by CPF particularly in individuals who are on daily occupational exposure to low doses of CPF.

Complex View on Poisoning with Nerve Agents and Organophosphates

OP/nerve agents are still considered as important chemicals acting on living organisms and widely used in human practice. Nerve agents are the most lethal chemical warfare agents. They are characterized according to their action as compounds influencing cholinergic nerve transmission via inhibition of AChE. The symptoms of intoxication comprise nicotinic, muscarinic and central symptoms, for some OP/nerve agents, a delayed neurotoxicity is observed. Cholinesterases (AChE and BuChE) are characterized as the main enzymes involved in the toxic effect of these compounds including their molecular forms. The activity of both enzymes (and molecular forms) is influenced by inhibitors and other factors such as pathological states. There are different methods for cholinesterase determination, however, the most frequent is the method based on the hydrolysis of thiocholine esters and following detection of free SH-group of the released thiocholine. The diagnosis of OP/nerve agents poisoning is based on anamnesis, the clinical status of the intoxicated organism and on cholinesterase determination in the blood. Some principles of prophylaxis against OP/nerve agents poisoning comprising the administration of reversible cholinesterase inhibitors such as pyridostigmine (alone or in combination with other drugs), scavengers such as preparations of cholinesterases, some therapeutic drugs and possible combinations are given. Basic principles of the treatment of nerve agents/OP poisoning are described. New drugs for the treatment are under experimental study based on new approaches to the mechanism of action.

New-onset diabetes mellitus after living-donor liver transplantation: association with graft synthetic function

BACKGROUND AND PURPOSE

It is now known that post-transplant graft function after deceased-donor liver transplantation and living-donor liver transplantation (LDLT) differ; however, there is no report assessing the relationship between graft function and the development of new-onset diabetes mellitus after transplantation (NODAT). We conducted this study to identify the predictive risk factors for NODAT, including graft function after LDLT.

METHODS

The subjects of this study were 175 adult recipients who underwent LDLT at Kyoto University Hospital between 2006 and 2010, and survived for more than 3 months (median observation period, 1046 days).

RESULTS

The 1-, 2-, and 3-year incidences of NODAT after LDLT were 26.1, 32.0, and 33.4%, respectively. Pre-transplant diabetes was associated with poor survival (p = 0.0048), whereas NODAT was not associated with patient survival. In the multivariate analysis, recipient age ≥40, a tacrolimus trough level ≥8 ng/mL 3 months after LDLT, and cholinesterase (ChE) <185 IU/L 3 months after LDLT were the independent risk factors for NODAT.

CONCLUSIONS

Poor graft synthetic function 3 months after LDLT as well as older age of the recipient and a higher tacrolimus concentration were strongly associated with NODAT development after LDLT.

Post-Effort Changes in Activity of Traditional Diagnostic Enzymatic Markers in Football Players' Blood

Background

Long-term and intensive physical effort causes metabolic and biochemical adaptations for both athletic and non-athletic objectives. Knowing the importance of aerobic training in football players, the aim of this study was to evaluate changes in the activity of: creatinine kinase (CK), creatine kinase MB (CKMB), lactate dehydrogenase (LDH), α-hydroxybutyrate dehydrogenase (HBDH), cholinesterase (ChE) and alkaline phosphatase (ALP) in response to a semi-long distance outdoor run under aerobic conditions among both female and male football players.

Methods

Sixteen participants aged 21.9±2 years (women) and 18.4±0.5 years (men), all of them voluntarily recruited football players, took part in an outdoor run, the women covering a distance of 7.4±0.3 km while men covered a distance of 10.7±1.0 km. Plasma activities of the studied enzymes were determined using an appropriate diagnostic assay kit.

Results

Our results indicate that total LDH activity could be a useful tool in evaluating physical fitness among athletes. We simultaneously established that ChE could not be a marker useful in assessing metabolic response to physical effort in athletes. Moreover, our results suggest that post-effort changes in ALP activity might be used to estimate early symptoms of certain vitamin deficiencies in an athlete’s diet.

Conclusions

We confirmed that the assessment of activity of selected traditional diagnostic enzymatic markers provides information about muscle state after physical effort.

Effects of maternal undernutrition during late pregnancy on the development and function of ovine fetal liver

This study investigated the effects of maternal undernutrition during late pregnancy on the development and function of ovine fetal liver. Eighteen ewes with singleton fetuses were allocated to three groups at d 90 of pregnancy: Restricted Group 1 (RG1, 0.175MJMEkgBW(-0.75)d(-1), n=6), Restricted Group 2 (RG2, 0.33MJMEkgBW(-0.75)d(-1), n=6) and a Control Group (CG, ad libitum, 0.67MJMEkgBW(-0.75)d(-1), n=6). Fetuses were recovered at slaughter on d 140. Fetuses in the RG1 group exhibited decreased (P<0.05) liver weight, total antioxidant capacity (T-AOC), superoxide dismutase activity (SOD), cholinesterase (CHE), total protein (TP), globulin (GLB), and alanine transaminase (ALT). In addition, intermediate changes were found in the RG2 fetuses, including decreased liver weight, T-AOC and CHE (P<0.05). In contrast, increases in fetal hepatic collagen fibers and reticular fibers, glutathione peroxidase (GSH-Px), malondialdehyde (MDA), nitric oxide (NO), nitric oxide synthase (NOs), monoamine oxidase (MAO), albumin (ALB)/GLB, aspartate transaminase (AST), and AST/ALT were found in the RG1 fetuses (P<0.05). The RG2 fetuses had increased fetal hepatic collagen fibers, NOs and MAO (P<0.05) relative to the control fetuses. These results indicate that impaired fetal hepatic growth, fibrosis, antioxidant imbalance and dysfunction were associated with maternal undernutrition.

Which exposure stage (gestation or lactation) is more vulnerable to atrazine toxicity? Studies on mouse dams and their pups

Either during gestation or lactation, the experimental mouse dams received one of the following treatments: (a) diet free of pesticide; (b) diet enriched with atrazine (ATZ); 31.0 μg kg⁻¹; (c) diet free of pesticide + oral vitamin E (α-tocopherol; 200 mg kg⁻¹ per mouse); and (d) diet enriched with ATZ (31.0 μg kg⁻¹) + oral vitamin E (200 mg kg⁻¹ per mouse). At the weaning, pups and dams were killed and selected organs and blood samples were collected for analyses. Compared with the control results, ATZ induced alteration in a number of biochemical and histopathological parameters either in the dams or their offspring. The ameliorative effect of vitamin E, based on estimating the “Ameliorative Index; AI” to malondialdehyde (MDA) and superoxide dismutase (SOD) ranged between 0.95 and 1.06 (≈1.0) for the dams and the pups either in gestational or lactational exposure routes. In general, the mouse pups were more vulnerable to ATZ toxicity than their mothers and exposure during gestation was suggested to be more effective than during lactation. The findings may support the need to further investigating the adverse effects of exposure to low doses of commonly used pesticides, especially during pregnancy and breast-feeding as well as effects on newborn child.

Alteration of cholinesterase activity as possible mechanism of silver nanoparticle toxicity

Due to their broad-spectrum antimicrobial activity, silver nanoparticles (AgNPs) have been used in a large number of commercial and medical products. Such proliferated AgNP production poses toxicological and environmental issues which need to be addressed. The present study aimed to investigate the effects of AgNPs on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), important enzymes in areas of neurobiology, toxicology and pharmacology. Three different AgNPs, prepared by the chemical reduction using trisodium citrate, hydroxylamine hydrochloride (Cl-AgNPs), and borohydride following stabilization with poly(vinyl alcohol), were purified and characterised with respect to their sizes, shapes and optical properties. Their inhibition potential on AChE and BChE was evaluated in vitro using an enzyme assay with o-nitrophenyl acetate or o-nitrophenyl butyrate as substrates, respectively. All three studied AgNPs were reversible inhibitors of ChEs. Among tested nanoparticles, Cl-AgNP was found to be the most potent inhibitor of both AChE and BChE. Although the detailed mechanism by which the AgNPs inhibit esterase activities remains unknown, structural perturbation of the enzyme may be the common mode of ChE inhibition by AgNPs.

Treatment with endotracheal therapeutics after sarin microinstillation inhalation exposure increases blood cholinesterase levels in guinea pigs

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in the blood and tissues of animals that are treated with a number of endotracheally aerosolized therapeutics for protection against inhalation toxicity to sarin. Therapeutics included, aerosolized atropine methyl bromide (AMB), scopolamine or combination of AMB with salbutamol, sphingosine 1-phosphate, keratinocyte growth factor, adenosine A1 receptor antisense oligonucleotide (EPI2010), 2,3-diacetyloxybenzoic acid (2,3 DABA), oxycyte, and survanta. Guinea pigs exposed to 677.4 mg/m(3) or 846.5 mg/m(3) (1.2 LCt(50)) sarin for 4 min using a microinstillation inhalation exposure technique and treated 1 min later with the aerosolized therapeutics. Treatment with all therapeutics significantly increased the survival rate with no convulsions throughout the 24 h study period. Blood AChE activity determined using acetylthiocholine as substrate showed 20% activity remaining in sarin-exposed animals compare to controls. In aerosolized AMB and scopolamine-treated animals the remaining AChE activity was significantly higher (45-60%) compared to sarin-exposed animals (p < 0.05). Similarly, treatment with all the combination therapeutics resulted in significant increase in blood AChE activity in comparison to sarin-exposed animals although the increases varied between treatments (p < 0.05). BChE activity was increased after treatment with aerosolized therapeutics but was lesser in magnitude compared to AChE activity changes. Various tissues showed elevated AChE activity after therapeutic treatment of sarin-exposed animals. Increased AChE and BChE activities in animals treated with nasal therapeutics suggest that enhanced breathing and reduced respiratory toxicity/lung injury possibly contribute to rapid normalization of chemical warfare nerve agent inhibited cholinesterases.

Biochemical alterations induced by Zn and Cd individually or in combination in the serum of Oreochromis niloticus

Measurement of serum biochemical parameters in response to metal exposures can be especially useful to help identify target organs of toxicity as well as the general health status of animals. Oreochromis niloticus were exposed to 5.0 mg/L Zn, 1.0 mg/L Cd, and 5.0 mg/L Zn + 1.0 mg/L Cd mixture for 7 and 28 days, and alterations in serum enzyme activities and ion levels were measured. Significant changes in all the biochemical parameters were found to be time dependent. Following metal exposure, alkaline phosphatase activity was elevated at both exposure periods. No changes in activities of lactate dehydrogenase and lipase were observed in response to single or combined Zn and Cd exposure at 7 days while they increased at 28 days. Fish exposed to metals showed a decrease in cholinesterase activity at 7 days followed by a return to control levels at the end of the exposure period. The individual and combined effects of metals caused a decline in levels of Na(+), Cl(-), and Ca(2+), especially at 28 days. K(+) level increased at 7 days but it returned to control levels with increasing duration of exposure. This study indicated that the alterations in serum parameters may be a result of the target tissue (i.e., liver, gill, and kidney) damage and dysfunction induced by the metals and that these parameters can thus be used to assess the effects of metals on organisms.

Serum cholinesterase activity in the diagnosis of nonalcoholic fatty liver disease in type 2 diabetic patients

The aim of the study was to compare the serum cholinesterase activities of a group of type 2 diabetic patients showing clinical evidence of nonalcoholic fatty liver disease to those of age and sex-matched type 2 diabetics who showed no evidence of liver disease, and healthy control subjects to determine, if serum cholinesterase can be used to diagnose nonalcoholic fatty liver disease in type 2 diabetic patients. Mean serum cholinesterase activity in diabetics with nonalcoholic fatty liver disease was found to be statistically significantly lower than in diabetics without liver disease and in healthy subjects. There was no statistically significant difference between the mean values of serum cholinesterase activities of non-liver disease diabetics and healthy control subjects. It was found that serum cholinesterase activity of 1640IU/L or less differentiated type 2 diabetic subjects with nonalcoholic fatty liver disease from diabetic subjects who were free of liver disease with a diagnostic sensitivity of 87.5% and specificity of 75%. It is suggested that routine monitoring of serum cholinesterase activities from the time of diagnosis of type 2 diabetes mellitus may reveal the earliest time for the change in serum cholinesterase activities in diabetics that signals the onset of nonalcoholic fatty liver disease.

Common null variant, Arg192Stop, in a G-protein coupled receptor, olfactory receptor 1B1, associated with decreased serum cholinesterase activity

AIM

Non-functioning single nucleotide polymorphisms (nSNPs) that result in premature termination codons, that is null-alleles of the respective genes, may have phenotypic effects on clinical parameters. We conducted association studies involving several G-protein coupled receptors (GPCRs) that harbor nSNPs, using clinical parameters of liver function in a general population consisting of 2969 Japanese adults.

METHODS

SNP typings were performed with TaqMan and Invader assays. Quantitative associations between genotypes and clinical parameters were analyzed by analysis of variance. Linkage disequilibrium (LD) was tested by Haploview Version 3.3. Haplotype-based association was performed using the haplo.stats program.

RESULTS

A significant correlation (P = 0.0057) was identified between serum cholinesterase activity (CHE) and an nSNP (Arg192Stop) in the olfactory receptor (OR) 1B1 gene, a member of the GPCR gene family. This nSNP was associated with decreased serum CHE (P = 0.0013). LD analysis based on eight selected SNPs at the locus revealed three LD blocks. The Arg192Stop nSNP was located on the second LD block, which covered one-third of the 3'-portion of the gene.

CONCLUSION

These results suggested that the null-allele of OR1B1 might affect metabolism of serum cholinesterase in carriers of this nSNP.

Low serum level of cholinesterase at recurrence of pancreatic cancer is a poor prognostic factor and relates to systemic disorder and nerve plexus invasion

OBJECTIVES

Systemic disorder is a characteristic of advanced pancreatic cancer. Clinical prognostic factors in earlier disease state than terminal stage are expected to be sensitive markers for the foresight of systemic disorder. This study aimed to find the associations between these sensitive markers and morphological factors of primary tumor that may indicate finding a way of pathogenesis of systemic disorder.

METHODS

The current study examined 75 patients who received macroscopic curative resection for pancreatic cancer in our institution as follows: (1) identification of clinical prognostic factors at initial recurrence after resection of primary tumor and (2) analysis of correlations between clinical prognostic factors and histological findings in primary tumor.

RESULTS

Important prognostic factors were peritoneal dissemination and serum levels of carbohydrate antigen 19-9 and cholinesterase. Only low levels of serum cholinesterase correlated to nerve plexus invasion in histological findings of primary tumor. Patients with low cholinesterase levels show systemic disorder, including poor performance status, anemia, and hypoalbuminemia.

CONCLUSIONS

Nerve invasion may thus result in low functional state of the liver followed by systemic disorder. This mechanism may be useful for elucidating cancer cachexia in future studies.

An unexpected plasma cholinesterase activity rebound after challenge with a high dose of the nerve agent VX

Organophosphorus chemical warfare agents (nerve agents) are to be feared in military operations as well as in terrorist attacks. Among them, VX (O-ethyl-S-[2-(diisopropylamino)ethyl] methylphosphonothioate) is a low volatility liquid that represents a percutaneous as well as an inhalation hazard if aerosolized. It is a potent irreversible cholinesterase (ChE) inhibitor that causes severe signs and symptoms, including respiratory dysfunction that stems from different mechanisms. VX-induced pulmonary oedema was previously reported in dogs but mechanisms involved are not well understood, and its clinical significance remains to be assessed. An experimental model was thus developed to study VX-induced cardiovascular changes and pulmonary oedema in isoflurane-anaesthetized swine. In the course of this study, we observed a fast and unexpected rebound of plasma ChE activity following inhibition provoked by the intravenous injection of 6 and 12 microg kg(-1) of VX. In whole blood ChE activity, the rebound could stay unnoticed. Further investigations showed that the rebound of plasma esterase activity was neither related to spontaneous reactivation of ChE nor to VX-induced increase in paraoxonase/carboxylesterase activities. A bias in Ellman assay, haemoconcentration or severe liver cytolysis were also ruled out. All in all, these results suggest that the rebound was likely due to the release of butyrylcholinesterase into the blood stream from ChE producing organs. Nature of the organ(s) and mechanisms involved in enzyme release will need further investigations as it may represent a mechanism of defence, i.e. VX scavenging, that could advantageously be exploited.

Serum cholinesterase activity helps to distinguish between liver disease and non-liver disease aberration in liver function tests

The diagnostic usefulness of a single determination of serum cholinesterase activity to distinguish between overt liver disease and non-liver disease clinical problems in which a few of the traditional liver function tests are abnormal was assessed. Using three groups of subjects comprising liver disease, non-liver disease, and healthy controls, we have shown that serum cholinesterase activity helped to distinguish between liver disease and non-liver disease in subjects who had abnormality of a few liver function tests. Serum cholinesterase activity helped also to distinguish between the liver disease subjects and healthy controls. There was no statistically significant difference between the mean serum cholinesterase activities of non-liver disease subjects and healthy controls. We suggest that determination of serum cholinesterase activity is a cost-effective diagnostic means of differentiating between overt liver disease and non-liver diseases where there may be aberration of some liver function tests.

Changes in liver and plasma acetylcholinesterase in rats with cirrhosis induced by bile duct ligation

Classical studies of cholinesterase activity during liver dysfunction have focused on butyrylcholinesterase (BuChE), whereas acetylcholinesterase (AChE) has not received much attention. In the current study, liver and plasma AChE levels were investigated in rats with cirrhosis induced after 3 weeks of bile duct ligation (BDL). BDL rats showed a pronounced decrease in liver AChE levels (approximately 50%) compared with sham-operated (non-ligated, NL) controls; whereas liver BuChE appeared unaffected. A selective loss of tetrameric (G4) AChE was detected in BDL rats, an effect also observed in rats with carbon tetrachloride-induced cirrhosis. In accordance, SDS-PAGE analysis showed that the major 55-kd immunoreactive AChE band was decreased in BDL as compared with NL. A 65-kd band, attributed in part to inactive AChE, was increased as became the most abundant AChE subunit in BDL liver. The overall decrease in AChE activity in BDL liver was not accompanied by a reduction of AChE transcripts. The loss of G4 was also reflected by changes observed in AChE glycosylation pattern attributable to different liver AChE forms being differentially glycosylated. BDL affects AChE levels in both hepatocytes and Kupffer cells; however, altered AChE expression was mainly reflected in an alteration in hepatocyte AChE pattern. Plasma from BDL rats had approximately 45% lower AChE activity than controls, displaying decreased G4 levels and altered lectin-binding patterns. In conclusion, the liver is an important source of serum AChE; altered AChE levels may be a useful biomarker for liver cirrhosis.

In vitroenzyme inhibition activities of crude ethanolic extracts derived from medicinal plants of Pakistan

Twenty two crude ethanolic extracts from 14 indigenous medicinal plants were subjected to enzyme inhibition screening against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and lipoxygenase enzymes (LO). Three extracts showed activity against AChE, nine extracts were found to be active against BChE and four extracts inhibited the enzyme LO. The most significant inhibition activities (> or =50%) were found in extracts derived from Aloe vera (leaves), Alpinia galanga (rhizome), Curcuma longa (rhizome), Cymbopogon citratus (leaves), Ocimum americanum (leaves), Ocimum americanum (stem) and Withania somnifera (roots).

Inhibition of human plasma cholinesterase by malachite green and related triarylmethane dyes: Mechanistic implications

The inhibitory effects of the cationic triarylmethane (TAM+) dyes, pararosaniline (PR+), malachite green (MG+), and methyl green (MeG+) on human plasma cholinesterase (BChE) were studied at 25 degrees C in 100 mM Mops, pH 8.0, with butyrylthiocholine as substrate. PR+ and MG+ caused linear mixed inhibition of enzyme activity. The respective inhibitory parameters were K(i) = 1.9 +/- 0.23 microM, alpha = 13 +/- 48, beta = 0 and K(i) = 0.28 +/- 0.037 microM, alpha = 23 +/- 7.4, beta = 0. MeG+ acted as a competitive inhibitor with K(i) = 0.12 +/- 0.017 microM (alpha, infinity, beta, not applicable). The K(i) values were within the same range reported for a number of ChE inhibitors including propidium ion, donepezil, and the phenothiazines, suggesting that TAM+s are active site ligands. On the other hand, the alpha values failed to correlate with values previously reported for a number of ChE inhibitors. It appears that mixed inhibition is the combined result of more than one type of binding and S-I interference. The impact of ligands at the choline-specific and peripheral anionic sites (or, possibly, accessory structural domains) on BChE activity needs to be studied in further detail.

Organophosphates/nerve agent poisoning: mechanism of action, diagnosis, prophylaxis, and treatment

OP/nerve agents are still considered as important chemicals acting on living organisms and are widely used. They are characterized according to their action as compounds influencing cholinergic nerve transmission via inhibition of AChE. Modeling of this action and extrapolation of experimental data from animals to humans is more possible for highly toxic agents than for the OP. The symptoms of intoxication comprise nicotinic, muscarinic, and central symptoms; for some OP/nerve agents, a delayed neurotoxicity is observed. Cholinesterases (AChE and BuChE) are characterized as the main enzymes involved in the toxic effect of these compounds, including molecular forms. The activity of both enzymes (and molecular forms) is influenced by inhibitors (reversible, irreversible, and allosteric) and other factors, such as pathological states. There are different methods for cholinesterase determination; however, the most frequent is the method based on the hydrolysis of thiocholine esters and subsequent detection of free SH-group of the released thiocholine. The diagnosis of OP/nerve agent poisoning is based on anamnesis, the clinical status of the intoxicated organism, and on cholinesterase determination in the blood. For nerve agent intoxication, AChE in the red blood cell is more diagnostically important than BuChE activity in the plasma. This enzyme is a good diagnostic marker for intoxication with OP pesticides. Some other biochemical examinations are recommended, especially arterial blood gas, blood pH, minerals, and some other specialized parameters usually not available in all clinical laboratories. These special examinations are important for prognosis of the intoxication, for effective treatment, and for retrospective analysis of the agent used for exposure. Some principles of prophylaxis against OP/nerve agent poisoning comprising the administration of reversible cholinesterase inhibitors such as pyridostigmine (alone or in combination with other drugs), scavengers such as preparations of cholinesterases, some therapeutic drugs, and possible combinations are given. Basic principles of the treatment of nerve agent OP poisoning are described. They are based on the administration of anticholinergics (mostly atropine but some other anticholinergics can be recommended) as a symptomatic treatment, cholinesterase reactivators as a causal treatment (different types but without a universal reactivator against all OP/nerve agents) as the first aid and medical treatment, and anticonvulsants, preferably diazepam though some other effective benzodiazepines are available. New drugs for the treatment are under experimental study based on new approaches to the mechanism of action. Future trends in the complex research of these compounds, which is important not only for the treatment of intoxication but also for the quantitative and qualitative increase of our knowledge of toxicology, neurochemistry, neuropharmacology, clinical biochemistry, and analytical chemistry in general, are characterized.

The effects of Ni2+, Co2+, and Mn2+ on human serum butyrylcholinesterase

The effects of Ni2+, Co2+, and Mn2+ on human serum butyrylcholinesterase (BChE, acylcholine acylhydrolase E.C. 3.1.1.8) were investigated in this study. Inhibition kinetics of BChE were studied using butyrylthiocholine (BTCh) as substrate. The "1/v" versus "1/[BTCh]" plots in the absence (control plot) and in the presence of the metal ions intersected above 1/[BTCh]-axis for all trace elements. In addition, when the concentrations of the cations were increased at 4 mM BTCh, velocities decreased and drove to zero at high concentrations of the trace elements. These results demonstrate that Ni2+, Co2+, and Mn2+ are linear mixed-type inhibitors of BChE. alphaK(i) values have been determined as 53.20 mM,152.25 mM, and 190.24 mM for Ni2+, Mn2+, and Co2+, respectively, by using nonlinear regression analysis. From the comparison of alphaK(i) values of the trace elements, it can be said that BChE has more affinty to binding Ni2+ than Co2+ and Mn2+.

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.

A new perspective on thermal inactivation kinetics of human serum butyrylcholinesterase

Butyrylcholinesterase purified from human serum as 6600-fold was heated at 37 degrees, 40 degrees, 45 degrees, and 50 degrees C for 24 hr. It was observed that the enzyme heated at 45 degrees C for 24 hr converted to a stabilized form and followed Michaelis-Menten kinetics, whereas the enzyme samples, heated at the other temperatures for 24 hr, shown negative cooperativity with respect to its substrate, butyrylthiocholine. Even the sample heated at 45 degrees C for 12 hr shown negative cooperativity. On the contrary to the heated enzyme at 40 degrees C for 24 hr, the heated enzyme at 45 degrees C for 24 hr could not be reactivated when it was kept at 4 degrees C for 24 hr. In the kinetic studies, it was found that substrate analogs choline and benzoylcholine inhibited both the native enzyme and the enzyme heated at 45 degrees C for 24 hr competitively, whereas succinylcholine was the partial competitive inhibitor of native enzyme but the pure competitive inhibitor of the heated enzyme.

Selective activity of butyrylcholinesterase in serum by a chemiluminescent assay

In a previous study, we showed that purified commercial esterase activity can be detected in a chemiluminescent assay based on the hydrolysis of 2-methyl-1-propenylbenzoate (MPB) to 2-methyl-1-propenol, which is subsequently oxidized by the horseradish peroxidase (HRP)-H(2)O(2) system. The purpose of this study was to verify the applicability of this assay to human serum. The existence of an esterase activity capable of hydrolysing MPB is indicated by the fact that the MPB-serum-HRP-H(2)O(2) system consumes oxygen and emits light. Both signals were abolished by prior serum heat inactivation and were preserved when serum was stored at < or =4 degrees C. Addition of aliesterase inhibitors, such as fluoride ion and trichlorfon or the cholinesterase inhibitor eserine, totally prevents light emission. The butyrylcholinesterase-specific substrate benzoylcholine causes a delay in both O(2) uptake and light emission, while the specific acetylcholinesterase substrate, acetyl-beta-methylcholine, had practically no effect. Purified butyrylcholinesterase, but not acetylcholinesterase, triggered light emission. The finding that butyrylcholinesterase is responsible for the hydrolysis of MPB in serum should serve as the basis for the development of a specific chemiluminescent assay for this enzyme.

Inhibition effects of benactyzine and drofenine on human serum butyrylcholinesterase

Benactyzine and drofenine are widely used anticholinergic drugs. Benactyzine is used to treat organophosphate poisoning and drofenine acts on smooth muscle to stop muscle spasms. Both of these drugs are esters. After they enter the bloodstream, they will interact with butyrylcholinesterase (BChE; acylcholine acyl hydrolase: EC 3.1.1.8), which has an ability to hydrolyze a wide variety of esters. Therefore, the kinetic analysis of their inhibitory effects on human serum BChE was examined using butyrylthiocholine as substrate. Both drugs were competitive inhibitors of BChE and the Ki values of benactyzine and drofenine were calculated to be 0.010 +/- 0.001 and 0.003 +/- 0.000 mM, respectively, using the Systat (version 5.03, 1991) nonlinear regression analysis software package. According to these parameters, drofenine is a more potent competitive inhibitor of BChE than benactyzine.

Inhibition kinetics of human serum butyrylcholinesterase by Cd2+, Zn2+ and Al3+: comparison of the effects of metal ions on cholinesterases

Butyrylcholinesterase (BChE, EC 3.1.1.8) has been purified about 6600-fold from human serum with a procedure including ammonium sulfate fractionation (55-70%) with acid step at pH 4.5 and procainamide-Sepharose 4B affinity chromatography. The purified enzyme exhibited negative cooperativity with respect to butyrylthiocholine (BTCh) binding at pH 7.5. Ks was found to be 0.128 +/- 0.012 mM. Inhibition kinetics of the enzyme by Cd2+, Zn2+ and Al3+ were studied in detail. The 1/v vs 1/[BTCh] plots in the absence (control plot) and in the presence of different concentrations of cations intersected above 1/[BTCh]-axis. The data were analyzed by means of a nonlinear curve fitting program. The results demonstrated that all of the three cations are the linear mixed-type inhibitors of BChE. Ca2+ and Mg2+ had no effect on the enzyme activity in the experimental conditions. But when the enzyme was inhibited by 0.5 mM Cd2+ or Zn2+, Ca2+ and Mg2+ partially reactivated the inhibited allosteric form of BChE. Results were compared with data obtained from brain BChE purified from sheep.

Inhibition of acetylcholine esterase and choline esterase by benzethonium chloride and avoidance of the benzethonium chloride carry-over inhibitory effect

It has been shown that benzethonium chloride produces linear mixed-type inhibition of choline esterase and acetylcholine esterase. These enzymes also show-reagent-carry-over inhibition if the enzyme activities are measured in plastic cuvettes in which previously protein has been determined by the alkaline benzethonium chloride method. Choline esterase is about 10-fold more sensitive to benzethonium chloride than acetylcholine esterase. With acetylthiocholine as substrate Michaelis-Menten constants for choline esterase and acetylcholine esterase are 85 mumol/l and 102 mumol/l, respectively. Carry-over inhibitory effect of benzethonium chloride can be avoided by washing the cuvettes, after protein determination by the benzethonium chloride method, with 5 ml/l Triton X-100, 5 ml/l Tween 20 or 10 g/l sodium dodecyl sulphate. The latter has a disadvantage in that it precipitates out at low temperatures. The dry slide method (Johnson & Johnson) for serum choline esterase is free of the inhibitory effect until the concentration of benzethonium chloride in the sample reaches about 200 mumol/l.

Cholinesterase activity in human pulmonary arteries and veins

1. Human isolated pulmonary vessels were treated with cholinesterase (ChE) inhibitors to determine the role of these enzymes in regulating vascular muscle tone. In addition, kinetic parameters were determined for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in human pulmonary vessel homogenates. 2. Carbachol (CCh) and acetylcholine (ACh) were equipotent contractile agonists in human pulmonary arteries (pD2 values, 5.28 +/- 0.05 and 5.65 +/- 0.16; Emax, 0.91 +/- 0.26 and 0.98 +/- 0.30 g wt. for CCh and ACh, respectively; n = 7). In venous preparations, ACh was ineffective and CCh induced small contractions (Emax, 0.08 +/- 0.04 g wt; n = 13). 3. In human pulmonary arteries following pretreatment with tetraisopropylpyrophosphoramide (iso-OMPA, 100 microM), an increased sensitivity to the contractile agonist ACh was observed (pD2 values, 5.80 +/- 0.13 and 6.37 +/- 0.19 for control and treated preparations, respectively; n = 5). This pretreatment had no effect on the CCh concentration response curve. In contrast, human pulmonary veins pretreated with iso-OMPA failed to elicit a contractile response to ACh. 4. Neither Iso-OMPA nor neostigmine elicited concentration-dependent contractions in human isolated pulmonary arteries or veins. These results suggest the absence of sufficient spontaneous release of ACh to modulate human pulmonary vessel basal tone. 5. CCh was less potent than ACh in relaxing precontracted human isolated pulmonary arteries (pD2 value, CCh: 6.55 +/- 0.15 and ACh: 7.16 +/- 0.13, n = 4) and veins (pD2 value, CCh: 4.95 +/- 0.13; n = 5 and ACh: 5.56 +/- 0.17; n = 6). Pretreatment of vessels with either iso-OMPA or neostigmine did not modify ACh relaxant responses in either type of preparation. 6. In human pulmonary veins, the ChE activity was two fold greater than in arteries (n = 6). Vmax for AChE was 1.73 +/- 0.24 and 3.36 +/- 0.26 miu mg-1 protein in arteries and veins, respectively, whereas Vss for BChE was 1.83 +/- 0.22 and 4.71 +/- 0.17 miu mg-1 protein, in these respectively. 7. In human pulmonary arteries, BChE activity may play a role in the smooth muscle contraction but not on the smooth muscle endothelium-dependent relaxation induced by ACh. A role for ChE activity in the control of venous tone is presently difficult to observe, even though this tissue contains a greater amount of enzyme than the artery.

Large-scale purification and long-term stability of human butyrylcholinesterase: a potential bioscavenger drug

Butyrylcholinesterase from human plasma (HuBChE) is a potential drug candidate for detoxification of certain harmful chemicals that contain carboxylic or phosphoric acid ester bonds. Large quantities of purified HuBChE, displaying a high stability upon long-term storage, are required for the evaluation of its therapeutic capacity and its pharmaceutical properties. Several modifications of a previously reported procedure enabled us to purify the enzyme > 15,000-fold from pools of up to 100 1 of human plasma. The three-step procedure is based on precipitation of plasma proteins by ammonium sulfate (step I) and batch adsorption of HuBChE on procainamide-Sepharose 4B gel (step II). Ammonium sulfate was also employed in the third stage to fractionate the final product from procainamide-containing HuBChE solution. The overall yield (63%) of electrophoretically pure enzyme was significantly higher than that previously reported (34%) for the purification of HuBChE from 12.5 1 of plasma or from 5 kg of Cohn fraction IV-4. Purified HuBChE was stored at 5 degrees C in 10 mM phosphate buffer (pH 7.4) containing 1 mM EDTA and 0.02% NaN3. The specific activity, protein migration on gel electrophoresis, thermostability at 54 degrees C and the mean residence time in the circulation of mice remained essentially constant for at least 46 months. The modifications introduced can provide large quantities of purified enzyme that maintains its activity and bioavailability properties for several years.

Influence of haemodialysis on lipase activity

Our aim was to determine whether the increase in serum pancreatic lipase values, reported in patients with chronic renal failure maintained on haemodialysis, is the result of haemoconcentration by fluid removal during dialysis, or whether it is due to lipase stimulation by endothelial lipoprotein lipase, induced by the heparin used as an anticoagulant. We therefore compared the increases in serum lipase, when heparin was used, with those observed when this was replaced by the antithrombotic agent, defibrotide, which has no effect on lipoprotein lipase. In addition, in order to determine the effects of haemoconcentration, variations in total protein concentration and haematocrit values were determined on the same samples, both before and after dialysis. The results showed a statistically significant post-dialysis increase in lipase only when heparin was used (p < 0.03). There was also a mean percentage post-dialysis increase of 16.2% in total protein (p < 0.0001) and 15.5% in haematocrit (p < 0.0001), due to fluid removal. No significant correlation in percentage increases was found between lipase vs total protein or haematocrit values. These findings suggest that heparin-induced lipoprotein lipase stimulation is the principal cause of the post-dialysis increase in pancreatic lipase, and that fluid removal during dialysis makes only a minor contribution to this increase.

Cholinesterase activity in pig airways and epithelial cells

Acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) activities were detected in bronchial and bronchial epithelial cell homogenates of the pig. In the bronchial homogenates, the maximal upstroke velocity (Vmax) of AChE and the maximal velocity after second substrate fixation (Vss) of BChE were 5.70 +/- 0.46 and 7.87 +/- 0.81 mU/mg protein, respectively. In the epithelial cell homogenates, a smaller amount of cholinesterase (ChE) was found: Vmax was 0.62 +/- 0.29 and Vss was 1.56 +/- 0.33 mU/mg protein for AChE and BChE, respectively. AChE activity was increased by 21 +/- 5% in the bronchial homogenates and by 54 +/- 14% in the epithelial cell homogenates, when intact bronchial segments were incubated with a cyclooxygenase inhibitor, indomethacin (INDO). These results suggest that prostanoids may be involved in the regulation of AChE activity in pig airways.

Changes in cholinesterase activities after daunorubicin administration to rabbits

1. Acetyl- and butyrylcholinesterase (AChE, BuChE) activities were studied in rabbits with experimentally induced daunorubicin cardiomyopathy. 2. A significant decrease of the plasma BuChE in the daunorubicin group was observed. 3. In the daunorubicin group, AChE activity in the heart was significantly decreased only in the interventricular septum. 4. BuChE activity was significantly decreased in the cardiac septum and ventricles and in the liver following daunorubicin treatment. 5. Changes in cholinesterase activities are probably caused by an effect of daunorubicin oon protein synthesis during the development of certain types of cardiomyopathy.

Intravenous cocaine induces platelet activation in the conscious dog

BACKGROUND

Cocaine consumption has been associated with thrombosis of coronary and peripheral arteries. Since cocaine has been found to induce platelet activation in vitro, we sought to establish whether cocaine induced platelet activation in vivo.

METHODS AND RESULTS

Chronically instrumented, conscious dogs were infused with cocaine (1 mg/kg), norepinephrine (0.2 to 0.4 mg/kg), or saline intravenously over 1 minute. Activated canine platelets were identified in whole blood collected from an indwelling aortic catheter by flow cytometric detection of the binding of a monoclonal antibody directed against the activation-dependent antigen P-selectin. Infusion of cocaine resulted in an elevation of mean arterial pressure (91 +/- 3 to 128 +/- 7 mm Hg [P < .01]) and heart rate (87 +/- 9 to 125 +/- 11 beats per minute [P < .01]). A similar change (P = NS) in mean arterial pressure followed norepinephrine infusion (100 +/- 5 to 137 +/- 13 mm Hg [P < .04]), whereas saline infusion had no effect. Cocaine resulted in a substantial but delayed increase in platelet P-selectin expression (14 +/- 7% [P < .08], 31 +/- 12% [P < .04], and 55 +/- 22% [P < .04] at 17, 22, and 27 minutes after drug infusion, respectively). The magnitude of this increase was similar to that found in blood treated ex vivo with the agonists ADP or PAF (23 +/- 7% and 53 +/- 15%, respectively). No significant increase in P-selectin expression was detected in the blood of animals that received norepinephrine or saline. Serum cocaine concentrations were highest immediately after infusion (538 +/- 55 ng/mL at 2 minutes) but declined rapidly (185 +/- 22 and 110 +/- 25 ng/mL at 17 and 32 minutes after infusion); in contrast, the increase in benzoylecgonine concentrations was delayed (from < 25 ng/mL in all but one animal [34 ng/mL] at 2 minutes to 46 +/- 4 and 71 +/- 11 ng/mL at 17 and 32 minutes, respectively, after infusion).

CONCLUSIONS

Intravenous cocaine induces activation of individual circulating platelets; this effect is not reproduced by infusion of norepinephrine at doses sufficient to exert similar hemodynamic effects. The delay in detection of activated platelets after treatment with cocaine may result from the adhesion and subsequent detachment of activated platelets; alternatively, cocaine metabolites, rather than the drug itself, may induce platelet activation.

Tissue distribution of human acetylcholinesterase and butyrylcholinesterase messenger RNA

Cholinesterase inhibitors occur naturally in the calabar bean (eserine), green potatoes (solanine), insect-resistant crab apples, the coca plant (cocaine) and snake venom (fasciculin). There are also synthetic cholinesterase inhibitors, for example man-made insecticides. These inhibitors inactivate acetylcholinesterase and butyrylcholinesterase as well as other targets. From a study of the tissue distribution of acetylcholinesterase and butyrylcholinesterase mRNA by Northern blot analysis, we have found the highest levels of butyrylcholinesterase mRNA in the liver and lungs, tissues known as the principal detoxication sites of the human body. These results indicate that butyrylcholinesterase may be a first line of defense against poisons that are eaten or inhaled.

The effect of age and frailty upon blood esterase activities and their response to dietary supplementation

1. The aims of this study were two-fold. First, to define ranges of blood esterase activities in three groups, namely young subjects, fit community dwelling elderly and frail, chronically hospitalised elderly subjects, and second, to determine whether low blood esterase activities in the frail patients could be altered by increasing their nutritional intake. 2. Plasma cholinesterase, aspirin esterase, paraoxonase and phenylacetate esterase activities were all significantly lower in the frail elderly compared with the young and fit elderly volunteers. The activity of red blood cell esterase was not different in the frail elderly. 3. Fourteen frail elderly patients were randomly assigned to receive either hospital meal provision plus supplemental feeding with Build-up (Nestle) and Maxijul (SHS Ltd) or hospital provision alone for 8 weeks. Dietary intake was measured for all patients at the start of the study and at week 8. Measurements of blood esterase (cholinesterase, phenylacetate esterase, paraoxonase, aspirin esterase and red blood cell esterase), albumin and anthropometric indices (weight, triceps skinfold thickness and mid arm circumference) were made before the study and repeated at week 4 and 8. 4. There was a significant increase in plasma cholinesterase at week 4 (P < 0.05) but this was not statistically significant at week 8. There were no significant changes in any of the other esterase activities or anthropometric measurements. 5. We conclude that the lower esterase activities of the frail chronically hospitalised elderly do not respond to dietary supplementation for a period of 8 weeks with routinely available products. The hypothesis that lower esterase activities are the direct result of undernutrition which would be corrected by dietary supplementation has not been supported by this study.

Inhibition kinetics of brain butyrylcholinesterase by Cd2+ and Zn2+, Ca2+ or Mg2+ reactivates the inhibited enzyme

1. The inhibition kinetics of sheep brain butyrylcholinesterase (BChE) (acylcholine acylhydrolase, EC 3.1.1.8) by Cd2+ and Zn2+ has been studied. 2. KS has been determined as 0.14 mM. Cd2+ and Zn2+ were the hyperbolic mixed-type inhibitors of BChE. Ca2+ and Mg2+ had no effect on the enzyme activity in the experimental conditions. 3. But when the enzyme was inhibited by 0.1 mM Cd2+ or Zn2+, Ca2+ and Mg2+ reactivated the inhibited form of BChE.

Sheep brain pseudocholinesterase: inhibition kinetics of the partially purified enzyme by some substrate analogues

Pseudocholinesterase (ChE) (acylcholineacylhydrolase, EC 3.1.1.8) has been partially purified (about 270-fold) from sheep brain. The procedure included ammonium sulfate fractionation (20-80%), DEAE-Trisacryl M chromatography and procainamide-Sepharose 4B affinity chromatography. The molecular weight of purified ChE was found to be 290,000 by gel filtration. Kinetic properties of the enzyme have been studied using the substrate analogues choline, succinylcholine and benzoylcholine. It was shown that the inhibition was partially competitive.

Purification and immunological characterization of pigeon serum butyrylcholinesterase. Implications on environmental monitoring and toxicological testing of birds

Butyrylcholinesterase (EC 3.1.1.8) (BChE) was purified from pigeon serum to electrophoretic homogeneity by a four-step procedure involving blue sepharose CL-6B chromatography, ion exchange chromatography, procainamide affinity chromatography and gel filtration. An overall 2789-fold purification was achieved, with a final specific activity of 61.35 mumol/min/mg. The purified enzyme separated into two peaks when filtered through a column of Sephacryl S-300, a smaller peak containing the tetrameric form of BChE (C4) and a larger peak containing the monomeric form of BChE (C1). Native polyacrylamide gel electrophoresis (PAGE) of both peaks revealed single protein bands which coincided with esterase activity, with approximate M(r) values of 84,000 and 340,000, respectively. The C1 monomer represented 85-90% of the activity found in the pigeon serum. It is not clear whether this polymorphism of BChE in vertebrates contributes to the wider inter-individual variations observed in xenobiotics elimination kinetics and in the response to the pharmacological and toxic effects of pesticides. PAGE of the monomeric form of the enzyme in the presence of sodium dodecyl sulphate showed only one protein band with a M(r) of 84,000, while that of the tetrameric form revealed two bands, a major protein band (84,000) and a minor band (170,000), representing the monomer and the dimer of the dissociated tetrameric BChE enzyme under reducing conditions. Highly specific polyclonal antibodies were raised in rabbits against the purified enzyme. These antibodies cross-reacted with other avian BChEs, a criterion which make them useful for the immunopurification of other BChEs from different species as well as for biomonitoring and toxicological studies on the role of esterases as an indicator of avian exposure to organophosphorous pesticides.

Factors affecting inter-individual variation in human plasma cholinesterase activity: body weight, height, sex, genetic polymorphism and age

The influence of body weight, height, age and sex on plasma cholinesterase activity (ChE) in 650 males and 437 females with ChE-1 phenotype U (genotype ChEuChEu or ChEuChEs) or UA (genotype ChEuChEa) was studied in a multiple regression model. ChE was not influenced by age (p > 0.01), but, like other liver synthesized plasma enzymes, highly (p < 0.001) influenced by body weight and height. In a logarithmic scale ChE followed a linear model (R = 0.535, p < 0.001) with randomly distributed residuals, InChE = 3.286-0.308 x ChE-1 phenotype-0.104 x sex + 0.00765 x weight - 0.00723 x height (U = 1, UA = 2; male = 1, female = 2; kg; cm). A simplified model based on body-mass index (BMI = weight divided by squared height, kg/m2), InCHE = 2.016-0.308 x ChE-1 phenotype - 0.091 x sex + 0.0230 x BMI, showed the same goodness-of-fit (R = 0.533). In a non-logarithmic scale both multiple regression models failed to fit cases with high ChE activity. A model for a 'standardized' plasma ChE in which the effects of ChE-1 phenotype, sex, body weight and height are eliminated, is proposed to compare ChE in unmatched population groups when using this enzyme activity as a biomarker in environmental or occupational medicine.

Ricinus communis agglutinin I reacting and non-reacting butyrylcholinesterase in human cerebrospinal fluid

Differences in glycosylation of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in human brain, plasma and cerebrospinal fluid (CSF) have been investigated by means of their interaction with agarose-immobilized lectins. Most of the AChE in brain and CSF was associated to concanavalin A (Con A), Lens culinaris (LCA) and Triticum vulgaris (WGA) agglutinins, but little activity was adsorbed to Ricinus communis agglutinin I (RCAI). Brain, plasma and CSF BuChE was almost fully bound to Con A, LCA and WGA-agarose. Brain BuChE was unable to react with RCA (RCA-BuChE), the plasma enzyme was completely bound to the lectin (RCA+BuChE) and BuChE from CSF of normal children was partially fixed to RCA (RCA +/- BuChE). BuChE in CSF of children with meningitis fully reacts with the lectin. The data suggest that the proportion of RCA+BuChE in CSF of children with meningitis is increased, this enzyme probably coming from plasma.

Characterization of cDNA clones encoding rabbit and human serum paraoxonase: the mature protein retains its signal sequence

Serum paraoxonase hydrolyzes the toxic metabolites of a variety of organophosphorus insecticides. High serum paraoxonase levels appear to protect against the neurotoxic effects of organophosphorus substrates of this enzyme [Costa et al. (1990) Toxicol. Appl. Pharmacol. 103, 66-76]. The amino acid sequence accounting for 42% of rabbit paraoxonase was determined by (1) gas-phase sequencing of the intact protein and (2) peptide fragments from lysine and arginine digests. From these data, two oligonucleotide probes were synthesized and used to screen a rabbit liver cDNA library. A clone was isolated and sequenced, and contained a 1294-bp insert encoding an open reading frame of 359 amino acids. Northern blot hybridization with RNA isolated from various rabbit tissues indicated that paraoxonase mRNA is synthesized predominately, if not exclusively, in the liver. Southern blot experiments suggested that rabbit paraoxonase is coded by a single gene and is not a family member of closely related genes. Human paraoxonase clones were isolated from a liver cDNA library by using the rabbit cDNA as a hybridization probe. Inserts from three of the longest clones were sequenced, and one full-length clone contained an open reading frame encoding 355 amino acids, four less than the rabbit paraoxonase protein. Each of the human clones appeared to be polyadenylated at a different site, consistent with the absence of the canonical polyadenylation signal sequence. Of potential significance with respect to the paraoxonase polymorphism, the derived amino acid sequence from one of the partial human cDNA clones differed at two positions from the full-length clone. Amino-terminal sequences derived from purified rabbit and human paraoxonase proteins suggested that the signal sequence is retained, with the exception of the initiator methionine residue [Furlong et al. (1991) Biochemistry (preceding paper in this issue)]. Characterization of the rabbit and human paraoxonase cDNA clones confirms that the signal sequences are not processed, except for the N-terminal methionine residue. The rabbit and human cDNA clones demonstrate striking nucleotide and deduced amino acid similarities (greater than 85%), suggesting an important metabolic role and constraints on the evolution of this protein.

Relationship between serum pseudocholinesterase and triglycerides in experimentally induced diabetes mellitus in rats

This study was designed to understand the reasons for the increase in serum pseudocholinesterase activity in diabetes mellitus. Streptozotocin-induced diabetic rats were used for the study. Serum pseudocholinesterase activity increased with the induction of diabetes (381.5 units/l +/- 11.8) compared to the non-diabetic rats (243.1 units/l +/- 7.2). Serum triglycerides, total low density lipoprotein and glycerol also increased concurrently with the development of diabetes. Insulin treatment of the diabetic rats normalized serum glucose concomitant with the reduction of pseudocholinesterase activity, triglycerides, total low density lipoprotein and glycerol. Heparin injection appeared to activate lipoprotein lipase in the diabetic rats by showing a marked fall in serum triglyceride and total low density lipoprotein levels but not in pseudocholinesterase activity. Administration of tetraisopropylpyrophosphoramide a specific pseudocholinesterase inhibitor, inhibited serum and adipose tissue pseudocholinesterase activity by greater than 80% and liver greater than 50%. Concurrent with the inhibition of pseudocholinesterase activity serum triglyceride, low density lipoprotein and glycerol decreased significantly. In normal rats treatment with tetraisopropylpyrophosphoramide also reduced serum lipoproteins markedly, while glycerol only showed a marginal decrease. Glycerol was used as a marker of adipose tissue lipolysis and total low density lipoprotein which is defined as lipoproteins of density less than 1.063 (LDL + VLDL).(ABSTRACT TRUNCATED AT 250 WORDS)