Pseudocholinesterase Research Articles

Evaluation of acetylcholine esterase activity in the blood of workers exposed

Introduction:Organophosphate and carbamate insecticides pose major environmental pollution problems and health hazards to people and animals. These insecticides inhibit cholinesterase (ChE) activity in the nervous tissues and neuromuscular junctions. The measurement of blood ChE is a useful tool for monitoring exposure to organophosphate and carbamate insecticides. The purpose of the present study was to use a modified electrometric technique for measuring blood ChE in workers exposed to the organophosphate and carbamate insecticides in Kirkuk, Iraq. Method: A modified electrometric method was used to measure ChE activity in the whole blood of male workers (n = 40) exposed to organophosphate and carbamate insecticides, for a duration of not less than six years. Healthy male volunteers (n =12) not exposed to insecticides served as controls. Following in vitro inhibition of pseudo cholinesterase by quinidine sulfate, true cholinesterase activity was estimated in the blood of the subjects. After in vitro addition of the organophosphate (chlorpyrifos and methidathion, 0.5 and 1 µM) and carbamate (carbaryl, 5 and 10 µM) insecticides to the reaction mixtures, inhibitions of blood ChE were also determined. Results: Mean values of ChE activities (pH/20 min) in the whole blood of healthy non-exposed subjects and insecticide-exposed workers were 1.41and 1.2, respectively. Whole blood ChE activities of the exposed workers was significantly lower than those of healthy individuals. Conclusions: These findings indicate the usefulness of the modified electrometric method for monitoring blood ChE activity in insecticide-exposed workers and there was a significant effect of these Organophosphate and carbamate insecticides on the activity of Ach esterase in workers blood. .

Effectiveness of therapeutic plasma exchange in patients with intermediate syndrome due to organophosphate intoxication

ObjectiveWe aimed to determine effectiveness of therapeutic plasma exchange (TPE) in patients with intermediate syndrome (IMS) due to organophosphate (OP) intoxication. MethodsPatients diagnosed with IMS due to OP intoxication were included in this prospective study. Therapeutic plasma exchange procedure was performed with fresh frozen plasma as a replacement fluid via Fresenius-AS-TEC 204 device by Therapeutic Apheresis Unit to patients who developed IMS during follow-up. Samples were taken from patient's blood and waste plasma collected in the device before and after TPE procedure to be studied in laboratory for detection of organic phosphate and pseudocholinesterase (PChE) levels. In this study, SPSS 18.0 software package was used for statistical analysis of the data obtained. Level of statistical significance was taken as P < .05 for all tests. ResultsOf all 17 patients, 4 (23.5%) were female, and 13 (76.5%) were male. A statistically significant decrease was detected in organic phosphate levels in the plasma of patients after TPE procedure (P = .012). A statistically significant increase was detected in PChE levels in the plasma of patients after TPE procedure (P = .014). Of 17 patients included in the study, 13 patients showed clinical improvement and were discharged after the TPE process. ConclusionIn our study, it was observed that a significant decrease in the level of blood plasma OP and a significant increase in the level of PChE were achieved with TPE process in the early period of IMS due to OP poisoning. This study indicates that TPE is one of the effective treatment options for IMS due to OP intoxication.

Prognostic significance of estimation of pseudocholinesterase activity and role of pralidoxime therapy in organophosphorous poisoning

Background:Organophosphorous (OP) poisoning is one of the most common poisonings seen in India. OP compounds act through inhibition of enzyme acetylcholinesterase and estimation of pseudocholinesterase (PCE) activity strengthens the diagnosis in clinically uncertain cases of OP poisoning. The role of pralidoxime (PAM) therapy in OP poisoning has been controversial.Study Objectives:This study was aimed to determine the prognostic significance of estimation of PCE activity and also to assess the role of PAM therapy in OP poisoning.Materials and Methods:Patients of suspected OP poisoning of age >12 years admitted to emergency unit at a tertiary healthcare center of north India were enrolled. Patients were categorized into two groups; group A who were given intravenous atropine and group B who were given injectable PAM along with atropine. Serum PCE level was estimated at the time of admission in all patients and severity of OP poisoning was assessed according to PCE level. Requirement of atropine, oxygen inhalation, intubation and ventilatory support, total hospital stay, and mortality were compared between different classes of severity and also between Groups A and B.Results:This study included a total of 70 subjects, 35 in each group with mean age of 24.99 ± 8.7 years. Out of 70 subjects 49 (70%) were male and 21 (30%) were female. Forty nine patients (70%) of OP poisoning were with suicidal intent while 21 (30%) cases were accidentally poisoned. In all suicidal cases route of poisoning was ingestion whereas in all the accidental cases route of exposure was inhalational. PCE levels were reduced in all the cases and the mean level was 3,154.16 ± 2,562.40 IU/L. The total dose of atropine required, need for oxygen inhalation and need for intubation and ventilatory support, mean duration of hospital stay and mortality rate (P = 0.003) were higher in moderate to severe cases and did not have significant difference between Groups A and B.Conclusion:The study recommends estimation of PCE level at admission to classify severity of OP poisoning and to estimate prognosis. This study did not find any beneficial role of PAM therapy in reducing morbidity as well as mortality.

Adaptation of Common Carp (Cyprinus carpio L.) to Regular Swimming Exercise II. Metabolism

Altogether 24 (12 control and 12 treated) growing (initial bodyweight: 50.4 ± 20.1 g) common carps (Cyprinus carpio L.) were subjected to a regular training protocol for 35 days, with daily 30 min strenuous exercise bouts aiming to describe blood serum clinicochemical alterations. Samples were taken 4 times (0 as control and 3 time points during training, every 9th day) from all fi sh. In the nitrogenous serum compounds the training protocol increased albumin and oxidized glutathione concentration at time point 3, while neither total protein, nor creatinine reacted to swimming. From the lipid metabolites triacylglycerol provided higher values at time point 3. Total and HDL cholesterol concentrations were unaltered, meanwhile the HDL percentage in the total cholesterol fraction provided an age-associated increase and a signifi cantly lower fi nal value in the trained group. Within enzymes aspartate and Alanine Aminotransferase (AST and ALT) provided markedly higher activity values at time point 3. Gamma-GT, pseudo cholinesterase, alkaline phosphatase and lactate dehydrogenase (LDH) showed no signifi cant changes induced by regular swimming. In the serum ions training exerted temporary hypokalemic and hypocalcemic effect (time point 2), while sodium, inorganic phosphate and magnesium were unaffected by exercise. Both groups showed an age-associated increase in the serum sodium concentrations. It was assumed that even longer term regular submaximal, but exhaustive exercise exerts only mild effect on the substrate metabolism of carp, a slowly swimming (with burst-like movements) benthic feeder.

Pseudocholinesterase in gestational diabetes: positive correlation with LDL and negative correlation with triglyceride

Low pseudocholinesterase (PChE) activity accompanies pregnancy, liver disease, renal failure, and certain drug therapies. The aim of this study was to investigate a possible relationship among PChE and plasma insulin levels, lipid profile, and inflammatory response ingestational diabetes. This study included 165 women aged 20–40 years. Subjects were divided into four groups as follows:Control group, 29 non-pregnant healthy women; GroupNGT, 61 healthy pregnant women (normal glucose tolerance);Group GD, 62 pregnant women with gestational diabetes; and Group AGT, 13 pregnant women with abnormal glucose tolerance. Gestational ages were between 34 and 40 weeks. Plasma PChE, triglyceride, high-/lowdensity lipoprotein (HDL, LDL), glycated hemoglobin A1c(HbA1c), insulin, C-reactive protein (CRP), and white blood cell (WBC) levels were measured in all subjects. There were no statistically significant differences in plasma PChE, insulin, and LDL levels between the groups. Plasma triglyceride, HbA1c, WBC, and CRP levels were significantly higher in Group GD and Group AGT compared to the other groups (P\0.000). There was a positive correlation between increased PChE and LDL,while a negative correlation was observed between PChE and triglyceride in Group GD. There was a positive correlation between increased CRP and HbA1c and a negative correlation among CRP and LDL and triglyceride in Group GD. PChE activity was not significantly different between the groups. However, there was a positive correlation between PChE and LDL levels in pregnant women with GD, suggesting that LDL levels in pregnant women with GD may help to predict the risk of prolonged apnea in situations in which PChE activity cannot be measured.

Pseudocholinesterase Deficiency: A Case Report and Literature Review

A 72-year-old male underwent neck dissection and parotidectomy with facial nerve preservation. Endotracheal intubation was facilitated with succinylcholine. Prolonged muscle paralysis which was first detected after failure to stimulate the facial nerve with electrocautery, lasted five hours. Laboratory tests indicated pseudocholinesterase (PChE) deficiency. A thyroidectomy one month later was performed uneventfully using rocuronium as a muscle relaxant. Literature review revealed a total of 40 PChE deficiency cases being reported since 1956.

Early appearance and possible functions of non-neuromuscular cholinesterase activities

The biological function of the cholinesterase (ChE) enzymes has been studied since the beginning of the twentieth century. Acetylcholinesterase plays a key role in the modulation of neuromuscular impulse transmission in vertebrates, while in invertebrates pseudo cholinesterases are preeminently represented. During the last 40 years, awareness of the role of ChEs role in regulating non-neuromuscular cell-to-cell interactions has been increasing such as the ones occurring during gamete interaction and embryonic development. Moreover, ChE activities are responsible for other relevant biological events, including regulation of the balance between cell proliferation and cell death, as well as the modulation of cell adhesion and cell migration. Understanding the mechanisms of the regulation of these events can help us foresee the possible impact of neurotoxic substances on the environmental and human health.

Assessment of the severity of organophosphate (fenitrothion) poisoning based on its serum concentration and clinical parameters

Background. Fenitrothion (MEP) is the most frequent cause of organophosphate pesticides (OP) poisoning in Japan, but clinical parameters to predict its severity remain uncertain. Method. We evaluated 26 cases (12 males and 14 females) of MEP poisoning brought to our critical care center. Regarding acute lung injury (ALI) as a hallmark complication leading to poor recovery, we divided patients into two groups: cases without ALI (Grp1, n = 14), and cases who developed ALI (Grp2, n = 12) at various points after the poisoning. Serial changes in clinical parameters and laboratory test results were compared between them. Results. The median MEP concentrations on arrival (min∼max) for Grp1 and Grp2 were 2.3 (0.5–5.1) and 4.6 (1.1–14.0) μg/ml, respectively. Serum pseudo-cholinesterase (PChE) levels on arrival were 21(< 10–59) U/L in Grp1 and < 10 in Grp2. Based on individual patient kinetics, we estimated MEP concentration at 2 and 24 hours after ingestion, and determined cutoff values for differentiating the two groups for each time point as 4.0 μg/ml and 0.5 μg/ml, respectively. By logistic regression analysis, two groups were distinguished with accuracy of 92.3% based on their time of arrival after ingestion and initial MEP concentration. Clinical parameters associated with ALI were days with miosis, days with PChE below 100 U/L, and days requiring administration of atropine. Conclusion. The severity of MEP poisoning is closely associated with both time to presentation after ingestion and initial MEP concentration. Serial monitoring of MEP concentrations in the first 24 hours is also useful in predicting the clinical course.

Plasma pseudo cholinesterase deficiency leading to seven hour apnoea in a child undergoing adeno-tonsillectomy

Objective: We report a rare, silent, potentially fatal operative complication of seven hour apnoea in a patient undergoing adenotonsillectomy secondary to deficiency of plasma cholinesterase. Awareness of this hereditary disorder is important to otolaryngologist as; it is difficult to diagnose, can be unexpectedly alarming for parents and the surgeon. Methods: Case report and review of world literature. Results: A four-year male with obstructive sleep apnoea underwent a routine elective adenotonsillectomy; there was no spontaneous recovery of respiration following surgery. He was transferred to the intensive care unit and 7 h later was successfully weaned from the ventilator and extubated. A plasma cholinesterase level of 4561 U/L was discovered much later. Conclusion: To our knowledge this is the first case report of pseudo cholinesterase deficiency reported in otolaryngology literature and first in Oman. The patient should receive information about the condition, the associated risks, inheritance and need for testing other family members.

Impact of heavy metal pollution on the hemogram and serum biochemistry of the libyan jird, Meriones libycus

The stress profiles of the hemogram and serum biochemistry were determined in the context of heavy metal (Cd, Cu, Hg, Ni and Pb) exposure in the wild libyan jird, Meriones libycus, from one of Riyadh’s polluted areas versus a reference site. Coupling the pronounced drop in platelets (PLT) (28%) and mean platelet volume (MPV) (17%) with the insignificant responses of other red blood cell indices, suggests bone marrow suppression that is characterized by thrombocytopenia as an initial abnormality. The species-specific stress leukogram for M. libycus is expressed by leukocytosis (66%), monocytosis (40%), lymphocytosis (23%) with eosinopenia (81%) and neutropenia (42%). Hyperglycemia (50%), hyper-low-density-lipoproteinemia (38%), hypocortisolism (85%) and hypotriglyceridemia (55%) depicted serum biochemistry profile. In polluted jirds, the elevated activities of pseudocholinesterase (PChE) and serum marker enzymes (alanine aminotransferase ALT, aspartate aminotransferase AST and creatine kinase CK) strongly suggest functional damage of the liver and/or heart. A potential role of PChE in low-density lipoprotein (LDL) metabolism is implied in the joint rise of both indices and in the recognized relationship between PChE and lipid metabolites. While increased utilization in lipid metabolism and energy synthesis could rationalize the inhibition of the normal patterns of triglycerides and lactate dehydrogenase (LDH), the inhibited activities of LDH could additionally be attributed to its hormetic behavior towards low and high metal concentrations. The overall findings presented here documented the relevance of M. libycus in biomonitoring and predicting the risk imposed on human populations living in polluted areas.

Managment of Organophosphate Poisoning Without Pralidoxim- Is It Possible .................IJMTFM (2011) 1(2):75-77

Introduction: Organophosphate compounds are used as insecticides, nerve gases, ophthalmic agents, and antihelmintics.The primary mechanism of action of organophosphate pesticides is inhibition of acetylcholinesterase (AChE). However Pralidoxim has been introduced as organophosphate `s antidote but recent studies establish that pralidoxim has unclear benefit in treatment of organophosphate poisoning.We explain two cases of organophosphate poisoning that they treaeted well without pralidoxim. The first case was a 36-years old man with history of organophosphates poisoning. He was under mechanical ventilation. Atropine was initiated due to muscarinic signs such as salivation, bronchorrhea and auscultation of alveolar rhales. On admission day, the pseudocholine esterase level was 235 unit per liter. Pralidoxime was not available, so we did not use it for management of this patient.The patient was discharged when he was in free symptom completely on the 22 th day. The second case was a 23 years old woman with the history of deliberate self poisoning with organophosphate compounds. Atropine was started and she was under mechanical. However, pralidoxim was not available. The pseudocholine esterase level was 1690 unit per liter on the first day which dropped to 952 unit per liter on the 2 nd day. After 9 days the discharged from the hospital. Discussion: Pralidoxim has been introduced as organophosphate`s antidote, on the other hand, it has benefit in organophosphate poisoning theoretically, but patients can be treated without it. Key words: Organophosphate, Poisoning, Pralidoxim

Determination of pseudocholinesterase serum activity among Agrinion pesticide applicators pre- and post-exposed to organophosphates (fenthion and dimethoate)

Organophosphate (OP) pesticides are used in agriculture in order to raise crop production. The aim of this study was to investigate the biological effects of two OPs, fenthion, and dimethoate, among 270 farm workers in the area of Agrinion (Western Greece) by measuring the serum butyrylcholinesterase (BChE) activity during the years 2004–2006. The BChE activity was photometrically analyzed before and after exposing to OP. Results showed that (1) the median BChE activity was reduced in the spraying period in comparison with the non-spraying period (7604 versus 9557 units L−1), (2) a significant difference in median pseudocholinesterase (PChE) activity was also observed between the two OPs (fenthion applicators −26.87%, dimethoate applicators −15.95%), (3) the duration of OP spraying influenced the mean BChE activity, which was −9.83% after 1 day, −23.81% after 2–3 days, and −25.26% after 4–7 days of spraying, (4) reduced levels of the mean value of PChE activity was observed in occupational applicators in exposure periods (5446 units L−1), and in non-exposure periods (6950 units L−1), as well, and (5) the extent of using protective equipment influenced the mean levels of BChE activity: −23.9% without any protection, −15% with partial protection, and −7.4% in those applicators with full protective equipment. In conclusion, the mean value of serum BChE activity was reduced after exposure to two OPs and this reduction depends on the particular OP, the duration of the exposure, and use or not of personal protective equipment by pesticide applicators.

Comparative study of intubating conditions after Rocuronium and Suxamethonium (study of 80 cases)

Comparative study of intubating conditions after Rocuronium and Suxamethonium (study of 80 cases)

Biochemical blood markers and sampling sites in forensic autopsy

Forensic pathologists often hesitate to use biochemical blood markers due to the risk of large postmortem changes and deviations from healthy subjects. Biochemical analyses of postmortem blood, if possible, may help to evaluate pathological status and determining the cause of death in forensic diagnosis, for example, in sudden unexpected death without obvious cause, or young adults with no apparent cause of death or antemortem information. Even commercially available biochemical markers were re-evaluated in the blood samples of 164 forensic autopsy cases. Biochemical markers examined were HbA1c, fructosamine, blood nitrogen urea (BUN), creatinine, total protein, total bilirubin, γ-glutamyl transpeptidase (γ-GTP), triglyceride, total cholesterol, C-reactive protein (CRP) and pseudocholine esterase (pChE). We collected cardiac blood (left cardiac blood and right cardiac blood) and peripheral blood (femoral vein blood) to clarify the differences in measured values by sampling site. The measured values were analyzed in relation to postmortem interval, etiology of death and sampling sites. Of all eleven markers, HbA1c is the most useful and reliable because of its negligible postmortem changes and small deviation from healthy subjects. Total bilirubin, BUN, CRP and total cholesterol can be useful if we set appropriate limit ranges and pay attention to the interpretation. For the evaluation of changes due to postmortem intervals, none of the markers except for triglyceride showed significant changes up to three days postmortem. As for sampling sites, femoral vein blood is generally recommended considering postmortem changes, but left cardiac blood was suitable for creatinine, pChE, and total cholesterol. For clinical forensic diagnosis of biochemical blood markers, we must determine the “forensic abnormal value” after collecting more cases by known causes with more information about the population.

Recovery from Ultra-High Dose Organophosphate Poisoning After “in-the-Field” Antidote Treatment: Potential Lessons for Civil Defense

Organophosphate poisoning is associated with a high mortality rate due to respiratory failure, dysrhythmias, and multi-organ failure. We report two cases of survival after “in-the field” antidote treatment of very severe organophosphate poisonings. Two patients orally ingested large amounts of the organophosphorous agent oxydemeton-methyl in suicide attempts, resulting in the hypercholinergic syndrome in both. Resuscitation included early administration of antidote by emergency medical personnel as well as high-dose atropine. Plasma levels of pseudo cholinesterase were initially very low in both patients. Long-term mechanical ventilation was necessary, and both patients developed aspiration pneumonia. At discharge, no major neurological deficits were present. Prompt antidote treatment and aggressive supportive emergency and intensive care unit therapy contribute to improved survival after acute organophosphate poisoning. We believe that in cases of mass poisonings—for example, terrorist activity—therapy must be available on the scene as soon as possible. This also may require decentralized antidote storage.

Prognostic and diagnostic value of serum pseudocholinesterase, serum aspartate transaminase, and serum alinine transaminase in malignancies treated by radiotherapy

There is substantial evidence that environmental factors cause or accelerate the onset of malignancy. Environmental factors, due to the presence of many pollutants and carcinogenic agents, alter cellular growth, which leads to biochemical changes in the blood. In the present study, we estimated serum pseudocholinesterase (PCHE), serum aspartate transaminase (AST), and serum alanine transaminase (ALT) in 92 patients with head and neck cancer and 71 patients with cancer of the uterine cervix; all of them were patients attending our department for radiation therapy. We also estimated PCHE, AST, and ALT levels in 30 healthy normal individuals. The estimations in cancer patients were done before the start of radiotherapy, midway through radiotherapy (30 Gy dose), at the end of radiotherapy, and during subsequent monthly follow-up visits over a period of at least 6 months. We have observed that the PCHE levels were lower (31-49% of normal value) in all patients with malignancies, except in those with stage II head and neck cancers. We also found that the levels start increasing as radiotherapy progresses. The patients with no detectable/visible disease activity at 6 months follow-up showed PCHE values in the normal range. Similarly, the AST and ALT values were much higher (138-229% of normal value) in all the malignant cases as compared to the normal healthy individuals. The values decrease and approach normal levels as radiotherapy progresses and, in 92% of head and neck cancer cases [stages IIA, IIB, and IIIA] with no disease activity, the PCHE, AST, and ALT were normal or near normal; the corresponding figure in cancer cervix cases was 89%. From the present study we conclude that PCHE, AST, and ALT can be used as good prognostic biochemical tumor markers in the management of malignancies of the head and neck and uterine cervix.

Electrometric measurement of plasma, erythrocyte, and whole blood cholinesterase activities in healthy human volunteers

The measurement of blood cholinesterase activity is a useful tool for monitoring exposure to organophosphate and carbamate insecticides. Blood cholinesterase activity is measured colorimetrically or electrometrically. Recently, a simple and practical electrometric method has been described and validated for measuring blood cholinesterase activity in people and animals. The purpose of the present report was to use the modified electrometric technique for measuring blood (plasma, erythrocyte and whole blood) cholinesterase activities in apparently healthy human volunteers in Mosul, Iraq. Cholinesterase activities in the plasma, erythrocytes, and whole blood of healthy male (n = 72) and female (n = 31) volunteers were measured by an electrometric method; the method involved the addition of 0.2 ml of blood sample to 3 ml of distilled water followed by 3 ml of barbital-phosphate buffer solution (pH 8.1). The pH (pH1) of the mixture was measured, and then 0.1 ml of 7.5% of acetylcholine iodide, as a substrate, was added. The reaction mixture was incubated at 37 degrees C for 20 minutes. The pH (pH2) of the reaction mixture was measured after the end of the incubation period. Enzyme activity was expressed as DeltapH/20 min = pH1- pH2 - (DeltapH of the blank). The blank was without the blood sample. Following in vitro inhibition of pseudo cholinesterase by quinidine sulfate, true cholinesterase activity was estimated in the plasma of the subjects. After in vitro addition of the organophosphate (chlorpyrifos and methidathion, 0.5 and 1 microM) and carbamate (carbaryl, 5 and 10 microM) insecticides to the reaction mixtures, inhibitions of blood cholinesterases were measured. Mean reference cholinesterase activities (DeltapH/20 min) in the plasma, erythrocytes, and whole blood of male subjects were 0.98, 1.39, and 1.41, respectively. Females were 0.85, 1.22, and 1.23, respectively. Ten minutes after in vitro addition of quinidine sulfate to inhibit pseudo cholinesterase activity in the plasma, the estimated true cholinesterase activities in males and females were 0.08 and 0.07 DeltapH/20 min, respectively. The percentage of true cholinesterase in the plasma of males and females was 8.2. Using the modified electrometric method, various percentages of cholinesterase inhibitions in the plasma, erythrocytes, and whole blood were detected after in vitro addition of the organophosphate insecticides (chlorpyrifos and methidathion) and the carbamate insecticide (carbaryl) to the reaction mixtures. These findings are the first collective report of human plasma, erythrocyte, and whole blood cholinesterase activities as determined by the modified electrometric method, and they could serve as reference points for future studies that involve human exposure to anticholinesterase pesticides.

Validation of an Automated Spectrophotometric Assay for the Determination of Cholinesterase Activity in Canine Serum

The determination of enzymatic activity of cholinesterase is a useful diagnostic method to detect exposure to anticholinesterase compounds in human and in veterinary medicine. We validated a modification of the Ellman method in canine serum and applied it to the diagnosis of dogs poisoned with anticholinesterase substances. The method used butyrylthiocholine as substrate and potassium hexacyanoferrate as chromophore. The reference range calculated on 60 clinically healthy dogs was set between 3405 and 6561 U/L (chi-square test for normal distribution, p > 0.05). The overall mean intra-assay and inter-assay coefficients of variation were 0.53% and 3.83%, respectively. The assay was linear when using two sera with 12,538 U/L and 6604 U/L serum cholinesterase activity (r(2) = 0.997) and 0.999, respectively). The mean recovery values of pooled sera with a mean pseudocholinesterase (PChE) activity of 12,081 U/L and pooled sera with a mean PChE activity of 3415 U/L were 103.5% and 102.8%, respectively. Six dogs with a diagnosis of anticholinesterase compound intoxication showed a decrease in cholinesterase activity of at least 50% of normal activity with a mean +/- SD of 487 +/- 291 U/L ranging from 169 to 847 U/L. This technique conforms to the current standard for precision, linearity and accuracy and is a useful method for the complementary diagnosis of organophosphate or carbamate insecticide intoxication in dogs.

The influence of catecholamines on pseudocholinesterase enzymatic activity. Results of a laboratory investigation

Acceleratory and inhibitory receptors have been described on the pseudocholinesterase (PCHE) molecule. An increased PCHE activity has been reported in patients with chronic pain and anxiety, conditions known to be correlated with increased plasma catecholamine levels. Aim of this laboratory investigation was to determine whether catecholamines have an effect on PCHE activity, as this knowledge could help to define the role of PCHE in the assessment of stress. After Ethics committee approval and written informed consent, 3 ml of blood was collected from five healthy volunteers. Fourteen samples of 50 mul each were prepared from each of the volunteer's plasma. Epinephrine (25, 50, 100, 200, 400 and 1000 pg) and norepinephrine (50, 100, 200, 400, 800 and 2000 pg) were added to samples of each subject. Sodium-chloride solution was added to control samples. PCHE activity was photometrically assessed. PCHE activity was significantly higher after the addition of epinephrine (median 8304 versus 7386 U/l). This effect was not dose-dependent. PCHE activity did not change after addition of norepinephine. This mechanism might explain previous findings that showed higher levels of PCHE activity in the presence of chronic pain and anxiety. In the absence of a dose-response curve in the concentration range studied, PCHE activity does not appear to be suitable for the assessment of levels of stress.

Temperature, the benzoylcholine substrate, and fluoride inhibition of pseudocholinesterase

To the Editor: The magnitude of sevoflurane’s (and enflurane’s) effect on fluoride inhibition of pseudocholinesterase (PCHE) deserves attention in modern anesthetic practice. Nearly all studies dealing with this topic1–3 refer to the study of Kambam et al.4 who reported an inhibition of PCHE between 16 to 73% with 10 to 100 μmol·L–1 fluoride, the concentrations usually obtained during sevoflurane (and enflurane) anesthesia. Since we could not confirm this inhibition with mivacurium and butyrylthiocholine as substrates and at temperatures between 28 to 37°C3,5 we investigated fluoride inhibition of PCHE with benzoylcholine at 25°C, the substrate and temperature Kambam et al. used in their study, and at 37°C, the temperature currently recommended for determination of enzymatic activity. After approval by our Local Ethics Committee and with written informed consent, serum samples of eight healthy volunteers were obtained, spiked with fluoride (0, 10, 50 and 100 μmol·L–1) and adjusted to 25°C and 37°C, respectively. Thereafter, 50 μmol·L–1 benzoylcholine were added, and at timed interval aliquots were withdrawn to measure the concentrations of benzoylcholine by high-performance liquid chromatography. After calculating the half-lives with KINETICA 2000 (InnaPhase Corp. Philadelphia, PA, USA) a one-factor (fluoride concentration) analysis of variance with a post hoc Dunnett test was performed at each temperature, using the fluoride-free sample as the control category. The results are presented in the Figure. At 25°C there was an increase of the benzoylcholine half-time of 9.3% with 10 μmol·L–1 fluoride, and a 36% increase with 50 μmol·L–1 fluoride. The 68% increase in benzoylcholine half-time was significant (P < 0.05) at a concentration of 100 μmol·L–1. In contrast, no change was observed over the same range of fluoride concentrations at 37°C. We thus confirm one aspect of the study of Kambam et al.4 who measured PCHE activity at 25°C with a photometric assay. In contrast, when using a high-performance liquid chromatography assay at clinically relevant body temperature (37°C) and with fluoride concentrations up to 100 μmol·L–1, fluoride inhibition of PCHE is not apparent, whether using the substrates mivacurium and butyrylthiocholine3,5 or benzoylcholine, as reported here. In conclusion, the influence of substrate and temperature on fluoride inhibition of PCHE must be taken into consideration when interpreting the results of investigations with sevoflurane and enflurane.