Decrease In AChE Activity Research Articles

Transient modulation of acetylcholinesterase activity caused by exposure to dextran-coated iron oxide nanoparticles in brain of adult zebrafish

Superparamagnetic iron oxide nanoparticles (SPIONs) are of great interest in nanomedicine due to their capability to act simultaneously as a contrast agent and as a targeted drug delivery system. At present, one of the biggest concerns about the use of SPIONs remains around its toxicity and, for this reason, it is important to establish the safe upper limit for each use. In the present study, SPION coated with cross-linked aminated dextran (CLIO-NH2) were synthesized and their toxicity to zebrafish brain was investigated. We have evaluated the effect of different CLIO-NH2 doses (20, 50, 100, 140 and 200mg/kg) as a function of time after exposure (one, 16, 24 and 48h) on AChE activity and ache expression in zebrafish brain. The animals exposed to 200mg/kg and tested 24h after administration of the nanoparticles have shown decreased AChE activity, reduction in the exploratory performance, significantly higher level of ferric iron in the brains and induction of casp8, casp 9 and jun genes. Taken together, these findings suggest acute brain toxicity by the inhibition of acetylcholinesterase and induction of apoptosis.

Imidacloprid induced alterations in enzyme activities and energy reserves of the land snail, Helix aspersa

The in vivo sublethal toxic effects (0.2 and 0.6 LD50) of topically applied imidacloprid on biochemical biomarkers in the land snail, Helix aspersa was examined. Biochemical perturbations were assessed by measuring the three enzymatic (Acetylcholinesterase, AChE; catalase, CAT and glutathione-S-transferase, GST) activities and three energy reserves (protein, glycogen and lipids) in the snails. Snail samples were taken from each sublethal dose and control groups at 1, 3 and 7 days after treatment. The results revealed that there were overall decrease in AChE activity as well as depletion of lipids and glycogen contents in the imidacloprid-treated snails compared to control groups. The CAT and GST activities of treated snails with the sublethal doses of imidacloprid were significantly higher than those of untreated controls along the three times of exposure. Moreover, an increase in the level of total proteins was observed in animals treated with 0.6 LD50 imidacloprid compared to control groups. The alterations in all tested biochemical perturbations were most pronounced with the 0.6 LD50 than 0.2 LD50. This study suggests that alterations of the enzyme activities and energy reserves in this species that could be useful as biomarkers of imidacloprid exposure in the evaluation of terrestrial impacts of this insecticide.

Extraction and chemical characterization of Angelica sinensis polysaccharides and its antioxidant activity

In the present study, the Angelica sinensis polysaccharides (ASP) extraction procedure was optimized by an L9 (34) orthogonal array experimental design (OAD) with four factors at three levels. Under the optimal extraction condition (extraction time 180min, ratio of water to solid 6, extraction temperature 100°C, and extraction number 4), extraction yield of ASP was 5.6%. Rabbits were fed for 40 days with A. sinensis polysaccharides at a dose of 150 or 300mg/kg body weight, respectively. At the end of 40 days, animals received cerebral ischemia reperfusion operation. CT perfusion imaging (CTP) analysis showed that rCBF and rCBV were significantly increased, whereas rMTT and rTTP were decreased in the ischemia cerebral tissue compared to CIR group rabbits. ASP significantly decreased oxidative damage, and increased antioxidant enzymes activities in brains of CIR animals. Moreover, ASP significantly enhanced the Ach, Na+,K+-ATPase, Ca2+,Mg2+-ATPase and glucose levels, decreased AChE activity in brain tissue of the experimental animals. These results suggest a potent role of ASP in protection of brain oxidative injury in CIR animals.

Neurotoxic effects of lambda-cyhalothrin modulated by piperonyl butoxide in the brain ofOreochromis niloticus

The objective of this research was to investigate the neurotoxic effects of pyrethroid pesticide lambda-cyhalothrin by the modulation of cytochrome P450 with piperonyl butoxide in the brain of juvenile Oreochromis niloticus. The fish were exposed to 0.48 μg L(-1) (1/6 of the 96-h LC50 ) lambda-cyhalothrin and 10 μg L(-1) piperonyl butoxide for 96 h and 15 days. tGSH, GSSG, TBARS contents, GPx, GR, GST, and AChE enzymes activities were determined by spectrophotometrical methods and Hsp70 content was analyzed by ELISA technique. Lambda-cyhalothrin had no significant effect on the components of GSH redox system, lipid peroxidation and Hsp70 levels but inhibited AChE activity. In the presence of piperonyl butoxide, lambda-cyhalothrin caused increases in tGSH, GSSG, TBARS and Hsp70 contents, GST activity, and decrease in AChE activity. Present results showed that in the presence of piperonyl butoxide, lambda-cyhalothrin caused neurotoxic effects by increasing oxidative stress. Adaptation to its oxidative stress effects may be supplied by GSH-related antioxidant system. Piperonyl butoxide revealed neurotoxic effect of lambda-cyhalothrin.

Effect of Sailuotong capsule on intervening cognitive dysfunction of multi-infarct dementia in rats

To study the effect of Sailuotong capsule (Sailuotong) on learning and memory functions of multi-infarct dementia (MID) rats and its mechanism. All SD rats were divided into five groups, namely the sham operation group, the model group, the positive group, the low dosage Sailuotong-treated group and the high dosage Sailuotong-treated group. The multi-infarct dementia model was established by injecting the micro-sphere vascular occlusive agent. On the 10th day after the successful operation, the rats were administered intragastrically with distilled water, memantine hydrochloride (20 mg x kg(-1)) and Sailuotong (16.5 mg x kg(-1) and 33.0 mg x kg(-1)) once a day for 60 days respectively, in order to detect the effect of Sailuotong in different doses on the latent period and route length in Morris water maze and the activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AchE) in brain tissues. Compared with the sham operation rats, it had been observed that the latent period and route length of MID rats in Morris water maze were significantly increased (P < 0.05 or P < 0.01), and the activity of ChAT in brain tissues was significantly decreased (P < 0.05). After the intervention with Sailuotong for sixty days, the latent period and route length of MID rats in Morris water maze significantly shrank (P < 0.05 or P < 0.01). Additionally, Sailuotong decreased AchE activity, while increasing ChAT activity in brain tissues of MID rats (P < 0.05 or P < 0.01). Sailuotong capsule can improve cognitive dysfunction of MID rats to some extent. Its mechanism may be related to its different regulation of activities of ChAT and AchE in brain tissues.

Effects of geroprotective peptides on the activity of cholinesterases and formation of the soluble form of the amyloid precursor protein in human neuroblastoma SH-SY5Y cells

Age related decline of cognitive functions in humans is a result of degeneration of cholinergic neurones and acetylcholine deficit in certain brain structures. In this connection, inhibitors of cholinesterases capable of preventing further decline of acetylcholine levels are widely used for treatment of cognitive disorders, in particular in Alzheimer’s disease (AD). Despite a wide range of anticholinesterase drugs available to date most of them have side-effects and are not always beneficial in older patients. Moreover, there are two forms of cholinesterases, namely acetyl- and butyrylcholinesterases (AChE and BuChE) which have different levels of their expression, localisation and functions in the brain. Since with age there is a decrease of AChE activity and an increase of BuChE, the design of selective inhibitors for each enzyme is required. In the present work the effects of synthetic geroprotective peptides vilon (Lys-Glu) and epithalon (Ala-Glu-Asp-Gly) on the activity of AChE and BuChE in human neuroblasoma cells SH-SY5Y have been studied. Also we performed an analysis of the effects of these peptides on the activity of the α-secretase of amyloid precursor protein (APP) which participates in non-amyloidogenic processing of APP releasing a soluble fragment of APP, and possibly in formation of a soluble form of AChE. It was found that incubation of cells during 24 hours in the presence of 50 nM of vilon and epithalon resulted in a decrease of the activity of soluble and membrane-bound forms of AChE and BuChE on average by 30–60%. Both peptides mostly inhibited membrane-bound forms of the enzymes but to a greater extent BuChE. Epithalon was also found to be capable of activation of α-secretase by 20–25%. The data obtained suggest that vilon and epithalon have selective anticholinesterase properties and that epithalon can also stimulate APP cleavage and increase production of its soluble neuroprotective form.

Biochemical, physiological and behavioural markers in the endobenthic bivalve Scrobicularia plana as tools for the assessment of estuarine sediment quality

The aim of this study was to link the responses at different levels of biological organisation of the endobenthic bivalve Scrobicularia plana differentially exposed to anthropogenic pressure. Clams were collected in April 2008 from three estuaries along a pollution gradient (Goyen<Loire<Seine). Biomarkers of defence (metallothionein concentration and glutathione- S-transferase activity) were activated in the Loire and the Seine. Biomarkers of damage revealed neurotoxicity (decreased AChE activity) and impairment of digestive enzyme activities (cellulase or amylase) in these estuaries. The highest lactate dehydrogenase activity was registered in the Loire estuary, in parallel with enhanced levels of vanadium (a metal present in petroleum), likely as a consequence of a small oil spill that occurred one month before the sampling collection. Physiological biomarkers (energy reserves as glycogen, lipids and proteins, condition and gonado-somatic indices) showed a few intersite differences. However, the median size was significantly lower in clams exposed to direct (chemicals) or indirect (available food) effects in the most contaminated site. Burrowing behaviour was disturbed in clams from both of the Loire and Seine estuaries, a response probably due to physiological impairment rather than to avoidance of contaminated sediment. The activation of defence mechanisms towards metals (metallothionein) and other classes of contaminants (the biotransformation enzyme glutathione- S-transferase) do not ensure a total protection since a number of impairments were observed at the infra-organismal (AChE and digestive enzyme activities) and individual (burrowing behaviour) levels in relation to the degree of anthropogenic pressure. However, even in the most contaminated estuary (Seine), historical records do not show a consistent decrease of S. plana populations.

AGE-DEPENDENT DECLINE IN ERYTHROCYTE ACETYLCHOLINESTERASE ACTIVITY: CORRELATION WITH OXIDATIVE STRESS

Oxidative stress hypothesis offers a mechanism for the aging process and its involvement in other pathologies such as diabetes and neurodegenerative diseases like Alzheimer. AChE activity in erythrocytes may be considered as a marker of central cholinergic status. The present study was undertaken to (i) determine the activity of erythrocyte AChE as a function of human process (ii) correlate AChE activity with oxidative stress during human aging. Blood was collected from healthy subjects (n = 37) 22-82 years. Erythrocyte AChE activity, MDA and plasma antioxidant capacity in terms of FRAP was measured spectrophotometrically. There was a marked decrease in AChE activity with increasing age. The reduction in activity of AChE correlated well with increased lipid peroxidation and a decrease in FRAP values. Decreased antioxidant defense, and alteration in membrane rheology during aging process both may contribute towards decreased activity of AChE in erythrocyte membrane. This finding may help in explaining the neuronal complications taking place under conditions of oxidative stress, aging, and dementia.

Biochemical evaluation of hepatic damage in subchronic exposure to malathion in rats: Effect on superoxide dismutase and catalase activities using native PAGE

The aim of this study was the evaluation of the hepatic damages following a subchronic exposure to malathion, an organophosphorus (OP) insecticide. Malathion was administered intragastrically in 1 ml corn oil containing 100 mg/kg Body Weight daily for 32 days. Malondialdehyde (MDA) concentration superoxide dismutase (SOD) and catalase (CAT) activities were analysed using a non-denaturing electrophoresis. The serum activities of Pseudocholinesterase (PchE), aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) were determined. Malathion exposure leads to a significant decrease in AchE activity, an increase in hepatic MDA, and in serum ASAT and ALAT activities. A positive correlation between serum transaminases levels and hepatic MDA was demonstrated. These results indicate that malathion exposure induced lipid peroxidation LPO, a process of degradation of membrane lipids, involving the deterioration of the cellular integrity. We have recorded a slight increase in antioxidant enzymes activities. This leads us to suggest an insufficient elimination of free radicals, causing cytotoxic effects. To cite this article: R. Rezg et al., C. R. Biologies 331 (2008).

Zeatin Supplement Improves Scopolamine-Induced Memory Impairment in Mice

In this study, our aim was to clarify the ameliorative effects of zeatin, a development hormone in plants. Zeatin mitigated cognitive deficits and showed AChE inhibition in scopolamine (Scop)-induced mice following 21 d of zeatin treatment. After administration of Scop for 30 min, each mouse performed Y-maze and step-down latency tasks as a check on immediate against cognitive function. The results showed that zeatin administration attenuated Scop-induced memory damage and decreased AChE activity in the mice. This suggests that zeatin might be useful for protecting cognitive dysfunction, as well as for reducing the activation of AChE in dementia.

Alterations of acetylcholinesterase activity after traumatic brain injury in rats

Objective: The cholinergic system is highly vulnerable to traumatic brain injury (TBI). However, limited information is available to what extent the degrading enzyme acetylcholinesterase (AChE) is involved. The present study addresses this question.Method: Thirty-six anaesthetized Sprague-Dawley rats were subjected to sham operation or to TBI using controlled cortical impact (CCI). The AChE activity was histochemically determined in frozen brain slices at 2, 24 and 72 hours after TBI.Results: High enzyme activity was observed in regions rich in cholinergic innervation such as the olfactory tubercle, basal forebrain, putamen and superior colliculi. Low activity was found in the cortex, cerebellum and particularly in the white matter. A decrease of AchE activity (20–35%) was found in the hippocampus and hypothalamus already at 2 hours after TBI. An increase of ∼30% was found in the basal forebrain at 2 and 24 hours. No changes occurred at 72 hours.Conclusion: The findings are consistent with impairment of the cholinergic neurotransmission after TBI and suggest the involvement of the AChE in short-term regulatory mechanisms.

Changes in Blood Cell Membrane Properties in HIV Type-1-Infected Patients

To evaluate the possible HIV-1 infection-induced changes in cell membrane properties and in calcium signaling, membrane fluidity, acetylcholinesterase (AChE, a glycosylphosphatidylinositol-anchored protein) activity, and intracellular calcium concentration ([Ca2(+)](int)) were evaluated in lymphocytes and erythrocytes of infected individuals, previous to their engagement in antiretroviral therapy. Membrane fluidity was assessed by fluorescence spectroscopy measurements, using the fluorescence probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH). AChE activity was determined by the colorimetric Ellman's method and [Ca2(+)](int) using the fluorescent fura-2 acetoxymethyl ester. When compared with the control group, lymphocytes of infected patients presented significantly decreased membrane fluidity, decreased AChE activity, and increased [Ca2(+)](int). Erythrocytes from HIV-infected patients presented decreased [Ca2(+)](int) when compared with the control group and decreased membrane fluidity near the lipid/water interface. Our data show that HIV-1 infection leads to biochemical and biophysical changes in the membrane itself and in membrane protein activity in lymphocytes (average of infected and noninfected subpopulations) and even in erythrocytes. The present observations are in agreement with a process of facilitated propagation of the infection to new cells, stimulation of virion production, and maintenance of a reservoir of erythrocyte-bound infectious virus.

Biochemical biomarkers in adult female perch ( Perca fluviatilis) in a chronically polluted gradient in the Stockholm recipient (Sweden)

A battery of biochemical biomarkers and the ∑PCB concentration in adult female perch ( Perca fluviatilis) verified an aquatic pollution gradient with the city of Stockholm (Sweden) as a point source of anthropogenic substances. The investigation included both an upstream gradient, 46 km westwards through Lake Mälaren, and a downstream gradient, 84 km eastwards through the Stockholm archipelago. Besides the main gradient from Stockholm, there were strong indications of pollution coming from the Baltic Sea. The results indicated a severe pollution situation in central Stockholm, with poor health status of the perch, characterised by increased specific EROD activity in the liver, increased liver EROD somatic index, decreased AChE activity in the muscle, increased amount of DNA adducts in the liver, and a high concentration of biliary 1-pyrenol. In addition, laboratory exposure to common EROD inducers elicited an abnormal response, suggestive of chronic intoxication.

Changes of acetylcholinesterase activity after long-term exposure to sarin vapors in rats

In our study, rats were exposed to sarin vapors for 240 min at four different concentrations (0.30, 0.43, 0.58 and 0.82 microg/L) in a whole-body inhalation chamber. The acetylcholinesterase activity (AChE, EC 3.1.1.7) was measured in the whole blood, frontal cortex (FC), pontomedullar area (PM) and basal ganglia (BG). Convulsions and hypersalivation were observed in only one animal of the group exposed to the highest sarin concentration. The decrease in blood AChE activity was significant in all animals exposed to sarin vapors. The highest inhibition of AChE activity (61%) was determined in animals exposed to sarin vapors at a concentration of 0.82 microg/L. In the PM, AChE activity was decreased in all experimental groups, significantly only in the group exposed to sarin vapors at a concentration of 0.58 microg/L. Our results show that in long-term exposure to low concentrations of sarin, the significant decrease in AChE activity in the blood is followed by significant changes of AChE activity in the PM only. This part of the brain seems to be more sensitive than the FC or BG.

Acetylcholinesterase activity in Lycopersicon esculentum and its phytochrome mutants

Using the radiometric method, the activity of acetylcholinesterase (AChE, E.C. 3.1.1.7) was studied in seedlings of wild type (WT) and of phytochrome mutants of tomato ( Lycopersicon esculentum Mill.). The activity of this enzyme was inhibited by an excess of substrate and by two well-known inhibitors of animal AChE, eserine and neostigmine. The activity of AChE was found in all etiolated organs as well as in light-grown seedlings. Under both conditions, the highest level of the enzyme activity was detected in cotyledons and the lowest one in root tissue. The enzyme activity was phytochrome-controlled. In WT etiolated seedlings red (R) light decreased AChE activity, whereas far red (FR) light abolished the red light effect. Furthermore, in light-grown WT seedlings the level of the enzyme activity was about twice higher than in etiolated plants. However, in the aurea phytochrome mutant of tomato, deficient in biosynthesis of a phytochrome chromophore, light had no effect on the AChE activity. In case of hp, fri and tri mutant seedlings, R and FR affected the AChE activity in a different way. Based on our results, we suggest that the type I of phytochrome is involved in the regulation of AChE activity. The type II of this photoreceptor influences the rate of the AChE synthesis de novo.

Involvement of L-triiodothyronine in acetylcholine metabolism in adult rat cerebrocortical synaptosomes.

Despite the recently emerging notion of thyroid-hormone involvement in neurotransmission in the adult mammalian brain, adequate evidence for a cellular basis of the process is still lacking. The present study indicates the involvement of thyroid hormones in cholinergic system of the adult rat cerebral cortex. Administration of L-triiodothyronine (T3, 0.025 to 4 microg/g) in single doses increased the synaptosomal acetylcholinesterase (AchE) and Mg2+-ATPase activity maximally at 24 hours in a dose-dependent way. Propylthiouracil (PTU)-treated hypothyroid rats showed a significant increase in AchE and Mg2+-ATPase activity compared to euthyroid rats. T3-treatment on hypothyroid rats decreased AchE activity in synaptosomes compared to the hypothyroid synaptosomal values. Mg2+-ATPase activity found in (PTU + T3)-treated group and T3-treated group remained high. These results predict that T3 stimulates acetylcholine (Ach) metabolism by increasing AchE activity as well as uptake of the released Ach through an increase in synaptosomal Mg2+-ATPase activity. This indicates a positive impact of T3 on the cholinergic system in the adult mammalian brain.

An unusual photohaemolytic property of riboflavin

Riboflavin (RF) is a known photoreactive and phototoxic molecule. However, unlike other photosensitizers, it does not induce photohaemolysis of erythrocytes by itself. On the other hand, illuminated RF caused haemolysis but in the presence of serum or plasma. The kinetics of photohaemolysis in the presence of serum/plasma has been studied by monitoring the rate of haemolysis spectrophotometrically and morphological changes at erythrocytes membrane by scanning electron microscopy. We found that the extent of mammalian RBC membrane damage was dependent on the concentration of RF or hematoporphyrin (HP) (0–20 μg/ml) and dose of sunlight (0–20 min). The RBC membrane-damaging potential of illuminated HP was not affected by the presence of plasma in the reaction system. Furthermore, RF showed a protective role against photohaemolysis caused by photoexcited HP if erythrocytes were preincubated with RF in the absence of serum/plasma. For mechanistic studies, biochemical parameters such as acetylcholinesterase activity (AChE) and formation of TBA-reactive substance (TBA-RS) were analysed in RBC and RBC+plasma under a similar set of experimental conditions. We observed about a 25% decrease in AchE activity as a synergistic action of RF or HP (20 μg/ml) and sunlight (30 min) in both cases (RBC or RBC+plasma). Interestingly, illuminated RF caused about a 125% increase of TBA-RS in a reaction system consisting of RBC+plasma. On the other hand, an increase in the production of TBA-RS by illuminated RF was not observed in the absence of plasma/serum, in the reaction system. These results suggested that photooxidation of RBC membrane lipids by illuminated RF, under the influence of plasma/serum, may be one of the causes of membrane modification leading to RBC lysis.

In vivo inhibition and recovery of brain acetylcholinesterase in topmouth gudgeon (Pseudorasobora parva) following exposure to fenitrothion

Freshwater fish, topmouth gudgeon (Pseudorasobora parva), were pretreated with piperronyl butoxide (PBO) or triphenyl phosphate (TPP) and then exposed to different concentrations of fenitrothion (FNT) in a static system. Evaluation of brain acetylcholinesterase (AchE) activity after 24, 48 and 96 h pesticide exposure indicated that AchE activity decreased as the concentration increased. Fish pretreated with TPP exhibited significantly decreased AchE activity whilst in the PBO pretreated group, increased activity was observed as compared with those exposed to FNT alone. The pattern of AchE recovery was also assessed in fish previously exposed for 96h and then transferred to clean (chemical free) water. Following 8 days of recovery period, the AchE activity of those exposed to FNT alone and pretreated with TPP was still lower than that of the control. This study showed that FNT may cause hazard to fish after field application.

Combined effects of glucocorticoids and electromechanical activity on the acetylcholinesterase expression in the fast rat muscle

Protein synthesis is impaired in the glucocorticoid (GC)-treated fast mammalian muscle. Electromechanical activity was reported to alleviate this effect. Acetylcholinesterase (AChE; EC 3.1.1.7) synthesis in the skeletal muscle is regulated by both, GCs and electromechanical activity. In light of the above reports, one would expect that electrical stimulation will prevent GC -mediated fall of AChE synthesis in the muscle. On the other hand, a substantial body of evidence suggests that electromechanical activity exerts its effect at the AChE mRNA level, while GCs most probably act at the translational or early posttranslational level. Different levels of action would be more consistent with the independent and therefore additive influences of the two regulatory factors. In order to ascertain whether glucocorticoid and electromechanical effects interact in the control of AChE activity, we compared the effects of GCs on normal, nonstimulated fast rat skeletal muscle, with those of GC-treated and simultaneously electrically stimulated (tonic pattern, 10 Hz) muscle. Untreated and stimulated-only muscles were used as respective controls. The effects on the fast extensor digitorum longus muscle and slow soleus muscle, treated similarly were compared. As expected, chronic GC treatment and electrical stimulation of fast rat muscles with slow activity patterns both downregulated AChE activity. However, no additional decrease in AChE activity was observed, if stimulated fast muscle was simultaneously treated with GCs, suggesting that slow pattern of electromechanical activity prevents GC-mediated downregulation of AChE. The most plausible explanation of this observation is, that muscle activity blocks expression of some generally acting factors, which are induced by GCs and are responsible for the impaired synthesis of several proteins including AChE.

Glucocorticoids differentially control synthesis of acetylcholinesterase and butyrylcholinesterase in rat liver and brain

Mammalian organisms posses two cholinesterases: acetylcholinesterase (AChE, EC 3.1.1.7.) and butyrylcholinesterase (BuChE, EC 3.1.1.8.). A clear explanation for this dual expression of acetylcholine-hydrolyzing enzymes is still missing. Better knowledge on how these two enzymes respond to various physiological or pharmacological factors would importantly contribute to the understanding of their function. The aim of the present study is to elucidate glucocorticoid (GC) influences on the synthesis of AChE and BuChE in rat liver and brain. Female Wistar rats were treated with dexamethasone until body weight loss was greater than 15%, signaling full expression of a GC response. At this stage, liver and brain were isolated and AChE and BuChE activities were determined in their homogenates. A new approach, based on precise radiometric measurements of AChE and BuChE activities in the polysomal fractions, prepared under non-denaturing conditions, was used to study GC influences on the early stages of biosynthesis of both enzymes. We found a differential GC influence on AChE and BuChE. In brain, only BuChE activity was affected (−30%), while AChE remained practically unchanged. In liver, BuChE activity fell by 60%, while AChE lost only 18% of its control activity. In case of BuChE, decreased activities in the whole homogenates correlated with decreased activities in the polysomal fractions, suggesting that early stages of enzyme biosynthesis were primarily affected. On the other hand, decreased AChE activity in liver homogenates was not paralleled by a significant change at the level of polysomal AChE activity in this organ, suggesting that higher AChE turn-over is primarily responsible for the decreased activity in homogenate. These results, together with the GC-mediated elimination of the correlation between brain and liver BuChE activities, strongly support the proposal of Edwards and Brimijoin (J.A. Edwards, S. Brimijoin, Effects of hypophysectomy on acetylcholinesterase and butyrylcholinesterase in the rat, Biochem. Pharmacol. 32 (1983) 1183–1189) that BuChE is regulated by systemically acting factors, including various hormones, while regulation of AChE is primarily tissue-specific.