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PubMed1988

Effect of carboxylesterase inhibition on carbamate protection against soman toxicity.

The ability of the carbamates pyridostigmine and physostigmine to protect against the lethal effects of soman, an extremely toxic anticholinesterase agent, was measured in rats, guinea pigs and rabbits. Pharmacologically equivalent doses of these carbamates that inhibited 70% of the blood acetylcholinesterase in each species were injected i.m. 25 min before s.c. injection with soman. Pretreatment with either carbamate, in combination with 17.4 mg/kg of atropine, produced protection against soman toxicity in all species. When protection was expressed as the ratio between the soman LD50 values in carbamate-protected animals and control animals, this protective ratio varied 3-fold between species (2.1-6.1 for pyridostigmine; 2.2-6.6 for physostigmine). When protection was expressed as the difference in the soman LD50 values between carbamate-protected animals and control animals, this protective difference was consistent among species (126 +/- 19 micrograms/kg). Species variation in protective ratios was observed largely because the control LD50 values defining soman toxicity in unprotected animals varied among species (20 micrograms/kg in rabbits, 28 micrograms/kg in guinea pigs and 126 micrograms/kg in rats). The species variation of the soman LD50 values in control animals was eliminated by pretreating animals with cresylbenzodioxaphosphorin oxide, which reduced the species variation in soman detoxification. The LD50 values for soman in cresylbenzodioxaphosphorin oxide-treated animals (9.8-15.6 micrograms/kg) did not differ significantly between species. Similarly, protective ratios for carbamates against soman in cresylbenzodioxaphosphorin oxide-treated animals were also clustered in a narrow range (8.5-11.4 for pyridostigmine; 9.0-13.4 for physostigmine) that did not differ significantly, regardless of species or carbamate.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed2006

Rapid separation and determination of carbamate insecticides using isocratic elution pressurized capillary electrochromatography.

An isocratic elution pressurized CEC (pCEC) system was used to separate and determine ten carbamate insecticides. It was found that introduction of the electrical field, supplementary pressure, and SDS in the proposed method greatly improved the speed, column efficiency, selectivity, and repeatability for separation and determination of carbamates. On a capillary column of 75 microm ID packed with 3 microm octadecyl silica, baseline separation and detection of ten analytes was performed by using a mobile phase consisting of 30% v/v ACN and 70% v/v of 5 mmol/L ammonium acetate (pH 6.5) containing 1 mmol/L SDS and 0.01% triethylamine (TEA). Under the optimum conditions ten carbamate insecticides could be completely separated within 20 min. For the real vegetable samples, an SPE procedure for the cleanup of matrices was carried out prior to pCEC analysis. The detection limits of 0.05-1.6 mg/kg for ten carbamates and mean recoveries of 51.3-109.2% for eight kinds of vegetable samples at different concentrations of carbamates with RSD less than 11.4% were obtained, respectively. The proposed method has been proved to be effective in the rapid analysis of carbamate residues in vegetables.

Buffers↗
PubMed1987

Biochemical interactions of carbamates and ecothiophate with the activated conformation of nicotinic acetylcholine receptor.

Purified Torpedo nobiliana electric organ acetylcholine receptor (AChR) was reconstituted into membranes containing natural phospholipids supplemented with cholesterol (25% w/w). The reconstituted system facilitates the study of the effects of drugs on the regulation of the AChR channel complex under both resting and carbachol (carb)-stimulated conditions. Neostigmine (Neo) was the only carbamate to induce activation of [3-H]-phencyclidine ([3-H]-PCP) binding to the channel sites, acting as a weak agonist. The activation of [3-H]-PCP binding is dependent upon the nature of the reconstituted systems, with carb/Neo activation ratios of 8, 3, and 1 for the intact purified AChR vesicles fraction (PVF), the PVF reconstituted in phospholipid/cholesterol (CRPVF), and the PVF reconstituted in phospholipid (RPVF), respectively. The carbamates Neo, physostigmine (Physo), and pyridostigmine (Pyrido) inhibited carb-activated [3-H]-PCP binding with Ki values of 10, 20, and 1,600 microM, respectively. The inhibition was mixed competitive-noncompetitive in nature. The characteristic response of CRPVF to carb-stimulated [22-Na] influx was inhibited by the three carbamates, with IC-50 values of 6, 50, and 1,000 microM for Neo, Physo, and Pyrido, respectively. The quaternary ammonium organophosphate ecothiophate (Eco) inhibited carb-stimulated [22-Na] influx with potency similar to that of Neo. Preincubation of AChR preparation with the carbamates and ecothiophate caused a reduction in the binding of [125-I]-alpha-bungarotoxin ([125-I]-alpha-BGT) with the following decreasing order of potency: Neo less than Physo less than Eco less than Pyrido. Calcium has a direct modulatory role on the time-course inhibition of [125-I]-alpha-BGT binding by these drugs. While we observed a high potency of Neo and Physo in inhibiting [125-I]-alpha-BGT binding, it was undetectable for the carbamate insecticide 2-methyl-2-(methylthio)propionaldehyde-O-(methylcarbamoyl)oxime (aldicarb). These data suggest that the potent anticholinesterase carbamate agents interact differently with the AChR and its ionic channel. Their interactions with the nicotinic AChR channel system can be described as (a) weakly agonist, (b) directly acting on the open conformation of the channel, and (c) blocking the AChR-binding sites.

Biotransformation↗
PubMed1991

Carbamate ester prodrugs of dopaminergic compounds: synthesis, stability, and bioconversion.

Various carbamic acid esters (CAE) of a new class of dopaminergic drugs, 5-substituted 8-chloro-7-hydroxy-3-methyl-2,3,4,5- tetrahydro-1 H-3-benzazepines, were synthesized and evaluated as prodrug forms with the aim of protecting the parent phenols against first-pass metabolism following oral administration. Monosubstituted CAE were found to be highly unstable at pH 7.4 and 37 degrees C, the half-lives of hydrolysis being between 4 and 40 min. Plasma from various species catalyzed the hydrolysis of the carbamates. N,N-Disubstituted carbamates, on the other hand, were stable both in buffer and plasma solutions. They showed a very potent inhibition of butyrylcholinesterase (EC 3.1.1.8), but were less potent inhibitors of the specific erythrocyte acetylcholinesterase (EC 3.1.1.17). In vitro incubations of an N,N-dimethylsubstituted carbamate ester (10) with liver microsomes from mouse and rat showed an appreciable formation of the parent phenolic compound. This bioconversion is suggested to occur via an initial cytochrome P-450-catalyzed hydroxylation to give an N-hydroxymethyl derivative which spontaneously decomposes to the N-monomethylcarbamate. It is concluded that N,N-disubstituted carbamate esters may be potentially useful prodrugs for the 7-hydroxy-3-benzazepines, whereas N-monosubstituted carbamates appear to be too chemically and enzymatically labile.

Amino Acids↗
PubMed1977

Vascular changes in the lungs of rats after the intravenous injection of pyrrole carbamates.

The effects on the lung of some synthetic compounds related to monocrotaline pyrrole have been studied and compared with those previously found with that compound. When injected into a systemic vein doses of pyrrole mono- and dicarbamate produced acute pulmonary oedema. Pyrrole alcohol and ethyl carbamate had no such effect and although furyl carbamate did not cause pleural effusion in rats it did so in mice. Like monocrotaline pyrrole, when injected into other vessels the pyrrole carbamates produced oedema in the region of the first capillary bed encountered. When colloidal carbon was injected intravenously after the pyrrole carbamates, carbon "labelling" was seen in both the post-capillary venules and the capillaries of the lungs. On the whole, venular "labelling" occurred before capillary "labelling" which was best seen when the carbon was injected more than 4 hr after the pyrrole. The distribution of the carbon as seen by electron microscopy is described. No "labelling" was seen after furyl carbamate. The effects of the synthetic pyrrole esters were similar to those of monocrotaline pyrrole. Although both the pyrrole carbamates were less active on a molecular basis they had a broader action on the pulmonary vasculature causing venular as well as capillary "labelling". To affect the lungs acutely the compound had to have the pyrrole ring structure and at least one ester side-chain.

Animals↗
PubMed2003

Considerations on ultra trace analysis of carbamates in water samples.

A new routine method for the ultra trace analysis of carbamates in water samples is presented, using solid-phase extraction followed by high-performance liquid chromatography coupled to atmospheric pressure electrospray ionisation mass spectrometry (SPE-LC-ESI-MS). Instrumental conditions of LC-ESI-MS in the selected ion monitoring (SIM) mode, showed excellent linear response for the six N-methyl carbamates studied (aldicarb, carbaryl, carbofuran, methomyl, oxamyl and pirimicarb) in the range from 1 to 50 microg/l and a precision having a relative standard deviation below 7.8% was achieved. Instrumental limits of detection of 0.10 microg/l were found for these carbamates, with the exception of methomyl for which 0.50 microg/l was measured. The SPE assays were shown to be easy, fast, very sensitive, requiring a low volume (50 ml) of water sample. For laboratory-spiked water samples having 0.03 and 0.30 microg/l of individual N-methyl carbamates, higher selectivities were achieved in cartridges having octadecylsilica, polystyrene-divinylbenzene and N-vinylpyrrolidane-divinylbenzene as solid phases, for which reasonable average recoveries were obtained. Ten replicates using octadecylsilica SPE cartridges, showed average recoveries between 73.7 and 92.6% with a relative standard deviation lower than 14.7%. The present methodology evidences good robustness, accuracy and precision for monitoring of N-methyl carbamates in water samples, and is shown to be a suitable alternative to replace the currently dedicated analytical systems. The limits of detection for the analysis of N-methyl carbamates in water samples reached in the present methodology (0.5 to 3 ng/l), clearly cover the maximum concentration admissible for pesticides, established by the European Union directive on water quality.

Aldicarb↗
PubMed1989

New anticancer agents: alterations of the carbamate group of ethyl (5-amino-1,2-dihydro-3-phenylpyrido[3,4-b]pyrazin-7-yl)car bamates.

The ethyl (1,2-dihydropyrido[3,4-b]pyrazin-7-yl)carbamates have been reported to bind with cellular tubulin, to produce an accumulation of cells at mitosis, and to exhibit cytotoxic activity against experimental neoplasms in mice. Studies on the disposition of ethyl (5-amino-1,2-dihydro-2-methyl-3-phenylpyrido[3,4-b]pyrazin-7 -yl)carbamate (8) in mice showed that one metabolite was formed by cleavage of the ethyl carbamate moiety. Analogues with alterations in the carbamate group were prepared by transformations at the carbamate of 8, by reductive cyclization of nitropyridine intermediates, and by hydride reduction of the ring of heteroaromatic compounds. In vitro and in vivo evaluations of analogues indicated that a carbamate group was required for activity. No significant change in activity was observed when ethyl was replaced by methyl. However, activity was reduced when ethyl was replaced with bulky aliphatic groups and when ethoxy was replaced with a methylamino group. Also, the activity of 8 was decreased by acetylation of the 5-amino group and was destroyed by substitution of an amino group at the 8-position.

Animals↗
PubMed2005

Enantioselective lithiation of O-alkyl and O-alk-2-enyl Carbamates in the presence of (-)-sparteine and (-)-alpha-isosparteine. A theoretical study.

Quantum chemical DFT calculations at the B3LYP/6-31G(d) level have been used to study the enantioselective lithiation/deprotonation of O-alkyl and O-alk-2-enyl carbamates in the presence of (-)-sparteine and (-)-alpha-isosparteine. Complete geometry optimization of the precomplexes consisting of the carbamate, the chiral ligand, and the base (iPrLi), for the transition states of the proton-transfer reaction, and for the resulting lithio carbamates have been performed in order to quantify activation barriers and reaction energies. For the lithiodeprotonation of ethyl carbamate 12 in the presence of (-)-sparteine (5) the preferred abstraction of the pro-S proton (by 2.75 kcal/mol) gives the (S)-lithio derivate (S)-14, which is in good agreement with experimental observations. (-)-alpha-Isosparteine (6) is predicted to be significantly less selective favoring the abstraction of the pro-R proton by 1.2 kcal/mol. The O-alkenyl carbamate 17 as an example of an allylic carbamate is more easily lithiated than 12. As for 12 (-)-sparteine (5) favors the abstraction of the pro-S proton, although with smaller preference (0.7 kcal/mol). Structural parameters are discussed to rationalize the theoretical results.

Carbamates↗
PubMed1993

Release of thiurams and carbamates from rubber gloves.

A method for quantitative determination of thiuram and carbamate derivatives released from rubber gloves into synthetic sweat is presented. The analysis was based upon determination of ester derivatives using gas-chromatography/mass spectrometry and isotope-dilution. The detection limit was 0.1 mg thiuram/carbamate in 200 ml synthetic sweat (0.5 ppm). The release of thiurams and carbamates from 5 household and 5 surgical types of gloves into synthetic sweat was determined. Each of the natural rubber gloves released varying amounts of thiurams (0-4.3 mg) as well as carbamates (0-8.1 mg). 22 thiuram-sensitized patients were patch tested with pieces of the gloves. Gloves releasing considerable amounts of thiurams and/or carbamates seemed to cause more positive patch test reactions in these patients than gloves releasing smaller amounts. Surgical gloves made from natural rubber caused a substantial larger number of positive patch test reactions than household gloves made from natural rubber. The amounts released per cm2 of the gloves were of the same order of magnitude as the content per cm2 patch test of thiuram mix, diluted 1:10. The accessibility of a quantitative, chemical analysis for thiurams and carbamates released from rubber gloves makes it reasonable to ask for declarations of rubber gloves. Proposals for threshold values for release of thiurams and carbamates from rubber gloves may be given in the future.

Carbamates↗
PubMed1982

The relationship between chemical structure and the in vivo metabolism of an homologous series of n-alkyl carbamates.

The metabolism and pharmacokinetics of carbonyl [14C] labelled ethyl, n-butyl, n-hexyl and n-octyl carbamates has been examined in rats after oral and intravenous administration. Hydrolysis of the carbamate group was a major metabolic fate, particularly of the more water soluble carbamates. Conversely, with increasing lipophilicity increasing amounts of omega-1 oxidation products were found both in plasma and urine. The plasma pharmacokinetic data could not be explained by a simple bi-exponential model, ethyl carbamate in particular showing unexpectedly persistent blood levels. A model has been proposed to explain the pharmacokinetic data for ethyl, n-butyl, n-hexyl and n-octyl carbamates. The essential features of this model are that carbamate is thought not to be in equilibrium between the peripheral and central compartment and that hydrolytic metabolism takes place in the peripheral compartment while oxidative metabolism to urinary metabolites occurs in the central compartment.

Animals↗
PubMed1980

Effects of carbamates on whole blood cholinesterase activity: chemical protection against soman.

The toxicity (LD50) of several carbamates, all reversible inhibitors of cholinesterase (ChE), were determined in male rabbits. These include isopropyl methylphenyl carbamate (IMPC), pyridostigmine, neostigmine, benzpyrinium and physostigmine. When 1/9 of the LD50 of the above carbamates was individually combined with atropine (A) and benactyzine (B), mecamylamine (M) or chloropromazine (CPZ) and administered to rabbits in a pretreatment regimen, most animals could be protected from a 10 LD50 challenge of Soman. If CPZ, M or B was omitted from this regimen, no rabbits survived this challenge of Soman. The protection afforded against Soman was found to be related to reversible inhibition of ChE by the carbamates; reversible ChE inhibition varied with the route of injection and with the physical properties of the carbamate. Oral administration of pyridostigmine, a quaternary carbamate, provided protection for 24 hours. When the pretreatment included four components (pyridostigmine, A, M and B), the LD50 of Soman was raised 30.8 times in rabbits.

Animals↗
PubMed2000

Importance of the lipophilic group in carbamates having histamine H3-receptor antagonist activity.

In order to evaluate changes in the lipophilic part of designed carbamates concerning their potential histamine H3-receptor antagonist properties a new series of O-[3-(1H-imidazol-4-yl)propanol]carbamates was derived containing N-mono- or di-alkenyl, alkynyl, cycloalkyl, or double-branched alkyl substituents. The compounds were tested in vitro for their H3-receptor antagonist activity on synaptosomes of rat cerebral cortex and shared moderate to high antagonist activity in vitro. In this series 3-(1H-imidazol-4-yl)propyl N-(4-pentenyl)carbamate (4) was the most potent compound in vitro (Ki = 6.3 nM). H3-receptor antagonist activity in the central nervous system (CNS) was detected for most compounds in the in vivo H3-receptor assay based upon measurement of brain N tau-methylhistamine levels after p.o. administration to mice. The most effective carbamate in vivo, 3-(1H-imidazol-4-yl)propyl N-(allyl)carbamate (3), showed higher CNS potency (ED50 = 0.48 mg/kg p.o.) than the reference antagonist thioperamide. For some novel carbamates their histamine H1- and H2-receptor activities were determined on isolated organs of guinea-pig thereby demonstrating their high H3-receptor selectivity.

Animals↗
PubMed1992

Inhibition of carbonic anhydrases I and II by N-unsubstituted carbamate esters.

We previously showed that the zinc metalloenzyme carbonic anhydrases (CA I and II isozymes) bind "neutral" amides and related compounds as anions through coordination of their deprotonated amide nitrogen to the active site zinc (Rogers, J. I., Mukherjee, J., and Khalifah, R. G. (1987) Biochemistry 26, 5672-5679). Urethan, the ethyl carbamate ester, was among such compounds. The present study was designed to test whether other N-unsubstituted carbamate esters of pharmacological interest (as sedatives, hypnotics, anxiolytics, and skeletal muscle relaxants) were capable of binding to CA in the same manner. We studied the interaction of human CA I and II with urethan, phenyl carbamate, ethinamate, meprobamate, and methocarbamol. Phenyl carbamate studies were greatly complicated by its uncatalyzed hydrolysis via an elimination mechanism to form cyanate, a powerful CA inhibitor. In general, the compounds display: 1) slow on-off inhibition binding kinetics in the seconds range, 2) maximal inhibitor affinity at alkaline pH, and 3) characteristic three-band visible spectra of their complexes with cobalt-substituted CA I. These properties are shared with the previously studied amide inhibitors and are taken as evidence that the deprotonated carbamate nitrogen coordinates to the active site metal ion. CA I appeared to bind carbamate esters more tightly than CA II, an unusual 1000-fold selectivity being seen in the case of methocarbamol. The inhibition by these drugs is not sufficiently strong to implicate CA I and II in their mechanism of action. However, it does suggest the possible existence of previously unsuspected similarities between binding to CA and to their physiological receptors or targets, particularly the involvement of zinc.

Binding Sites↗
PubMed1982

Comparison of sister chromatid exchange induction and known carcinogenic activities of vinyl and allyl carbamates.

In vivo sister chromatid exchange (SCE) induction by vinyl and allyl carbamates was examined in alveolar macrophage, bone marrow, and regenerating liver cells of C57BL/6J x DBA/2J F1 mice. Allyl carbamate was effective in producing increases in SCE frequencies (relative to base-line SCE) over a dose range of 220 mumol/kg (approximately 2 times base line) to 2.2 mmol/kg (3 times base line). In general, alveolar macrophage and regenerating liver cells had higher responses, although not significantly, than did bone marrow. Vinyl carbamate produced significant increases in SCE frequencies over a dose range of 10 mumol/kg (2 times base line) to 75 mumol/kg (8 to 10 times base line). At the highest dose, SCE frequencies in extrahepatic tissues of hepatectomized mice were significantly higher than in intact mice and, within hepatectomized mice, alveolar macrophage and regenerating liver cell responses were greater than were bone marrow responses. Vinyl carbamate was approximately 30 times as potent a SCE inducer than we reported previously for ethyl carbamate. To date, our studies of six different carbamate esters have indicated a striking similarity in relative potencies for SCE induction and their known tumorigenic potencies.U

Animals↗
PubMed1981

Potency of some carbamates as multiple tissue sister chromatid exchange inducers and comparison with known carcinogenic activities.

The ethyl, ethyl N-hydroxy, isopropyl, and methyl esters of carbamic acid were examined for their abilities to induce sister chromatid exchanges (SCEs) in alveolar macrophages, bone marrow, and regenerating liver cells of C57BL/6J X DBA/2J F1 mice. The relative potencies in inducing SCE, ethyl greater than ethyl N-hydroxy- greater than isopropyl, paralleled previously described activities for induction of lung adenomas in strain A mice. The noncarcinogenic methyl carbamate was inactive in the SCE assay. Relative to bone marrow, regenerating liver and alveolar macrophage cells demonstrated increased susceptibility to carbamate-induced SCE. Of all carbamates studied, only the directly active compound, ethyl N-hydroxycarbamate, produced distinctly different responses in extrahepatic tissues of hepatectomized and intact mice. In intact mice, SCE levels induced by ethyl carbamate in bone marrow and alveolar macrophage cells were not significantly different whether assay followed the last of 12 (three times weekly) serial injections of 2.2 mmol/kg each or after a single injection of 2.2 mmol/kg. Linear regression relationships of log ethyl carbamate versus log SCE or log adenoma response were found to be parallel with the two assays having similar sensitivities.

Animals↗
PubMedDate not supplied

Study of respiratory failure in organophosphate and carbamate poisoning.

OBJECTIVE: To study the clinical profile and cholinesterase levels of subjects of organophosphate and carbamate poisoning and to identify those subjects who would require ventilatory support. DESIGN: Prospective, observational study. SETTING: Intensive care unit of a tertiary care urban hospital. SUBJECTS: Fifty-two patients admitted with a diagnosis of organophosphate or carbamate poisoning. OUTCOME MEASURES: Subject survival and ventilator requirement. INTERVENTION: Treatment with atropine and pralidoxime and mechanical ventilation for patients with respiratory failure. Clinical features were monitored at every stage, and blood for plasma and red blood cell cholinesterase levels was collected on admission. RESULTS: According to the ingested poison, subjects were divided into four groups: organophosphates (13 subjects), mixed organophosphate and carbamate (18), carbamates (13), and a fourth miscellaneous group (8). Dyspnea and vomiting were the most common symptom and miosis and cyanosis were the most frequently observed signs. Plasma and red cell cholinesterase levels were lowest in the mixed poison group and highest in the carbamate group. Twenty-seven subjects developed Type I respiratory failure and 7 had Type II respiratory failure. Mechanical ventilation was required in 31 subjects. Overall 33 subjects survived. A scoring system, on a point scale of 16, was developed using miosis, unconsciousness, fasciculations, and plasma cholinesterase levels to predict ventilator requirement. CONCLUSION: This study helps to identify at an early stage those patients with organophosphate or carbamate poisoning who would ultimately require ventilatory support. We found miosis, unconsciousness, fasciculations, and a low plasma cholinesterase level to be of greatest predictive value.

Adolescent↗
PubMed1995

Role of metabolism in ethyl carbamate-induced suppression of antibody response to sheep erythrocytes in female Balb/C mice.

A possible role of metabolism by cytochrome P450 (P450) in ethyl carbamate-induced suppression of the antibody response to a T-cell-dependent antigen, sheep erythrocytes (SRBCs), was investigated in female Balb/C mice. When mice were treated with ethyl carbamate intraperitoneally for 14 consecutive days at 25, 50, 100, 200 and 400 mg/kg, the antibody response was significantly suppressed from 200 mg/kg. These doses also caused a decrease in thymus weight. An acute dosing of ethyl carbamate at 1 g/kg also caused not only a significant suppression of the antibody response, but also a decrease in thymus weight. The antibody response was most likely to be the IgM antibody response, which was demonstrated in a haemagglutination study. When mice were pretreated with phenobarbital (80 mg/kg) for 3 days to induce P450 enzymes, followed by administration of ethyl carbamate intraperitoneally for 7 consecutive days, the antibody response was more suppressed than in saline-pretreated controls. Moreover, a study using aminoacetonitrile, a P450 inhibitor, showed that the antibody response suppressed by ethyl carbamate was completely recovered by the inhibitor. The present results suggest that metabolism of ethyl carbamate by P450 may be the critical pathway to produce metabolites capable of suppressing the antibody response.

Animals↗
PubMed2004

Role of B-esterases in assessing toxicity of organophosphorus (chlorpyrifos, malathion) and carbamate (carbofuran) pesticides to Daphnia magna.

In this study, the cladoceran Daphnia magna was exposed to two model organophosphorous and one carbamate pesticides including malathion, chlorpyrifos and carbofuran to assess acetylcholinesterase (AChE) and carboxylesterase (CbE) inhibition and recovery patterns and relate those responses with individual level effects. Our results revealed differences in enzyme inhibition and recovery patterns among the studied esterase enzymes and pesticides. CbE was more sensitive to organophosphorous than AChE, whereas both CbE and AChE showed equivalent sensitivities to the carbamate carbofuran. Recovery patterns of AChE and CbE activities following exposure to the studied pesticides were similar with 80-100% recoveries taking place 12 and 96 h after exposure to organophosphorous and carbamates pesticides, respectively. The physiological role of AChE and CbE inhibition patterns in Daphnia was examined by using organophosphorous and carbamate compounds alone and with specific inhibitors of CbE. Under exposure to organophosphorous pesticides, survival of Daphnia juveniles was impaired at AChE inhibition levels higher than 50% whereas under exposure to the carbamate carbofuran low levels of AChE inhibition affected mortality. Inhibition of CbE by 80-90% increased toxicity to organophosphorous and carbamate pesticides by up to two- and four-fold, respectively. Our results suggest that both AChE and CbE enzymes are involved in determining toxicity of Daphnia to the studied chemicals and that AChE inhibition levels higher than 50% can be considered of environmental concern to Daphnia species.

Animals↗