전기뱀장어 및 집파리 AChE를 이용한 살충제의 In Vitro AChE 저해 시험

이시혁,이준호,조광연 한국응용곤충학회 1992 한국응용곤충학회지 Vol.31 No.2

신규화합물의 in Vitro AChE 저해력을 평가하기 위한 저해시험법의 확립을 목적으로 실험을여 다음과 같은 결과를 얻었다. {TEX}$I_{50}${/TEX} 산출이 가능한 고정시간 저해시험(fixed time inhibition test)의 경우, DFP, DDVP 및 paraoxon과 같은 대표적 AChE 저해제의 저해력 평가에 적당한 저해시간은 10분 정도로 조사되었으며, 10분간의 저해조건하에서 ester group을 보유한 신규화합물의 저해여부 및 정도의 평가에 효과적인 시험농도는 10$\mu$M 수준으로 판정되었으나 다른 화합물의 경우에는 보다 높은 농도로부터 단계적 저해시험이 필요한 것으로 보였다. {TEX}$K_{d}${/TEX}, {TEX}$k_{3}${/TEX} 및 {TEX}$k_{i}${/TEX}와 같은 저해상수의 산출을 위한 경시적 저해시험(Progressive inhibition test)에 있어서, 본 실험의 장시간 저해(0.8~13.3분)와 낮은 저해제농도(1$\times${TEX}$10^{-9}${/TEX}~2$\times${TEX}$10^{-6}${/TEX}M)의 조건하에서는 극히 낮은 {TEX}$K_{d}${/TEX}(1.3$\times${TEX}$10^-{8}${/TEX}~5.6$\times${TEX}$10^{-7}${/TEX}M) 및 {TEX}$K_{3}${/TEX}(0.21~{TEX}$0.27min^{-1}${/TEX})가 관찰되었으나 저해제간의 저해독성 조사에는 충분한 타당성을 가지는 것으로 조사되었다. 또한 DFP, paraoxon 및 신규화합물인 KH501간의 현격한 저해력 차이는 {TEX}$K_{d}${/TEX}의 차이 즉, 저해제와 AChE간의 친화력 차이에 기인된 것으로 판명되었다. 따라서 AntiChE 스크리닝에 있어서 1차단계에서는 고정시간 저해법을 통하여 산출된 {TEX}$I_{50}${/TEX}를 바탕으로 하여 저해력 유무 및 정도를 파악하고, 1차단계에서 고도의 AChE 저해력이 인정된 신규 화합물을 대상으로 2차단계인 경시적 저해법을 이용하여 저해양상 및 특성을 조사하는 것이 합리적인 체계일 것으로 생각되어진다. Experiments were conducted to establish an in vitro AChE inhibition test system to evaluate the potency of AChE inhibition of new chemical compounds. For a fixed time inhibition test, optimal inhibition (incubation) time to evaluate their AChE inhibition potency was 10 min. for AChE inhibitors such as DFP, DDVP, and paraoxon. The concentration of new chemical compounds with an ester group for evaluation of their inhibition potency was 10 $\mu$M under 10 min. preincubation conditions. However, the stepwise inhibition test with higher concentrations seemed to be needed for other chemical compounds. For a progressive inhibition test to calculate inhibition constants such as $K_d$, $K_3$ and $K_i$, extremely low $K_d(1.3\times10-^85.6\times10^{-7})$ and $K_3$(0. 21-0.27 $min^{-1}$) were observed under lagged preincubation time (0.8-13.3 min) and low in¬hibitor concentrations $(1\times10-^92\times10-^6M)$. However, this method seemed to be useful for comparison of AChE inhibition potency among inhibitors. Differences in inhibition potency among DFP, paraoxon, and KH501 were due to the differences in $K_d$, in other words, differences in affinities between inhibitors and AChEs. Therefore, AntiChE screening should consist of two steps. The first step is to evaluate the potency of AChE inhibition based on $I_50$ valuse obtained from fixed time inhibition tests. The second step is to study inhibition patterns and characteristics of chemical compounds selected in the first step.

Acetylcholinesterase 효소 저해도와 GC/MS 방법을 이용한 녹차의 잔류농약 분석

김영화,허경혜 한국차학회 2013 한국차학회지 Vol.19 No.2

본 연구에서는 AChE의 저해도와 GC/MS 분석방법을 이용하여 녹차의 잔류농약(chlorpyrifos, fenitrothion, methidathion)을 분석하였다. Chlorpyrifos의 최대잔류허용량 (MRL)2 ppm에서 AChE의 활성이 75% 저해되었고 여기에 녹차추출물이 첨가된 경우에는 83% 저해를 나타내었다. 그러나 AChE 활성저해는 2 ppm보다 훨씬 낮은 농도에서 저해도 값에 변화를 보이지 않았다. Chlorpyrifos 표준농약의 경우와 녹차추출물이 첨가된 경우에서 각각 0.01 ppm과 0.1ppm 이상의 농도에서는 농약의 농도가 높아져도 활성의 저해도에는 차이가 없었다. Fenitrothion와 methidathion는 MRL 0.2 ppm에서 1-2% AChE 활성저해를 나타내었다. 두 농약의 농도를 20 ppm까지 계속 높여감에 따라 점진적인 AChE 저해도의 증가를 나타냄으로써 농도와 저해도간의 좋은 상관관계를 나타내었다. 반면 이 두 농약에 녹차추출물이 첨가되면 모두 5 ppm부터 AChE 저해도 값에 차이가 나타나지 않았기 때문에, 농약의 농도 증가에 따른 저해도의 지속적인 상관관계가 나타나지 않았다. 이상의 결과 각 농약별로 AChE활성을 저해하는 정도가 다르며, 녹차에 의해서도 영향을 받는 저해정도가 다르다는 것을 알 수 있었다. 따라서 적절한 검사방법을 운용하기 위해서는 농약의 종류 뿐 만 아니라 각각의 시료에 따른 표준검량곡선이 요구된다. GC/MS 분석으로 표준농약과 녹차추출물이 첨가된 농약의 회수율을 비교한 결과, 90-109%의 매우 높은 회수율을 나타내었다. Most pesticidal action is the result of inhibiting acetylcholinesterase (AChE) at the nerve endings(cholinergic synapses). The residues of organophosphate pesticides in green tea were analyzed using a modified Ellman method (acetylcholinesterase inhibition assay) and GC/MS analysis. Chlorpyrifos inhibits the AChE activity directly, but not fenitrothion and methidathion. Chlorpyrifos and chlorpyrifos with green tea exhibited 75% and 83% AChE inhibition at the maximum residue limit (2 ppm), respectively. On the other hand, AChE inhibition was already saturated at 0.01 ppm and 0.1 ppm chlorpyrifos and chlorpyrifos with green tea, respectively. Fenitrothion and methidathion represented 1-2% AChE inhibition at their maximum residue limit (0.2 ppm). The AChE inhibition reaction of those pesticides was not saturated, even at 20 ppm, whereas it was saturated at 5 ppm of the pesticide with green tea. These results suggest that the AChE method requires a specific standard curve for each pesticide with agriculture products. When pesticides with green tea were analyzed by GC/MS, the recovery rate of the pesticides was 90-109%. The calibration curve revealed GC/MS to have high sensitivity and was suitable for the precise quantification of pesticides. On the other hand, the analysis takes too much time and requires highly trained technicians.

Evolutionary distribution of two different acetylcholineterases in various insect species

Young Ho Kim,Si Hyoeck Lee 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.10

Almost all insect species possess two different acetylcholinesterases (AChE1 and AChE2) but it still remains unknown which AChE plays a major role in synaptic transmission. To predict the evolutionary distributions of functional AChE, relative amount and activity of two AChEs were investigated by native-PAGE in conjunction with Western blotting using AChE1- and AChE2-specific antibodies. Among 39 insect species examined, AChE1 was expressed as the main enzyme in 26 insect species across diverse taxa, suggesting that AChE1 likely plays a more crucial role in these insects. In contrast, AChE2 was predominantly expressed in remaining insect species, including paleopteran insects, suggesting that the replacement of AChE1 function with AChE2 is an old event. As expected, only AChE2 was detected in Cyclorrhaphan flies, supporting the notion that AChE2 in Cyclorrhapha has completely replaced the physiological functions of AChE1 during the evolution of Diptera. Taken together, contrary to the common belief that AChE1 is the major enzyme in most insects, many insect species across various taxa employ AChE2 as the main AChE, suggesting that functional transition from AChE1 to AChE2 has occurred rather universally and randomly with multiple independent origins within the class Insecta. This finding should provide valuable insights into which AChE has evolved to undertake the synaptic function and how functional diversification of AChE has occurred.

점박이응애의 독성 시험방법과 유기인계 살비제 AChE 활성저해에 관한 연구

김도익,이승찬 한국응용곤충학회 1992 한국응용곤충학회지 Vol.31 No.1

점박이응애(Tetranychus urticae Koch)에 대한 독성시험방법을 비교하고, 감수성계통을 누대도태하여 in vivo에서 저항성 발달수준과 in vitro에서의 AChE insensitivity의 관계를 실험한 결과는 다음과 같다. 점박이응애의 살비제 저항성 수준결정의 독성시험방법중 slide dip법 (CV=8.7%)은 leaf dip법(CV=12.2%) 이나 leaf disc법(CV=13.6%)보다 변이가 적고 정확도가 높을 뿐만 아니라 처리방법이 간편하고 한가지 농도에 대하여 여러 계통을 동시에 처리할 수 있고 처리 후의 조건을 균일하게 유지시킬 수 있으며 기주식물 없이 시험이 가능하였다. topical application법(CV=8.1%) 역시 정확도는 높았으나 시험 조작이 어렵고 필요한 장비의 구입 비용이 더 들며 시간이 많이 소요되는 단점이 있었다. 두 유기인제에 의한 누대도태결과 22세대 carbophenothion 도태개체군은 동일약제에 156배의 저항성이 발달하였으며, ethion에 대하여 128배의 저항성 반응을 보였다. 24세대 ethion 도태개체군은 동일약제에 64.1배의 저항성 발달이 되었으며, carbophenothion에 대하여도 65배의 저항성 반응을 보였다. 도태개체군의 AChE 활성저해도를 보면 감수성계통에 비하여 carbophenotion 누대계통은 carbohenothion은 3.3배, ethion은 2.7배의 활성저해도를 보였다. 또한 ethion 도태개체군에 대해서는 ethion은 2.6배 carbophenothion은 3.0배의 활성저해도를 나타냈다. 위와 같이 in vivo에서의 저항성 발달 수준과 in vitro에서의 AChE 저해도와는 밀접한 관계가 있는 것으로 보아 유기인계 살비제에 대한 점박이응애의 저항성 발현에는 AChE의 insensitivity가 주요인으로 작용하는 것으로 생각된다. These studies were carried out to compare toxicological test methods of two spotted spider mite, Tetranychus urticae Koch,; and to investigate relationship between in vivo resistant level of highly acaricide-selected population, and in vitro insensitivity of the AChE in the same population to carbophenothion and ethion. The slide dip method (CV = 8.7%) was of more accuracy and suitability than that of the leaf dip method(CV=12.2%) and leaf disc method (CV= 13.6 %) in determination of the resistant levels of twospotted spider mite to acaricides. The slide dip method also had the advantages of simple treatment with different populations on a slide at the same time, standardization of post-treatement conditions and living plants exclud￢ed from the test. Even though the topical application method(CV =8.1 %) showed high accuracy, it had the demerits of the much time consuming, need of expensive equipment and difficulty of test manipulation. For a limited time, the 22nd successive carbophenothion-selected population of two-spotted spider mite showed 156- and 128-fold resistant levels to carbophenothion and ethion(both alPs), respectively. However, the 24th successive ethion-selected population revealed 64.1- and 65-fold resistant levels to ethion and carbophenothion, respectively. In the inhibition of AChE activity, the carbophenothion-selected population showed 3.3- and 2.7-fold insensitivity in AChE activity to carbophenothion and ethion, respectively. Likewise, the ethion -selected population exhibited 3- and 2.6-fold insensitivity in AChE activity to carbophenothion and ethion, respectively, as compared with that of susceptible population. As a result, a good relation was recognized between in vivo resistance to organophosphorous acaricides and in vitro insensitivity of the AChE to corresponding inhibitors.

토사자의 Acetylcholinesterase 저해 활성에 관한 연구

류승엽 ( Lyu Seung Yeob ),박용기 ( Park Yong Gi ),강병수 ( Kang Byeong Su ) 대한본초학회 2003 大韓本草學會誌 Vol.18 No.4

N/A Objectives : In the course of searching for acetylcholinesterase(AChE) inhibitors from Semen of Cuscuta Australis R. BR in Korea and Cuscuta Austmlis R. BR in ChiM This study was carried out to investigate the effects protecting or improving Alzheimer`s disease of the acetylcholimsterase(AChE) inhibitors. Methods : This oriental drugs was extracted with 8oo/o methanol in room temperature and the extract was fives fractionation by hexane, chlorofm, ethylacetate, butanol and water. A mouse model of passive avoidance was used for recovery effect of Cuscutu Austmlis R. BR in Korea and Cuscuta Austmlis R. BR in China. on learning and memory deficits induced by scopolamine.. Results : 1. Acetylcholinesterase(AChE) inhibitors of Cuscuta Austmlis R. BR in Korea and Cuscutu Austmlis R. BR in China were investigated. It was found that Cuscuta Austmlis R. BR in Korea(64%) showed significantly inhibitory effect on AChE than in the Cuscuta Austmlis R. BR in China (29%). 2. Recovery effect on scopolamine-induced memory impairment in a mouse model of passive avoidance of Cuscuta Austmlis R. BR in Korea and Cuscuta Australis R. BR in China were investigated. Cuscuta Austmlis R. BR in Korea showed significant recovery effect on than Cuscuta Australis R. BR in China. 3. Acetylcholinesterase(AChE) inhibitors for recovery effect on scopolamine - induced memory impairment in a mouse model of passive avoidance of Cuscuta Australis R. BR in Korea and Cuscuta Australis R. BR in China were investigated. Cuscuta Australis R. BR in Korea increased acetylcholinesterase (AChE) inhibitors than Cuscuta Austmlis R. BR in China 4. The activity of DPPH and SOD of Cuscuta Austmlis R. BR in Korea were increase than Cuscuta Australis R. BR in China, but catalase were decrease than Cuscuta Austmlis R. BR in China. Conclusion : According to the above results, we found that ethylacetate extract of Semen of Cuscuta Austmlis R. BR in Korea showed significant inhibitory effect on AChE.

Soluble acetylcholinesterase is possibly involved in chemical defence

Young Ho Kim,Si Hyeock 한국응용곤충학회 2017 한국응용곤충학회 학술대회논문집 Vol.2017 No.04

Acetylcholinesterase (AChE) is a target enzyme of organophosphate (OP) and carbamate (CB) insecticides. Point mutation in AChE is one of the major mechanisms of OP and CB resistance. Recently, we investigated soluble AChEs abundantly expressed in the non-neuronal tissues of the honey bee Apis mellifera and fruit fly Drosophila melanogaster. Pre-incubation of OP and CB insecticides with honey bee soluble AChE showed a significant reduction in the inhibition of catalytic AChE activity. In the fruit fly, expression of soluble AChE was induced by insecticide exposure, and the wild-type fly expressing both soluble and membrane-anchored AChEs was more tolerant to insecticide than the transgenic fly expressing only membrane-anchored AChE. These findings suggested that soluble form of AChE is possibly involved in chemical defense against xenobiotics, including insecticides.

Inhibitory Effect of Bee Venom Herbal Acupuncture Solution on Acetylcholinesterase in PC 12 Cells

Choi Yang-sik,Choi Do-young,Lee Jae dong,Koh Hyung-kyun,Kim Jong-in 대한침구의학회 2008 대한침구의학회지 Vol.25 No.2

목적 : Acetylcholine은 콜린과 아세트산의 에스테르로 인체에서 중요한 신경전달물질로 Acetylcholine- sterase(AChE)라는 효소에 의해 분해된다. Alzheimer’s disease, ataxia, myasthenia gravis, Parkinson’s disease 등의 질환에 AChE 억제제가 사용되어 왔으며 최근 한약재의 AChE 억제 효능에 관한 연구들도 진행되고 있다. 봉독은 관절염, 통풍 등의 질환에 응용되어 왔으며 진통효과 및 항염증작용에 대한 임상적, 실험적 연구가 많이 보고되어 왔으나 AChE 억제효과에 대한 연구는 아직까지 보고된 바 없다. 본 연구에서는 봉독약침액과 봉독의 과민반응 유발항원 중 하나인 Phospholipase A2 억제효능이 있는 것으로 알려진 상백피를 혼합한 상백피봉독약침액의 AChE 억제효과를 알아보았다. 방법 : PC12 세포주에서 추출한 AChE와 0.1, 0.01 and 0.001㎎/㎖ 농도의 봉독약침액 및 상백피봉독약침액을 60분간 반응시켰다. 효소면역측정법(ELISA)을 이용하여 흡광도를 10분, 30분, 60분 경과시 각각 측정한 후 효소활성저해도(%)를 계산하였다. 효소활성저해도(%) = [(Cc–Ce)/Cc]×100 Cc : 대조군 흡광도, Ce : 실험군 흡광도 결과 : 1. 봉독약침액은 0.1, 0.01, 0.001㎖/㎎의 농도에서 30분 경과 후부터 유의성 있는 억제효과를 나타내었다. 2. 상백피봉독약침액은 0.1㎖/㎎ 농도에서 10분 경과 후부터 유의성 있는 억제효과를 나타내었고, 0.01㎖/㎎ 농도에서 30분경과 시 유의성 있는 억제효과를 나타내었다. 3. 봉독약침액과 상백피봉독약침액의 AChE 억제효과 비교에서 봉독약침액의 억제효과가 상백피봉독약침액보다 뛰어났다. 요약 : 봉독약침액과 상백피봉독약침액의 AChE 억제효과를 확인하여 두 군 모두 유의성 있는 결과를 얻을 수 있었다. 앞으로 알츠하이머병이나 치매와 같은 신경퇴행성 질환에 대한 봉독의 임상적 활용 및 보다 넓은 범위에 대한 연구가 필요할 것이라 사료된다.

Study on Biochemical Pollutant Markers for Diagnosis of Marine Pollution III. Changes in Cholinesterase Activity of Flounder(Paralichthys olivaceus)in the Yellow Sea

최진호,김동우,문영실,박청길,양동범,Choi, Jin-Ho,Kim, Dong-Woo,Moon, Young-Sil,Park, Chung-Kil,Yang, Dong-Beom Korean Society of Life Science 1997 생명과학회지 Vol.7 No.1

해양오염의 진단을 위한 생화학적 오염지표 설정의 기초 연구의 일환으로, 오염이 심각한 서해(또는 황해)산 넙치(Paralchthys olvaceus)의 노 및 근육중의 아세틸콜린에스테라아제(AChE) 및 무털릴콜린에스테라아제(butyrylcho-linesterase:BChE)의 활성, 그리고 전산탈수소효소(lactate dehydrogenase:LDH)의 활성을 분석${\cdot}$평가하였다. 서해안의 양식산의 넙치의 뇌 및 근육증의 AChE의 활성은 동해안의 포항의 자연산 넙치의 노 및 근육의 AChE의 활성 대비 각각 40-50% 미 40-55% 정도나 유의적으로 저하되었을 뿐만 아니라 서해안의 자연산 넙치의 뇌 및 근욱중의 AChE의 활성 대비 각각 15-40% 및 25-35% 정도나 유의적으로 저하되었다. 또 서해안의 양식산 넙치의 뇌 및 근육중의 BChE의 활성은 동해안 포항의 자연산 넙치의 뇌 및 근육중의 BChE의 활성 대비 각각 70-75% 및 65-75% 정도나 유의적으로 저하되었ㅇ르 뿐만아니라 서해안의 자연산 넙치의 뇌 및 근육중의 BChE의 활성 대비 각각 50-75% 및 45-50% 정도나 유의적으로 저하되었다. 한편 서해안의 양식산 넙치의 혈약중의 LDH의 활성은 동해안 포항의 자연산 넙치의 혈액중의 LDH의 활성 대비 10-50%정도나 유의적으로 증가하였을 뿐만 아니라 서해안의 자연산 넙치의 혈액중의 LDH의 활성 대비 20-25% 정도나 유의적으로 증가하였다. 따라서 서해안의 양식산 넙치의 오염 뿐만 아니라 자연산 넙치의 오염 가능성도 있다는 사실을 알 수 있다. This study was designed as a part of efforts to investigate the biochemical pollutant markers for diagnosis of maine pollutions by changes in cholinesterase activity of the flounder (Paralichthys olivaceus)in Yellow Sea of Korea. Acetylcholinesterase (AChE) activities in brain and muscle of cultured flounders in Yellow Sea were remarkably lower (40-50% and 40-55%, respectively)than those of wild flounder in Pohang (control) of East Sea, but AChE activities in brain and muscle of wild flounders in Yellow Sea were significantly lower(15-40% and 25-35%, respectively)than those of wild flounder in Pohang of East Sea. Butyrylcholinesterase(BChE) activities in barin and muscle of cultured flounders in Yellow Sea were remarkably lower(70-75% and 65-75%, respectively) than those of wild flounder in Pohang of East Sea, but BChE activities in barin and muscle of wild flounders in Yellow Sea were significantly lower (15-40%and 25-35%, respectively)than those of wild flounder in Pohang of East Sea. Lactate dehydrogenase (LDH) activities in serum of cultured flounders in Yellow Sea were significantly 10-50% higher than those of wild flounder in Pohang of East Sea, but LDH activities in serum of wild flounders in Yellow Sea were significantly 20-25% higher than those of wild flounder in Pohang of East Sea. It suggests that AChE and BChE activities in brain and muscle of cultured and wild flounders of Yellow Sea may be used as the most effective mean in a biochemical markers for diagnosis of pollutant effects by organophosphorus pesticides.

황련청심음(黃連淸心飮)의 항산화 및 AChE 억제 효과에 관한 연구

김헌일 ( Hun Il Kim ),유종호 ( Jong Ho Kim ),이상택 ( Sang Taek Lee ),한윤승 ( Seung Yun Han ),김근우 ( Geun Woo Kim ),구병수 ( Byung Soo Koo ) 대한한방신경정신과학회 2006 동의신경정신과학회지 Vol.17 No.1

Objective: An water extract of the Hwang-Ryun-Chung-Sim-Um (HRC) was assessed to determine the mechanisms of its antioxidant activity. In addition, the HRC was examined in vitro for the inhibitory effect on the acetylcholinesterse (AChE). Methods: The HRC exhibited a concentration-treatment; scavenging α,α-diphenyl-β-picrylhydrazyl (DPPH) radical, linoleic acid oxidation in a thiocyanate assay system, hydroxyl radical-induced DNA nicking. We investigated mRNA levels such as catalase activity, superoxide-dismutase and glutathione peroxidase. The water extract of HRC showed inhibitory effect on AChE activity. Result: The HRC extract showed dose-dependent free radical scavenging activity, including DPPH radicals and hydroxyl radicals, using different system. The HRC was also found to be effective in protecting plasmid DNA against the strand breakage induced by Hydroxyl radicals in Fenton`s reaction mixture. Futhermore, catalase mRNA expression levels increased, but SOD1 and MnSOD was not expressed. HRC in a various concentration-dependent decreased AChE mRNA levels and inhibitory effect showed AChE. Conclusion: According to the above results, it is supposed that HRC is applicable to the Dementia-type of Alzheimer clinically.

Protective Effect of Physostigmine and Neostigmine against Acute Toxicity of Parathion in Rats

Jun, Jung-Won,Kim, Young-Chul The Pharmaceutical Society of Korea 1991 Archives of Pharmacal Research Vol.14 No.4

The effects of physostigmine and neostigmine on the parathin induced toxicity were examined in adult female rats. Physostigmine $(100\;{\mu}g/kg,\;ip)$ or neostigmine $(200\;{\mu}g/kg,\;ip)$ inhibited acetylcholinesterase (AChE) and cholinesterase (ChE) activities in blood, brain and lung when the enzyme activity was measured 30 min after the treatment. At the doses of two carbamates equipotent on brain AChE, neostigmine showed greater inhibition on peripheral AChE/ChE. The enzyme activity returned to normal in 120 min following the carbamates except in the lung of rats treated with neostigmine. Carbamates administered 30 min prior to parathion (2 mg/kg) antagonized the inhibition of AChE/ChE by parathion when the enzyme activity was measured 2 hr following parathion. Neostigmine showed greater protective effect on peripheral AChE/ChE. The effect of either carbamate on AChE/ChE was not significant 2 hr beyond the parathion treatment. Carbamates decreased the mortality of rats challenged with a lethal dose of parathion (4 mg/kg, ip) either when treated alone or in combination with atropine (10 mg/kg, ip). Lethal action of paraoxon (1.5 mg/ks ip), the active metabolite of parathion was also decreased by the carbamate treatment indicating that the protection was not mediated by competitive inhibition of metabolic conversion of parathion to paraoxon. The results suggest that carbamylation of the active sites may not be the sole underlying mechanism of protection provided by the carbamates.