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1.
Esterase activity hydrolyzing both [1RS,trans]- and [1RS,cis]-permethrin was detected in crude homogenates of the following southern armyworm (Spodoptera eridania Cramer) larval tissues: cuticle, gut, fat body, head capsule, Malpighian tubules, and silk gland. Neither substrate was detectably hydrolyzed by hemolymph. The highest esterase activities per insect equivalent of tissue were found in cuticle, gut, and fat body for the trans isomer and in cuticle and gut for the cis isomer. Each preparation hydrolyzed the trans isomer more rapidly, but the degree of specificity varied greatly between tissues. Differences in apparent Km and Vmax values between the three most active tissues were threefold or less for trans isomer hydrolysis, but differences between tissues of up to 100-fold were found for Km and Vmax values for cis isomer hydrolysis. Hydrolysis of the trans isomer in cuticle, gut, and fat body homogenates was only partially inhibited by α-naphthyl N-propylcarbamate (NPC). Concentrations of NPC giving maximal inhibition of trans isomer hydrolysis had little effect on the hydrolysis of the cis isomer. These results demonstrate that pyrethroid-hydrolyzing activity is broadly distributed in insect tissues and results from the combined activity of several esterases with different properties. It is likely that the trans and cis isomers of permethrin are hydrolyzed by separate enzymes in this insect.  相似文献   

2.
The organophosphorus pesticides profenofos, sulprofos, O-ethyl O-(4-nitrophenyl) phenylphosphonothioate (EPN), and S,S,S,-tributyl phosphorotrithioate (DEF) administered intraperitoneally to mice at 0.5 to 5 mg/kg strongly inhibit the liver microsomal esterase(s) hydrolyzing trans-permethrin. Profenofos, EPN, and DEF at 25 mg/kg increase the intraperitoneal toxicity of fenvalerate > 25-fold and of malathion > 100-fold. Topically applied profenofos, sulprofos, and DEF significantly synergize the toxicity of cis-cypermethrin to cabbage looper larvae and house fly adults but these phosphorus compounds are much less effective in synergizing the toxicity of trans-permethrin. The magnitude of synergism appears to depend on the species, organophosphorus compound, and pyrethroid involved. Profenofos, sulprofos, and EPN do not significantly alter the persistence of trans-permethrin on bean foliage.  相似文献   

3.
Separate esterase activities of rat and mouse liver microsomes hydrolyzing malathion, trans-permethrin, and cis-permethrin were differentiated on the basis of their sensitivities to inhibition by paraoxon and α-naphthyl N-propylcarbamate (NPC). In rat liver microsomes, the malathionhydrolyzing activity was more sensitive to both inhibitors and showed a different time course of NPC inhibition than the activities hydrolyzing the permethrin isomers. Paraoxon completely inhibited trans-permethrin hydrolysis, but only partially inhibited that of cis-permethrin. The paraoxonsensitive trans- and cis-permethrin-hydrolyzing activities were not differentially inhibited, but separate inhibition curves were obtained for the inhibition of trans- and cis-permethrin hydrolysis by NPC. The mouse liver esterase activity hydrolyzing trans-permethrin showed a similar paraoxon sensitivity to that of rat liver, but that the paraoxon-sensitive portion of the cis-permethrinhydrolyzing activity was 5.5-fold less sensitive to paraoxon than the corresponding rat liver activity and was clearly differentiated from the mouse liver trans-permethrin-hydrolyzing activity. The mouse liver malathion-hydrolyzing activity was 100-fold less sensitive to paraoxon and 14-fold less sensitive to NPC than the corresponding rat liver activity. Rat and mouse liver esterase activities hydrolyzed trans- and cis-permethrin at similar rates under standard assay conditions, but mouse liver esterases were 10-fold less active in hydrolyzing malathion. The higher specific activity of rat liver malathion-hydrolyzing esterases resulted from the greater apparent affinity and maximum velocity for malathion hydrolysis. These results demonstrate that the hydrolysis of malathion, trans-permethrin, and cis-permethrin by rat and mouse liver microsomal preparations involves several esterases with differing substrate specificities and inhibitor sensitivities.  相似文献   

4.
The penetration, excretion, and metabolism of topically applied [14C]permethrin and [14C]cypermethrin have been examined in larvae of the porina moth Wiseana cervinata to determine the factors which affect body levels of unchanged pyrethroids. Metabolism was by hydrolysis and to a lesser extent oxidation and the primary metabolites were quickly conjugated to water-soluble products. Little excretion occurred and body levels of unchanged pyrethroids were dependent on the interaction of penetration and metabolism. cis-Cypermethrin was more resistant to metabolism than trans-cypermethrin and cis- and trans-permethrin. trans-Permethrin most readily penetrated into larvae. The body levels of unchanged permethrin were enhanced by pretreatment of larvae with the metabolic inhibitors carbaryl or piperonyl butoxide. Tolerance of the pasture pest porina to the synthetic pyrethroids is discussed in relation to these findings.  相似文献   

5.
The potency of six dietary pyrethroids, as toxicants and inhibitors of weight gain in first- and fourth-instar Tribolium castaneum (Herbst) larvae, decreased in the order of cis-cypermethrin and deltamethrin > trans-cypermethrin and cis-permethrin > fenvalerate and trans-permethrin. Dosages that reduced larval weight also delayed pupation and emergence, probably due to their antifeeding activity. Three oxidase inhibitors (piperonyl butoxide, O, O-diethyl O-phenyl phosphorothioate, and O-isobutyl O-prop-2-ynyl phenylphosphonate), at a dietary concentration of 100 mg kg?1, had little or no effect on the toxicity of trans-permethrin, but strongly synergised the toxicity of cis-cypermethrin by about 3-, 3- and 10-fold, respectively. Piperonyl butoxide also synergised the toxicity of cis-permethrin, trans-cypermethrin and deltamethrin, but not that of fenvalerate. On the other hand, an esterase inhibitor, profenofos, did not enhance the potency of any of the α-cyano-3-phenoxybenzyl pyrethroids. Oxidases appear to be more important than esterases in pyrethroid detoxification by T. castaneum larvae.  相似文献   

6.
Microsomal esterases of mouse and rat liver readily cleave the trans- but not the cis-isomers of resmethrin (5-benzyl-3-furylmethyl chrysanthemate). The ester linkage also appears to undergo oxidative cleavage when esterase attack is minimal, i.e., with (+)-cis- and particularly (?)-cis-resmethrin in microsome-NADPH systems and with any of the isomers when NADPH is added to microsomes pretreated with TEPP. Metabolites retaining the ester linkage are detected in significant amounts only with (+)-cis-resmethrin in which case they are formed by oxidation at either the trans(E)- or cis(Z)-methyl group of the isobutenyl moiety with or without oxidation of the benzylfurylmethyl group. Metabolites of each acid moiety include chrysanthemic acid and up to six derivatives of this acid formed by oxidation at the trans(E)- or cis(Z)-methyl group yielding the corresponding alcohol, aldehyde, or acid, with chrysanthemate isomer and enzyme source variations in the preferred site of oxidation. The major identified metabolite of the alcohol moiety is either benzylfurylmethanol or the corresponding carboxylic acid depending on the enzyme system used. In the course of microsomal oxidation, a fragment from the alcohol but not the acid moiety of (+)-trans- and (+)-cis-resmethrin is strongly bound to microsomal components. These findings confirm in vivo studies on the isomeric variations in metabolism of the resmethrin components.  相似文献   

7.
An esterase which hydrolyzes the ester bond of trans-permethrin has been partially purified from homogenates of larvae of the cattle tick. The final (gel filtration) step showed two distinct peaks of p-nitrophenylbutyrate-hydrolyzing activity. The trans-permethrin-hydrolyzing activity of the lower-molecular-weight enzyme cochromatographed with the p-nitrophenylbutyrate-hydrolyzing activity of that enzyme. Little trans-permethrin hydrolysis was observed in the high-molecular-weight peak. The yield of the low-molecular-weight enzyme increased on extraction of the homogenates with Triton X-100. Inhibition studies using the low-molecular-weight enzyme and trans-permethrin as substrate indicated that hydrolysis was due largely to a carboxylesterase (EC 3.1.1.1).  相似文献   

8.
Strains of Culex quinquefasciatus Say, selected with biopermethrin [(1R)-trans-permethrin] or with (1R)-cis-permethrin, were examined in the larval stage for crossresistance to 30 pyrethroids, DDT, dieldrin, temephos, propoxur, and two organotin compounds. The (1R)-trans-Permethrin-R strain [resistance factor (RF) = 4100-fold] and the (1R)-cis-Permethrin-R strain (RF= 450-fold) of C. quinquefasciutus were cross-resistant to all pyrethroids tested [RF= 12-fold for an allethrin isomer to about 6000-fold for (RS,RS)-fenvalerate] as well as to DDT (RF= about 2000-fold). However, they were not significantly Cross-resistant to dieldrin, temephos, propoxur, and the two organotin compounds. Changes in the alcohol moiety, structural isomerism, and susceptibility of the cyclopropane C-3 side chain to oxidative attack are important factors in determining the level of cross-resistance to various pyrethroids. Limited synergism of the pyrethroids by S,S,S-tributyl phosphorotrithioate and piperonyl butoxide (PB), and of DDT by chlorfenethol and PB, suggested that some non-metabolic mechanism, such as kdr, may be an important component of resistance to pyrethroids as well as to DDT in this mosquito.  相似文献   

9.
Observations suggest that more than one mechanism is responsible for the increased tolerance to permethrin in the larval stage of Lucilia sericata. While the penetration rate of permethrin was much reduced in larvae, they remained more tolerant than adults when this compound was injected. Following the injection of sublethal amounts of [3H]-(1 RS)-trans-permethrin, a substantial proportion of the dose was accumulated and retained in the larval fat body. In adults, less permethrin was absorbed and retained in the tissues. However, compared to the larvae, detoxication was faster, haemoplasm levels were lower, and substantially more breakdown products were excreted. The injection of sublethal amounts of permethrin into the larva led to severe disruption of sensory function. These findings suggest that an important difference may exist between adults and larvae in either the sensitivity of vital sites within the nervous system, or in the sequence of events which follow nervous system disruption and lead to death.  相似文献   

10.
Dieldrin and two of its metabolites, 6,7-trans-dihydroaldrindiol, and 6,7-cis-dihydroaldrindiol, were studied with regard to their toxicity to the American cockroach, effects on ganglia of the ventral nerve cord, and penetration into the ventral nerve cord of poisoned cockroaches. An approximate LD50 for injected doses of dieldrin was 0.45 mg/kg. After injection at 115 mg/kg, the trans isomer of aldrin diol caused about 70%, and the cis isomer about 50% mortality. Injected doses of 40 mg/kg of the three compounds appeared in the ventral nerve cord to the extent of 0.13–0.26% of the doses. Dieldrin was more potent, but slower acting than the diols in causing synaptic after-discharge and elevated spontaneous activity in isolated nerve cords. The results are discussed in relation to other studies on these compounds. It was concluded that, in the American cockroach, dieldrin, rather than either of the diols, is the insecticidal agent in dieldrin poisoning, and that metabolic conversion of dieldrin to the cis and/or trans aldrindiol constitutes a detoxification.  相似文献   

11.
The hydrolysis of trans-permethrin and α-naphthyl acatate by midgut, fat body, and cuticle homogenates from Pseudoplusia includens (Walker) was monitored during the development of the last instar. The midgut homogenates appeared to have two pH optima (7.6 and 8.6) for the hydrolysis of trans-permethrin, the fat body homogenates had one optimum (7.4–7.8), and the cuticle homogenates had a major optimum at 6.6. Hydrolysis of both substrates peaked during the late feeding stages for midgut and cuticle homogenates, although relative changes were not the same. Hydrolysis of trans-permethrin peaked during the late feeding stage in fat body homogenates, while hydrolysis of α-naphthyl acetate continually increased through the prepupal stage. Thus, the hydrolysis of α-naphthyl acetate is not necessarily associated with the hydrolysis of trans-permethrin. The LD50 values for trans-permethrin on the different stages appeared to reflect the influence of hydrolysis.  相似文献   

12.
The action of cis-permethrin, which evinced a strong negative correlation of toxicity with temperature in larvae of the pyrethroid-susceptible Yeerongpilly and pyrethroid-resistant DDT-R and Malchi strains of the cattle tick, was accounted for by a simple binding mechanism. The mechanism assumed that a single pyrethroid molecule binds to a single site and inactivates it, and that the equilibrium constant which describes the ensuing equilibrium between concentrations of free pyrethroid, unoccupied site, and inactivated site then varies with temperature according to the van't Hoff equation. From van't Hoff plots of the data the enthalpies of binding of cis-permethrin to sites in larvae of each of the above strains were calculated to be ?87, ?92, and ?102 kJ mol?1, respectively. It was concluded from these results that the kdr-type insensitivity (≈6×, in terms of resistance) observed in DDT-R and Malchi ticks could not be explained by altered binding sites at the site of action. It was suggested that the insensitivity might be explained by altered access to the site of action.  相似文献   

13.
The nature of target site or knockdown resistance (kdr) to DDT and pyrethroids was studied by investigating specific binding of [14C] DDT and [14C] cis-permethrin to the previously established membrane receptors from the heads of susceptible (sbo) and resistant (kdr) strains of the house fly, Musca domestica L. In vivo studies showed the heads from sbo flies bound two to three times more DDT than those from kdr flies at all doses tested. Reduced binding was also observed in kdr flies in in vitro [14C] DDT binding assays. Scatchard analysis indicated that kdr flies have the same affinity but fewer receptors per milligram protein in the CNS than sbo flies. Assays with [14C] cis-permethrin also showed binding was much reduced in kdr flies in comparison with sbo flies. Based on these results, the nature of the target site insensitivity of kdr flies may relate to their having a reduced number of receptors for the insecticides.  相似文献   

14.
Adult Rana pipiens pipiens (Shreber) are highly sensitive to insecticidal α-cyano-3-phenoxybenzyl esters administered subcutaneously, i.e., LD50 0.13–0.35 mg/kg for deltamethrin and the most potent isomer of each of cis-cypermethrin, fenpropathrin, and fenvalerate and 0.65 mg/kg for (1R,αS)-trans-cypermethrin. Pyrethroids lacking the α-cyano substituent [pyrethrins, S-bioallethrin, kadethrin, and the Cis- and trans-isomers of (1R)-tetramethrin, (1RS)-resmethrin, (1R)-phenothrin, and (1R)-permethrin] vary greatly in their toxicity (LD50 0.14 to > 60 mg/kg) and the trans isomers are much less toxic than the corresponding cis isomers. The trans/cis specificity is due in large part to relative detoxification rates based on synergism studies with the resmethrin and permèthrin isomers and liver pyrethroid esterase assays with the permethrin and cypermethrin isomers. Poisoning by the noncyano compounds involves hyperactivity and tremors whereas by the cyanophenoxybenzyl esters involves tonic seizures and choreoathetosis, i.e., types I and II syndromes, respectively. Picrotoxinin, t-butylbicyclophosphate, and five other small cage compounds give a third type of syndrome with clonic seizures. Diazepam and its 2′-fluoro-4-methyl-4,5-dihydro analog (RO 5-3636) are more effective than 23 other compounds tested in protecting against deltamethrin toxicity. Diazepam is most effective in alleviating the Type II syndrome, intermediate with the type I syndrome, and is not active with picrotoxinin.  相似文献   

15.
Considering a potential application of selected biochemically activated insect hormonogen substances (juvenogens) against pest termite species, we aimed this study to describe the metabolism of these compounds by termites and soil bacteria and to evaluate the potential impact of their metabolites on the environment. Radiolabelled derivatives of the juvenogens cis- and trans-isomers of ethyl N-{2-[4-(2-butanoyloxycyclohexyl)methyl]phenoxy}ethyl carbamate were metabolized by the termite Reticulitermes flavipes and the bacteria Bacillus simplex and Bacillus sp., strain 05 (GenBank EU399813) giving rise to different numbers of metabolites. The trans-isomer of the juvenogen was metabolized by both Bacillus species into its parent synthetic structure, ethyl trans-N-{2-[4-(2-hydroxycyclohexyl)methyl]phenoxy}ethyl carbamate, while the cis-isomer was metabolized into further products. Both racemic juvenogens were metabolized bytermites, affording mainly the parent juvenoids. In terms of ecotoxicity, the trans-juvenogen shows a significantly lower toxicity than the cis-juvenogen. In contrast, the toxicity of the cis-juvenoid (main degradation product of cis-juvenogen) is higher than the toxicity of trans-juvenoid (main degradation product of trans- juvenogen). The precursors of the two juvenogens cis- and trans-2-(4-hydroxybenzyl)cyclohexanol were also tested but exhibited a low toxicity. The results demonstrate that bacteria can metabolize the juvenogen in liquid media culture and have implications for the development of a strategy for bioremediation of soil. Moreover, the products of the biodegradation exhibited low toxicity. Both juvenogens have a high juvenilizing effect, cause low mortality and are stable within a period of two weeks.  相似文献   

16.
Preseizure and seizure EEG patterns elicited by the pyrethroid insecticides, deltamethrin and cis-permethrin, were compared in immobilized Sprague-Dawley rats. Deltamethrin (1–3 mg/kg, iv) produced a preseizure EEG pattern of high-amplitude, slow, 2- to 5-Hz synchronized cortical waves or spike-wave complexes. cis-Permethrin (20–40 mg/kg, iv) elicited an immediate EEG change characterized by 6- to 12-Hz high-amplitude waves with intermingled high-voltage spikes. DDT (50–70 mg/kg, iv) produced a sustained EEG activation similar to that seen after cis-permethrin, but of higher frequency. All three insecticides produced generalized EEG seizure activity, but this was more prominently associated with poisoning due to deltamethrin. cis-Permethrin and DDT gave rise to EEG seizures only at lethal doses. Electrodes stereotaxically positioned in ventral hippocampus, caudate, putamen, thalamus, septum, red nucleus, and cerebellum detected no preferential activation of any of these subcortical sites in either preconvulsive or convulsive phases of poisoning. These results indicate that both deltamethrin and cis-permethrin can have marked effects on mammalian EEG activity. This does not support the hypothesis of differing sites of action, i.e., peripheral vs. central, for the two types of compound. The more pronounced seizure-inducing action of deltamethrin may instead reflect a greater efficacy of cyanopyrethroids at target sites within the central nervous system.  相似文献   

17.
The metabolism of the pyrethroid insecticide cypermethrin has been studied in rats using three forms of 14C-labelling (benzyl-, cyclopropyl- and cyano-) and separate cis- and trans- isomers. The proportion of the dose absorbed from the intestines (50–70% at 2–3 mg kg?1) is rapidly metabolised and eliminated. The major reaction is cleavage of the ester bond to afford the constituent cis- and trans- acids which are conjugated with glucuronic acid and eliminated in the urine. The 3-phenoxybenzyl portion of the molecule is probably released as the α-hydroxynitrile, which is converted via the aldehyde into 3-phenoxybenzoic acid. This compound is then largely hydroxylated and eliminated as a sulphate conjugate. The cyanide ion is metabolised via predictable routes, for instance, as thiocyanate. Cypermethrin is hydroxylated to some extent before hydrolysis. Most of this hydroxylation occurs at the methyl group trans to the cyclopropane carboxyl group, and at the 4-position of the phenoxy group. cis- Cypermethrin is slightly more stable than the trans-isomer.  相似文献   

18.
The in vivo metabolism of phenthoate (O,O-dimethyl S-[α-(carboethoxy)benzyl]phosphorodithioate) was followed in rats after oral administration of a nontoxic dose of 100 mg/kg. The same metabolic study was conducted following coadministration of 0.5% O,S,S-trimethyl phosphorodithioate (OSS-Me). When administered alone, phenthoate was metabolized principally by carboethoxy ester hydrolysis and cleavage of the PO and CS bonds, resulting in at least six metabolites. The primary urinary metabolite excreted was phenthoate acid. Coadministration of 0.5% OSS-Me did not alter the types of metabolites excreted. However, a reduction of the carboxylesterase-catalyzed product (phenthoate acid) was observed, indicating that the enzyme responsible for the major pathway of phenthoate detoxication was inhibited. Alternate detoxication processes did not compensate for the reduction in carboxylesterase-catalyzed detoxication. It was concluded that inhibition of the carboxylesterase enzymes is the major cause of the potentiation of phenthoate toxicity by OSS-Me.  相似文献   

19.
Metabolism in mice of the separated cis- and trans-isomers of the pyrethroid insecticide cypermethrin (NRDC 149), (RS)-α-cyano-3-phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate, was investigated in each case with preparations that were 14C-labelled in the benzyl and cyclopropyl moieties. Radioactivity from the trans-isomer was mainly excreted in the urine and that from the cis-isomer in the faeces. Elimination of both isomers was rapid except for a small portion (approximately 2%) of the cis-isomer which was released from the fat with a half-life of approximately 13 days. Metabolism of cypermethrin occurred mainly by ester cleavage and elimination of the cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl- cyclopropanecarboxylic acid moieties as glucuronide conjugates. The α-cyano-3-phenoxybenzyl alcohol released by ester cleavage was mainly converted to 3-phenoxy-benzoic acid which was partly eliminated unchanged, partly conjugated with aminoacids (mainly taurine) and glucuronic acid, and partly oxidised to 3-(4-hydroxyphenoxy) benzoic acid which was excreted as the sulphate conjugate. Metabolites retaining the ester linkage were formed by hydroxylation at various sites in the molecule with more hydroxylation of the cis- than of the trans-isomer occurring.  相似文献   

20.
Pyrethroids are divided into two classes (Types I and II) based on their effects on the cercal sensory nerves recorded in vivo and in vitro and on the symptomology they produce in dosed cockroaches, Periplaneta americana. Type I compounds include pyrethrins, S-bioallethrin, [1R,cis]resmethrin, kadethrin, the 1R,trans and 1R,cis isomers of tetramethrin, phenothrin, and permethrin, and an oxime O-phenoxybenzyl ether. Electrophysiological recordings from dosed individuals reveal trains of cercal sensory spikes and sometimes also spike trains from the cercal motor nerves and in the CNS. Low concentrations of these pyrethroids act in vitro to induce repetitive firing in a cercal sensory nerve following a single electrical stimulus. This in vitro measurement, standardized for evaluating structure-activity relationships, shows that only 1R, insecticidal isomers are highly effective neurotoxins. The most potent compounds on the isolated nerve are [1R,trans]- and [1R,cis]tetramethrin, each active at 3 × 10?13M. The poisoning symptoms of Type I compounds are restlessness, incoordination, hyperactivity, prostration, and paralysis. Type II compounds include [1R,cis,αS]- and [1R,trans,αS]cypermethrin, deltamethrin, and [S,S]fenvalerate. These α-cyanophenoxybenzyl pyrethroids do not induce repetitive firing in the cercal sensory nerves either in vivo or in vitro; moreover, they cause different symptoms, including a pronounced convulsive phase. Two other pyrethroids with an α-cyano substituent, i.e., fenpropathrin and an oxime O-α-cyanophenoxybenzyl ether, are classified as Type I based on their action on a cercal sensory nerve but the symptoms with these compounds resemble Type II. The two classes of pyrethroid action evident with the cockroach are discussed relative to their neurophysiological effects and symptomology in other organisms.  相似文献   

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