Etoxazole is Metabolized Enantioselectively in Liver Microsomes of Rat and Human in Vitro

Evaluation of Chiral Pesticide Chlorbufam at the Enantiomeric Level: Absolute Configuration, Separation, Herbicidal Activity, and Degradation in Soil

Chlorbufam is a photosynthesis inhibitor chiral herbicide with a pair of enantiomers, which is rarely a concern. In this work, the optically pure enantiomers of chlorbufam were first synthesized and characterized, and the enantioselective herbicidal activity and mechanism were studied. Chlorbufam enantiomers showed significant differences in bioactivity against Echinochloa crus-galli and Abutilon theophrasti, and R-(+)-chlorbufam was identified as the most active against the targeted organisms with higher bioactivity of 3.95 and 1.71 times than S-(-)-chlorbufam. Chlorbufam enantiomers exerted herbicidal activity by inhibiting photosynthesis according to the results of the determination of photosynthetic pigment contents and molecular docking. Additionally, a novel HPLC-MS/MS method was successfully developed and validated for the detection of chlorbufam enantiomers and further applied for the enantioselective degradation study in soil. As a result, chlorbufam was satisfactory enantioseparated with a resolution of 2.37 on a Chiralpak IH column using the mobile phase of acetonitrile and water (60:40, v/v). Good linearity for chlorbufam enantiomers was obtained with correlation coefficients ≥0.9990, and the recovery ranged from 74.1 to 119% with relative standard deviations ≤10.9% at three spiked levels. The degradation behaviors of chlorbufam enantiomers were significantly different, and S-(-)-chlorbufam was preferentially degraded. The findings encouraged the application of enantiopure R-(+)-chlorbufam herbicide to reduce dosage rates, decrease environmental risks, and protect human health.

Enantioselective Assessment of Etoxazole Enantiomers in Earthworms (Eisenia fetida): Bioaccumulation, Degradation, Transcriptome, and Oxidative Stress

This study systemically investigated the enantioselective bioaccumulation and degradation of etoxazole (ETZ) in earthworms along with the transcriptome and oxidative stress responses to ETZ enantiomer exposure. Based on the M-shaped bioaccumulation trends for ETZ enantiomers, R-ETZ was found to be preferentially bioaccumulated in earthworms. Sublethal toxicity analysis showed that S-ETZ induced greater changes in protein content, malondialdehyde content, detoxifying metabolic enzyme activity, and oxidative stress in earthworms, compared to those induced by R-ETZ. Integrated biomarker response analysis suggested that S-ETZ induced higher sublethal toxicity in earthworms than R-ETZ. Finally, transcriptomic analysis indicated that 845 and 314 genes were differentially expressed after R-ETZ and S-ETZ exposure, respectively, when compared to the nonexposed control group. Enrichment analysis indicated that these differentially expressed genes were primarily enriched in the digestion and absorption of proteins, lysosome, peroxisome, and peroxisome proliferator-activated receptor signaling pathways. These results suggest that earthworms exhibit distinct enantioselective responses to S-ETZ and R-ETZ. This study elucidates the enantioselective bioaccumulation, degradation, transcriptome, and oxidative stress characteristics of ETZ enantiomers in earthworms at the enantiomer level, offering a theoretical foundation to improve the risk assessment of ETZ in the soil-earthworm microsomes.

Some evidence supporting the use of optically pure R-(-)-diniconazole: Toxicokinetics and configuration conversion on chiral diniconazole

Diniconazole is a chiral pesticide that exists in two enantiomers, R-(-)-diniconazole and S-(+)-diniconazole, with the R-enantiomer being much more active than the S-enantiomer. Previous enantioselective toxicology studies of diniconazole focused mostly on simple environmental model organisms. In this study, we evaluated the toxicokinetics of the two diniconazole enantiomers in rats and mice to provide a more comprehensive risk assessment. The two enantiomers displayed clear differences in their stereoselective contents in vivo. The t1/2 of R-(-)-diniconazole was 7.06 ± 3.35 h, whereas that of S-(+)-diniconazole was 9.14 ± 4.60 h, indicating that R-(-)-diniconazole was eliminated faster in vivo. The excretion rates of R-(-)-diniconazole and S-(+)-diniconazole were 4.08 ± 0.50 % and 2.68 ± 0.58 %, respectively, indicating more excretion of R-(-)-diniconazole. S-(+)-diniconazole had a higher bioavailability than R-(-)-diniconazole (52.19 % vs. 42.44 %). S-(+)-Diniconazole was also found in relatively high abundance in tissues such as the stomach, large intestine, small intestine, cecum, liver, kidney, brain, and testes, with the abundance being 1.71-2.48-fold that of R-(-)-diniconazole. The selective degradation of both enantiomers in the tissues and their mutual conversion in vivo were not observed, and this could indicate that configuration conversion did not contribute to the differences in the content of enantiomers in the tissues. Instead, such differences were mainly caused by the differences in affinity of each enantiomer for the tissues. Furthermore, investigation of the interconversion between optically pure R-(-)-diniconazole and S-(+)-diniconazole monomers in soil revealed no interconversion. All of the above results indicated no interconversion between R-(-)-diniconazole and S-(+)-diniconazole in vivo and in the soil, and that S-(+)-diniconazole tends to have a greater potential to accumulate in vivo. Thus, if only R-(-)-diniconazole is used as a pesticide, the negative impact on mammals and the environment will be reduced, suggesting that in agriculture, the application of optically pure R-(-)-diniconazole may be a better strategy.

Systematic Stereoselectivity Evaluations of Tetramethrin Enantiomers: Stereoselective Cytotoxicity, Metabolism, and Environmental Fate in Earthworms, Soils, Vegetables, and Fruits

Tetramethrin is a widely applied type I chiral pyrethroid insecticide that exists as a mixture of four isomers. In the present study, its stereoselective cytotoxicity, bioaccumulation, degradation, and metabolism were investigated for the first time at the enantiomeric level in detail by using a sensitive chiral high-performance liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS) method. Results showed that among rac-tetramethrin and its four enantiomers, the trans (+)-1R,3R-tetramethrin had the strongest inhibition effect on the PC12 cells. In the earthworm exposure trial, the concentration of trans (-)-1S,3S-tetramethrin was 0.94-8.92 times in earthworms (cultivated in natural soil) and 1.67-5.01 times (cultivated in artificial soil) higher than trans (+)-1R,3R-tetramethrin, respectively. In the greenhouse experiment, the trans (+)-1R,3R-tetramethrin and cis (+)-1R,3S-tetramethrin were preferentially degraded. Furthermore, for rat liver microsome in vitro incubation, the maximum metabolism rate of cis (-)-1S,3R-tetramethrin was 1.50 times higher than its antipodes. Altogether, the aim of this study was to provide a scientific and reasonable reference for the possibility of developing a single enantiomer to replace the application of rac-tetramethrin, which could possess better bioactivity and lower ecotoxicity, and thus permit more reliable and accurate environmental monitoring and risk assessment.

Advances in the study of liver microsomes in the in vitro metabolism and toxicity evaluation of foodborne contaminants

Foodborne contaminants are closely related to anthropologic activities and represent an important food safety hazard. The study of metabolic transformation and toxic side effects of foodborne contaminants in the body is important for their safety assessment. Liver microsomes contain a variety of enzymes related to substance metabolism and biotransformation. An in vitro model simulating liver metabolic transformation is associated with a significant advantage in the study of the metabolic transformation mechanisms of contaminants. This review summarizes the recent progress in the application of liver microsomes in metabolic transformation and toxicity evaluation of various foodborne pollutants based on metabolic kinetics, molecular docking and enzyme inhibition studies. The purpose of this review is to distinguish the existing studies involving liver microsomes and provide strategies for their application in the future. Finally, the prospects and challenges of the liver microsomal model are discussed.

Kinetic Characteristics of Curcumin and Germacrone in Rat and Human Liver Microsomes: Involvement of CYP Enzymes

Curcumin and germacrone, natural products present in the Zingiberaceae family of plants, have several biological properties. Among these properties, the anti-NSCLC cancer action is noteworthy. In this paper, kinetics of the two compounds in rat liver microsomes (RLMs), human liver microsomes (HLMs), and cytochrome P450 (CYP) enzymes (CYP3A4, 1A2, 2E1, and 2C19) in an NADPH-generating system in vitro were evaluated by UP-HPLC–MS/MS (ultrahigh-pressure liquid chromatography–tandem mass spectrometry). The contents of four cytochrome P450 (CYP) enzymes, adjusting by the compounds were detected using Western blotting in vitro and in vivo. The t1/2 of curcumin was 22.35 min in RLMs and 173.28 min in HLMs, while 18.02 and 16.37 min were gained for germacrone. The Vmax of curcumin in RLMs was about 4-fold in HLMs, meanwhile, the Vmax of germacrone in RLMs was similar to that of HLMs. The single enzyme t1/2 of curcumin was 38.51 min in CYP3A4, 301.4 min in 1A2, 69.31 min in 2E1, 63.01 min in 2C19; besides, as to the same enzymes, t1/2 of germacrone was 36.48 min, 86.64 min, 69.31 min, and 57.76 min. The dynamic curves were obtained by reasonable experimental design and the metabolism of curcumin and germacrone were selected in RLMs/HLMs. The selectivities in the two liver microsomes differed in degradation performance. These results meant that we should pay more attention to drugs in clinical medication–drug and drug–enzyme interactions.

Herbicidal activity and differential metabolism of lactofen in rat and loach on an enantiomeric level

Enantioselectivity of chiral compounds is receiving growing concern. Lactofen, a chiral herbicide widely used in field crops and vegetables to control broadleaf weeds, is still sold as racemate. In this work, the herbicidal activity and metabolism behavior of lactofen were investigated on an enantiomeric level. Two common broadleaf weeds (Eclipta prostrata L. and Portulaca oleracea L.) were used to evaluate the herbicidal activity of rac-/R- and S-lactofen, and their metabolism behavior in loach and rat liver microsomes was explored. Higher herbicidal activity of S-lactofen was observed, with the 20d-EC₅₀ values being 1.9-3.4 times lower than R-lactofen. Both loach and rat liver microsomes had ability to metabolize rac-lactofen, with half-lives of 1.93 and 1.28 h, respectively. Enantioselective metabolism behaviors were observed in loach and rat liver microsomes and the direction of enantioselectivity were different. R-lactofen was preferentially metabolized in loach liver microsome, while S-lactofen was preferentially metabolized in rat liver microsome. No interconversion of R- and S-lactofen was found. Besides, the main metabolic pathways of R- and S-lactofen were found to be significantly different. R-lactofen was metabolized to R-desethyl lactofen in both loach and rat liver microsomes without further metabolism. However, S-lactofen was metabolized to both S-desethyl lactofen and acifluorfene in rat liver microsome, which was mainly metabolized to acifluorfene in loach liver microsome. This study indicated enantioselectivity and metabolites should be taken into consideration when overall evaluating the environmental behavior of lactofen.

Low-dose cadmium affects the enantioselective bioaccumulation and dissipation of chiral penflufen in zebrafish (Danio rerio)

Pesticides are currently extensively used in agriculture, forestry, animal husbandry, and environmental hygiene, and their residues have become a global environmental problem, which can easily form combined pollution with heavy metals. The present study examined the effects of chronic (28 days) aqueous exposure of chiral penflufen (rac-penflufen, R-(-)-penflufen and S-(+)-penflufen), a widely used fungicide, with/without cadmium (Cd), a highly toxic heavy metal in zebrafish (Danio rerio). After rac-penflufen individual or combined exposure with Cd, the bioaccumulation and residual levels of S-(+)-penflufen were significantly higher than R-(-)-penflufen, and the effects of Cd were insignificantly. But for penflufen enantiomer, the effects of Cd were more serious for R-(-)-penflufen, which could increase the bioaccumulation (up to1.73 times), inhibit the dissipation (up to 32.3%) and enhance the residue (up to 5.35 times) of R-(-)-penflufen in zebrafish, decreasing the enantioselectivity. However, significant increase of S-(+)-penflufen concentrations was only found in viscera under co-exposure of Cd. The tissue distribution of penflufen enantiomers were not affected by the presence of Cd, and no interconversion of the two enantiomers occurred regardless of the presence of Cd. These findings indicated that co-contamination with Cd could increase the persistence of R-(-)-penflufen in zebrafish, thus increasing the environmental risks. The significant differences of Cd effects on chiral pesticide enantiomer and racemate indicated that the combined pollution of heavy metal and chiral pesticide might have enantiomer-specific, which should raise concern, and the enantioselective mechanism deserve further study.

Stereochemistry of chiral pesticide uniconazole and enantioselective metabolism in rat liver microsomes

In this work, stereochemistry of uniconazole enantiomers and their metabolism behaviors in rat liver microsomes have been researched. Significance analysis has been applied in data processing. Absolute configurations of uniconazole enantiomers were identified through vibrational circular dichroism spectroscopy. According to their elution order from the chiral column using the CO₂-methanol (80:20, v/v) mixture, two eluted fractions were determined to be (R)-uniconazole and (S)-uniconazole, respectively. A high-efficient and sensitive LC-MS/MS chiral analysis method was established for investigating the metabolism of uniconazole enantiomers in rat liver microsomes. The metabolic half-life of (R)-uniconazole (38.7 min) in rat liver microsomes was half that of (S)-enantiomer (74.5 min), and maximum velocity of metabolism, Michaelis constant of metabolism as well as the intrinsic metabolic clearance of (R)-uniconazole were significantly higher than (S)-enantiomer (p < 0.05), which indicated that (R)-uniconazole was preferentially metabolized in rat liver microsomes. By the virtue of molecular docking, (R)-uniconazole exhibited a higher binding affinity to cytochrome CYP2D2 than (S)-enantiomer, which corroborated well with the metabolism results. This work will shed light on the risk assessment of uniconazole toward human health and the ecological environment.

Enantioselective metabolism of phenylpyrazole insecticides by rat liver microsomal CYP3A1, CYP2E1 and CYP2D2

The stereoselective difference of chiral pesticide enantiomers is an important factor of risk evaluation and the subject has received wide attention. In the present work, enantioselective metabolism of chiral phenylpyrazole insecticides including fipronil, ethiprole and flufiprole in rat liver microsomes was investigated in vitro. The result showed remarkable enantioselectivity for fipronil and ethiprole with the EF values of 0.11-0.58. The metabolite fipronil-sulfone was formed with the degradation of fipronil. R-Ethiprole to S-ethiprole transformation was observed, but not S-ethiprole to R-ethiprole. No enantioselective metabolism was observed for flufiprole with the EF values of 0.49-0.51. The enzymatic assays showed that the inhibition ratio of R-fipronil and S-ethiprole was 1.5-2.1times that of the corresponding enantiomers on CYP2E1 and CYP2D2 activity, leading to the enantioselective metabolism. The result of the homology modeling and molecular docking further revealed that S-fipronil (-7.56 kcal mol^-1) and R-ethiprole (-6.45 kcal mol^-1) performed better binding with CYP2E1 and CYP2D2, respectively. The results provided useful data for the risk evaluation of chiral phenylpyrazole insecticides on ecological safety and human health.

Stereoselective in vitro metabolism of cyproconazole in rat liver microsomes and identification of major metabolites

The vast usage of agrochemicals enhances food security globally but may pose challenge to understand the risk assessment to non-target organisms and human beings, and liver microsomes are responsible for metabolism of these agrochemicals in vivo. In this study, stereoselective metabolism of chiral triazole fungicide cyproconazole in rat liver microsomes has been investigated through chiral LC-MS/MS technique. The half-lives of four cyproconazole stereoisomers were different ranging from 95 to 187 min, and (2S, 3R)-cyproconazole preferentially metabolized in rat liver microsomes. In addition, the results from metabolism kinetic study indicated that rat liver microsomes showed the stronger potency to deplete (2S, 3R)-cyproconazole than the others. Then, homology modeling and molecular docking results revealed that the docking energy between (2S, 3R)-cyproconazole and the cytochrome P450 CYP3A1 (-7.46 kcal⋅mol^-1) was higher than the others, meaning that (2S, 3R)-cyproconazole exhibited the strongest binding ability to this enzyme. Moreover, two main metabolites of cyproconazole coming from hydroxylation and dehydration were observed, and possible metabolic reactions of cyproconazole in rat liver microsomes were identified through using an LCQ ion trap mass spectrometer. This kind of systematic metabolic investigation of cyproconazole at chiral level would provide valuable information for ecological and human health risk assessment of chiral pesticides.

Etoxazole induces testicular malfunction in mice by dysregulating mitochondrial function and calcium homeostasis

Epidemiological relationships between pesticide use and male infertility have been suggested for a long time. Etoxazole (ETX), an oxazoline pesticide, has been extensively used for pest eradication. It is considered relatively safe and has low mammalian toxicity because it specifically inhibits chitin synthesis. However, ETX may have toxic effects on the reproductive system. In this study, we examined the effects of ETX on the reproductive system using mouse testis cell lines (TM3 for Leydig cells and TM4 for Sertoli cells) and C57BL/6 male mice. We confirmed that ETX has anti-proliferative effects on the TM3 and TM4 cell lines. Moreover, ETX induced mitochondrial dysfunction and hampers calcium homeostasis. Western blot analysis of MAPK and Akt signaling cascades was performed to demonstrate the mode of action of ETX at a molecular level. Moreover, ETX induced misregulation of genes related to testicular function. Upon oral administration of ETX in C57BL/6 male mice, testis weight was reduced and transcriptional expression related to testis function was altered. These results indicate that ETX induces testicular toxicity by inducing mitochondrial dysfunction and calcium imbalance and regulating gene expression.

Chiral Separation and Determination of Etoxazole Enantiomers in Vegetables by Normal-Phase and Reverse-Phase High Performance Liquid Chromatography

The chiral separation of etoxazole enantiomers on Lux Cellulose-1, Lux Cellulose-3, Chiralpak IC, and Chiralpak AD chiral columns was carefully investigated by normal-phase high performance liquid chromatography and reverse-phase high performance liquid chromatography (HPLC). Hexane/isopropanol, hexane/n-butanol, methanol/water, and acetonitrile/water were used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase component, mobile phase ratio, and temperature on etoxazole separation were also studied. Etoxazole enantiomers were baseline separated on Lux Cellulose-1, Chiralpak IC, and Chiralpak AD chiral columns, and partially separated on Lux Cellulose-3 chiral column under normal-phase HPLC. However, the complete separation on Lux Cellulose-1, Chiralpak IC, and partial separation on Chiralpak AD were obtained under reverse-phase HPLC. Normal-phase HPLC presented better resolution for etoxazole enantiomers than reverse-phase HPLC. Thermodynamic parameters, including ΔH and ΔS, were also calculated based on column temperature changes from 10 °C to 40 °C, and the maximum resolutions (Rs) were not always acquired at the lowest temperature. Furthermore, the optimized method was successfully applied to determine etoxazole enantiomers in cucumber, cabbage, tomato, and soil. The results of chiral separation efficiency of etoxazole enantiomers under normal-phase and reverse-phase HPLC were compared, and contribute to the comprehensive environmental risk assessment of etoxazole at the enantiomer level.

Toxicity risk assessment of pyriproxyfen and metabolites in the rat liver: A vitro study

Pyriproxyfen (PYR) is a type of aromatic juvenile hormone analog and a hygienic insecticide used in agriculture to control insect species. Therefore, assessing the metabolic behavior and toxic effects of PYR in mammals is the best means of evaluating its risks to human health. Previous studies have reported conflicting results regarding the toxicity risks of PYR and its metabolites in rat hepatocytes. We used ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to perform a chiral analysis of PYR and its metabolites investigating the enantioselective metabolism of PYR in rat liver microsomes. Our results concluded that the recoveries of PYR, metabolites A and B ranged from 81.13%-111.54 %, with RSD values of 0.01 %-6.52 %. The method limits of detection (LODs) and limits of quantification (LOQs) for PYR, metabolites A and B were in accordance with the analysis requirements. Previous studies have demonstrated the enantioselective metabolism of PYR and the generation of metabolites. Measurements of cell proliferation toxicity to rat hepatocytes, apoptosis and DNA damage induced by PYR and its metabolites in rat hepatocytes indicated that the metabolites reflected higher toxicity potential than PYR in rat hepatocytes. More studies about the molecular mechanism of PYR-induced toxicity are urgently needed in future work.

Etoxazole stereoselective determination, bioaccumulation, and resulting oxidative stress in Danio rerio (zebrafish)

An environmentally-friendly and fast analytical method for the stereoselective determination of etoxazole was developed and then applied to estimate stereoselective bioaccumulation and elimination in zebrafish using SFC-MS/MS. Optimal enantioseparation conditions were determined using a Chiralpak IG-3 column and CO₂/MeOH mobile phase (80/20, v/v), at 3.0 mL/min within 1 min, 30°Me and 18 MPa. A modified QuEChERS method was developed for zebrafish sample pretreatment, and mean recoveries were 88.43-110.12% with relative standard deviations ranging from 0.32 to 5.34%. The enantioselectives of etoxazole enantiomers in zebrafish during uptake and depuration phases were evaluated. Significant enantioselective bioaccumulation was observed, with preferential accumulation of (-)-R-etoxazole compared to its antipode, during uptake at both low and high exposure concentrations. The toxic effects of etoxazole on zebrafish were further explored, and activities of antioxidant enzymes were determined in liver of zebrafish. Significant changes were observed in the SOD and GST activities and in the MDA levels, which indicated the occurrence of oxidative stress in liver of zebrafish. The toxic effects exhibited time- and dose-dependent properties. These results can facilitate the accurate risk evaluation of etoxazole and provide basic knowledge for further study of biotoxicity mechanisms.

Enantioselective metabolism of four chiral triazole fungicides in rat liver microsomes

Triazole fungicides with one or two chiral centers are widely used worldwide. The liver microsomes plays a major role in the metabolism and systemic elimination of chiral pesticides after exposure. In this present work, enantioselective metabolism of four representative chiral triazole fungicides (prothioconazole, flutriafol, triticonazole, and epoxiconazole) in rat liver microsomes (RLM) was investigated using LC-MS/MS. Baseline separation of the four chiral fungicides and prothioconazole-desthio was achieved on Lux-cellulose-1. The results demonstrated that the R-enantiomers of flutriafol and triticonazole were preferentially metabolized with half-life ranged from 17.33 min to 99.00 min. The R,S-epoxiconazole accumulated with a half-life of 173.25 min. There was no stereoselectivity for prothioconazole. However, remarkable stereoselective metabolism was observed for prothioconazole-desthio. The results of enzyme kinetic revealed different affinities between the enantiomers and metabolic enzymes. In addition, homologous modeling and molecular docking results indicated that enantioselectivity were partially to enantiospecific binding affinities with CYP enzymes. This study highlights a new quantitative approach for stereoselective metabolism of chiral agrochemicals and provides more accurate data on risk assessment of triazole fungicides.

Stereoselective environmental behavior and biological effect of the chiral organophosphorus insecticide isofenphos‑methyl

The enantiomeric environmental behaviors, bioactivities and toxicities of isofenphos‑methyl enantiomers were characterized systematically in this study. (R)‑Isofenphos‑methyl was degraded preferentially in Yangtze River water and different types of vegetables with an enantiomeric fraction (EF) of 0.6 to 0.96. However, (R)‑isofenphos‑methyl was amplified in both Nanjing (EF = 0.32) and Nanchang (EF = 0.27) soil. Our investigations found that there no bidirectional chiral inversion occurred in either Yangtze River water or soils. The bioactivity of (S)‑isofenphos‑methyl was higher than that of its (R)‑enantiomer against different insect targets, such as Meloidogyne incognita, Nilaparvata lugens, Plutella xylostella and Macrosiphum pisi (3.7 to 149 times). (S)‑Isofenphos‑methyl showed higher toxicity for the nontarget organism (1.1 to 32 times). However, (R)‑isofenphos‑methyl possesses 4.0 times more potency than the (S)-form for the nontarget soil organism Eisenia foetida. This study generally could provide more scientific guidance for the corresponding risk assessments of pesticides in addition to providing a new theoretical basis for scientifically and rationally using isofenphos‑methyl.

Investigations on the effects of etoxazole in the liver and kidney of Wistar rats

Pesticides are used to protect crops and to eliminate pests, though non-target organisms such as mammals are also affected from their usage. Etoxazole (organoflourine pesticide) is an acaricide used to combat spider mites which are the parasites of various crops. The present study aims to investigate the effects of etoxazole on the level of MDA (malondialdehyde) and activities of CAT (catalase), GPx (glutathione peroxidase), and AChE (acetylcholinesterase) in liver and kidney tissues of Wistar rats (Rattus norvegicus var. albinos). Rats received etoxazole intraperitoneally with doses of 2.2, 11, and 22 mg/kg b.w./day for 21 days. Control rats received the same volume of the serum physiologic. Following etoxazole exposures, activities of CAT, GPx, and AChE in the liver and kidney of rats significantly decreased at all doses compared to control group. Oppositely, MDA levels in these tissues increased significantly at all doses following etoxazole exposures. The present study demonstrated that etoxazole, at all doses, had toxic effects in the liver and kidney parameters, suggesting their possible use as effective biomarkers in determining the toxic effects of etoxazole. This may suggest that these biomarkers could also be used as a tool to monitor pesticide-affected areas before severe toxic effects begin in non-target animals and humans.