In vitro and in vivo effects of some pesticides on carbonic anhydrase enzyme from rainbow trout (Oncorhynchus mykiss) gills

Here we investigated the in vitro and in vivo effects of the pesticides, deltamethrin, diazinon, propoxur and cypermethrin, on the activity of rainbow trout (rt) gill carbonic anhydrase (CA). The enzyme was purified from rainbow trout gills using Sepharose 4B-aniline-sulfanilamide affinity chromatography method. The overall purification was approx. 214-fold. SDS-polyacrylamide gel electrophoresis showed a single band corresponding to a molecular weight of approx. 29 kDa. The four pesticides dose-dependently inhibited in vitro CA activity. IC₅₀ values for deltamethrin, diazinon, propoxur and cypermethrin were 0.137, 0.267, 0.420 and 0.460 μM, respectively. In vitro results showed that pesticides inhibit rtCA activity with rank order of deltamethrin > diazinon > propoxur > cypermethrin. Besides, in vivo studies of deltamethrin were performed on CA activity of rainbow trout gill. rtCA was significantly inhibited at three concentrations (0.25, 1.0 and 2.5 μg/L) at 24 and 48 h.     

Enzymatic dynamics of catechol oxidase from Gastrolina depressa

Properties of the phenoloxidase (PO) from adult of Gastrolina depressa Baly (Coleoptera: Chrysomelidae) as well as effects of some metal ions and inhibitors on the activity of PO purified by (NH₄)₂SO₄ were determined. The optimal pH and temperature of the enzyme for the oxidation of catechol were determined to be at pH 7.5 and at 40 °C, respectively. The kinetic parameters for the oxidation of L-DOPA and catechol by the PO were 15.01 and 9.17 mM, respectively. The PO activity was strongly inhibited by Zn²⁺ and Cu²⁺, different to Mg²⁺ slightly. Both ascorbic acid and cysteine exhibited competitive inhibition and the inhibitory constants (K_i) were determined to be 2.22 mM and 0.40 mM, respectively.     

2,4-D and MCPA and their derivatives: Effect on the activity of membrane erythrocytes acetylcholinesterase (in vitro)

The effect of 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), and their derivatives: phenol, 2,4-dichlorophenol (2,4-DCP), 2,4-dimethylphenol (2,4-DMP), and catechol on the activity of acetylcholinesterase (AChE, EC 3.1.1.7) in human erythrocytes was studied. Phenol, MCPA, and 2,4-DMP did not significantly change AChE activity in human erythrocytes (in vitro). Decrease of AChE activity was observed under the highest applied dose of 2,4-D—500 and 1000 ppm. Decrease of AChE activity exposed to 2,4-DCP and catechol was noted and depended on the doses of applied compounds. The relationship between activities and substrate concentrations (curves) was analyzed for reactions of acetylcholinesterase. Catalytic constants K_m and V_max were calculated from the Michaelis curve. Statistically significant decrease of V_max and K_m was observed in the activity of AChE incubated with 2,4-DCP and catechol, revealing mixed inhibition type of AChE inhibition (this compound may affect not only on enzyme but also on complex ES as well). 2,4-D decreases V_max but do not change K_m value, what reveals non-competitive type of AChE inhibition by this compounds. Non-competitive inhibition does not depend on the substrate concentrations but only on the inhibitor concentration and its K_i value, characterizes the affinity of inhibitors towards enzyme. In conclusion, changes of AChE activity upon 2,4-D, 2,4-DCP, and catechol are the consequences of direct interactions between compounds and the enzyme and indirect via membrane modification and increase of Reactive Oxygen Species.     

七种新烟碱类杀虫剂对韭菜迟眼蕈蚊幼虫及蚯蚓的选择毒力

为筛选出高效安全的韭蛆防治药剂,室内采用胃毒触杀联合毒力法比较了吡虫啉、啶虫脒、噻虫嗪、噻虫胺、呋虫胺、烯啶虫胺、噻虫啉与毒死蜱和高效氯氟氰菊酯等6种对照药剂对韭菜迟眼蕈蚊幼虫的毒力,同时用人工土壤法测定了13种药剂对蚯蚓的急性毒性,并通过盆栽试验验证了其对韭蛆和蚯蚓的选择毒力。结果表明,吡虫啉、噻虫胺、呋虫胺、噻虫啉、噻虫嗪对韭菜迟眼蕈蚊4龄幼虫的毒力明显高于6种对照药剂,对虫酰肼的相对毒力倍数分别为101.6、55.0、32.9、27.2、13.6;13种供试药剂中,除吡虫啉、啶虫脒、噻虫胺、呋虫胺对蚯蚓中等毒性外,其余均为低毒;盆栽试验中,吡虫啉、噻虫嗪、毒死蜱、噻唑膦、高效氯氟氰菊酯的防虫效果和保苗效果均分别高于其它药剂,但其中只有噻虫嗪对蚯蚓没有明显致死作用。     

Purification and biochemical characterization of glutathione S-transferases from three strains of Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae): Implication of insecticide resistance

Glutathione S-transferases (GSTs) catalyzing the conjugation of reduced glutathione (GSH) to a vast range of xenobiotics including insecticides were investigated in the psocid Liposcelis bostrychophila Badonnel. GSTs from susceptible and two resistant strains (DDVP-R for dichlorvos-resistant strain and PH₃-R for phosphine-resistant strain) of L. bostrychophila were purified by glutathione-agarose affinity chromatography and characterized by their Michaelis-Menten kinetics towards artificial substrates, i.e., 1-chloro-2,4-dinitrobenzene (CDNB), in a photometric microplate assay. The specific activities of GSTs purified from two resistant strains were significantly higher than their susceptible counterpart. For the resistant strains, GSTs both showed a significantly higher affinity to the substrate GSH while a declined affinity to CDNB than those of susceptible strain. The inhibitory potential of ethacrynic acid was very effective with highest I₅₀ value (the concentration required to inhibit 50% of GSTs activity) of 1.21 μM recorded in DDVP-R. Carbosulfan also exhibited excellent inhibitory effects on purified GSTs. The N-terminus of the purified enzyme was sequenced by Edman degradation, and the alignment of first 13 amino acids of the N-terminal sequence with other insect GSTs suggested the purified protein was similar to those of Sigma class GSTs.     

Purification and partial characterization of a glutathione S-transferase from the two-spotted spider mite, Tetranychus urticae

Glutathione S-transferases (GSTs) are known to catalyze conjugations by facilitating the nucleophilic attack of the sulfhydryl group of endogenous reduced glutathione on electrophilic centers of a vast range of xenobiotic compounds, including insecticides and acaricides. Elevated levels of GSTs in the two-spotted spider mite, Tetranychus urticae Koch, have recently been associated with resistance to acaricides such as abamectin [Pestic. Biochem. Physiol. 72 (2002) 111]. GSTs from acaricide susceptible and resistant strains of T. urticae were purified by glutathione-agarose affinity chromatography and characterized by their Michaelis-Menten kinetics towards artificial substrates, i.e., 1-chloro-2,4-dinitrobenzene and monochlorobimane. The inhibitory potential of azocyclotin, dicumarol, and plumbagin was low (IC₅₀ values > 100 μM), whereas ethacrynic acid was much more effective, exhibiting an IC₅₀ value of 4.5 μM. GST activity is highest in 2-4-day-old female adults and dropped considerably with progressing age. Furthermore, molecular characteristics were determined for the first time of a GST from T. urticae, such as molecular weight (SDS-PAGE) and N-terminal amino acid sequencing (Edman degradation). Glutathione-agarose affinity purified GST from T. urticae strain WI has a molecular weight of 22.1 kDa. N-terminal amino acid sequencing revealed a homogeneity of ≈50% to insect GSTs closely related to insect class I GSTs (similar to mammalian Delta class GSTs).     

Studies on glutathione transferase from grasshopper (Zonocerus variegatus)

Glutathione transferase (GST) was purified from the hindgut of grasshopper (Zonocerus variegatus) a polyphagous insect. The purified enzyme had a native molecular weight of 40 kDa and a subunit molecular weight of 19 kDa. The purified enzyme could conjugate glutathione (GSH) with 1-chloro-2,4-dinitrobenzene (CDNB), paranitrobenzylchloride, paranitrophenylacetate, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBDCl), and 1,2-dichloro-4-nitrobenzene (DCNB) with specific activities of 3.3 ± 0.3, 0.49 ± 0.10, 0.10 ± 0.002, 1.2 ± 0.2, and 1.7 ± 0.4 μmol/min/mg protein, respectively. CDNB appears to be the best substrate with a specificity constant, k_cat/K_m, of 1.8 ± 0.1 × 10⁻⁴ M⁻¹ S⁻¹. The kinetic mechanism of Z. variegatus GST (zvGST) in the conjugation of GSH with some electrophilic substrates appears complex. Conjugation of GSH with DCNB was inhibited by high DCNB concentration, while with NBDCl, as the electrophilic substrates, different values of K_m were obtained at high and low concentrations of the substrates. Cibacron blue, hematin, S-hexylglutathione, and oxidized glutathione inhibited the enzyme with I₅₀ values of 0.057 ± 0.004, 0.80 ± 0.2, 33 ± 2 μM, and 5.2 ± 0.3 mM, respectively. The nature of inhibition by each of these inhibitors is either competitive or non-competitive at varying GSH or CDNB as substrates. NADH and NAD⁺ inhibited the enzyme with an I₅₀ value of 0.4 ± 0.01 and 11 ± 1 mM, respectively. NADH at a concentration of 0.54 mM completely abolished the activity. As part of its adaptation, the flexible kinetic pathway of detoxication by zvGST may assist the organism in coping with various xenobiotics encountered in its preferred food plants.     

五种农药对中华蜜蜂和意大利蜜蜂工蜂的经口毒性比较

分别采用"小烧杯法"和"饲喂管法"测定了5种农药对中华蜜蜂和意大利蜜蜂工蜂的经口毒性。比较了2种方法的优缺点以及2个蜂种对农药毒性的敏感程度差异。结果表明:无论是"意蜂"还是"中蜂","小烧杯法"得到的半致死浓度(LC50)均不同程度地低于"饲喂管法";与"意蜂"相比,"中蜂"对药剂更敏感,可能更适用于农药的毒理评价实验。     

Characterization of glutathione S-transferase of the rice leaffolder moth, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae): Comparison of its properties of glutathione S-transferases from other lepidopteran insects

An enzyme that possesses the glutathione S-transferase (GST) activity was found in the rice leaffolder moth, Cnaphalocrocis medinalis. The enzyme was purified to homogeneity for the first time by ammonium sulfate fractionation and affinity chromatography. The resultant enzyme revealed a single band with a molecular mass of 24 kDa by SDS-polyacrylamide gel electrophoresis under reduced conditions. When assayed with 1-chloro-2,4-dinitrobenzene, a universal substrate for GST, the purified GST had an optimum pH at 8.0, and was fairly stable at pH 3-10 and at temperatures below 50 °C. The enzyme was also able to conjugate glutathione to 4-hydroxynonenal, a cytotoxic lipid peroxidation product. The present GST was inhibited by fenitrothion, permethrin, and deltamethrin, suggesting that the GST could be involved in metabolizing these organophosphorus and pyrethroid insecticides.     

Properties of acetolactate synthase from sulfonylurea-resistant Scirpus juncoides Roxb. var. ohwianus T. Koyama

Properties of acetolactate synthase (EC 4.1.3.18; ALS) from sulfonylurea-resistant (SUR) Scirpus juncoides Roxb. var. ohwianus T. Koyama were studied biochemically and physiologically in comparison with those from sulfonylurea-susceptible weed (SUS). GR₅₀ values for growth inhibition and I₅₀ values for ALS inhibition by imazosulfuron were determined for both SUR and SUS. Imazosulfuron controlled the SUS above 80% at the dosage more than 10 g a.i./ha but did not control the SUR at the even great dosage of 1000 g a.i./ha. The rates required for 50% growth inhibition of the SUR relative to the SUS (R/S ratio) were 271-fold. The I₅₀ value for inhibition of ALS from the SUS was 15 nM, compared to I₅₀ of >3000 nM for inhibition of ALS from the SUR. These results suggest that a resistance may due to an altered ALS that is insensitive to imazosulfuron. The K_m (pyruvate) value of ALS from the SUR was similar to the K_m for ALS from the SUS, suggesting that a mutation resulting in resistance does not change the affinity of the enzyme for pyruvate. The specific activity of the SUR ALS was similar to that of the SUS ALS, which indicates that resistance is not an over-expression of the enzyme. ALS activity from both biotypes was inhibited by isoleucine, valine, and leucine in this order. However, the SUR ALS was less sensitive to inhibition by valine than the SUS ALS.     

Oxidation of pesticides by purified microsomal FAD-containing monooxygenase from mouse and pig liver

The ability of purified microsomal FAD-containing monooxygenase from mouse and pig liver to oxidize pesticides has been investigated. The kinetic constants, K_m and V_max, were determined for a number of pesticide substrates including thioether-containing organophosphorus compounds and carbamates as well as (di)alkyldithiocarbamates. In general, the mouse liver enzyme had K_m values higher than those of the pig liver enzyme. Values for V_max were similar regardless of substrate, although the V_max typical of the mouse liver enzyme was approximately twice that of the pig liver enzyme. The thioether-containing organophosphorus compounds were the best substrates for both enzymes followed by the thioether-containing carbamates. The (di)alkyldithiocarbamates were relatively poor substrates for both pig and mouse liver microsomal FAD-containing monooxygenases.     

The effect of CDAA (N,N,-diallyl-2-chloroacetamide) pretreatments on subsequent CDAA injury to corn (Zea mays L.)

The effects of CDAA (N,N-diallyl-2-chloroacetamide) pretreatment on subsequent CDAA injury to corn were examined and compared with the effects of the herbicide protectant R-25788 (N,N,-diallyl-2,2-dichloroacetamide). In addition, the effects of CDAA pretreatment on subsequent CDAA metabolism were determined. It was found that 5μM CDAA protected corn from injury by 200 μM CDAA when given as a 2.5- or 1-day pretreatment. R-25788 at similar concentrations did not protect corn from subsequent R-25788 injury. Pretreatment with CDAA increased GSH levels of corn roots by 61% within 1 day, and these levels did not increase with a longer 2.5-day pretreatment with CDAA. GSH-S-transferase activity was assayed spectrophotometrically using CDNB (1-chloro-2,4-dinitrobenzene). A 1-day pretreatment with CDAA increased the root GSH-S-transferase activity by 35%, but did not affect shoot GSH-S-transferase activity. A 2.5-day pretreatment resulted in a 50% increase in root GSH-S-transferase activity but no response of the shoot enzyme was observed. Even longer pretreatments with CDAA did not result in any further increases in enzyme activity. When corn roots pretreated with CDAA for 2.5 days were excised and incubated with radiolabeled CDAA, they exhibited greater rates of uptake and metabolism than did nonpretreated roots. With in vitro studies, a fairly high rate of nonenzymatic degradation of CDAA was observed. However, the enzymatic rate was always double that of the nonenzymatic rate under the experimental conditions used. It is concluded that elevations in the GSH levels and GSH-S-transferase activities of corn roots following CDAA pretreatments may be involved in the protection of corn from subsequent CDAA injury.     

Brusatol isolated from Brucea javanica (L.) Merr. induces apoptotic death of insect cell lines

Brucea javanica (L.) Merr. is a medicine plant distributed widely throughout Asia where its bitter fruits have been used traditionally in medicine for treating various ailments and controlling some pests. In recent years, concerns over the potential impact of synthetic pesticides on human health and environment have now become more pressing to develop environmentally friendly pesticides. In this paper, brusatol, a quassinoid, was isolated from the fruit of B. javanica, and identified using X-ray crystallographic analysis. Results showed that brusatol has potent contact toxicity (LD₅₀, 2.91 μg/larva, 72 h) and anfieedant activity (AFC₅₀, 17.4 mg/L, 48 h) against the third-instar larvae of Spodoptera exigua. Brusatol demonstrated cytotoxic effects to the tested insect cell lines, IOZCAS-Spex-II and Sf21, in a time- and dose-dependent manner. After brusatol treatment, apoptotic cell death with the DNA fragmentation, activation of caspase-3 and release of cytochrome c was preliminarily observed in both IOZCAS-Spex-II and Sf21. These results indicated the existence of apoptotic death with the mitochondrial-dependent pathway induced by brusatol in Sf21 and IOZCAS-Spex-II cell lines. Our studies will provide important knowledge to understand mechanisms of action of brusatol and to develop brusatol and its derivatives as insecticides.     

Inhibitory effects of Schiff analogs of salicylidene aniline on phenoloxidase from Pieris rapae L. (Lepidoptera: Pieridae)

In order to gain insight into the development of insecticides with novel modes of action, the effects of salicylidene aniline (a), salicylidene-4-chloroaniline (b), salicylidene-4-bromoaniline (c), and salicylidene-4-nitroaniline (d) on partially purified phenoloxidase (PO) from Pieris rapae L. were investigated. The results showed that the 4 compounds could inhibit PO activity, and the inhibitor concentrations leading to a loss of 50% activity (IC₅₀) were estimated to be 0.025 mmol L⁻¹, 0.732 mmol L⁻¹, 0.471 mmol L⁻¹, and 0.675 mmol L⁻¹, respectively. Meanwhile, all the inhibitors showed reversible competitive inhibition, except (d), which showed reversible mixed inhibition. The K_I values were determined as 0.106 mmol L⁻¹, 10.059 mmol L⁻¹, 8.390 mmol L⁻¹, and 20.198 mmol L⁻¹ for the four compounds, respectively. The UV-vis spectra of (a) and (d) in the presence of copper ions and the enzyme showed that (a) could directly chelate the copper ions of PO; however, (d) could neither chelate the additional copper ions nor the copper ions of PO.     

Effect of some herbicides on CO2 fixation,intermediates pattern,and ruDP-carboxylase and FDPase activities of spinach chloroplasts

We have studied the inhibitory effect of the herbicides phenmediphan, chloroxuron, dinoseb, dichlobenil, dicamba, 2,4-D, 2,4-DB, and 2,4-DP on photosynthetic CO₂ fixation and on the level of intermediates of the CO₂ assimilation cycle by isolated chloroplasts, as well as their in vitro activities on the enzymatic systems ribulose-1,5-diphosphate carboxylase and fructose-1,6-bisphosphatase. Phenmedipham showed the strongest inhibition of CO₂ assimilation, with an I₅₀ of 0.05 μM, followed by chloroxuron and dinoseb, with a 50% inhibition in the range of 0.5–1 μM. A weaker inhibitory effect, with an I₅₀ of 50 μM, is promoted by 2,4-DB, whereas dicamba and 2,4-DP showed this inhibition at 100 μM; dichlobenil and 2,4-D were completely ineffective. In the presence of phenmedipham and chloroxuron, the $\text{trioses-}\text{P}\text{P}\text{-glycerate}$ ratio showed a sharp decrease, which means an inhibition of the P-glycerate reduction step by a low NADPH synthesis; a low ratio is also promoted by 2,4-D, but it may be a consequence of induced collateral metabolic pathways of P-glycerate. Dinoseb showed a 25% inhibition of ribulose-1,5-diphosphate carboxylase activity in the concentration range of 10–100 μM and an I₅₀ of 50 μM of the fructose-1,6-bisphosphatase. Thus these effects could contribute, in addition to the photochemical ones, to an explanation of the dinoseb inhibition of CO₂ assimilation by isolated chloroplasts. The other herbicides tested showed a weak or no effect on these enzyme systems.     

Inhibition of termite cellulases by carbohydrate-based cellulase inhibitors: Evidence from in vitro biochemistry and in vivo feeding studies

Efficacy of three prototype termite cellulase inhibitors, cellobioimidazole (CBI), fluoromethylcellobiose (FMCB) and fluoromethylglucose (FMG) was investigated using biochemical and feeding assays. Optimal conditions for measuring endoglucanase, exoglucanase and β-glucosidase activities were first determined. The three inhibitors were then tested under optimal conditions against enzyme fractions that represented endogenous (foregut/salivary gland/midgut) and symbiotic (hindgut) cellulases. In vitro, CBI and FMCB both inhibited exoglucanase and β-glucosidase activity (I₅₀s in nM and mM range, respectively). Feeding assays showed significant impacts on both survivorship and feeding stimulation by FMCB and CBI. Enzymatic measurements on feeding assay survivors showed impacts on all three cellulase activities by CBI and lesser impacts by FMG and FMCB. Validative bioassays with the sugars glucose, maltose and cellobiose showed no feeding stimulation or mortality as occurred in feeding inhibitor bioassays. These results indicate efficacy for two cellobiose-based inhibitors, FMCB and CBI, suggesting potential for these inhibitors as novel termite control agents.     

Isolation,characterization, and properties of factor F1 from mitochondrial preparations of housefly (Musca domestica L.) thorax

A water-soluble Mg²⁺-dependent ATPase (coupling factor F₁) was isolated from the mitochondria of housefly thorax. It comprised about 14% of the proteins from a crude preparation. The F₁ preparation was nearly homogeneous as assessed by gel electrophoresis, isoelectric focusing, and electron microscopy. It was composed of five subunits with the following apparent molecular weights: α, 68,000; β, 61,000; γ, 38,000; δ, 27,000; and ?, 17,500. The isoelectric pH (pI) of this protein was 7.3. F₁ had a pH optimum of 8.2 and a temperature optimum between 37 and 45°C. The enzyme was fairly stable at 25°C. Nearly complete loss of activity was noticed at 0°C, while at 0 or 25°C, glycerol (20%) partially stabilized the enzyme activity against such inactivation. The K_m value of the enzyme with respect to ATP was 0.4 mM. The activity was stimulated by low concentrations of 2,4-dinitrophenol. The enzyme was inhibited by azide, p-hydroxymercuribenzoate, and guanidine hydrochloride. Oligomycin and the pesticides pyrethrin, cyhexatin, and DDT have no effect on the enzyme activity. However, all of these chemicals inhibited intact Mg²⁺- ATPase. The results are discussed in the light of differential responses of soluble and intact ATPase to these pesticides.     

p-Dimethylaminobenzenediazo sodium sulfonate (Fenaminosulf)-reductase from Pseudomonas fragi Bk9

p-Dimethylaminobenzenediazo sodium sulfonate (DABDS)-reductase catalyzing the conversion of DABDS to N,N-dimethyl-p-phenylenediamine was purified to homogeneity from the cell-free extracts of Pseudomonas fragi Bk₉, crystallized, and its properties studied. The homogeneity of the enzyme was ascertained by gel electrophoresis and immunodiffusion studies. The molecular weight of the enzyme as determined by the gel filtration method was found to be approximately 87,000. The enzyme was optimally active at pH 7 and 45°C, with an activation energy of 2.5 kcal/mol. NADH, NADPH, and GSH could not function as cofactors, while the enzyme required dithiothreitol as an electron donor. From the Lineweaver-Burk plots, the K_m values were calculated to be 0.90 and 3.53 mM for DABDS and dithiothreitol, respectively. The enzyme did not show any requirement for metal ions and was inhibited to varying degrees by different sulfhydryl reagents.     

Inhibitory effects of 4-dodecylresorcinol on the phenoloxidase of the diamondback moth Plutella xylostella (L.) (Lepidoptera Plutellidae)

Phenoloxidase (PO) is a key enzyme in the developmental process of insects that is responsible for catalyzing the hydroxylation of monophenols and the oxidation of o-diphenols. In the present investigation, the PO of Plutella Xylostella (L.)(Lepidoptera Plutellidae) was partially purified with 40% saturated (NH₄)₂SO₄ and Sephadex G-100 gel filtration, and the effects of 4-dodecylresorcinol on the monophenolase and o-diphenolase activity of PO were studied. The results showed that 4-dodecylresorcinol could inhibit monophenolase and o-diphenolase activity. In addition, following 4-dodecylresorcinol treatments, the lag time of PO for oxidation of l-tyrosine was obviously lengthened and the steady-state activity was decreased. The inhibitor was found to be competitively reversible with a K_i of 0.201 mM and an estimated IC₅₀ (inhibition concentration showing 50% of the maximum inhibition) of 0.160 mM for monophenolase and 0.369 mM for diphenolase. The ability of 4-dodecylresorcinol to inhibit PO activity may be associated with its ability to directly affect copper at the active site     

Comparative effects of lindane and deltamethrin on mortality, growth, and cellulase activity in earthworms (Eisenia fetida)

Laboratory tests were conducted to compare the effects of various concentrations of lindane and deltamethrin on mature earthworms (Eisenia fetida) cultured in artificial soil during typical acute (14d) and subchronic (42d) exposure periods. The effects of the two pesticides on earthworm mortality, growth inhibition, and cellulase activity were determined for different exposure durations. The toxicity order for earthworm mortality from the 14-day exposure was lindane > deltamethrin, with median lethal concentrations (LC₅₀) of 162.1 and 432.9 mg kg⁻¹, respectively. Earthworms exposed to deltamethrin showed dose-dependent toxic effects on growth and cellulase activity only from the acute exposures, whereas lindane’s effects on these activities were seen correlated with both the acute and subchronic doses. Also, changes in biomass and cellulase activity during the subchronic exposure period appear to be a more sensitive parameter than the LC₅₀ value in assessing pesticidal injury.