Comparative studies on chlorpyrifos and methyl parathion induced oxidative stress in different parts of rat brain: Attenuation by antioxidant vitamins

Organophosphate (OP) pesticides are among the most widely used synthetic chemicals for controlling a wide variety of pests. Chlorpyrifos (o,o′-diethyl-o-3,5,6-trichloro-2-pyridyl phosphorothionate, CPF) is among the leading OP pesticides used extensively throughout the world including India while methyl parathion (o,o-di methyl-o-p-nitrophenyl phosphorothioate, MPT) another OP compound, widely used as insecticide and acaricide to control many biting or sucking pests of agricultural crops. Present study was carried out to compare the chronic toxicity of CPF and MPT, their potential to generate oxidative stress and ameliorating effects of antioxidant vitamins in brain of rats. Results of the present study clearly demonstrated that the oral exposure of CPF or MPT, generated oxidative stress in different parts of rat brain consequently accumulating malondialdehyde (MDA) and 4-hydroxynonanal (4HNE), the two major end products of lipid peroxidation, in all the three brain regions i.e. fore-, mid- and hind-brain. The levels of hydrogen peroxide (H₂O₂) were also increased in all the three brain regions when compared with control. CPF and MPT exposure caused decrease in the levels of reduced glutathione (GSH) and increase in the levels of oxidized glutathione (GSSG) in all the three brain regions. The increase in the levels of MDA, 4HNE, H₂O₂ and GSSG was less pronounced when CPF or MPT was given to the rats fed with a mixture of vitamin A, E and C. The present findings clearly show that oral intake of a mixture of vitamin A, E and C protects the rats from MPT or CPF induced oxidative stress and suggest that this treatment alleviates the toxicity of these pesticides to a greater extent.     

Acute, subacute and subchronic administration of methyl parathion-induced testicular damage in male rats and protective role of vitamins C and E

Methyl parathion is an organophosphate insecticide that has been used in agriculture and domestic for several years. Vitamin C (200 mg/kg bw per day) + vitamin E (200 mg/kg bw per day), methyl parathion (0.28 mg/kg bw per day) and vitamin C (200 mg/kg bw per day) + vitamin E (200 mg/kg bw per day) + methyl parathion (0.28 mg/kg bw per day) combination were given to rats orally via gavage for 7 weeks. Body and testis weights, sperm counts, sperm motility, sperm morphology and histopathological changes in the testes were investigated at the end of 24 h, 4th and 7th weeks comparatively with control group. No pathological changes were observed in all parameters at the end of 24 h. When methyl parathion-treated group and vitamins C and E + methyl parathion-treated group were compared to control group, body and testis weights decreased significantly at the end of 4th and 7th weeks. It was observed that, at the end of 4th and 7th weeks there was a statistically significant decrease in sperm counts and sperm motility, increase in abnormal sperm morphology when methyl parathion- and vitamins C and E + methyl parathion-treated group were compared to control group. While sperm counts increased at the end of 4th and 7th weeks, sperm motility increased at the end of 7th week when vitamins C and E + methyl parathion-treated group compared with methyl parathion-treated group, no changes were observed in abnormal sperm morphology at the end of 4th and 7th weeks. In our light microscopic investigations, after 4 and 7 weeks of methyl parathion exposure, necrosis and edema were observed in the seminiferous tubules and interstitial tissues. After 4 and 7 weeks of vitamins C and E + methyl parathion exposure, degenerative changes were detected in the seminiferous tubules while no pathological findings were observed in the interstitial tissues. According to the present study, we conclude that vitamins C and E reduces methyl parathion testicular toxicity, but it does not protect completely.     

Effects of dichlorvos on lipid peroxidation in mice on subacute and subchronic periods

In this study, the effects of dichlorvos to lipid peroxidation were investigated at subacute and subchronic periods. Dichlorvos was given with drinking water to Swiss Albino male mice in three dosage levels as 10, 20, and 40 mg/kg b.w. Lipid peroxidation was evaluated by determining the malondialdehyde (MDA) levels in plasma, determining the superoxide dismutase and catalase activities in erythrocytes. The analysis of these enzymes was done in blood samples collected from mice on the days 15 and 45. The results showed that MDA levels increased in dichlorvos treated groups. Actually MDA levels in control and dichlorvos treated groups were determined (as nmol/ml) 10.49, 13.83, 14.30, and 14.50, respectively, at subacute period; 7.77, 8.15, 10.88, and 12.33, respectively, at subchronic period. Catalase activity in erythrocytes decreased at subacute and subchronic periods in dichlorvos treated groups. At subacute period CAT activities were determined (as k/mg Hb) in control and dichlorvos treated groups, 563.45, 532.11, 524.76, and 497.08, respectively; 660.53, 588.84, 525.85, and 512.01, respectively, at subchronic period. When subacute and subchronic periods were compared with each other; it was shown that SOD and CAT activities increased at subchronic period.     

Methyl parathion induced nephrotoxicity in male rats and protective role of vitamins C and E

Methyl parathion is an organophosphate insecticide that has been used in agriculture and domestic for several years. Vitamin C (200 mg/kg bw per day) + vitamin E (200 mg/kg bw per day), methyl parathion (0.28 mg/kg bw per day) and vitamin C (200 mg/kg bw per day) + vitamin E (200 mg/kg bw per day) + methyl parathion (0.28 mg/kg bw per day) combination were given to rats orally via gavage for 7 weeks. Body and kidney weights, malondialdehyde (MDA) levels and histopathological changes were investigated at the end of 4th and 7th weeks comparatively with control group. When methyl parathion-treated group and vitamins C and E + methyl parathion-treated group were compared to control group body and kidney weights decreased significantly at the end of 4th and 7th weeks. MDA levels increased in kidney tissues of the methyl parathion- and vitamins C and E + methyl parathion-treated groups compared to control group. MDA levels decreased significantly in vitamins C and E + methyl parathion treated group compared with methyl parathion treated group at the end of 4th and 7th weeks. In our light microscopic investigations, after 4 weeks of methyl parathion exposure, glomerular atrophy and vascular dilatation, and after 7 weeks, necrosis and edema were observed in the kidney tissues. After 4 weeks of vitamins C and E + methyl parathion exposure, mononuclear cell infiltrations, and after 7 weeks, calcification were detected in the kidney tissues.     

Acute effects of methyl parathion and diazinon as inducers for oxidative stress on certain biomarkers in various tissues of rainbowtrout (Oncorhynchus mykiss)

Present study aimed mainly to assess oxidative stress pesticides such as methyl parathion (MP) and diazinon, which are widely used insecticides and contaminate aquatic ecosystems, on certain biomarkers in various tissues of rainbowtrout (Oncorhynchcus mykiss). Biomarkers selected for stress monitoring were malondialdehyde (MDA) and antioxidant defense system (ADS) mainly reduced glutathione (GSH), glutathione reductase (GR), peroxidase (GSH-PX), transferase (GST) and superoxidedismutase (SOD) activities in the liver, gills and muscle of fishes exposed to 0.5 and 1 ppm dosages of MP and diazinon for 24, 48 and 72 h. According to these results, after the administrations of MP and diazinon promote MDA content in some of the tissues of fishes treated with both dosages of MP and diazinon. With regard to the ADS, GSH-Px, GST, SOD, GR activities and GSH levels fluctuated after 24, 48 and 72 h in all the treatment groups compared with controls. Collective results demonstrated that exposure of fish to pesticides induced an increase in MDA joined with fluctuated ADS. This may reflect the potential role of these parameters as useful biomarkers for assessment of water pollution.     

Comparison of the effect of subacute organophosphate exposure on the cortical and peripheral evoked activity in rats

Organophosphates are irreversible blockers of acetylcholinesterase and are widely used as insecticide agents. Their action is not limited to the target organisms so that occupational or food-borne exposure of humans usually leads to neurotoxicity in which several other mechanism, apart from cholinesterase inhibition, may play a role. In the present study, rats were treated with three different organophosphates (chlorfenvinphos, diisopropyl fluorophosphate, and dimethoate) for 4 weeks, and alterations in two forms of stimulus evoked activity—somatosensory and visual cortical sensory evoked potentials and peripheral nerve action potential—were compared. In the treated rats, there was significant increase in the somatosensory evoked response latency and non-significant increase in its duration. In the visual evoked potential, only duration was altered. The conduction velocity of the peripheral nerve was decreased. Comparison of the changes in the cortical- and peripheral evoked activity showed that the slowed peripheral impulse conduction only partly explains the increase in the cortical response latency. Hence, possible mechanisms of direct cortical action of the organophosphates are also discussed.     

Effects of atropine and pralidoxime pretreatment on serum and cardiac oxidative stress parameters in acute dichlorvos toxicity in rats

Recent several studies have reported that oxidative stress could be an important component of the mechanism of cardiotoxicity due to organophosphate-induced toxicity. The aim of this study is to evaluate the oxidative and antioxidative parameters in cardiac toxicity of organophosphate poisoning, and determine the effects of atropine and pralidoxime on this parameters. The experimental groups were randomly divided into five groups as control (corn oil), dichlorvos (30 mg/kg), atropine (10 mg/kg), pralidoxime (40 mg/kg), and atropine (10 mg/kg) + pralidoxime (40 mg/kg) groups. Serum cholinesterase levels were suppressed with dichlorvos, and these reductions were inhibited with atropine and/or pralidoxime pretreatment. Serum, but not cardiac, total free sulfhydryl groups and paraoxonase activities were significantly increased in the pralidoxime group when compared to the control group. Serum arylesterase activities were elevated in the dichlorvos, atropine, pralidoxime, and atropine + pralidoxime groups when compared to the control group (P < 0.05). Total oxidant status, oxidative stress index, malondialdehyde and catalase activities in serum and cardiac tissues were not markedly different between the groups. No significant changes were also observed with cardiac myeloperoxidase and serum ceruloplasmin activities. In conclusion, these results showed that acute dichlorvos administration did not cause marked cardiac damage, and oxidative stress probably does not play a major role in dichlorvos-induced poisoning. On the other hand, especially pralidoxime treatment markedly increased the serum total free sulfhydryl groups, paraoxonase and arylesterase activities. However, the underlying mechanisms for these changes are not exactly known.     

Effect of methyl parathion and chlorpyrifos on certain biomarkers in various tissues of guppy fish, Poecilia reticulata

Tests of acute toxicity were performed on the most common species of aquarium fish, Poecilia reticulata. Guppies (P. reticulata) were exposed to progressive concentrations of methyl parathion (MP) and chlorpyrifos (CPF); a semi-static method according to guidelines of OECD was used. Tests of acute toxicity were conducted using 10 fish for each separate concentration and for the control group. The results were subjected to probit analysis to determine the 96 h LC₅₀ values. The 96 h LC₅₀ values of MP and CPF to P. reticulata were 8.48 ppm/L (5.98–10.89) and 0.176 ppm/L (0.313–0.224) respectively. In addition, behavioral changes at each concentration were observed for the individual fish. Fish were exposed for 96 h to different sublethal concentrations of MP and CPF (¼ LC₅₀, 1/8 LC₅₀ and 1/10 LC₅₀) and their oxidative stress-induction potential was estimated in brain, liver and gills of fish. MDA content is induced in all tissues but maximum rise was observed in gills (161% and 153% for MP and CPF respectively). With regard to antioxidant defense system (ADS), GSH level decreased in the brain, liver and gills of tissues of MP treated fishes (22%, 6% and 13% respectively) and showed increase in brain and gills CPF treated (23% and 21% respectively). CAT, GST, GR and SOD levels fluctuated in all treatment groups relative to the control. Brain AChE showed dose-dependent inhibition in fish exposed to the higher concentrations reached 45% and 66% for MP and CPF respectively. Collective findings demonstrated that pesticide exposure of fish induced an increase in MDA and fluctuated ADS along with inhibited AChE. These findings may be used as valuable biomarkers for evaluation of water pollution.