Pesticide-contaminated feeds in integrated grass carp aquaculture: toxicology and bioaccumulation.

Effects of dissolved pesticides on fish are widely described, but little is known about effects of pesticide-contaminated feeds taken up orally by fish. In integrated farms, pesticides used on crops may affect grass carp that feed on plants from these fields. In northern Vietnam, grass carp suffer seasonal mass mortalities which may be caused by pesticide-contaminated plants. To test effects of pesticide-contaminated feeds on health and bioaccumulation in grass carp, a net-cage trial was conducted with 5 differently contaminated grasses. Grass was spiked with 2 levels of trichlorfon/fenitrothion and fenobucarb. Unspiked grass was used as a control. Fish were fed at a daily rate of 20% of body mass for 10 d. The concentrations of fenitrothion and fenobucarb in pond water increased over time. Effects on fish mortality were not found. Fenobucarb in feed showed the strongest effects on fish by lowering feed uptake, deforming the liver, increasing blood glucose and reducing cholinesterase activity in blood serum, depending on feed uptake. Fenobucarb showed increased levels in flesh in all treatments, suggesting bio-concentration. Trichlorfon and fenitrothion did not significantly affect feed uptake but showed concentration-dependent reduction of cholinesterase activity and liver changes. Fenitrothion showed bioaccumulation in flesh which was dependant on feed uptake, whereas trichlorfon was only detected in very low concentrations in all treatments. Pesticide levels were all detected below the maximum residue levels in food. The pesticide-contaminated feeds tested did not cause mortality in grass carp but were associated with negative physiological responses and may increase susceptibility to diseases.

[Metabolic resistance to organophosphate insecticides in Anopheles aquasalis Curry 1932, Libertador municipality, Sucre State, Venezuela]. / Resistencia metabólica a insecticidas organofosforados en Anopheles aquasalis Curry 1932, municipio Libertador,estado Sucre, Venezuela.

INTRODUCTION: A study of insecticide resistance was undertaken at focal level in the localities Catuaro, Guayana, Platanito and Rio de Agua, Libertador County, Sucre State, Venezuela, a region with malaria transmission, where Anopheles aquasalis is the main vector. OBJECTIVE: Insecticide resistance was assessed in the organophosphate insecticides fenitrothion and pirimiphos methyl, both of which are used in the control of Anopheles aquasalis. MATERIALS AND METHODS: In adult mosquitoes, biological tests were performed and identification of resistance mechanisms in vitro by biochemical tests. RESULTS: Elevated levels of alpha and beta esterases were detected, as well as altered acetylcholinesterase activity. Multifunction oxidase enzymes in populations of Anopheles aquasalis in three of the locations evaluated were also altered; therefore, both enzyme systems may be involved in the expression of resistance to organophosphate insecticides in the study populations. The enzyme activity of glutathione-S-transferase was noted only in Rio de Agua. CONCLUSIONS: A better understanding of the resistance to insecticides was obtained in this species of medical importance. These findings will assist the implementation the practice of insecticide rotation as a strategy within an integrated management program.

Toxicological evaluation and bioavailability of (14)C-fenitrothion bound residues on soybeans towards experimental animals.

Under local practice of Egyptian conditions, the application of (14)C-fenitrothion on soybeans at a dose of 10mg insecticide/kg grains, led to the formation of 21% of (14)C-bound residues (non-extractable) after 24 weeks of storage. The external residues were 20% and the internal extracts were 55% of the applied dose. Feeding studies on rats revealed that bound residues were bioavailable. After feeding rats for three days with bound (14)C-fenitrothion residues, the main portion of radioactivity was eliminated via expired air (42%), urine (20%) and feces (11.5%). About 15% of the administered radioactivity was distributed among various organs as, liver, kidney, lung, fat, intestine, blood, heart, and brain. Toxicity of bound residues of (14)C-fenitrothion in stored soybeans was studied in mice through feeding experiments for three months at a concentration of 1.9 mg/kg. The maximum inhibition in plasma and erythrocyte cholinesterase activity was observed 22.5%, 18.9% and 8.6%, 9% after one and seven days, respectively. The obtained results showed a slight significant elevation after three months in the activity of liver enzymes alanine amino transferase, aspartate amino transferase and alkaline phosphatase. A moderate increase in blood urea nitrogen and creatinine concentration was observed in the treated groups at the end of the experimental period. The detected levels of albumin and total protein showed no significant compared to the control values, of controlled animals, after three months.

Prognostic factors and toxicokinetics in acute fenitrothion self-poisoning requiring intensive care.

OBJECTIVE: We aimed to evaluate prognostic factors and toxicokinetics in acute fenitrothion self-poisoning. METHODS: We reviewed 12 patients with fenitrothion self-poisoning admitted to the intensive care unit between 2003 and 2006. We compared the characteristics, initial vital signs, physiological scores, corrected QT interval on electrocardiogram and laboratory data (serum fenitrothion concentration and cholinesterase activity) of non-survivors and survivors. Furthermore, we evaluated the correlation between the prognostic factors and severity of poisoning (lengths of intensive care unit and hospital stays), and the toxicokinetics of the patients. RESULTS: In the 2 non-survivors, the estimated fenitrothion ingestion dose and the serum fenitrothion concentration at the emergency department and at 24 h after ingestion were significantly higher than those in the 10 survivors. (P = 0.008, 0.003, and 0.04, respectively). In the 10 survivors, the serum fenitrothion concentration at 24 h after ingestion was significantly correlated with the lengths of intensive care unit and hospital stays (P = 0.004 and 0.04, respectively); however, the initial vital signs, physiological scores, corrected QT interval on electrocardiogram at the emergency department, and serum cholinesterase activity did not show any correlation. In five patients successfully fitted to a two-compartment model, the distribution and elimination half-lives were 2.5 and 49.8 h, respectively, which is compatible with the slow and prolonged clinical course of fenitrothion poisoning. CONCLUSION. Estimated fenitrothion ingestion dose and serum fenitrothion concentration at the emergency department and at 24 h after ingestion may be useful prognostic factors in acute fenitrothion self-poisoning. Furthermore, we should take care for the patients whose serum fenitrothion concentration is high.

Inhibition and recovery of maternal and foetal cholinesterase enzymes following fenitrothion administration in CD rats.

The purpose of this study was to characterize tissue esterase activity and blood fenitrothion concentrations in the rat dam and foetus following in-utero exposure to the organophosphate insecticide fenitrothion. Time-mated, 8-week-old rats were gavaged on gestation day 19 with 0, 5, or 25 mg fenitrothion kg-1. Fenitrothion was absorbed rapidly from the gastrointestinal tract, with peak maternal and foetal blood levels observed 0.5-1.0 h after dosing. Fenitrothion concentrations in maternal and foetal blood were virtually identical and demonstrated a non-linear dose-response relationship. Acetylcholinesterase and carboxylesterase activities in maternal liver and blood and in foetal liver and brain decreased within 30-60 min of fenitrothion exposure. Esterase inhibition occurred at a fenitrothion dose (5 mg kg-1) that has not been previously associated with reproductive toxicity, suggesting that esterase inhibition should be considered as the critical effect in risk assessments for this pesticide.

Fenitrothion-induced changes in lipids of rats.

The dose-dependent lipid accumulation caused by fenitrothion administration is associated with alteration of the ratio of various components of phospholipids and neutral lipids in various organs of rats up to 48 h. The concentration of triacylglycerol, phosphatidyl choline, phosphatidyl ethanolamine and phosphatidyl glycerol increased in liver, kidney and brain in treated rats whereas phosphatidyl serine was greatly reduced. High-performance liquid chromatography and gas-liquid chromatography were used for quantiative analysis of phospholipids and triacylglycerol. The changes in relative composition of various lipids by fenitrothion administration may lead to malfunctioning and alteration of biological properties.

Biodegradation and bioaccumulation of fenitrothion in rat liver.

The biodegradation of fenitrothion O,O-dimethyl-O-(3-methyl-4-nitro phenyl) phosphorothioate was investigated in rat liver after administration of various doses (5 mg/100 g body weight and 20 mg/100 g body weight) in acute treatment and 1 mg/100 g body weight in chronic treatment. High performance liquid chromatography of the pesticide and its metabolites formed in liver in acute treatment showed time-dependent sequential conversion of pesticide into three major metabolites within 24 h. These metabolites were separated and purified to homogenity by HPLC and characterized by IR spectroscopy as O,O-dimethyl-O-(3-methyl-4-amino phenyl) phsophorothioate (metabolite 1), O,O-dimethyl phosphorothioate (metabolite II) and O,O-dimethyl phosphate (metabolite III) in the fi rst dose (5 mg/100 g body weight). Metabolite II was found to be different in the second dose (20 mg/100 g body weight) and identified as O,O-dimethyl O-3-methyl-4-amino phenyl phosphate. The results with the fi rst dose indicated reduction of the nitro group in fenitrothion as step I followed by hydrolytic clevage of the P-O-aryl bond in metabolite I and oxidative desulphurylation of metabolite II. At higher dose (20 mg/100 g body weight) oxidative desulphurylation takes place as step II followed by hydrolysis of metabolite II. The bioaccumulation of fenitrothion within 60 days during chronic treatment showed no metabolite but continuous reduction in fenitrothion concentration, indicating excretion of pesticide and its products in urine and in faeces.

Fenitrothion: toxicokinetics and toxicologic evaluation in human volunteers.

An unblinded crossover study of fenitrothion 0.18 mg/kg/day [36 times the acceptable daily intake (ADI)] and 0.36 mg/kg/day (72 X ADI) administered as two daily divided doses for 4 days in 12 human volunteers was designed and undertaken after results from a pilot study. On days 1 and 4, blood and urine samples were collected for analysis of fenitrothion and its major metabolites, as well as plasma and red blood cell cholinesterase activities, and biochemistry and hematology examination. Pharmacokinetic parameters could only be determined at the higher dosage, as there were insufficient measurable fenitrothion blood levels at the lower dosage and the fenitrooxone metabolite could not be measured. There was a wide range of interindividual variability in blood levels, with peak levels achieved between 1 and 4 hr and a half-life for fenitrothion of 0.8-4.5 hr. Although based on the half-life, steady-state levels should have been achieved; the area under the curve (AUC)(0-12 hr) to AUC(0-(infinity) )ratio of 1:3 suggested accumulation of fenitrothion. There was no significant change in plasma or red blood cell cholinesterase activity with repeated dosing at either dosage level of fenitrothion, and there were no significant abnormalities detected on biochemical or hematologic monitoring.

Evaluation of respiratory and cutaneous doses and urinary excretion of alkylphosphates by workers in greenhouses treated with omethoate, fenitrothion, and tolclofos-methyl.

This research evaluated exposure pathways across work tasks for three organophosphate pesticides in a group of greenhouse workers. During reentry in ornamental plant greenhouses, five male workers were monitored for five consecutive days. Skin contamination (excluding hands) was evaluated with nine pads of filter paper placed on the skin. Hand contamination was assessed by washing with 95% ethanol. Respiratory exposure was evaluated by personal air sampling. The respiratory dose was based on a lung ventilation of 20 L/min. The doses absorbed were estimated assuming 10% skin penetration and 100% lung retention. Urinary alkylphosphates were assayed in the 24-hour urine samples of the days on which exposure was evaluated. Respiratory exposure was usually less than skin contamination, being 4.5 +/- 8.4%, 9.9 +/- 10.0%, and 49.5 +/- 26.6% (mean +/- standard deviation) of total exposure for omethoate, tolclofos-methyl, and fenitrothion, respectively. Multiple regression analysis showed that urinary alkylphosphate (nmol/24 hours) (y) was significantly correlated (r = 0.716, p < 0.001) with the respiratory doses of the three active ingredients absorbed the same day (x1) and with the cutaneous dose absorbed the previous day (x2). The relationship was expressed by the equation y = 0.592x2 + 0.117x, + 156.364. The doses of omethoate absorbed by one worker were more than 45 times the acceptable daily intake (ADI) of 1.41 nmol/kg body weight (b.w.) The ADI for fenitrothion and tolclofos-methyl (10.8 and 212.6 nmol/kg body weight, respectively) were never exceeded. High absorption by one worker underlines the importance of correct use of protective clothing. In this study the hands were always a source of contact with the pesticides. Greater precautions should be taken to reduce contamination (clean gloves, constant use of gloves).

Pesticide toxicokinetics in fish: accumulation and elimination.

Bioaccumulation of fenitrothion in the European eel (Anguilla anguilla) was studied using two sublethal concentrations of this pesticide in a flow-through test system. The pesticide concentrations used were one-tenth (0.002 ppm) and one-fifth (0.04 ppm) the 96-h LC50 of fenitrothion in this species. Steady state was reached early (2 h) when the animals were exposed to 0.02 ppm of toxicant, and after 48 h when the animals were exposed to 0.04 ppm. Toxicokinetic parameters for fenitrothion in eel muscle (K1, K2, and T1/2) were calculated for both experiments. The highest bioconcentration factor was calculated for animals exposed to 0.04 ppm of toxicant, indicating the relationship between the bioconcentration in muscle tissue and the disposition of fenitrothion in the medium. After transfer to clean water (depuration phase), the animals rapidly eliminated the pesticide accumulated. Excretion rate constants (K2) were 0.06 and 0.04 h-1 in both experiments and the half-lives of fenitrothion in muscle tissue were less than 24 h. After 24 h of the recovery period, fenitrothion was not detected in eel muscle of those animals exposed to 0.02 ppm, and in eels exposed to 0.04 ppm of toxicant, a reduction of 91% was reached by the end of the period.

Uptake and elimination kinetics of a pesticide in the liver of the European eel.

This study was undertaken to determine the bioconcentration-elimination process of fenitrothion in the liver of the european eel (Anguilla anguilla). The animals were exposed to two sublethal fenitrothion concentrations corresponding to 1/5 and 1/10 of LC50 96-h in a flow-through test system. Uptake kinetics were determined from liver burdens measured at 2, 8, 24, 48, 56, 72 and 96 hours exposure. After pesticide exposure, animals were transferred to clean water for 72 hours. Fenitrothion elimination was determined after 12, 24, 48 and 72 hours of recovery period. The insecticide showed a high bioconcentration tendency. Steady-state was reached after 48 hours exposure when the animals where exposed to the lowest concentration. This was followed with a rapid elimination process when the animals were transferred to clean water. Animals exposed to 0.04 ppm showed an early accumulation of the toxicant into the liver, and a steady-state was reached after 8 hours. The elimination rate constant K2 of 0.0096 h-1 and 0.06 h-1 were estimated from the data. The biotransformation rate of fenitrothion in the European eel were low as indicated by a relatively short half-life (11.55 h) of the insecticide. An increase in the Hepatosomatic Index was observed after 96 hours of exposure, but no significant differences were found between control and exposed animals.

Bioconcentration and excretion of fenitrothion in the brain of the eel (Anguilla anguilla).

The bioconcentration of fenitrothion in the brain of the european eel (Anguilla anguilla) and its posterior elimination have been studied. Animals were exposed to a sublethal concentration of fenitrothion (0.04 mg/L) for 96 hours in a flow-through test system. After this pesticide exposure, animals were transferred to clean water for 72 hours more. Bioconcentration and elimination processes of fenitrothion were studied in blood and brain. This insecticide showed a strong tendency to bioconcentrate into selected tissues. A steady-state was observed in blood in few hours. Highest accumulation was detected in brain, where any steady-state could be observed. Elimination started rapidly from both tissues when a recovery period was allowed. Elimination kinetics were adjusted to one-compartment model. K2 of 0.015 and 0.044 hr-1 were calculated for fenitrothion in blood and brain. These K2 values were related with a relatively short half-live of fenitrothion in the analyzed tissues; probably due to the low biotransformation rate of this toxicant in the european eel. That fact would protect the animals against many biotransformation products even more toxic than the parent fenitrothion.

Effect of activated charcoal and atropine on absorption and/or exsorption of organophosphorus compounds in rats.

Effects of activated charcoal and atropine for the removal of organophosphorus compounds, which remain in the gastrointestinal tract or have already been absorbed into the systemic circulation, were investigated in rats. Activated charcoal extensively adsorbed the organophosphates fenitrothion, tolelofos methyl, piperophos and salithion, and its immediate administration after oral ingestion of fenitrothion remarkably reduced serum fenitrothion levels, but had no effect on the serum levels of the compound which had been absorbed from the gastrointestinal tract. Thus, all of the organophosphorus compounds were poorly exsorbed (0.002-0.39% of the dose in 120 min) from the blood into the intestinal lumen probably due to their extensive protein binding and large distribution volumes. Atropine inhibited absorption of fenitrothion in the perfusion in-situ and also delayed the absorption of the compound in-vivo, but had no significant effect on exsorption of fenitrothion. The serum fenitrothion levels on treatment with both atropine and charcoal significantly decreased compared with those of the control. We conclude that, oral activated charcoal will not be able to enhance the elimination of organophosphorus compounds which have already been absorbed into the systemic circulation, but constituted useful method for the removal of the compounds remaining in the gastrointestinal tract because of its excellent adsorptive capacity.

Metabolic fate of fenitrothion in liver, kidney and brain of rat.

The metabolic fate of fenitrothion, O,O-dimethyl-O-(3-methyl-4-nitro phenyl) phosphorothioate, was investigated in rat tissues during the first 24 hours following the intramuscular administration of the pesticide in the animal. High performance liquid chromatography (HPLC) of the pesticide and its metabolites formed in liver, kidney and brain showed the time-dependent sequential conversion of the pesticide into three major metabolites. These metabolites were separated and purified to homogeneity by HPLC and characterized by IR spectroscopy as O,O-dimethyl-O-)3-methyl-4-aminophenyl) phosphorothioate (metabolite I), O,O-dimethyl phosphorothioate (metabolite II), and O,O-dimethylphosphate (metabolite III). These results indicated reduction of the nitro group in fenitrothion aas the first step, followed by the hydrolytic cleavage of the P-O-aryl bond in metabolite I and the oxidative desulphurylation of metabolite II. Fenitrothion was found to induce ultrastructural changes in liver cells especially after 12 h exposure nuclear membrane was completely distorted, nuclear intactness was totally lost and smooth endoplasmic reticulum and Golgi apparatus were abnormally enlarged. In 24 h, however, the regeneration of the nuclear material was observed.

Metabolic activation of the organophosphorus insecticides chlorpyrifos and fenitrothion by perfused rat liver.

The present study was undertaken to characterize the metabolic activation of the organophosphorus insecticides chlorpyrifos [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothionate] and fenitrothion [O,O-dimethyl O-(3-methyl-p-nitrophenyl) phosphorothionate] by intact rat liver. Single-pass perfusions of rat livers with chlorpyrifos or fenitrothion to steady state conditions resulted in the appearance of their corresponding oxygen analogs in effluent. In addition, detoxification of chlorpyrifos oxon [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphate] or fenitrooxon [O,O-dimethyl O-(3-methyl-p-nitrophenyl) phosphate] by rat blood did not proceed at a rate rapid enough to prevent passage of at least some of these chemicals from liver to extrahepatic tissues, suggesting that hepatic biotransformation of chlorpyrifos and fenitrothion by rat liver results in their net activation. Although male rat livers produced more chlorpyrifos oxon and fenitrooxon from chlorpyrifos and fenitrothion, respectively, than did livers from female rats, the acute toxicities of chlorpyrifos and fenitrothion were greater in females than in males. Therefore, differences in hepatic activation of chlorpyrifos and fenitrothion in males and females cannot account for the sex differences in their acute toxicities in the rat. Finally, S-methyl glutathione and S-p-nitrophenyl glutathione were not detected in effluent or bile of livers perfused with fenitrothion, suggesting that glutathione-mediated biotransformation of this insecticide does not occur to any significant degree in intact liver.

[Delayed Sumithion intoxication].

A case of delayed Sumithion (fenitrothion) intoxication is reported. A 52-year-old man ingested 10 ml of Sumithion in order to commit suicide with alcohol and triazoram. Several hours later, he was admitted to our hospital because of clouding consciousness. On admission, he was somnolent, but had no other symptoms, especially suggested organophosphorus intoxication. After 40 hours, fasciculation and salivation, which are early symptoms of organophosphorus intoxication, gradually appeared. The concentration of Sumithion in the blood was measured during the course and its metabolism was represented phalmacokineticaly by a 2-compartment model. The retarded metabolism of the Sumithion was suggested by this model. It is considered that the retarded metabolism of Sumithion caused the delayed intoxication.