Effects of propanil on the European eel Anguilla anguilla and post-exposure recovery using selected biomarkers as effect criteria

Effects of environmental cocaine concentrations on COX and caspase-3 activity, GRP-78, ALT, CRP and blood glucose levels in the liver and kidney of the European eel (Anguilla anguilla)

Cocaine is one of the most widely used illicit drugs in the world, and as a result of incomplete removal by sewage treatment plants it is found in surface waters, where it represents a new potential risk for aquatic organisms. In this study we evaluated the influence of environmental concentrations of cocaine on the liver and the kidney of the European eel (Anguilla anguilla). The eels were exposed to 20 ng L^-1 of cocaine for fifty days, after which, three and ten days after the interruption of cocaine exposure their livers and kidneys were compared to controls. The general morphology of the two organs was evaluated, as well as the following parameters: cytochrome oxidase (COX) and caspase-3 activities, as markers of oxidative metabolism and apoptosis activation, respectively; glucose-regulated protein (GRP)78 levels, as a marker of endoplasmic reticulum (ER)-stress; blood glucose level, as stress marker; serum levels of alanine aminotransferase (ALT), as a marker of liver injury and serum levels of C-reactive protein (CRP), as a marker of the inflammatory process. The liver showed morphologic alterations such as necrotic areas, karyolysis and pyknotic nuclei, while the kidneys had dilated glomeruli and the renal tubules showed pyknotic nuclei and karyolysis. In the kidney, the alterations persisted after the interruption of cocaine exposure. In the liver, COX and caspase-3 activities increased (COX: P = 0.01; caspase-3: P = 0.032); ten days after the interruption of cocaine exposure, COX activity returned to control levels (P = 0.06) whereas caspase-3 activity decreased further (P = 0.012); GRP78 expression increased only in post-exposure recovery specimens (three days: P = 0.007 and ten days: P = 0.008 after the interruption of cocaine exposure, respectively). In the kidney, COX and caspase-3 activities increased (COX: P = 0.02; caspase-3: P = 0.019); after the interruption of cocaine exposure, COX activity remained high (three days: P = 0.02 and ten days: P = 0.029 after the interruption of cocaine exposure, respectively) whereas caspase-3 activity returned to control values (three days: P = 0.69 and ten days: P = 0.67 after the interruption of cocaine exposure, respectively). Blood glucose and serum ALT and CRP levels increased (blood glucose: P = 0.01; ALT: P = 0.001; CRP: 0.015) and remained high also ten days after the interruption of cocaine exposure (blood glucose: P = 0.009; ALT: P = 0.0031; CRP: 0.036). These results suggest that environmental cocaine concentrations adversely affected liver and kidney of this species.

Potential attenuation of biochemical parameters and enzymatic functions in Cyprinus carpio fingerlings by Phenthoate 50 EC insecticide exposure

The risks of the health-associated problems of pesticide-exposed non-target organisms are ubiquitous, therefore an emerging concern to strike the balance between benefit and risk factors. In the present study, by elucidating multiple biomarkers, the effects of Phenthoate 50 EC on the acute toxicity tests and different pathophysiological changes of common carp (Cyprinus carpio) fingerlings were studied in time- and concentration-dependent manners. The LC₅₀ of Phenthoate 50 EC for the fish was 7.39 (6.716-8.076) ppm at 96 h. As an indicator of neurotoxicity, compared to the control group, significant (P < 0.01) reduction in brain acetylcholinesterase (AChE) activity was observed, whereas plasma glutamate-oxalacetate transaminase (PGOT) and plasma glutamate pyruvate transaminase (PGPT) activities were increased significantly (P < 0.01) at the doses of 2.22 and 3.69 ppm of Phenthoate 50 EC, respectively. Histopathological changes in the insecticide-treated fish liver suggested the hepatic tissue damages, while alteration of the blood, gills and kidney morphology; progressive decrease (P < 0.05) in the serum calcium levels; and significantly (P < 0.01) decreased blood glucose level at 2.22 and 3.69 or 5.17 ppm of Phenthoate 50 EC demonstrated the oxidative stress and requirement of the up-surging energy demands due to the exposure of this organophosphate chemical. These results advice the modulation caused by this widely used agrochemical on the physiology of aquatic fauna by changing the enzymatic and biochemical indices at cellular level.

Development and application of fluorescence sensor and test strip based on molecularly imprinted quantum dots for the selective and sensitive detection of propanil in fish and seawater samples

Molecularly imprinted quantum dots (MIP-QDs) were successfully synthesized via reversed-phase microemulsion and used as the specific recognition element and signal probe of a fluorescence sensor or test strip to achieve the highly sensitive detection of propanil. The physical-chemical characteristics and excellent selectivity of MIP-QDs were elucidated. Under optimized parameters, the MIP-QDs had good linearity at the propanil concentration range of 1.0 μg/L to 20.0 × 10³ μg/L by fluorescence quenching. The developed MIP-QD-based fluorescence sensor showed good recoveries ranging from 87.2 % to 112.2 %, and the relative standard deviation was below 6.0 % for the fish and seawater samples. In addition, the limits of detection (LODs) for fish and seawater were 0.42 μg/kg and 0.38 μg/L, respectively. The fluorescence test strip developed on the basis of the MIP-QDs also displayed satisfactory recoveries of 90.1 %-111.1 %, and the LOD for propanil in the seawater sample was 0.6 μg/L. The proposed fluorescence sensor and test strip were successfully used in propanil determination in environment and aquatic products.

Evidence of an Important Role of Photochemistry in the Attenuation of the Secondary Contaminant 3,4-Dichloroaniline in Paddy Water

The secondary pollutant 3,4-dichloroaniline (DCA) is produced by the biological degradation of several herbicides, including propanil in paddy fields. The enzymatic hydrolysis of propanil yields DCA with almost quantitative yield. DCA undergoes rather fast photodegradation in paddy water, mostly by direct photolysis. An exception might be represented by the cases (rather rare in paddies) of quite high nitrate concentration (around 50 mg of NO₃^- L^-1), when DCA degradation by CO₃^•- would play a comparable role to that by direct photolysis. The experimentally measured photoreactivity parameters were used as input data for a photochemical model, which predicted a DCA lifetime of 0.5-1 days in sunlit paddy fields in late May, when propanil is usually applied. The model predictions compare remarkably well with the DCA attenuation data reported in field studies, carried out in paddies in temperate regions. Moreover, a consecutive reaction model based on typical biological (propanil) and photochemical (DCA) lifetimes reproduced quite well the time trends of both compounds in paddies, as reported in the literature. These successful comparisons suggest that photodegradation in general, and direct photolysis in particular, may play a key role in DCA attenuation in paddy water.

Phototransformation of the Herbicide Propanil in Paddy Field Water

When irradiated in paddy-field water, propanil (PRP) undergoes photodegradation by direct photolysis, by reactions with ^•OH and CO₃^•-, and possibly also with the triplet states of chromophoric dissolved organic matter. Irradiation also inhibits the nonphotochemical (probably biological) degradation of PRP. The dark- and light-induced pathways can be easily distinguished because 3,4-dichloroaniline (34DCA, a transformation intermediate of considerable environmental concern) is produced with almost 100% yield in the dark but not at all through photochemical pathways. This issue allows an easy assessment of the dark process(es) under irradiation. In the natural environment, we expect PRP photodegradation to be important only in the presence of elevated nitrate and/or nitrite levels, e.g., [NO₃^-] approaching 1 mmol L^-1 (corresponding to approximately 60 mg L^-1). Under these circumstances, ^•OH and CO₃^•- would play a major role in PRP phototransformation. Because flooded paddy fields are efficient denitrification bioreactors that can achieve decontamination of nitrate-rich water used for irrigation, irrigation with such water would both enhance PRP photodegradation and divert PRP dissipation processes away from the production of 34DCA, at least in the daylight hours.

European eel (Anguilla anguilla) plasma biochemistry alerts about propanil stress

Propanil stress response in the eel (Anguilla anguilla) was examined. Eels were exposed to 3.16 mg/L for 72 hr and allowed to recover for 96 hr. Plasma levels of cortisol, lactate dehydrogenase (LDH), alkaline phosphatase (AP), aspartate aminotransferase (AST), cholesterol, triglycerides, glucose, ammonium, lactate, albumin, and total proteins as well as electrolytes (chloride, sodium, potassium, calcium and phosphorus) were determined. As a consequence of exposure, cortisol, AP, AST, and LDH increased. A hyperglycemic condition, together with hyperlactemia, hypoalbuminemia, hypoproteinemia, hypercholesterolemia and hypertriglycemia was registered. Ammonium increased during exposure concomitantly to hyponatremia, hypochloremia, hypocalcemia, hypophosphatemia, and hypokatremia. During recovery, chloride, sodium, potassium, ammonium, albumin and LDH normalized. At the end of the experiment, fish still exhibited hyperglycemia and hyperlactemia. Hypercalcemia was observed. Cholesterol, triglycerides, AP, and AST did not recuperate. These findings are important for assessing potential risks for areas where fish are grown near intensive herbicide use (i.e., paddy fields).

Metabolic responses of channel catfish (Ictalurus punctatus) exposed to phenol and post-exposure recovery

Metabolic adjustments were studied in channel catfish Ictalurus punctatus exposed to 1.5 mg L-1 of phe nol (10% LC50) for four days and recovered for seven days. Lower triacylglycerol (TGA) stores and increased muscle fat free acids (FFA) suggest fat catabolism in muscle. Remarkable liver FFA decrease (-31%) suggests liver fat catabolism as well. Increased muscular ammonia levels and ASAT (aspartate aminotransferase) and decreased plasma aminoacids suggest higher muscular amino acid uptake. Constant levels of glucose and increased liver glycogen stores, associated with lower amino acids in plasma, indicate gluconeogenesis from amino acids. This is supported by higher hepatic ALAT and ASAT. Higher hepatic LDH followed by lower plasma lactate may indicate that plasma lactate was also used as gluconeogenic substrate. Biochemical alterations were exacerbated during the post-exposure recovery period. Reduction in muscle and plasma protein content indicate proteolysis. A higher rate of liver fat catabolism was resulted from a remarkable decrease in hepatic TGA (-58%). Catabolic preference for lipids was observed in order to supply such elevated energy demand. This study is the first insight about the metabolic profile of I. punctatus to cope with phenol plus its ability to recover, bringing attention to the biological consequences of environmental contamination.

Energy reserves mobilization in the yellow eel as herbicide exposure effect

Thiobencarb and propanil are two of the most extensive used herbicides worldwide in rice cultivation. Especially scanty is the available information regarding the effect of herbicides on fish energy resources. In the present study, the effect of sublethal exposure to these herbicides on the energy reserves of juvenile eel Anguilla anguilla was compared. Eels were exposed to 72 h to the herbicide thiobencarb (0.22 mg L(-1)) or Propanil (0.63 mg L(-1)), and allowed to recover in clean water (144 h). Caloric content was determined in liver and skeletal muscle. Fish exposed to thiobencarb rapidly mobilized energy. Reserves from liver were depleted (21%) compared to control values (2.50 kcal g(-1)) at 2 h, whereas in muscle diminished between 12 and 72 h (35%) (control value 0.89 kcal g(-1)). Energy reserves from liver normalized after 144 h in water while in the skeletal muscle were still depleted (24%). Major harmful effects were induced by propanil. Caloric content in liver diminished from the first hours (depletion of 70% at 48h exposure) and in skeletal muscle a 60% (72 h). At the end of the recovery period, energy reserves in pre-exposed eels represented less than 50% compared to control animals. The study indicated that thiobencarb and propanil would constitute a great risk to animals inhabiting freshwater bodies nearby fields of application. Judging from the results, herbicides resulted toxic enough to mobilize fish energy stores. On the other hand, a period of six days in herbicide-free water was not enough time to allow fish to restore energy budgets.

Biochemical stress responses in tissues of the cichlid fish Cichlasoma dimerus exposed to a commercial formulation of endosulfan

Median lethal concentration (LC(50)) and sublethal effects of the commercial endosulfan formulation Zebra Ciagro(®) on the fish Cichlasoma dimerus were studied. The 96-h LC(50) was estimated as 17.7 μg/L. In order to investigate sublethal effects, fish were exposed to 25% and 50% LC(1) (3.4 and 6.8 μg/L, respectively). Endosulfan (ED) significantly increased the hemoglobin concentration and white blood cell count after 96 h. Differential leukocytes count was also altered, due to an increase in the percentage of neutrophils in exposed fish. The hepatopancreatic tissue of fish under ED treatment showed a decrease in aspartate aminotransferase and alanine aminotransferase and an increase in alkaline phosphatase. Lipid peroxidation levels in the 6.8-μg/L ED-containing group were higher than those in control fish for all organs tested (gills, hepatopancreas, and brain).

Short-term exposure to sublethal tebuconazole induces physiological impairment in male zebrafish (Danio rerio)

The aim of the present study was to assess the physiological response of male zebrafish Danio rerio to the fungicide tebuconazole and recovery in fungicide-free water. Acute toxicity tests were carried out and the median lethal concentration (LC(50)) from 24 to 96 h was calculated. The fish were exposed to a sublethal fungicide concentration of 230 microg/L for 7 or 14 days and allowed to recover for 7 or 14 more days, respectively. Whole-body levels of vitellogenins, triglycerides, cholesterol, glucose, lactate and proteins as well as the activities gamma-glutamil transpeptidase (gamma-GT), alanin aminotransferase (AlAT), alkaline phosphatase (AP) and lactate dehydrogenase (LDH) were assayed; corpulence factor (k) was also calculated. Fish exhibited significant increase of vitellogenins (Vtg), which continued to increase after 14 days of recovery. Levels of glucose, lactate, cholesterol and triglycerides increased after 7 and 14 days of exposure. Finally, cholesterol and glucose recovered after 14 days of recovery whereas triglycerides and lactate continued to be elevated. Proteins and k remained unaltered the entire experiments. AAT, AlAT and AP enhanced during exposure and did not recover at the end (except AlAT). A longer recovery period should be necessary to re-establish fish physiology. These results alert about the multiple disruptive physiological actions that tebuconazole may have on fish.

Physiological effects of tricyclazole on zebrafish (Danio rerio) and post-exposure recovery

Short-term effects of tricyclazole on male zebrafish (Danio rerio) physiology were examined joint to the degree of recovery after exposure. Fish were exposed to 142 microg/L (1/100 LC(50)-96 h) of tricyclazole for 7 (Exp.1) and 14 days (Exp.2) and then allowed to recover for 7 or 14 more days, respectively. Whole-body triglycerides, cholesterol, glucose, lactate and total proteins were measured as well as the aspartate aminotransferase (AAT), alanine aminotransferase (AlAT), alkaline phosphatase (AP) and lactate dehydrogenase (LDH) activities as biomarkers of intermediary metabolism; gamma-glutamyl transpeptidase (gammaGT) as biomarker of oxidative detoxification processes and vitellogenin (Vtg) concentration as endpoint for endocrine disruptor effect were also determined. Corpulence factor (k) was calculated. Fungicide exposure in zebrafish resulted in an increased of triglycerides, cholesterol, glucose and lactate levels, however the total protein content did not change. LDH, AlAT and AAT enhanced while AP activity decreased. Corpulence factor (k) also decreased. At the end of the recovery periods cholesterol and glucose levels recovered whereas triglycerides and lactate continued to elevate. Induced disorders on the selected enzymes remained and did not recover at the end of experiments. Fish exhibited significant increases of Vtg during the overall experimental times as a consequence of the fungicide exposure. These findings are of importance in the assessment of the potential risk of new fungicides as tricyclazole on aquatic ecosystems.