Effects of subchronic exposure to simazine on zebrafish (Danio rerio).

OBJECTIVES: Simazine is a triazine herbicide which has been used for a long period in agriculture and in the aquatic environment for control of weeds and algae. The aim of this study was to investigate the effects of subchronic exposure to simazine on growth and the development of histopathological changes in selected organs (gills, kidney, liver) in Danio rerio. METHODS: Juvenile growth tests were performed on D. rerio according to the OECD method No. 215. Fish at the age of 20 days were exposed to the environmental simazine concentration commonly detected in Czech rivers (0.06 µg.L-1) and a range of sublethal concentrations of simazine (0.6, 6.0 and 60.0 µg.L-1) for 28 days. RESULTS: There were no significant differences (p<0.05) between the specific growth rates (r) of the test groups and those of both control groups. Histopathological examination revealed pathological changes in fish exposed to a simazine concentration of 60.0 µg.L-1. The values of NOEC and LOEC of simazine were 6.0 µg.L-1 and 60.0 µg.L-1. CONCLUSIONS: The environmental concentration of simazine in Czech rivers did not have any effects on the growth and development of histopathological changes in D. rerio.

Biochemical markers of contamination in fish toxicity tests.

Markers of xenobiotic metabolization (cytochrome P450, ethoxyresorufin-O-deethylase, glutathione and glutathione-S-transferase) were investigated in the liver of the common carp Cyprinus carpio after 28-day exposure to different pesticide formulations.The fish exposed to herbicide Sencor 70 WG (metribuzin 700 g/kg) of 0.25 and 2.5 mg/l showed no change in cytochrome P450 and activity of ethoxyresorufin-O-deethylase when compared to control.Successor 600 (pethoxamid 600 g/l) of 0.06; 0.22 and 0.60 mg/l did not affect either cytochrome P450 or the activity of ethoxyresorufin-O-deethylase. However, in fish exposed to Successor 600 of 0.22 and 0.60 mg/l, there was a rise in glutathione and in the activity of glutathione-S-transferase (p<0.05), with Spearman's correlation r = 0.23 at p<0.05.Spartakus (prochloraz 450 g/l) of 0.36 and 1.08 mg/l induced cytochrome P450 and ethoxyresorufin-O-deethylase (p<0.05), with Spearman's correlation r=0.49 at p<0.01. Glutathione increased in fish exposed to 1.08 mg/l (p<0.05), the activity of glutathione-S-transferase rose (p<0.05) in all concentrations tested (0.108; 0.36 and 1.08 mg/l). Spearman's correlation between glutathione and GST was r=0.38; p<0.01).The obtained data contribute to a better understanding of detoxification of the selected xenobitics in fish. Although biomarkers of the first phase of metabolization are considered to be more sensitive, our results indicate higher sensitivity of the second phase biomarkers.

Comparison of diazinon toxicity to embryos of Xenopus laevis and Danio rerio; degradation of diazinon in water.

The aim of this study was to determine the toxic effect of diazinon (organophosphate insecticide) to embryos of Xenopus laevis and Danio rerio. The 96-h LC50 values showed higher toxicity of diazinon for X. leavis in standard solution (9.84 mg/L) compared to the pond water (12.64 mg/L). Teratogenic index for diazinon was 1.3 and 1.6, respectively. The 96-h LC50 diazinon values demonstrated similar sensitivity of embryos D. rerio (8.21-9.34 mg/L) and X. laevis in standard test solutions. Our results reflect that direct application of diazinon into the water can be associated with significant risks to aquatic organisms.

Effects of subchronic exposure to Spartakus (prochloraz) on common carp Cyprinus carpio.

OBJECTIVES: The aim of the study was to investigate effects of the fungicide formulation Spartakus (prochloraz 450 g.L-1) on common carp Cyprinus carpio through biometric, biochemical, haematological and antioxidant indices, induction of xenobiotic metabolizing enzymes and histological examination of selected tissues. DESIGN: The test was performed on juvenile fish, which was exposed to Spartakus (concentrations of prochloraz: 0.05; 0.15 and 0.38 mg.L-1) for 28 days. Haematological indices were assessed using unified methods of haematological examination in fish. Plasma biochemical indices were determined by biochemical analyzer. Concentration of total cytochrome P450 (CYP), glutathione (GSH) content and glutathione-S-transferase (GST) activity were determined spectrophotometrically in hepatopancreas. Activity of liver ethoxyresorufin-O-deethylase (EROD) activity was measured spectrofluorimetrically. Ferric reducing ability of plasma (FRAP) and ceruloplasmin activity were assessed spectrophotometrically. Histological changes in samples of hepatopancreas, skin, gills, spleen, head kidney and caudal kidney were examined by light microscopy. RESULTS: There was a significant rise in hepatosomatic index (HSI) (p<0.01), CYP and EROD (p<0.05) of fish exposed to prochloraz of 0.15 and 0.38 mg.L-1 whereas GST was induced by all concentrations tested and GSH by 0.38 mg.L-1 (p<0.05). Red blood cell count decreased significantly (p<0.05) in prochloraz of 0.05 and 0.15 mg.L-1. Plasma potassium increased (p<0.01) in all Spartakus treated groups, a decline in total protein (p<0.05), ALT, Na+ and Ca (p<0.01) was found in fish exposed to prochloraz of 0.38 mg.L-1. Ceruloplasmin activity was elevated (p<0.05) in the highest concentration tested, FRAP declined (p<0.05) in the same group. Histopathological changes in gills were demonstrated in all pesticide treated groups, with a decreased activity of skin mucous cells in prochloraz of 0.38 mg.L-1. CONCLUSION: The subchronic exposure to Spartakus influenced HSI, induced xenobitic metabolizing enzymes, initiated a disorder of selected plasma indices and a decline in red blood cell count, caused minor histological impairment, and affected antioxidant activities of the test fish.

Effects of subchronic exposure to Successor 600 (pethoxamid 600 g L-1) on common carp Cyprinus carpio.

OBJECTIVES: We investigated the effects of the herbicide preparation Successor 600 on biochemical and haematological indices and the histolopathological parameters of common carp after 28 day exposure. Furthermore, the hepatosomatic index and induction of xenobiotic metabolizing enzymes and biomarkers were assessed. DESIGN: Juvenile fish were exposed to sublethal concentrations of Successor(R) 600 (0.06 mg L-1, 0.22 mg L-1 or 0.60 mg L-1) for 28 days. Haematological indices were assessed using unified methods of haematological examination in fish. Plasma biochemical indices were measured by biochemical analyzer, the vitellogenin concentration in male fish plasma was estimated by direct sandwich ELISA. In hepatopancreas, ethoxyresorufin-O-deethylase (EROD) activity was measured spectrofluorimetrically, concentration of total cytochrome P450 (CYP), glutathion (GSH) content and glutathion-S-transferase (GST) activity were determined spectrophotometrically. Histological changes in samples of hepatopancreas, skin, gills, spleen, head kidney and trunk kidney were examined by light microscopy. RESULTS: Haemoglobin, MCH and MCHC were significantly (p<0.05) reduced in fish treated with Successor(R) 600 of 0.22 and 0.60 mg L-1. LDH was enhanced (p<0.05), in the highest concentration of the preparation. Vitellogenin was detected in all male fish, with no difference between groups. HSI, GSH and GST were elevated (p<0.05), owing to the exposure, whereas CYP and EROD were not affected. Slight histopathological changes were demonstrated in skin, gills and hepatopancreas, with steroid tissue in head kidney samples of 0.60 mg L-1 treated fish. CONCLUSION: Successor 600 affected the haematological profile of the treated fish, while the effects on biochemical indices were less expressed. Male plasma vitellogenin concentrations were not indicative of estrogen disruptive effects after 28 days. The importance of GSH and GST for the metabolisation were demonstrated. In contrast, CYP and EROD were not influenced by any concentration tested. HSI was found to reflex pollution with Successor 600. Histopathological indices caused by the treatment were observed in various tissue samples of the treated fish.

Terbutryn toxicity to Danio rerio: effects of subchronic exposure on fish growth.

OBJECTIVES: The aim of this study was to investigate effects of subchronic exposure to sublethal levels of terbutryn on growth and on histopathological changes in Danio rerio. DESIGN: The acute toxicity tests were performed on the juvenile stage of Danio rerio according to OECD No. 203 Fish, Acute Toxicity Test. The juvenile growth tests were performed on D. rerio according to the OECD method No. 215. Fish at the age of 20 days were exposed to the terbutryn environmental concentration commonly detected in the Czech rivers (0.02 microg L-1) and the range of sublethal concentrations of terbutryn (0.06, 0.2, 0.6 and 2 mg L-1) for 28 days. RESULTS: The 96hLC50 terbutryn mean value for the juvenile stage of D. rerio was 5.71 +/- 0.46 mg L-1. A significant decrease (p < 0.01) in the fish growth caused by terbutryn was observed in the concentration of 0.6 mg L-1. The value of NOEC was 0.2 mg L-1 and LOEC was 0.6 mg L-1 of terbutryn. We found the damage to tubular system of kidneys in the concentration of 0.6 mg L-1 of terbutryn. CONCLUSION: The environmental concentration of terbutryn in the Czech rivers did not have any effects on growth and on histopathological changes in D. rerio and this concentration is lower than determined LOEC and NOEC values of terbutryn.

Effects of subchronic metribuzin exposure on common carp (Cyprinus carpio).

OBJECTIVES: Effects of metribuzin on biochemical and haematological indices, induction of specific biomarkers and impacts on biometric parameters of Cyprinus carpio were investigated for subchronic conditions. METHODS: Juvenile fish were exposed to 0.175 mg.L-1 or 1.75 mg.L-1 metribuzin for 28 days. Haematological indices were assessed using unified methods of haematological examination in fish. Biochemical indices were determined by biochemical analyzer, hepatic vitellogenin content was estimated by direct sandwich ELISA. Cytochrome P450 concentration and ethoxyresorufin O-deethylase activity were measured in liver spectrophotometrically and spectrofluorimetrically, respectively. RESULTS: Increased haematocrit and RBC count were found in fish exposed to 1.75 mg.L-1 metribuzin compared to control fish (p<0.05). Other indices contents and biomarkers levels were not significantly changed by either concentration of metribuzin. CONCLUSION: Sublethal metribuzin pollution may have adverse impacts on haematological parameters in common carp.