The effects of Click 500 SC (terbuthylazine) on common carp Cyprinus carpio under (sub)chronic conditions

Effects of the herbicide formulation Click 500 SC (terbuthylazine 500 g/l) on common carp Cyprinus carpio were assessed through biometric, biochemical, haematological and antioxidant indices, induction of xenobiotic metabolizing enzymes and histological examination of selected tissues.

The fish were exposed to the formulation with terbuthylazine concentrations of 380 ng/l (environmental concentration); 60 µg/l and 550 µg/l for up to 91 days. Haematological indices were assessed using unified methods of haematological examination in fish. Biochemical indices in plasma were measured by biochemical analyzer, ferric reducing ability of plasma (FRAP) and ceruloplasmin activity were determined spectrophotometrically. Concentration of total cytochrome P450, glutathione-S-transferase activity and glutathione content were assessed spectrophotometrically in liver. Activity of liver ethoxyresorufin-O-deethylase (EROD) activity was measured spectrofluorimetrically. Histopathological examination of liver, skin, gills, spleen, cranial and caudal kidney was performed by light microscopy.

An increase (p<0.05) was observed in hepatosomatic index and condition factor in fish from the environmental concentration. A decrease (p<0.05) in haemoglobin and mean corpuscular haemoglobin concentration (MCHC) was found in fish treated with terbuthylazine of 550 µg/l. There was a decline in mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) (p<0.05) in terbuthylazine of 60 µg/l and 550 µg/l. Triglycerides (TAG) (p<0.01) were elevated in all pesticide-treated groups. Alanine aminotransferase (ALT) (p<0.01) and phosphorus (p<0.05) decreased in fish exposed to terbuthylazine of 60 µg/l and 550 µg/l, while albumin (p<0.01) rised in the same groups. An elevation in natrium (p<0.05) in terbuthylazine of 550 µg/l and a rise in protein (p<0.01) in the concentrations of 380 ng/l and 550 µg/l were observed. Correlations between several indices were significant. Ceruloplasmin activity and FRAP were augmented (p<0.01) in the highest concentration tested. Examined xenobiotic detoxification systems were not significantly affected by the exposure. Non-specific histopathological changes were found in the gills and skin of the test fish.

The fish treated with terbuthylazine developed a disorder in several haematological and plasma biochemical indices. The levels of markers of oxidative stress increased in response to the exposure. Examined systems involved in detoxification of xenobiotics did not reflect long-term contact with the herbicide. Detected histological lesions were non-specific. The environmental concentration of terbuthylazin affected biometric indices of the test fish.