Efeito do disseleneto de difenila sobre a toxicidade induzida por herbicidas em peixes

Abstract

Environmental contamination caused by frequent use of herbicides in agriculture has increased in last decades. The quinclorac and clomazone herbicides are widely used in agriculture, which can cause contamination to organisms, such as fish. However, it is necessary studies in order to minimize the toxic effects of these compounds on aquatic ecosystems. Micronutrients such as selenium, which is essential in the nutrition of fish, may have antioxidant functions against oxidative damage caused by herbicides. The objective of this study was to verify whether a diet supplemented with diphenyl diselenide [(PhSe)2], has a protective effect against damage induced by herbicides quinclorac and clomazone in fish species Cyprinus carpio (carp) and Rhamdia sp. (silver catfish). In the first experiment, carp were fed a diet without (PhSe)2 or a diet containing 3.0 mg/Kg of (PhSe)2 for 60 days and after were exposed to 1 mg/L of quinclorac for 192 h. Thiobarbituric acid reactive substances (TBARS), protein carbonyl, non-protein thiols (SHNP), ascorbic acid (AA), and the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST) were determined in liver, gills, brain and muscle of carp. The quinclorac increased TBARS levels in liver and gills, decreased NPSH levels in brain and muscle, AA in muscle, inhibited enzymes SOD in liver and GST in liver and brain. The (PhSe)2 reversed these effects by preventing the increase of TBARS in liver and gills and recovering GST activity in liver and NPSH in brain and muscle. In the second experiment, silver catfish were fed a diet without (PhSe)2 or a diet containing 3.0 mg/Kg of (PhSe)2 for 60 days and after were exposed to 1 mg/L of quinclorac for 192 h. We investigated the effect of (PhSe)2 on plasma metabolic changes, enzymes of intermediary metabolism, pro-oxidants parameters and antioxidant defense in the liver of silver catfish. The weight, length and hepatic somatic index (HSI) were also determined. Animals exposed to quinclorac showed a decrease at HSI, an increase lactate levels in plasma and in the enzymes fructose bifosfatase (FBPase), glucose-6-phosphatase (G6Pase), glycogen phosphorylase (GPase) and aspartate aminotransferase (AST) in liver. Furthermore, were observed increased of TBARS, decreased NPSH and AA levels and inhibition of SOD in liver of silver catfish. The (PhSe)2 was effective in protecting the liver of silver catfish by decreased TBARS, increasing NPSH levels, AA and the activity of SOD. However, the (PhSe)2 was not effective in recovery the effects caused by the increase of hepatic enzyme AST. In the third experiment investigated the ability of (PhSe)2 in reducing oxidative damage in the liver, gills and muscle of carp and silver catfish exposed to clomazone. Silver catfish and carp were fed with a diet without (PhSe)2 or a diet containing 3.0 mg/Kg of (PhSe)2 for 60 days and after were exposed to 1 mg/L of clomazone (192 h). At the end of the exposure period, oxidative parameters and antioxidant defenses were determined. Silver catfish exposed to clomazone showed increased TBARS in liver and muscle and protein carbonyl in liver and gills. In addition, decrease in levels of NPSH in liver and gills, AA in the liver and of enzyme glutathione peroxidase (GPx) in liver was observed. The (PhSe)2 reversed some effects caused by clomazone in silver catfish, preventing the increase in TBARS and protein carbonyl and by increasing NPSH and AA levels. Moreover, clomazone no caused apparent situation of oxidative stress in carp and thus cannot assess the role of (PhSe)2 in this species exposed to that herbicide. However, the (PhSe)2 in both species reduced per se the TBARS levels in liver and muscle, increased NPSH and AA levels and the activity of GPx in liver. Considering that exposure to herbicides is more frequent and that is the cause of several changes in fish, the results of these studies are of great importance, since the (PhSe)2 may represent an alternative to prevent or mitigate toxicity caused by herbicides in different fish species of commercial importance.