Respostas metabólicas e enzimáticas em jundiás, Rhamdia quelen (heptapteridae) e piavas Leporinus obtusidens (anostomidae) expostos a herbicidas utilizados na cultura do arroz

• Autor(a) principal: Miron, Denise dos Santos
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Manancial - Repositório Digital da UFSM
• dARK ID: ark:/26339/001300000p938
• Texto Completo: http://repositorio.ufsm.br/handle/1/4406
• topic: Herbicidas; Clomazone; Quinclorac; Metasulfuron metil; Jundiá; Piavas; CL50; Metabolismo e enzimas; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA

The effects of the toxic exposure of fish to the herbicides clomazone (isoxazolidinone-Gamit®), quinclorac (quinoline-Facet®) and metsulfuron methyl (sulfonylurea-Ally®), used in rice fields were investigated. Experiments were carried out with silver catfish (Rhamdia quelen) to establish an average lethal concentration in 96 hours (LC50 96 h) of exposure to herbicides as well as to determine brain and muscle AChE activity in this specie. In additional experiments, silver catfish were placed into water, for 45 days, taken from the rice cultivation after the application of herbicides. Survival parameters as well as growth and metabolic (glucose, lactate, glycogen and protein) were determined in this species. Piava (Leporinus obtusidens) were exposed (96 and 192 h) to clomazone in the concentration used for rice culture (0.5 mg/L) and recovery tests (192 h) in water free of herbicide were performed. Enzymatic (AChE and CAT), formation of TBARS, protein carbonylation and some metabolic parameters (glycogen, lactate, glucose and protein) were evaluated in different tissues. Results showed that LC50-96 h values for silver catfish were 7.32 mg/L for clomazone, 395 mg/L for quinclorac and no values were obtained for metsulfuron methyl, the fish survived in maximum concentration of 1200 mg/L. Our findings showed that clomazone is a potent inhibitor of AChE activity in silver catfish, showing an inhibition up to 83% in brain and 89% in muscle. However, quinclorac and metsulfuron methyl caused an increase of the brain AChE activity (98 and 179%, respectively) and a decrease in the muscle AChE activity (88 and 56% respectively). After 45 days of quinclorac exposure, silver catfish showed a decrease of 4% in the survival rates. In water with clomazone and quinclorac a reduction in the growth of fish was observed. In the liver tissue of silver catfish exposed to clomazone and quinclorac a glycogen increase and a reduction in the glucose and lactate levels were observed 9 indicating liver gluconeogenesis. In the muscle tissue, there was a decrease in the muscle glycogen, with a lactate increase. There was a decrease in the AChE activity in brain and heart of piava exposed to clomazone (96 and 192 h). AChE activity decreased in muscle after 192 h of exposure. Regarding the recovery of the AChE activity in piava, the inhibition persisted after 192 h in water free of herbicide in brain, muscle and eye. TBARS levels were increased in the brain of piava during the exposure periods, whereas an increase in liver and muscle was observed after 192 h of exposure. TBARS levels did not return to controls values during the recovery period, except for liver. The exposure of piava resulted in an increase in the formation of protein carbonyl in liver, which was not recovered. In liver, the reduction in the CAT activity is related to the increase in liver TBARS, showing that this herbicide causes oxidative damage. Furthermore, in this study the glycogen levels in kidneys of piava exposed to clomazone showed an increase whereas lactate, glucose and protein values to these tissues were decreased. In muscle tissue of piava exposed to clomazone (96 h) was demonstrate a glycogen increased that after recovery returned to the values of control. Muscle tissue of piavas also showed lactate increased, a decreased glucose and protein, however lactate levels not were recovered. These results demonstrate that after exposing piava to clomazone (96 and 192 h) some metabolic and enzymatic changes could not be recovered, even exposing the fish to water free of herbicide (192 h). The results of this study showed that the exposure of fish to herbicides used in rice culture affects the cholinergic system, as well as the metabolic and oxidative parameters causing a condition of oxidative stress. Therefore, the parameters evaluated in piava and silver catfish may be recommended for the monitoring of water contamination by clomazone, quinclorac and metsulfuron methyl.