RESUMO
The exposure to a world-wide used herbicide atrazine (ATZ) (96h exposure to 2, 10, and 100µgL(-1)), was investigated on the freshwater fish Rhamdia quelen through a multi biomarker approach. Liver histopathology revealed leukocyte infiltration, hepatocyte vacuolization like steatosis and necrosis areas, leading to raised lesion index levels in all tested concentrations. The increase of free melanomacrophage numbers was observed. Gill filaments revealed considerable loss of the microridges on pavement cells at 10 and 100µgL(-1) of ATZ, and a significantly increased of chloride cell (CC) number and density on apical surface area at 100µgL(-1) of ATZ. CAT, GST, GPx, and GR activities were inhibited by all tested concentrations. GSH levels were reduced in individuals exposed to 100µgL(-1). Osmoregulatory function was also disturbed. We observed an increase of plasma magnesium concentrations at 10µgL(-1). Additionally the inhibition of branchial carbonic anhydrase activity was observed at 100µgL(-1). In the kidney, carbonic anhydrase activity decreased only in the group exposed to 2µgL(-1). These results suggest that ATZ, represents a potential ecotoxicological hazard and can be hepatotoxic and nephrotoxic even low concentrations. The current study was the first to show the nephrotoxic effect of ATZ in fish. Besides, in Brazil, the environmental protection agency (CONAMA) establishes that the maximum allowed level of dissolved ATZ in water is 2µgL(-1), but the present results showed that this concentration may cause histopathological, biochemical and physiological changes in R. quelen.
Assuntos
Atrazina/toxicidade , Herbicidas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Atrazina/metabolismo , Brasil , Catalase/metabolismo , Peixes-Gato/fisiologia , Água Doce , Brânquias/efeitos dos fármacos , Brânquias/metabolismo , Brânquias/patologia , Glutationa/metabolismo , Glutationa Peroxidase/metabolismo , Herbicidas/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Poluentes Químicos da Água/metabolismoRESUMO
In our sustained effort to understand mechanisms of mercury toxicity in fish, the histopathological effects of a 96-h acute exposure to water-borne inorganic mercury (inorganic Hg) (15 micro gL(-1)), as well as those of a single dietary dose of inorganic and methyl mercury (methyl Hg) (0.260.05 micro g.Hgg(-1) body weight), over 30 days were examined. Samples of gills, olfactory epithelium, kidneys, and liver of arctic charr, Salvelinus alpinus, were studied using light and electron microscopy. The distribution of dietary inorganic and methyl Hg in the intestinal epithelium was determined using 203Hg microautoradiography. Gills of fish exposed to water-borne inorganic Hg presented a severe disorganization of epithelial cells after 12h and modifications of cilia of ciliated olfactory cells appeared after 24h. Nevertheless, a partial recovery was seen in both tissues by the end of the 96-h exposure period. Liver was little affected by water-borne and single-trophic-dose contamination of inorganic Hg, but dietary methyl Hg had drastic effects, despite its low dosage, with severe necrosis and alterations of cytoplasmic organization. Microautoradiograms showed that inorganic Hg was distributed evenly in the intestinal epithelium, whereas methyl Hg was found at very specific locations on the epithelial surface.