RESUMO
Diazinon is a moderately persistent organ phosphorus pesticide largely used in agriculture. The purpose of this study was to evaluate the histopathological damages induced by diazinon in gills, kidney, spleen, and intestine tissues of rainbow trout, Oncorhynchus mykiss. The fishes were exposed to sub-lethal concentrations of diazinon [0.1 and 0.2 mg/L] for a period of 28 days. Tissues analyzed by a microscope were normal in the control group. The histological alterations in gills were characterized by epithelial hyperplasia, necrosis of epithelial filament and lamellar fusion, edema and curling of secondary lamellae. Glomerular lesions, shrinking of the glomerulus and enlargement of space inside Bowman's capsule, dwindling of the tubular lumen, degeneration and necrosis of renal tubules were observed in the kidney tissue of the exposed fish. The spleen tissue showed disorder in ellipsoids cellular and deposition hemosiderin in melanomacrophage centers. Exfoliate of mucosal epithelium, lymphocyte infiltration to lamina propria, reduction of the elastic properties and capillary bleeding were seen in intestine tissue of fish exposed to diazinon. In conclusion, these results indicate the existence of a direct relationship between the pollution of ecosystems by organ phosphorus pesticides such as diazinon and histopathological disorders in different tissues of exposed fishes