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Diseases of Aquatic Organisms

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DAO 21:35-52 (1995)  -  doi:10.3354/dao021035

Cytopathology of liver and kidney in rainbow trout Oncorhynchus mykiss after long-term exposure to sublethal concentrations of linuron

Oulmi Y, Negele R-D, Braunbeck T

ABSTRACT: Hepatic and renal cytopathological alterations in fingerling rainbow trout Oncorhynchus mykiss following 5 wk exposure to 30, 120, and 240 ug l^(-1) linuron [3(3,4-dichlorophenyl)-1-methoxy-1-methylurea] were studied by electron microscopy. Ultrastructural alterations were detected in liver and kidney at >=30 ug l^(-1), 2 orders of magnitude below conventional LC_(0). The response suggested a dose-response relationship with a change from adaptive to degenerative features at 120 ug l^(-1). Hepatocyte changes included: stimulation of mitosis; segmentation of nuclei; partial reorganization of heterochromatin; multiplication of nucleoli; fractionation, vesiculation and transformation of rough endoplasmic reticulum (RER) into myelinated bodies; induction of smooth endoplasmic reticulum; moderate steatosis; apparent proliferation of mitochondria, peroxisomes, Golgi fields and lysosomal elements; depletion of glycogen; perisinusoidal lipid accumulation; elevated rate of hepatocytes in various stages of necrosis; infiltration and increased phagocytic activity of macrophages. Reactions of renal tubular cells were differentiated in different nephron segments. Major alterations by site in kidney were (1) renal corpuscle: lobulation of podocyte nuclei; (2) proximal segment I: elevated heterogeneity of all cell components, increased heterochromatin and nuclear size, rearrangement of RER, proliferation of Golgi fields, novel lysosomal elements, decreased mitochondria and lysosomes at 240 ug l^(-1); (3) proximal segment II: nuclear lobulation, binucleated cells, proliferation of lysosomes and peroxisomes (lower concentrations), decreased peroxisomes and mitochondria (240 ug l^(-1)), crystalline inclusions in lysosomal matrix, fragmentation, degranulation and circular arrangement of RER; (4) distal segment: induction of giant mitochondria with longitudinal crystalline inclusions, atypical lysosomes with long crystalline matrix inclusions, and augmentation of various lysosomal elements. Comparison of linuron-induced cellular alterations with cytopathological effects by potential linuron breakdown products, namely 4-chloroaniline and 3,4-dichloroaniline, revealed a high degree of similarity of cytopathological phenomena, indicating that part of the changes observed after linuron exposure might well be due to the action of linuron metabolites.

KEY WORDS: Rainbow trout . Liver . Kidney . Ultrastructure . Linuron . 4-Chloroaniline . 3,4-Dichloroaniline . Cytopathology

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