CYTOPATHOLOGY OF LIVER AND KIDNEY IN RAINBOW-TROUT ONCORHYNCHUS-MYKISS AFTER LONG-TERM EXPOSURE TO SUBLETHAL CONCENTRATIONS OF LINURON

Hepatic and renal cytopathological alterations in fingerling rainbow t rout Oncorhynchus mykiss following 5 wk exposure to 30, 120, and 240 m u g l(-1) linuron [3(3,4-dichlorophenyl)-1-methoxy-1-methylurea] were studied by electron microscopy. Ultrastructural alterations were detec ted in liver and kidney at greater than or equal to 30 mu g l(-1), 2 o rders of magnitude below conventional LC(0). The response suggested a dose-response relationship with a change from adaptive to degenerative features al 120 mu g l(-1). Hepatocyte changes included: stimulation of mitosis; segmentation of nuclei; partial reorganization of heteroch romatin; multiplication of nucleoli; fractionation, vesiculation and t ransformation of rough endoplasmic reticulum (RER) into myelinated bod ies; induction of smooth endoplasmic reticulum; moderate steatosis; ap parent proliferation of mitochondria, peroxisomes, Golgi fields and ly sosomal elements; depletion of glycogen; perisinusoidal lipid accumula tion; elevated rate of hepatocytes in various stages of necrosis; infi ltration and increased phagocytic activity of macrophages. Reactions o f renal tubular cells were differentiated in different nephron segment s. Major alterations by site in kidney were (1) renal corpuscle: lobul ation of podocyte nuclei; (2) proximal segment I: elevated heterogenei ty 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 mu g 1(-1); (3) proximal segment II: nuclear lobulation, binucleated cells, proliferat ion of lysosomes and peroxisomes (lower concentrations), decreased per oxisomes and mitochondria (240 g mu l(-1)), crystalline inclusions in lysosomal matrix, fragmentation, degranulation and circular arrangemen t of RER; (4) distal segment: induction of giant mitochondria with lon gitudinal crystalline inclusions, atypical lysosomes with long crystal line matrix inclusions, and augmentation of various lysosomal elements . Comparison of linuron-induced cellular alterations with cytopatholog ical effects by potential linuron breakdown products, namely 4-chloroa niline and 3,4-dichloroaniline, revealed a high degree of similarity o f cytopathological phenomena, indicating that part of the changes obse rved after linuron exposure might well be due to the action of linuron metabolites.