Assessment of water and sediment contamination in small streams by means of cytological and biochemical alterations in isolated rainbow trout (Oncorhynchus mykiss) hepatocytes
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Isolated hepatocytes of rainbow trout (Oncorhynchus mykiss) were exposed to (1)native waters and acetone sediment extracts ofthe Krähenbach and the Körsch, twosmall streams in southwest Germanycharacterized by different levels of chemicalcontamination, as well as (2) differentconcentrations (1 ×, 10 ×, 50 ×) of anartificial mixture of 20 contaminants (PAHs,PCBs, pesticides) typical of the chemicalburden of the more heavily contaminatedKörsch. Following exposure for up to 3 d,hepatocytes were analyzed by means of electronmicroscopy and enzyme biochemistry to evaluatesublethal cytotoxic effects. Results documentthat dilutions of Krähenbach and Körschsurface water and sediment extracts inducemultiple time- and dose-dependent structuraland functional changes in hepatocytes. Betweenboth rivers as well as between free water phaseand sediment, significant differences in thetoxic burden could be detected. Consistently,however, both morphological and biochemicalresponses induced by samples from the moreseverely polluted river Körsch were morepronounced than those of the moderatelycontaminated river Krähenbach, whichindicates that the differential pollution ofthe two rivers directly translates into theextent of biochemical and morphological changesin hepatocytes. Cytopathological effectsincluded deformation of nuclear envelopes andincrease of heterochromatin, heterogeneity ofmitochondria, vesiculation of cisternae of therough endoplasmic reticulum, as well asproliferation of the smooth endoplasmicreticulum. Peroxisomal and lysosomalproliferation could be correlated tostimulation of the corresponding markerenzymes, catalase and acid phosphatase. In bothrivers, activities of lactate dehydrogenase andalanine aminotransferase as markers ofcytosolic glycolysis and protein metabolismwere increased indicating a general stimulationof cellular metabolism. Similar changes wereinduced by exposure to the artificial chemicalmixture resembling the chemical contaminationof the Körsch. Cytological changes inisolated hepatocytes thus not only serve todiscriminate between different levels ofcontamination of water, but may also help todifferentiate between pollution levels ofsediments.
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