Evaluation of the genotoxic potential of lambda-cyhalothrin using nuclear and nucleolar biomarkers on fish cells.

Micronucleus formation in fish erythrocytes, as an indicator of chromosomal damage, has been increasingly used to detect the genotoxic potential of environmental contaminants. Nucleolar organizer regions (NORs) stained with colloidal silver techniques indicate sites of active RNA transcription. The number and size of NORs in interphase nuclei reflect cellular activities such as proliferation and differentiation of cells. In this study, nuclear (micronucleus frequency) and nucelolar (changes in quantitative characteristics of nucleoli) biomarkers were used to evaluate the functional and structural genotoxic effects of the pyrethroid insecticide lambda-cyhalothrin on Garra rufa (Pisces: Cyprinidae). The frequency of micronuclei was examined in blood smears obtained from fishes exposed to three different concentrations (0.005, 0.01, 0.05 microg/l) for a period of 36 h. Nucleolar parameters (the average number of nucleoli per cell; the volume of a single nucleolus; and the percentage of cells with heteromorphic paired nucleoli) were examined in epithelial cells obtained from the edge of caudal fins at the 90th and 180th minutes of exposure. Results of both tests demonstrated the genotoxic potential of pyrethroid lambda-cyhalothrin on G. rufa. The frequency of micronucleated erythrocytes was significantly increased while the nucleolar parameters were repressed by lambda-cyhalothrin treatment. Our results confirmed that the use of nucleolar biomarkers on fish fin cells, in addition to micronucleus test, could provide valuable information in aquatic genotoxicity studies.