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EVALUATION OF GENETIC DAMAGE IN FISH EXPOSED TO PESTICIDES IN FIELD AQUATIC MICROCOSMS
Citation:
Chang, L W., J R. Meier, G P. Toth, AND D. W. Graham. EVALUATION OF GENETIC DAMAGE IN FISH EXPOSED TO PESTICIDES IN FIELD AQUATIC MICROCOSMS. Presented at Environmental Mutagen Society, New Orleans, LA, April 8-13, 2000.
Description:
Single cell gel electrophoresis (SCG) and micronucleus (MN) assays were used to measure DNA strand breaks and chromosomal damage in fish blood erythrocytes as biological indicators of exposure to alachlor and atrazine in a surrogate aquatic ecosystem. Caged common carp (Cyprinus carpio) were exposed to either 0, 10, 25, 50 and 100 ug/L alachlor for 60 days or 0, 3, 10, 30 and 100 ug/L atrazine for 30 days in field microcosms. Benzo(a)pyrene (BaP), 0.76 ug/L) was used as a positive control. Blood samples from 6 fish of each treatment group were taken by caudal puncture at 0, 1, 4, 30 and 60 days after exposure. For the SCG assay, the overall mean values of tail length, tail moment and % tail DNA were analyzed by computerized image analysis for the extent of DNA damage. For the MN assay, blood smears were stained with acridine orange. The ratio of polychromatic erythrocytes (PCE) to normochromatic erythrocyte (NCE) and MN frequencies were scored manually by fluorescence microscopy. The results of the SCG assay indicate alachlor induced statistically significant dose-related DNA damage in carp blood erythrocytes as shown by three parameters during the entire exposure period. The level of damage reached a peak at 50-100 ug/L. For atrazine, a maximal response was seen at a concentration of 10 ug/L, followed by a plateau of the dose-response curve at 30 and 100 ug/L. BaP induced significant DNA damage at 0.76 ug/L. For all three chemicals, significant increases in damage were seen by one day after exposure, with the peak response being at day 4, followed by a slight decline in response at day 30 or 50. As for the MN assay, the results show the PCE frequencies were very low on most of the carp blood smears of both control and exposed fish. The PCE level decreased from day 4 to day 30 of the study duration. No MN were found in any PCE or NCE in any of the fish including those exposed to BaP. These surrogate ecosystem studies demonstrate the usefulness of the SCG assay for monitoring chemical stressors with genotoxic activity in aquatic ecosystems. The negative MN results are inconclusive because of the low erythrocyte turnover in the fish.