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INDICATORS OF GENETIC DAMAGE IN MODEL STREAM FISH USING CONTROLLED LABORATORY EXPOSURES
Citation:
Meier, J R., L W. Chang, P A. Wernsing, AND S. Gibbs. INDICATORS OF GENETIC DAMAGE IN MODEL STREAM FISH USING CONTROLLED LABORATORY EXPOSURES. Presented at Environmental Mutagen Society, New Orleans, LA, April 8-13, 2000.
Description:
The micronucleus (MN) and single cell gel electrophoresis (SCG) assays are being applied to peripheral blood cells from several fish species using model genotoxicants and envirornmentally relevant pollutants. In initial studies, bluegill sunfish (Lepomis macrochirus, 4 to 5 per treatment group) were exposed by i.p. injection to 4-nitroquinoline n-oxide (NQO) at doses of 0, 7.5, 15 and 30 mg/kg or to mitomycin C (MMC) at doses of 0, 1 and 2 mg/kg. Blood samples were taken by caudal puncture at 1 and 3 days after exposure for NQO and at 1, 2, 4, and 8 days for MMC. For the SCG assay, the tail length, tail moment and 5 tail DNA parameters were analyzed by computerized image analysis. For MN assay, acridine orange-stained blood smears were scored manually for micronuclei in polychromatic erythrocytes (PCE) and normochromatic erythorcytes (NCE). Control MN frequencies at all time points were very low (mean = 0.08 MN/1,000 PCEs). No MN were induced at 1 day after exposure to either chemical. By 3 days, a significant elevation in MNPCEs was seen at all thee NQO doses. Significant increases in MN were also observed with MMC, with a peak response of 15 MN/1,000 PCEs at 4-8 days after treatment. For both chemicals, time- and dose-dependent toxicity to the erythropoietic system was observed, based on a decreased PCE:NCE ratio. Evaluation of DNA damage using the SCG assay indicated a significant, dose-related response at 1 day for both NQO and MMC. By 3 days after NQO treatment, the level of DNA damage declined slightly, and for MMC no significant responses were observed at 2-8 days after treatment. These results indicate that monitoring SCG and MN endpoints in fish erythrocytes may provide complementary indicators of exposure of differing duration to genotoxic environmental contaminants.