Detection of Genotoxic Insult as DNA strand breaks in fish blood cells by agarose gel electrophoresis

DNA, isolated from the blood cells of bluegill sunfish (Lepomis macrochirus) exposed in the lab to bedded sediment collected from a site contaminated with genotoxic compounds (i e, PAHs, PCBs, and heavy metals), was examined for strand breakage by agarose gel electrophoresis Before electrophoresis the blood cells were embedded in agarose plugs and incubated with proteinase After electrophoresis under both neutral (pH 7) or alkaline (pH 12) conditions, the median molecular length (MML) of the DNA distributed in the gel was determined These quantitative measures were used to estimate the difference in the number of double and single strand breaks between DNA preparations Both types of strand breakage were found to be greater in fish exposed to sediment contaminated with genotoxic compounds as compared to nonexposed fish A statistically significant correlation was demonstrated between the MML value obtained by the electrophoretic assay reported here and the F value (measure of DNA double strandedness) obtained by the alkaline unwinding assay