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 macroc hirus) exposed in the lab to bedded sediment collected from a site con taminated with genotoxic compounds (i.e., PAHs, PCBs, and heavy metals ), was examined for strand breakage by agarose gel electrophoresis. Be fore electrophoresis the blood cells were embedded in agarose plugs an d incubated with proteinase. After electrophoresis under both neutral (pH 7) or alkaline (pH 12) conditions, the median molecular length (MM L) of the DNA distributed in the gel was determined. These quantitativ e measures were used to estimate the difference in the number of doubl e- and single-strand breaks between DNA preparations. Both types of st rand breakage were found to be greater in fish exposed to sediment con taminated with genotoxic compounds as compared to nonexposed fish. A s tatistically significant correlation was demonstrated between the MML value obtained by the electrophoretic assay reported here and the F va lue measure of DNA double-strandedness) obtained by the alkaline unwin ding assay.