Detection of DNA strand breaks in isolated mussel (Mytilus edulis L.) digestive gland cells using the "comet" assay

Isolated mussel (Mytilus edulis L.) digestive gland cells were analyzed using the single-cell gel electrophoresis or "comet" assay to assess the ability of potential aquatic contaminants to induce DNA strand breaks (SBs) and to investigate the potential application of this technique as part of an aquatic biomonitoring regime. Freshly prepared cell suspensions from digestive gland were exposed in vitro to hydrogen peroxide (H2O2, 0-200 mu M), 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX, 0-200 mu M), benzo[a]pyrene (BaP, 0-200 mu M), 1-nitropyrene (1-NP, 0-250 mu M) and nitrofurantoin (NF, 0-1000 mu M) for 1 h in the dark at 15 degrees C in the presence of the DNA repair inhibitor cytosine-beta-D-arabinofuranoside (araC). DNA strand breakage was measured using the comet assay. There were significant concentration-dependent increases in the percentage of DNA in the comet tail (mean values +/- SD) for all doses compared with controls (P < 0.05) with H2O2 (up to 61.4 +/- 5.1% at 100 mu M), MX (up to 34.3 +/- 2.2% at 200 mu M), BaP (up to 24.7 +/- 5.1 at 100 mu M), 1-NP (up to 54.7 +/- 5.0% at 200 mu M), and NF (up to 68.1 +/- 4.5% at 500 mu M). There was a decrease (P < 0.05) in viability (eosin Y exclusion) of exposed compared with control cells at 200 mu M H2O2 and BaP only, This study has demonstrated the potential of the comet assay to detect DNA strand breakage at subcytotoxic concentrations of a range of agents, some of which require metabolic activation, This may provide a sensitive, but nonspecific, molecular biomarker of genotoxicity. (C) 1998 Academic Press