EVALUATION OF THE COMET ASSAY AS A METHOD FOR THE DETECTION OF DNA-DAMAGE IN THE CELLS OF A MARINE INVERTEBRATE, MYTILUS-EDULIS L. (MOLLUSCA, PELECYPODA)

The potential application of the comet assay for monitoring the effect of DNA damaging agents on the marine mussel, Mytilus edulis tan impor tant pollution indicator organism), was explored. A detailed investiga tion of the baseline levels of single-strand breaks in isolated gill c ells, and how they were affected by age/size of animal, time since col lection, feeding regime, in vivo vs, in vitro exposure conditions, and by antioxidant supplementation was undertaken. The level of cometing in untreated controls was found to be highly variable over time (fluct uations between low and very high DNA damage occurred over just 14 day s post collection). No difference was observed between age/size and fe eding regime of the animals. On exposure to 0, 100, 500 and 1000 mu M H2O2, it was observed that the in vitro exposure produced a markedly m ore homogeneous dose response compared to the in vivo studies (where g ill cells were exposed as a tissue). An important finding of our resea rch was the effect of prior supplementation of the animals' diet with 1 mg/ml alpha-tocopherol acetate (vitamin E compound), which resulted in a marked reduction in the levels of DNA damage expressed by the neg ative controls, without influencing the actual response to H2O2 (0, 5, 25, and 100 mu M) and N-nitrosodimethylamine, NDMA (0, 5, 25, and 100 mM), The effect of vitamin E supplementation was to increase the sens itivity of the comet assay at the lower end of the dose range. This st udy demonstrated the potential application of the comet assay to the g ill cells of the mussel, M. edulis. Although preliminary findings sugg est that antioxidant supplementation can improve the sensitivity of th e assay by lowering the baseline damage in untreated animals, our conc lusion is that the assay has mon potential for use in an in vitro cont ext for the screening of agents destined for release or disposal into the marine environment. (C) 1998 Elsevier Science B.V.