Genotoxic profile of chemicals in relation to their carcinogenic potency

Abstract

The random amplified polymorphic DNA (RAPD) is a useful assay for the detection of genotoxin-induced DNA damage and mutations. In this study, we have further evaluated the potential of this assay to measure benzo(a)pyrene [B(a)P]-induced DNA changes, and repair (in kinetic experiments) as well as transgenerational effects in the water fleas, Daphnia magna. The organisms, which reproduce parthenogenetically, were exposed to 50 μg L−1 B(a)P for 3 or 6 days and were allowed to recover in clean medium for 12 or 9 days, respectively. Qualitative and quantitative changes were observed in RAPD profiles generated not only from the B(a)P exposed Daphnia but also from previously treated organisms during the recovery experiments. The fact that some of the RAPD changes disappeared at the end of both recovery experiments suggested that the DNA effects were fully repaired or reversed. In addition, some of the B(a)P-induced RAPD alterations detected in parental D. magna were also observed in the offspring patterns. This suggested that DNA alterations that occurred in germ cells were probably transmitted to the next cohorts. The present study shows that the RAPD method can be useful to qualitatively assess the kinetics of DNA changes, repair and transgenerational effects and such effects could potentially be linked to survival and reproductive success at higher levels of biological organisation. In addition, the water fleas have efficient capabilities to repair or reverse B(a)P-induced DNA effects. Finally, unrepaired or misrepaired genetic damage induced by genotoxins such as B(a)P could be transmitted to next generations in these parthenogenetically reproducing organisms.