Formation of DNA adducts in the gill tissue of Mytilus galloprovincialis treated with benzo[a]pyrene.

The formation of DNA adducts was evident after treatment of spawned or resting Mediterranean mussels (Mytilus galloprovincialis Lmk.) with 0.5-100 mu g/l of benzo[a]pyrene for 2 and 3 days. Reference DNA samples, in vitro radiolabelled with 0.5, 5, 50 mu M H-3-anti (+/-)-B[a]P-diol-epoxide, were initially used to compare two DNA purification procedures. Following a standard four-step extraction starting with phenol, in comparison to a simplified single-step extraction without phenol, we obtained lower yields of bound radioactivity in the reference DNA samples. After simplified DNA purification and nuclease P1 enhanced P-32-postlabelling assay we detected a reproducible dose-dependent increase of a specific spot in gills of mussels treated with B[a]P, although this spot was present in low amounts. Short (2 days) and prolonged (27 days) pretreatment of mussels with a polychlorinated biphenyl mixture, Aroclor 1254, did not increase the levels of B[a]P-related adducts. On the whole, these results indicate the formation of detectable amounts of DNA reactive intermediates in gills of mussels treated with B[a]P. Although the pathway of formation and the molecular identity of the specific adducts remain unclear, their presence suggests that polycyclic aromatic hydrocarbons may cause genetic damage in marine mussels.