THE ANALYSIS OF DNA ADDUCT FORMATION, REMOVAL AND PERSISTENCE IN THE COMMON MUSSEL MYTILUS-EDULIS EXPOSED TO 4-NITROQUINOLINE 1-OXIDE

P-32-postlabelling was used for the detailed analysis of 4-nitroquinol ine I-oxide (4-NQO) induced DNA adduct formation, removal and persiste nce in the marine shellfish Mytilus spp. The results had a number of i mportant implications concerning the use of such DNA adducts as dosime ters of environmental genotoxin exposures. Our studies indicated that the maintenance of the Mytilus specimens under controlled laboratory c onditions can result in the induction of stress-related adducts' seemi ngly related to the nature of the experimental set-up. The studies als o indicated that the absorption and activation of genotoxins in this s pecies appear to affect the rate of adduct formation, and that the max imum levels of adducts may not necessarily be induced immediately afte r the cessation of a genotoxin exposure. In addition, Mytilus specimen s were shown to possess a significant capacity to remove these genotox in-induced DNA adducts, The removal of these adducts appeared to be bi phasic in nature, with the rapid removal of a large proportion of addu cts occurring within 48 h of the cessation of the exposure, followed b y a slow rate of adduct removal over the remaining period of the studi es. Despite the relatively efficient removal of the majority of these genotoxin-induced DNA adducts, a proportion remained up to 56 days aft er the initial exposure. The persistence of these genotoxin-DNA adduct s, combined with the information on the rates of adduct removal, indic ated that under well-defined conditions, such adducts could serve as s uitable biomarkers of environmental contamination. (C) 1998 Elsevier S cience B.V.