Genetic toxicity in dab Limanda limanda from the North Sea

Abstract

During the Bremerhaven Workshop, a battery of assays was employed aimed at the detection of genetic damage in dab Limanda limanda and at an understanding of the influence of pollution on the metabolism of chemical pro-mutagens. The presence of chernicaVDNA adducts was investigated by 32P-postlabelling (for bulky hydrophobic adducts) and by HPLC with electrochemical detection (for oxidised deoxyguanosine). No significant differences were seen between the various sites analysed along the transect. Bacterial mutagenicity assays (Salmonella typhimurium strains TA100 and TA98) were also unable to detect frame-shift or base-pair mutagens in liver extracts or in bile samples following treatment with the deconjugating enzyme, P-glucuronidase. There was no evidence of pollution-related unscheduled DNA synthesis in dab hepatocytes on the day after sampling. Unscheduled DNA synthesis was, however, induced by nitroquinoline oxide (but not 2-acetylaminofluorene) in dab hepatocytes from 2 stations of different pollution status. The extent of excision repair was similar at the 2 stations. Regarding the metabolism of pro-mutagens, liver enzymes were capable of converting 2-acetylaminofluorene to bacterial mutagens; a process requiring N-hydroxylation and deacetylation.

Antioxidant enzymes in liver of dab Limanda limanda from the North Sea

“…The guanine-derived lesion, 2,6-diamino-4-hydroxy-5-formamido-pyrimidine, characteristic of hydroxyl radical attack, was present in DNA from neoplastic hepatic tissues of English sole Parophrys vetulus from a polluted environment, and a role for it in neoplasia has been proposed (Malins et al 1990). The oxidised base 8-hydroxy-deoxyguanosine was also found in liver of Lirnanda lirnanda from the field (Chipman et al 1992). Increases in activities of antioxidant enzymes with exposure to xenobiotics have been observed, but the responses have been variable.…”

“…The same basic pro-and antioxidant processes observed in mammals exist in fish, including flatfish species (Shewfelt et al 1981, Winston & Di Giulio 1991, Chipman et al 1992. Evidence for this includes in vitro xenobiotic-stimulated oxyradical production and lipid peroxidation, the existence of antioxidant defences, and the detection of in vjvo oxidative damage.…”

“…the opposite effect to that observed for the intermediate stations relative to the inner and Dogger Bank stations. However, whatever the reasons for the putative altered oxidative stress along the pollution gradient, the lack of change in oxidised DNA bases (8-hydroxy-deoxyguanosine) in dab liver from the same stations (Chipman et al 1992) shows the effectiveness of the antioxidant defences.…”