32P-postlabeling analysis of DNA adduct formation and persistence in English sole (Pleuronectes vetulus) exposed to benzo[a]pyrene and 7H-dibenzo[c,g]carbazole

Mechanism of 7H-Dibenzo[c,g]carbazole metabolism in cytochrome P450 1A1: Insights from computational studies

7H-Dibenzo[c,g]carbazole (DBC) is a prevalent environmental contaminant that induces tumorigenesis in several experimental animals. Recently, it has been utilized to develop high-performance solar cells and organic phosphorescent materials. It is imperative to strengthen investigations of DBC metabolism to understand its potential risks to human health. In this study, human CYP1A1 was employed as the metabolic enzyme to investigate the metabolic mechanism of DBC by molecular docking, molecular dynamics (MD) simulation, and quantum mechanical (QM) calculation. The results indicate that DBC binds to CYP1A1 in two modes (mode 1 and mode 2) mainly through nonpolar solvation energies (ΔGnonpolar). The formation of the two binding modes is attributed to the anchoring effect of the hydrogen bond formed by DBC with Asp320 (mode 1) or Ser116 (mode 2). Mode 1 is a "reactive" conformation, while mode 2 is not considered a "reactive" conformation. C5 is identified as the dominant site, and the pyrrole nitrogen cannot participate in the metabolism. DBC is metabolized mainly by a distinct electrophilic addition-rearrangement mechanism, with an energy barrier of 21.74 kcal/mol. The results provide meaningful insights into the biometabolic process of DBC and contribute to understanding its environmental effects and health risks.

DNA damage and health effects in juvenile haddock (Melanogrammus aeglefinus) exposed to PAHs associated with oil-polluted sediment or produced water

The research objective was to study the presence of DNA damages in haddock exposed to petrogenic or pyrogenic polyaromatic hydrocarbons (PAHs) from different sources: 1) extracts of oil produced water (PW), dominated by 2-ring PAHs; 2) distillation fractions of crude oil (representing oil-based drilling mud), dominated by 3-ring PAHs; 3) heavy pyrogenic PAHs, mixture of 4/5/6-ring PAHs. The biological effect of the different PAH sources was studied by feeding juvenile haddock with low doses of PAHs (0.3-0.7 mg PAH/kg fish/day) for two months, followed by a two-months recovery. In addition to the oral exposure, a group of fish was exposed to 12 single compounds of PAHs (4/5/6-ring) via intraperitoneal injection. The main endpoint was the analysis of hepatic and intestinal DNA adducts. In addition, PAH burden in liver, bile metabolites, gene and protein expression of CYP1A, GST activity, lipid peroxidation, skeletal deformities and histopathology of livers were evaluated. Juvenile haddock responded quickly to both intraperitoneal injection and oral exposure of 4/5/6-ring PAHs. High levels of DNA adducts were detected in livers three days after the dose of the single compound exposure. Fish had also high levels of DNA adducts in liver after being fed with extracts dominated by 2-ring PAHs (a PW exposure scenario) and 3-ring PAHs (simulating an oil exposure scenario). Elevated levels of DNA adducts were observed in the liver of all exposed groups after the 2 months of recovery. High levels of DNA adduct were found also in the intestines of individuals exposed to oil or heavy PAHs, but not in the PW or control groups. This suggests that the intestinal barrier is very important for detoxification of orally exposures of PAHs.

7H-Dibenzo[c,g]carbazole: Metabolic pathways and toxicity

7H-Dibenzo[c,g]carbazole (DBC), a local and systemic carcinogen in animal studies, is a common environmental pollutant. It generally co-occurs in a variety of organic complex mixtures derived from incomplete combustion of organic matter. Despite high lipophilicity, DBC is more water-soluble and faster metabolized than the homocyclic aromatics. Moreover, greater polarity, high bioaccumulation potential, and persistence in the environment may imply DBC's higher biological significance and impact on human health, even at lower concentrations. The biotransformation pathways of DBC are incompletely known and the ultimate carcinogenic metabolite(s) are not clearly identified as yet. Structure-biological studies suggest two ways of activation: at the ring carbon atoms and at the pyrrole nitrogen. It is supposed that the particular pathway of biotransformation might be connected with the tissue/organ specificity of DBC. Cytochrome P450 (CYP) family of enzymes plays a pivotal role in the metabolism of DBC; though, the one-electron activation and the aldo-keto reductase-catalyzed oxidation are also involved in metabolic activation. Additionally, DBC can be photoactivated even at physiologically relevant doses of UVA light due to the extended aromatic ring system resulting in strong genotoxicity and oxidative stress. The goal of this review is to summarize current knowledge on mechanisms of DBC activation and possible implications for toxicity, genotoxicity, and carcinogenicity.

Molecular Mechanisms of Crude Oil Developmental Toxicity in Fish

With major oil spills in Korea, the United States, and China in the past decade, there has been a dramatic increase in the number of studies characterizing the developmental toxicity of crude oil and its associated polycyclic aromatic compounds (PACs). The use of model fish species with associated tools for genetic manipulation, combined with high throughput genomics techniques in nonmodel fish species, has led to significant advances in understanding the cellular and molecular bases of functional and morphological defects arising from embryonic exposure to crude oil. Following from the identification of the developing heart as the primary target of crude oil developmental toxicity, studies on individual PACs have revealed a diversity of cardiotoxic mechanisms. For some PACs that are strong agonists of the aryl hydrocarbon receptor (AHR), defects in heart development arise in an AHR-dependent manner, which has been shown for potent organochlorine agonists, such as dioxins. However, crude oil contains a much larger fraction of compounds that have been found to interfere directly with cardiomyocyte physiology in an AHR-independent manner. By comparing the cellular and molecular responses to AHR-independent and AHR-dependent toxicity, this review focuses on new insights into heart-specific pathways underlying both acute and secondary adverse outcomes to crude oil exposure during fish development.

DNA adducts in marine fish as biological marker of genotoxicity in environmental monitoring: The way forward

DNA adducts in fish represent a very important genotoxicity endpoint in environmental monitoring, being a pre-mutagenic lesion that plays an essential role in the initiation of carcinogenesis. The analysis of DNA adducts is a challenging task due to the low concentration of the analyte. Methods are available to determine the presence of DNA adducts, although further knowledge is required to fully understand the nature of the adducts and responsible xenobiotics (i.e. position of adduct in DNA, most active xenobiotic and metabolite forms, structural information). At present, ³²P-postlabeling is the most used method that has the required sensitivity for DNA adduct analyses in both human health and environmental monitoring. Development of new mass spectrometry based methods for identifying DNA adducts in complex matrixes is now considered as a necessary mission in toxicology in order to gain the necessary information regarding adduct formation and facilitate tracking sources of contamination. Mass spectrometry therefore represents the future of DNA adduct detection, bringing along a series of challenges that the scientific community is facing at present.

Toxic effects of 1-decyl-3-methylimidazolium bromide ionic liquid on the antioxidant enzyme system and DNA in zebrafish (Danio rerio) livers

Ionic liquids were recently found to be toxic to aquatic organisms. Therefore, the present study investigated the effects of 1-decyl-3-methylimidazolium bromide ([C10mim]Br) on oxidative stress and DNA damage in zebrafish. Male and female zebrafish were separated and exposed to five concentrations of [C10mim]Br (0, 5, 10, 20, and 40 mg L(-1)) and were sampled on days 7, 14, 21 and 28. Compared to control groups, the activities of antioxidant enzymes were significantly decreased at most exposure intervals. This decreased activity resulted in the production of excess reactive oxygen species (ROS) and increased malondialdehyde (MDA) content in zebrafish liver. Additionally, it was noteworthy that a clear dose-response was found for DNA damage. As for sex differences, significant differences in catalase (CAT) and ROS were found on the 7th day. In conclusion, the exposure of [C10mim]Br caused DNA damage, leading to antioxidant responses in zebrafish livers.

Screening of hydrophobic DNA adducts in flounder (Platichthys flesus) from the Baltic Sea

Neoplasia and other histopathological lesions in flounder (Platichthys flesus) liver have been investigated in several European sea areas, including the Baltic Sea. Several studies have been able to link neoplasm epizootics in fish with the exposure to genotoxins such as polycyclic aromatic hydrocarbons (PAHs). The level of hydrophobic DNA adducts in tissue DNA reflects the exposure of the organism to PAHs. Using hydrophobic DNA adduct levels as biomarkers, possible PAH exposure was assessed in flounder from 10 different sites in the Baltic Sea, collected during the years 1995-1997. The results show that the overall levels of hepatic DNA adducts were low and, in general, the chromatograms appeared clean. The highest levels of DNA adducts were found at two sites in the southern Baltic Sea. There were no statistically significant differences in adduct levels between the sites. Our results indicate that flounder from studied off shore sites of the Baltic Sea had not been exposed to a greater extent to large polycyclic hydrophobic hydrocarbons in their environment.

DNA adduct levels in fish from pristine areas are not detectable or low when analysed using the nuclease P1 version of the32P-postlabelling technique

In order to understand and apply DNA adduct formation in fish liver as a biomarker for aquatic pollution, information concerning the natural background levels in noncontaminated organisms, caused by endogenous compounds, is of fundamental importance. In this study, DNA adducts were analysed in liver of 11 fish species from arctic and sub-arctic areas in the northern Atlantic using the nuclease P1 version of the 32P-postlabelling technique. The collected fish were assumed not to have been influenced by anthropogenic pollution apart from possible long-range transported pollutants. As polycyclic aromatic hydrocarbons (PAHs) are thought to be fundamental in forming the type of DNA adducts detected by the method used, biliary PAH metabolite levels were measured in a selection of the investigated species. In all investigated individuals, the levels of PAH metabolites were undetectable. Controlled on-site exposure experiments with benzo[a]pyrene (polar cod) and laboratory experiments with crude oil (polar cod and Atlantic cod) were conducted. DNA adducts were formed in both these species. The field-sampled fish showed undetectable levels of DNA adducts or levels just above the detection limit. The present study supports the assumption that when DNA adducts are detected by the nuclease P1 version of the 32P-postlabelling method in fish liver, it can be interpreted as DNA damage caused by pollutants.

PCB77 (3,3',4,4'-tetrachlorobiphenyl) co-exposure prolongs CYP1A induction, and sustains oxidative stress in B(a)P-exposed turbot, Scophthalmus maximus, in a long-term study

Cytochrome P4501A (CYP1A), benzo(a)pyrene (B(a)P) activation and biliary elimination, phase II activities, and peroxisomal and antioxidant activities of turbot (Scophthalmus maximus) were studied in a long-term controlled experiment. Fish were serially exposed in water on day 1 and on completion of months 3, 6 and 9 to 0.1, 0.2, 0.1 and 0.1mg B(a)P/l, respectively, while another group was identically treated with additional PCB77 (3,3',4,4'-tetrachlorobiphenyl) at 1% of concomitant B(a)P (w/w). Temporally persistent responses were obtained by sampling on week 3 and 3 months from each latest exposure. Serial exposure to B(a)P+PCB77 progressively induced liver 7-ethoxyresorufin O-deethylase (EROD) activity and CYP1A protein levels (ELISA, western blotting) towards months 9, 12 and gill EROD activity on month 12. It associated with an apparent increase in liver benzo(a)pyrene diol epoxide (BPDE)-DNA adduct levels (ultrasensitive enzyme radioimmunoassay), and elevated bile B(a)P metabolite levels on month 9 females as compared to males. In contrast, B(a)P alone did not cause (p>0.05) comparable effects on liver EROD, CYP1A, adducts nor on bile metabolites. Both exposed groups demonstrated evidence for lasting oxidative stress as hepatic superoxide dismutase, catalase and glutathione peroxidase activities were significantly altered (p<0.05) with symptomatic pro-oxidant associations among them. Both treatments affected liver somatic index similarly (increase on month 3, decrease on month 9 in males). Continued exposure on month 18 (0.2mg B(a)P/l, 1% PCB77) followed by sampling 6 months later showed sustained induction (p<0.001) of hepatic EROD in B(a)P+PCB77 group, which was not seen in B(a)P alone treatment. Thus, PCB77 co-exposure prolonged CYP1A induction and contributed to a persistent oxidative challenge in B(a)P-exposed turbot. The results indicate synergistic effects of polycyclic aromatic hydrocarbon (PAH) and polychlorinated biphenyl (PCB) exposure in the aquatic environment.

Improved flatfish health following remediation of a PAH-contaminated site in Eagle Harbor, Washington

Eagle Harbor in Puget Sound, WA became a Superfund site in 1987 due to polycyclic aromatic hydrocarbons (PAHs) released chronically from a nearby creosoting facility. Early studies here (1983-1986) demonstrated up to an approximately 80% prevalence of toxicopathic liver lesions, including neoplasms, in resident English sole (Parophrys vetulus). These lesions in English sole are consistently associated with PAH exposure in multiple field studies, and one laboratory study. Later studies (1986-1988) incorporated biomarkers of PAH exposure and effect, including hepatic CYP1A expression and xenobiotic-DNA adducts, and biliary fluorescent aromatic compounds (FACs). Before site remediation, lesion prevalences and other biomarker values in this species from Eagle Harbor were among the highest compared to other sites in Puget Sound and the US Pacific Coast. To sequester PAH-contaminated sediments, in 1993-1994, a primary cap of clean sediment was placed over the most-contaminated 54acres, with a 15-acre secondary cap added from 2000-2002. Lesion prevalences and biomarker values before primary capping were reduced compared to 1983-1986, consistent with facility closure in 1988 and shore-based source controls begun in 1990. Liver lesion risk, hepatic CYP1A activities, and levels of biliary FACs from fish collected immediately after and at regular intervals up to 2 years after primary capping were variable relative to pre-capping. Over the entire monitoring period since primary capping (128 months), but particularly after 3 years, there was a significantly decreasing trend in biliary FACs, hepatic DNA adducts and lesion risk in English sole. In particular, lesion risk has been consistently low (<0.20) compared to primary cap initiation (set at 1.0), from approximately 4 years after primary capping through April 2004. These results show that the sediment capping process has been effective in reducing PAH exposure and associated deleterious biological effects in a resident flatfish, and that longer term monitoring of pollutant responses in biological resources, such as resident fish, is needed in order to demonstrate the efficacy of this type of remediation.

Resolving mechanisms of toxicity while pursuing ecotoxicological relevance?

In this age of modern biology, aquatic toxicological research has pursued mechanisms of action of toxicants. This has provided potential tools for ecotoxicologic investigations. However, problems of biocomplexity and issues at higher levels of biological organization remain a challenge. In the 1980s and 1990s and continuing to a lesser extent today, organisms residing in highly contaminated field sites or exposed in the laboratory to calibrated concentrations of individual compounds were carefully analyzed for their responses to priority pollutants. Correlation of biochemical and structural analyses in cultured cells and tissues, as well as the in vivo exposures led to the production and application of biomarkers of exposure and effect and to our awareness of genotoxicity and its chronic manifestations, such as neoplasms, in wild fishes. To gain acceptance of these findings in the greater environmental toxicology community, "validation of the model" versus other, better-established often rodent models, was necessary and became a major focus. Resultant biomarkers were applied to heavily contaminated and reference field sites as part of effects assessment and with investigations following large-scale disasters such as oil spills or industrial accidents. Over the past 15 years, in the laboratory, small aquarium fish models such as medaka (Oryzias latipes), zebrafish (Danio rerio), platyfish (Xiphophorus species), fathead minnow (Pimephales promelas), and sheepshead minnow (Cyprinodon variegatus) were increasingly used establishing mechanisms of toxicants. Today, the same organisms provide reliable information at higher levels of biological organization relevant to ecotoxicology. We review studies resolving mechanisms of toxicity and discuss ways to address biocomplexity, mixtures of contaminants, and the need to relate individual level responses to populations and communities.

DNA adducts, benzo(a)pyrene monooxygenase activity, and lysosomal membrane stability in Mytilus galloprovincialis from different areas in Taranto coastal waters (Italy)

The aim of this study was to investigate the impact of environmental pollution at different stations along the Taranto coastline (Ionian Sea, Puglia, Italy) using several biomarkers of exposure and the effect on mussels, Mytilus galloprovincialis, collected in October 2001 and October 2002. Five sampling sites were compared with a "cleaner" reference site in the Aeronautics Area. In this study we also investigated the differences between adduct levels in gills and digestive gland. This Taranto area is the most significant industrial settlement on the Ionian Sea known to be contaminated by polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, heavy metals, etc. Exposure to PAHs was evaluated by measuring DNA adduct levels and benzo(a)pyrene monooxygenase activity (B(a)PMO); DNA adducts were analyzed by 32P-postlabeling with nuclease P1 enhancement in both gills and digestive glands to evaluate differences between DNA adduct levels in the two tissues. B(a)PMO was assayed in the microsomal fraction of the digestive glands as a result of the high expression of P450-metabolizing enzymes in this tissue. Lysosomal membrane stability, a potential biomarker of anthropogenic stress, was also evaluated in the digestive glands of mussels, by measuring the latent activity of beta-N-acetylhexosaminidase. Induction of DNA adducts was evident in both tissues, although the results revealed large tissue differences in DNA adduct formation. In fact, gills showed higher DNA adduct levels than did digestive gland. No significant differences were found in DNA adduct levels over time, with both tissues providing similar results in both years. DNA adduct levels were correlated with B(a)PMO activity in digestive gland in both years (r = 0.60 in 2001; r = 0.73 in 2002). Increases were observed in B(a)PMO activity and DNA adduct levels at different stations; no statistical difference was observed in B(a)PMO activity over the two monitoring campaigns. The membrane labilization period in mussels from some stations was decreased in both years. No statistical differences were established in the membrane labilization times from 2001 to 2002. Our results suggest the existence of different sources and amounts of environmental contaminants at the stations investigated. The formation of DNA adducts confirms the existence of activation pathways in mussels and shows the importance of DNA adduct analysis in the gill tissue in addition to the more commonly used digestive gland; these results confirm the utility of lysosomal membrane stability as a biomarker of general stress. Overall, the integrated use of biomarkers of exposure and the effects of environmental contaminants on living marine organisms may help to better interpret the impact of pollutants in a marine coastal environment.

Metabolic interactions between low doses of benzo[a]pyrene and tributyltin in arctic charr (Salvelinus alpinus): a long-term in vivo study

We have previously reported that short-term, single exposure to a high dose of tributyltin (TBT), a widely used antifouling biocide, inhibited both the in vivo metabolism and metabolic activation of the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) in fish; (BaP), in turn, stimulated TBT metabolism. Here, we provide further mechanistic evidence of mutual metabolic interactions between BaP and TBT in response to long-term, repeated exposures to low doses. Juvenile Arctic charr (Salvelinus alpinus) received 10 separate i.p. injections (a single injection every 6 days) of BaP (3 mg/kg), TBT (0.3 mg/kg), or both in combination; control fish received corn oil vehicle only. Two days after the 2nd (Day 8), 6th (Day 32), and 10th dose (Day 56), blood, bile, and liver samples were collected and analyzed for a suite of biomarkers. HPLC/fluorescence analysis indicated that TBT cotreatment inhibited the formation of (+)-anti-BaP diol-epoxide adducts with plasma albumin (53%, Day 8), hepatic DNA (27%, Day 32), or both albumin and globin (50 and 58%, Day 56) compared to BaP alone. This antagonistic interaction was associated with a time-dependent modulation (inhibition at Day 8, enhancement at Day 32) of both cytochrome P450 (P450)1A-mediated ethoxyresorufin O-deethylase (EROD) activity and biliary BaP metabolite formation. TBT cotreatment also inhibited (39%) the BaP-mediated induction of hepatic glutathione S-transferase (GST) activity observed at Day 8. Treatment with TBT alone increased EROD activity (60%) at Day 32, but decreased both GST activity (70 and 37%) and glutathione content (24% and 16%) at Days 32 and 56, respectively. GC/MS analysis revealed that, at Day 56, BaP cotreatment increased (200%) the levels of biliary butyltin compounds, including mono- and dibutyltin metabolites. This potentiative interaction was associated with a protective effect of BaP cotreatment against the TBT-mediated decreases in GST activity and glutathione content. The current results demonstrate that, whereas TBT inhibited BaP bioactivation via a time-dependent modulation of P4501A induction, BaP stimulated the Phase II metabolism of TBT and/or its biliary excretion. The mutual metabolic interactions between these two widespread aquatic pollutants reinforce the need for long-term in vivo interactive studies at low doses.

Genotoxic and hepatic biotransformation responses induced by the overflow of pulp mill and secondary-treated effluents on Anguilla anguilla L

Pulp and paper mill effluent compounds pollute the aquatic environment and are responsible for increased biochemical alterations and genotoxicity in aquatic organisms such as fish. Adult eels (Anguilla anguilla L) were exposed during 8, 16, 24, and 72 h to the following conditions: (1) aerated, filtered, and dechlorinated tap water (C); (2) 2.5% (v/v) sewage water previously treated with activated sludge (T); (3) bleached kraft pulp and paper mill effluent collected at the river Vouga, close to an ancient sewage outlet (Portucel), diluted in tap water [25% (E25) and 50% (E50)]; and (4) bleached kraft pulp and paper mill effluent sediment [water-soluble fraction (S)]. Liver biotransformation induced by the above conditions was measured as ethoxyresorufin-O-deethylase (EROD), cytochrome P450 (P450) (Phase I), and glutathione-S-transferase (GST) (Phase II). Genotoxicity was also determined as blood/liver DNA strand breaks and erythrocytic nuclear abnormalities (ENA) induced on European eel (A. anguilla L). Liver EROD activity was significantly increased in eels at 8 and 16 h exposure to E25, as well as at 16, 24, and 72 h exposure to E50. S exposure induced liver EROD activity only at 24h. A significant decrease in liver P450 was observed at 72 h exposure to T, whereas a significant P450 increase at 16 h was followed by a significant decrease at 24h exposure to E25. Another P450 significant increase was noticed at 72 h exposure to S. Liver GST activity (Phase II) demonstrated a significant increase at 72 h exposure to E50 and to S. A significant decrease in blood DNA integrity was observed at 72 h exposure to T and at 24 and 72 h to S. Blood DNA integrity significantly decreased at 16 and 24 h exposure to E25, as well as at 8, 16, and 24 h exposure to E50. Liver DNA integrity significantly decreased at 72 h exposure to T and at 16 h exposure to S. Moreover, liver DNA integrity was significantly decreased at 24h exposure to E25 and E50, and 72 h to E50. A. anguilla L. increased ENA frequency was detected in T at 16, 24, and 72 h, whereas in E25 and S it was observed at 8, 16, and 24 h. Furthermore, E50 ENA frequency increased at 24 h exposure.

Fish bioaccumulation and biomarkers in environmental risk assessment: a review

In this review, a wide array of bioaccumulation markers and biomarkers, used to demonstrate exposure to and effects of environmental contaminants, has been discussed in relation to their feasibility in environmental risk assessment (ERA). Fish bioaccumulation markers may be applied in order to elucidate the aquatic behavior of environmental contaminants, as bioconcentrators to identify certain substances with low water levels and to assess exposure of aquatic organisms. Since it is virtually impossible to predict the fate of xenobiotic substances with simple partitioning models, the complexity of bioaccumulation should be considered, including toxicokinetics, metabolism, biota-sediment accumulation factors (BSAFs), organ-specific bioaccumulation and bound residues. Since it remains hard to accurately predict bioaccumulation in fish, even with highly sophisticated models, analyses of tissue levels are required. The most promising fish bioaccumulation markers are body burdens of persistent organic pollutants, like PCBs and DDTs. Since PCDD and PCDF levels in fish tissues are very low as compared with the sediment levels, their value as bioaccumulation markers remains questionable. Easily biodegradable compounds, such as PAHs and chlorinated phenols, do not tend to accumulate in fish tissues in quantities that reflect the exposure. Semipermeable membrane devices (SPMDs) have been successfully used to mimic bioaccumulation of hydrophobic organic substances in aquatic organisms. In order to assess exposure to or effects of environmental pollutants on aquatic ecosystems, the following suite of fish biomarkers may be examined: biotransformation enzymes (phase I and II), oxidative stress parameters, biotransformation products, stress proteins, metallothioneins (MTs), MXR proteins, hematological parameters, immunological parameters, reproductive and endocrine parameters, genotoxic parameters, neuromuscular parameters, physiological, histological and morphological parameters. All fish biomarkers are evaluated for their potential use in ERA programs, based upon six criteria that have been proposed in the present paper. This evaluation demonstrates that phase I enzymes (e.g. hepatic EROD and CYP1A), biotransformation products (e.g. biliary PAH metabolites), reproductive parameters (e.g. plasma VTG) and genotoxic parameters (e.g. hepatic DNA adducts) are currently the most valuable fish biomarkers for ERA. The use of biomonitoring methods in the control strategies for chemical pollution has several advantages over chemical monitoring. Many of the biological measurements form the only way of integrating effects on a large number of individual and interactive processes in aquatic organisms. Moreover, biological and biochemical effects may link the bioavailability of the compounds of interest with their concentration at target organs and intrinsic toxicity. The limitations of biomonitoring, such as confounding factors that are not related to pollution, should be carefully considered when interpreting biomarker data. Based upon this overview there is little doubt that measurements of bioaccumulation and biomarker responses in fish from contaminated sites offer great promises for providing information that can contribute to environmental monitoring programs designed for various aspects of ERA.

Ecogenotoxicology: the evolving field

The occurrence of chemical contaminants with DNA-damaging capacity in the environment represents a threat to human health as well as to the health of the ecosystem. This mini-review describes studies that were aimed to monitor at field conditions, the presence of such environmental toxicants and their DNA-damaging effects in aquatic and terrestrial species, as well as in birds. It is obvious that these studies, in particular are abundantly performed in fish and aquatic invertebrates, have brought forward new information on the levels and genotoxic effects of these compounds which complements data coming from monitoring the abiotic fractions of the ecosystem, thereby demonstrating that the ecogenotoxicological approach is fruitful. However, in order to assess the genotoxic impact on the health of the ecosystem, a second generation type of field studies is required focusing on adverse effects on biodiversity and on survival potency. For this, the application of DNA microarray-based technologies provides new opportunities.

Evidence of uptake, biotransformation and DNA binding of polyaromatic hydrocarbons in Atlantic cod and corkwing wrasse caught in the vicinity of an aluminium works

Feral Atlantic cod (Gadus morhua) and corkwing wrasse (Symphodus melops) were investigated for polyaromatic hydrocarbon (PAH) contamination in the Karmsund strait, western Norway. This strait is highly contaminated with PAHs, and a main source is the chronic release of gas-scrubbing effluents from a local aluminium works. In both species, the level of biliary PAH metabolites and hepatic DNA adducts were higher in fish collected near the aluminium works. Interestingly, a significantly higher level of both biliary PAH metabolites and hepatic DNA adducts was found in corkwing wrasse as compared to cod, indicating a higher potential for genotoxic effects in this species. Hepatic cytochrome P4501A (CYP1A) in cod estimated by ethoxyresorufin-O-deethylase and an immunoassay technique (ELISA), seemed to be weakly induced at the contaminated sites. At the most contaminated site, skin ulcers and fin erosion were detected in about 70 and 45% of the cods, respectively. The data demonstrated that both cod and corkwing wrasse may be suitable target species for PAH pollution monitoring.

Persistence of benzo[a]pyrene--DNA adducts in hematopoietic tissues and blood of the mummichog, Fundulus heteroclitus

The formation and persistence of benzo[a]pyrene (B[a]P)-DNA adducts were investigated in blood, liver and two hematopoietic tissues (anterior kidney and spleen) of the mummichog (Fundulus heteroclitus). Fish were injected with a single, sublethal dose of B[a]P (12 mg/kg body weight) and sampled from 8 to 96 days post-injection. 32P-Postlabeling analysis and storage phosphor imaging were used to resolve and quantify hydrophobic DNA adducts. One major DNA adduct was present in each of the examined tissues at all sampling times. This adduct had similar chromatographic characteristics to those of the adduct standard, 7R,8S,9S-trihydroxy-10S-(N(2)-deoxyguanosyl-3'-phosphate)-7,8,9,10-tetrahydro-benzo[a]pyrene (B[a]PDE-dG). Minor DNA adduct spots, representing less than 2% of the total DNA adducts, were observed in some liver, anterior kidney and spleen samples for up to 32 days post-injection. The B[a]P-DNA adducts reached maximal levels at 32 days post-injection and persisted for at least 96 days in all examined tissues. B[a]P-DNA adduct levels were significantly higher in the liver and anterior kidney than in the spleen from 16 to 96 days (P<0.001), although liver and anterior kidney DNA adduct levels were not significantly different at any time. This is the first controlled study to demonstrate the formation and persistence of B[a]P-DNA adducts in hematopoietic tissues and blood of fishes exposed to the prototypical polycyclic aromatic hydrocarbon, B[a]P. Although persistent DNA adducts are generally recognized as potential initiators of carcinogenic processes, adducts in these vital tissues may also lead to disruption of physiological functions such defense mechanisms and hematopoiesis.

DNA adduct formation in northern pike (Esox lucius) exposed to a mixture of benzo[a]pyrene, benzo[k]fluoranthene and 7H-dibenzo[c, g]carbazole: time-course and dose-response studies

The time-course and dose dependent formation of DNA adducts in juvenile northern pike (Esox lucius) following a single exposure to a mixture of benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF) and 7H-dibenzo[c,g]carbazole (DBC) were investigated by use of the (32)P-postlabelling assay. A complex adduct pattern was detected in liver and intestine of exposed fish. For the time-course studies fish were exposed either by oral administration or by intraperitoneal (i.p.) injection. Following a single i.p. injection of the mixture (40micromole/kg body weight of each substance) significantly elevated DNA adduct levels were detected in the liver after 1 day. Adduct levels were higher in liver than in intestine, in which significant elevation were detected from day 3 to 12. Following exposure via food (80micromole/kg body weight of each substance), adduct levels were detected in both liver and intestine 1 day after exposure, and continued to increase until day 3 in liver and day 6 in intestine. Calculation of a binding index, which compensates for differences in dosage, resulted in much higher adduct formation (five times in liver and 22 times in intestine) following oral exposure. Pikes receiving single oral doses of 12.5, 50, 100 or 200micromole/kg body weight of each substance exhibited significantly higher adduct levels in both liver and intestine compared to controls. Hepatic adduct levels were also higher in fish given 100 and 200micromole/kg compared to 12.5micromole/kg. Results from this study show that DNA adducts are rapidly formed in juvenile northern pike following both i.p. injection and feeding of a mixture of BaP, BkF and DBC. A maximum level was reached within a few days, which then persisted at approximately the same level for at least 9-12 days. The results also shows that higher levels of adducts were obtained following oral administration compared to i.p. injection, particularly in the intestine.

Enzymatic biomarker measurement and study of DNA adduct formation in benzo

The aim of this study was to improve the knowledge on the metabolic pathways involved in benzo[a]pyrene (B[a]P) activation and on the relationship between adduct levels and enzymatic biomarker activities. With this purpose, a model to assess pollutant exposure via food supply has been developed for the sentinel organism, Mytilus galloprovincialis. Mussels were fed for 4 weeks with B[a]P-contaminated feed (50 mg/kg dry weight mussel). Bioaccumulation was studied by determination of B[a]P concentration in whole mussel by GC/MS analysis. Different biomarkers of pollutant exposure were measured to assess the metabolic state of the exposed organisms. CYP1A-like immunopositive protein titration and B[a]P hydroxylase (BPH) activity were assessed as indicators of phase I biotransformation. Glutathione-S-transferase (GST) activity was measured as an indicator of the conjugation activities. Catalase (CAT) and DT-diaphorase (DTD) activities were assessed as potential biomarkers of oxidative stress, whereas acetylthiocholine esterase (AChE) activity was measured as an indication of possible neurotoxicity of B[a]P exposure. DNA adduct levels were determined in digestive gland DNA by applying the 32P-postlabeling technique with nuclease P1 enhancement. For the developed conditions of exposure, B[a]P concentration reached in whole mussel tissues was very high (>500 mg/kg d.w. mussel) and significant B[a]P-induced changes were recorded for each enzymatic biomarkers. BPH and CAT activities were significantly increased by B[a]P exposure, whereas GST in the gills, DTD and AChE were significantly depressed. On the other hand, no change in CYP1A-like immunopositive protein content was observed. Induction and increase with time of bulky B[a]P-related DNA adducts were demonstrated in the digestive gland, although at low levels (0.269+/-0.082 adduct/10e8 dNps at maximum) by the 32P-postlabeling assay. DNA adduct level was significantly correlated with whole mussel tissue B[a]P concentration, so were all the enzymatic biomarkers measured except to GST activity in both gill and digestive gland tissues. BPH, DTD, CAT and AChE displayed a strong correlation with adduct levels. These results demonstrate the neurotoxicity and the genotoxicity of B[a]P exposure in the mussel. The induction of bulky DNA adducts in mussels demonstrates the existence of activation pathways already identified in vertebrates. It validates also the suitability of this model for further studies on B[a]P metabolism in mussels. Our results support the proposal of BPH, AChE, DTD and CAT activities as suitable biomarkers of PAH exposure for these sentinel species.

In vivo formation of (+)-anti-benzo[a]pyrene diol-epoxide-plasma albumin adducts in fish

Benzo[a]pyrene (BaP), a procarcinogenic polycyclic aromatic hydrocarbon (PAH), is bioactivated to BaP diol-epoxides (BPDEs) that can form adducts with DNA and blood proteins. We report here for the first time the in vivo formation of adducts between BPDE and plasma albumin (Alb) from two fish species experimentally exposed to BaP. Brook trout (Salvelinus fontinalis) received either a single i.p. dose (10 mg/kg) or two separate i.p. doses (25 mg/kg; 7 days apart) of BaP, and blood was collected 2 (single exposure) or 3 (multiple exposure) days post-treatment. Arctic charr (Salvelinus alpinus) received 10 i.p. doses (3 mg/kg; a single dose every 6 days), and blood was collected 2 days after the second, sixth, and 10th injections. BPDE-Alb adducts were measured by an improved HPLC/fluorescence method developed to detect and quantify BaP-tetrols released after acid hydrolysis of adducted Alb. HPLC/fluorescence chromatograms of Alb from BaP-treated fish revealed only BaP-tetrol I-1, thus indicating the formation of adducts exclusively via the (+)-anti-BPDE metabolite. Levels of (+)-anti-BPDE-Alb adduct ranged from 0.68 to 19.6 ng of tetrol I-1 per gram of Alb. Notably, adduct level was not related to BaP dose and there was no accumulation of adducts with repeated exposure, which may indicate a very short half-life (< 2 days) of plasma Alb in fish. The data suggest that BPDE-Alb adducts in fish could be useful as a non-destructive biomarker of recent exposure to bioactivated BaP.

DNA adducts in perch (Perca fluviatilis) living in coastal water polluted with bleached pulp mill effluents

DNA adducts were analyzed by (32)P-postlabeling in liver and intestine of perch (Perca fluviatilis). Fish were collected in the receiving water of a bleached kraft pulp mill at Norrsundet, Sweden, on the coast of the Bothnian Sea, and in three different reference areas. Sampling was carried out the last week in September 1993, 1995, and 1997. Since 1984/1985 the pulping process at Norrsundet has been successively modified and an external waste-water treatment has been installed, resulting in lowered and altered effluent discharges. Nevertheless, perch captured in the water area closest to the mill (2 km) had significantly elevated levels of aromatic/hydrophobic DNA adducts in both liver and intestine when compared to perch captured 8 km away and in the reference areas. Autoradiograms indicated a diagonal zone consisting of multiple overlapping adducts, a pattern typical of exposure to a complex mixture of aromatic/hydrophobic genotoxic substances. No significant difference in adduct levels was detected between the years. Results from this study reveal that fish in the area closest to the mill are exposed to substances with a genotoxic potential.

DNA adducts in liver and leukocytes of flounder (Platichthys flesus) experimentally exposed to benzo

In the present study the levels of hydrophobic DNA adducts detected by 32P-postlabelling were followed in liver and leukocytes of flounder (Platichthys flesus) over 10 days following single i.p. injections of two doses of BaP (10 and 50 mg kg(-1) fish weight, respectively). DNA adducts were detected in both tissues of exposed fish 2 days post injection and continued to rise on day 5 and day 10. In flounder exposed to the lower dose of BaP, the levels of hepatic DNA adducts reached higher values on the fifth day compared with flounder exposed to the higher dose. However, at the end of the experiment, the DNA adduct level was again higher in fish from the high dose group compared with the low dose group. There was no substantial increase of DNA adducts in liver of flounder from the low dose group after day 5, while the adduct levels in flounder liver from the high dose group increased throughout the experiment. Earlier studies detecting DNA adducts in BaP-exposed flatfish with the 32P-postlabelling technique have reported declining adduct levels from about 2 days after the exposure, regardless of exposure route. In contrast, the results from our study did not confirm a rapid increase and successive decline of hydrophobic adducts in liver of BaP-exposed flounder.

DNA adduct formation and persistence in liver and extrahepatic tissues of northern pike (Esox lucius) following oral exposure to benzo[a]pyrene, benzo[k]fluoranthene and 7H-dibenzo[c,g]carbazole

The formation and persistence of DNA adducts in liver, intestinal mucosa, gills and brain of juvenile northern pike (Esox lucius) following oral exposure to benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF) and 7H-dibenzo[c,g]carbazol (DBC) were analysed by 32P-postlabelling. The dosage was 25 micromol/kg body weight of each substance, administered on 5 occasions with an interval of 12-14 days. Sampling was carried out 9 days after the second treatment, and 9, 16, 33 and 78 days after the fifth treatment. Pikes were also fed with the substances singly for comparison of adduct patterns. A complex pattern of adducts was detected in all examined tissues from fish treated with the mixture. Total adduct levels were highest in intestine (347+/-17.4 nmol adducts/mol nucleotides, mean+/-SE), followed by liver (110+/-9.3), gills (69+/-6) and brain (14+/-4.2). In pike treated with BaP alone, one major adduct was detected in all examined tissues. This BaP-adduct made up approximately 50% of the total amount of adducts in the brain. Corresponding values in liver, intestine and gills were 23, 31 and 34%, respectively. One relatively weak BkF-adduct and at least 10 different DBC-adducts were detected in all analysed tissues. Total adduct level in the intestine declined to 29.4% of the maximum value 78 days after the last exposure, while there was no significant decline in adduct levels in liver, gills or brain. The results suggest that intestine is more susceptible to adduct formation than liver after oral exposure, and that adduct levels in the intestine represent ongoing or relatively recent exposure. DNA adducts in the other investigated tissues were much more persistent and may therefore accumulate during long-term exposure.

An assessment of the genotoxic impact of the Sea Empress oil spill by the measurement of DNA adduct levels in selected invertebrate and vertebrate species

The grounding of the Sea Empress oil tanker resulted in the release of 72,000 tonnes of crude oil into Milford Haven, Wales, UK. Our initial studies indicated that this contamination resulted in elevated levels of DNA adducts in one of the area's native marine species Lipophrys pholis [B.P. Lyons, J.S. Harvey, J.M. Parry, An initial assessment of the genotoxic impact of the Sea Empress oil spill by the measurement of DNA adduct levels in the intertidal teleost Lipophrys pholis, Mutat. Res. 390 (1997) 263-268]. These original studies were extended and the genotoxic impact of the oil contamination was investigated in the invertebrates Halichondria panicea and Mytilus edulis, along with the vertebrate fish species L. pholis, Pleuronectes platessa and Limanda limanda. DNA adduct levels were assessed in these species over a period of 2-17 months after the incident. The studies indicate differences in the impact of acute oil contamination upon vertebrate and invertebrate species. The oil contamination did not induce any detectable elevations in adduct levels in the invertebrate species H. panicea and M. edulis. In contrast, the oil contamination did appear to induce adducts in the vertebrate teleost species L. pholis, P. platessa and Lim. limanda. Despite some difficulties in sampling, the data obtained 12-17 months after the spill suggested that the affected species recovered from the oil contamination. While the studies indicate that the genetic impact of the oil contamination was less severe than might have been expected, it remains possible that the DNA adducts detected in the teleosts could lead to genetic changes in these species in the future.

Molecular epizootiology of genotoxic events in marine fish: linking contaminant exposure, DNA damage, and tissue-level alterations

Molecular epizootiological studies are increasingly being used to investigate environmental effects of genotoxic contaminants. The assessment of damage to DNA and linking the damage to subsequent molecular, cellular, or tissue-level alterations is a central component of such studies. Our research has focused on the refinement of the 32P-postlabeling assay for measuring covalent DNA-xenobiotic adducts arising from exposure to polycyclic aromatic compounds, using DNA adducts as molecular dosimeters of genotoxic contaminant exposure in biomonitoring studies, and investigating the relationship of DNA adduct formation to toxicopathic liver disease, including neoplastic lesions. A combination of field and laboratory studies using the 32P-postlabeling assay has shown that DNA adducts in marine fish are effective molecular dosimeters of genotoxic contaminant exposure. Investigations of the relationship of DNA adduct formation to neoplastic liver disease have shown that elevated levels of DNA adducts in certain fish species from contaminated coastal sites are associated with increased prevalences of toxicopathic hepatic lesions, including neoplasms, and that the ability to assess DNA damage has helped to explain, in part, species differences in lesion prevalence. Moreover, in a study of a site in Puget Sound contaminated with polycyclic aromatic compounds, we have shown, for the first time, that elevated levels of hepatic DNA adducts are a significant risk factor for certain degenerative and preneoplastic lesions occurring early in the histogenesis of hepatic neoplasms in feral English sole (Pleuronectes vetulus). These latter findings coupled with our current studies of mutational events in the K-ras proto-oncogene should provide further mechanistic substantiation that mutagenic events resulting from exposure to complex mixtures of genotoxic polycyclic aromatic compounds are involved in the etiology of hepatic neoplasia in English sole.

Short- and intermediate-term carcinogenicity testing--a review. Part 2: available experimental models

Numerous experimental protocols for short- and intermediate-term carcinogenicity assays have been available for many years. This paper surveys various of these test systems in rodents, fish species, non-vertebrates and avian embryos in ovo. The mouse skin tumour assay and the rat liver foci assay were used to introduce the basic concepts of short- and intermediate-term carcinogenicity testing in the previous part of the review. The focus of this second part of the review is on rodent assays for carcinogenicity testing in the lung, kidney, urinary bladder, pancreas, stomach, oral cavity, small intestine, colon, and on the possibility to combine several target organs in multi-organ models. The potential use of various fish species, non-vertebrates and hatching eggs for carcinogenicity testing is outlined and the advantages and limitations are discussed. This review also presents the problem of validation of any carcinogenicity test system and proposes a strategy for contemporary safety assessment of chemicals with regard to the detection and evaluation of carcinogenicity.

Altered gene expression and genetic damage in North American fish populations

Populations of marine, estuarine, and freshwater fish from highly urban and industrialized sites in North America often exhibit elevated prevalences of neoplastic, preneoplastic, and nonneoplastic hepatic lesions, and sometimes epidermal neoplasms compared to conspecifics from more pristine reference locales. Positive statistical associations with environmental concentrations of PAHs and other xenobiotics and experimental laboratory studies suggest a chemical etiology to these epizootics. Studies have investigated the expression of carcinogenically relevant genes, the extent of overall DNA damage, somatic cell mutations, germ line polymorphisms, and overall levels of genetic diversity in fish from these populations and other polluted sites. In general, elevated levels of cytochrome P4501A expression have been found in fish from contaminated locales; however, inhibition of gene induction has been seen in hepatic lesions and in normal tissue in fish from the most contaminated sites, perhaps due to genetic adaptation or physiological acclimation. Levels of bulky hepatic DNA adducts, as detected by 32P-postlabeling, are almost always elevated in fish from populations that are exposed to highly contaminated environments. However, levels of DNA adducts were not always predictive of the vulnerability to neoplasia of populations and species from polluted sites. Elevated levels of oxygen radical-induced DNA damage have been observed in hepatic tumors, preneoplastic lesions, and normal livers in a single species of flatfish from contaminated sites; however, the prevalences of these alterations in other species and at other polluted sites has yet to be evaluated. Frequent alterations in the K-ras oncogene have been reported in hepatic neoplasms in several species from highly contaminated sites and also in embryos that were experimentally exposed to oil-contaminated sediments. Studies also suggest that heritable germ line polymorphisms, altered allelic frequencies, and reductions in overall genetic diversity may have occurred in some highly impacted populations; however, the origin and functional significance of altered allelic frequencies have largely yet to be evaluated. In summary, feral fish appear particularly sensitive to DNA alterations from xenobiotics, perhaps due to their unusually high levels of exposure, relatively inefficient DNA repair, and the high frequency of polyploidy in some taxa and provide excellent models to explore the relationships between xenobiotic exposure and altered gene structure and expression.

Field applications of the piscine anaphase aberration test: lessons from the Exxon Valdez oil spill

Several large-scale genotoxicity assessments have been performed in coastal marine areas that have demonstrated either localized or widespread genetic effects resulting from human activity. One common assessment method is the anaphase aberration test, a measurement of abnormal chromosome division, using embryolarval fishes. It can be used to detect the presence of mutagens within a poorly characterized complex mixture or monitor specific genotoxins and is easily adapted for laboratory screening. One comprehensive marine genotoxicity assessment was conducted using Pacific herring (Clupea pallasi) following the Exxon Valdez oil spill (EVOS) in Prince William Sound (PWS), AK in late March 1989. In early May, genetic damage was detected at many sites within the oil trajectory and was correlated with concentrations of polycyclic aromatic hydrocarbons characteristic of Exxon Valdez oil (EVO) in intertidal mussels. Effects were related spatially and temporally to oil exposure. Anaphase aberration rates decreased throughout May and June 1989, and by 1991, genotoxicity was undetectable. The abundance of the 1989 herring year class in PWS is significantly reduced; this is the first reported example linking genotoxicity to subsequent population level effects. This review describes the methodology for the anaphase aberration test using fish eggs, its applications for large-scale assessments and supportive laboratory studies, and its limitations for prediction of higher level effects on populations.

The analysis of DNA adduct formation, removal and persistence in the common mussel Mytilus edulis exposed to 4-nitroquinoline 1-oxide

32P-postlabelling was used for the detailed analysis of 4-nitroquinoline 1-oxide (4-NQO) induced DNA adduct formation, removal and persistence in the marine shellfish Mytilus spp. The results had a number of important implications concerning the use of such DNA adducts as dosimeters of environmental genotoxin exposures. Our studies indicated that the maintenance of the Mytilus specimens under controlled laboratory conditions can result in the induction of 'stress-related adducts' seemingly related to the nature of the experimental set-up. The studies also indicated that the absorption and activation of genotoxins in this species appear to affect the rate of adduct formation, and that the maximum levels of adducts may not necessarily be induced immediately after the cessation of a genotoxin exposure. In addition, Mytilus specimens were shown to possess a significant capacity to remove these genotoxin-induced DNA adducts. The removal of these adducts appeared to be biphasic in nature, with the rapid removal of a large proportion of adducts occurring within 48 h of the cessation of the exposure, followed by a slow rate of adduct removal over the remaining period of the studies. Despite the relatively efficient removal of the majority of these genotoxin-induced DNA adducts, a proportion remained up to 56 days after the initial exposure. The persistence of these genotoxin-DNA adducts, combined with the information on the rates of adduct removal, indicated that under well-defined conditions, such adducts could serve as suitable biomarkers of environmental contamination.

The application of the 32P-postlabelling assay to aquatic biomonitoring

The aquatic environment is known to contain a variety of natural and anthropogenic compounds that are capable of interacting with the genetic material of aquatic organisms. The increases in the levels of these anthropogenic contaminants, associated with widespread industrialisation, has led to the requirement for reliable methodologies to monitor their potential impact upon exposed aquatic organisms. Of the molecular techniques currently available, the 32P-postlabelling assay for the detection of DNA adducts offers considerable potential for the qualitative and quantitative assessment of genotoxin exposure. Here we describe several studies in which the technique was adapted for evaluation in two marine bioindicator species the common mussel Mytilus edulis and the flatfish Limanda limanda. Laboratory studies in which M. edulis specimens were exposed to 2-aminofluorene and 4-nitroquinoline 1-oxide confirmed the species' capacity to form genotoxin-related adducts. However, in further studies, no exposure-related adducts could be detected in M. edulis specimens placed in mesocosms containing environmentally realistic levels of anthropogenic contaminants. Biologically significant levels of adducts were detected in L. limanda specimens exposed to sediment bound contaminants under controlled conditions, although the levels did not appear to be statistically significant. An in situ study in which adduct levels were determined in L. limanda specimens from two sites of contrasting contamination levels proved to be more conclusive. The results were both biologically and statistically significant, suggesting that adduct levels could well be related to the levels of sediment-bound contaminants. Together the studies confirmed that the determination of the levels of DNA adducts could be used as indicators of the exposure of aquatic organisms to environmental genotoxins.

An initial assessment of the genotoxic impact of the Sea Empress oil spill by the measurement of DNA adduct levels in the intertidal teleost Lipophrys pholis

The Sea Empress oil spill resulted in the release of vast quantities of potentially genotoxic contaminants into the coastal environment of the county of Pembrokeshire (UK). We are at present attempting to determine the potential genotoxic impact of the incident upon the native marine species of the area. Here we describe the levels of DNA adducts in specimens of the intertidal teleost, Lipophrys pholis, exposed to extensive oil extensive oil contamination as an indication of exposure to potential genotoxins. We detected elevated levels of adducts in L. pholis specimens from an area that underwent heavy oil contamination as compared to specimens from a clean reference area devoid of oil contamination. These preliminary studies indicated that the oil contamination induced DNA adducts in the L. pholis specimens, which could potentially cause genetic damage in this native marine species. Further studies are now required to assess the full extent of the genotoxic impact of the oil spill upon the Pembrokeshire area's native marine life.

Fish micronuclei for assessing genotoxicity in water

Micronucleus assays with fish have been shown to be useful in vivo techniques for genotoxicity testing, and show potential for in situ monitoring of water quality. In this paper, we review the literature on the clastogenic effects of chemical and physical agents on fish cells, with emphasis on the induction of micronuclei in teleosts. Included in the review is a description of the mechanisms for formation of micronuclei in cells, and a summary of the various techniques that have been used for micronucleus analysis in fish. This review is directed to assisting laboratories in the development of fish genotoxicity assays for water quality monitoring.

Bioaccumulation of polycyclic aromatic hydrocarbons by marine organisms

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the marine environment, occurring at their highest environmental concentrations around urban centers. While they can occur naturally, the highest concentrations are mainly from human activities, and the primary sources are combustion products and petroleum. Two factors, lipid and organic carbon, control to a large extent the partitioning behavior of PAHs in sediment, water, and tissue; the more hydrophobic a compound, the greater the partitioning to these phases. These two factors, along with the octanol-water partition coefficient, are the best predictors of this partitioning and can be used to determine PAH behavior and its bioavailability in the environment. It is well known that the lipid of organisms contains the highest levels of hydrophobic compounds such as PAHs, and that organic carbon associated with sediment or dissolved in water can have the greatest influence on PAH bioavailability. Partitioning of combustion-derived PAHs between water and sediment may be much less than predicted, possibly because associations with particles are much stronger than expected. This reduced partitioning may produce erroneous results in predicting bioaccumulation where uptake from water is important. Accumulation of PAHs occurs in all marine organisms; however, there is a wide range in tissue concentrations from variable environmental concentrations, level and time of exposure, and species ability to metabolize these compounds. PAHs generally partition into lipid-rich tissues, and their metabolites can be found in most tissues. In fish, liver and bile accumulate the highest levels of parent PAH and metabolites; hence, these are the best tissues to analyze when determining PAH exposure. In invertebrates, the highest concentrations can be found in the internal organs, such as the hepatopancreas, and tissue concentrations appear to follow seasonal cycles, which may be related to variations in lipid content or spawning cycles. The major route of uptake for PAHs has been debated for years. For the more water-soluble PAHs, it is believed that the main route of uptake is through ventilated water and that the more hydrophobic compounds are taken in mainly through ingestion of food or sediment. There are many variables, such as chemical hydrophobicity, uptake efficiency, feeding rate, and ventilatory volume, which may affect the outcome. The route of uptake may be an important issue for short-term events; however, under long-term exposure and equilibrium conditions between water, prey, and sediment, the route of uptake may be immaterial because the same tissue burdens will be achieved regardless of uptake routes.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular dosimetry of DNA adducts in rainbow trout (Oncorhynchus mykiss) exposed to benzo(a)pyrene by different routes

Farm raised rainbow trout (Oncorhynchus mykiss) were exposed by various routes to benzo(a)pyrene (BP) as a representative carcinogenic polycyclic aromatic hydrocarbon (PAH). Following exposure of fish to the chemical by intraperitoneal (i.p.) injection, 32P-postlabelling studies indicated that non-feral trout were relatively resistant to the formation of BP-DNA adducts in liver. No adducts were detected in fish exposed to single doses (20 mg/kg) of BP. Multiple exposures (e.g. 2 x 25 mg/kg) were necessary in order for adducts to be detected, indicating that induction of the metabolising enzymes required for the bioactivation of BP is necessary. These studies provided reference information on DNA adducts for comparison with data from subsequent experiments at environmentally realistic low level exposures. Two types of low level aquatic exposure were carried out. The first procedure exposed fish for 30 days to a nominally constant low level (1.2 and 0.4 micrograms/l) of a homogeneous dispersion of BP in water, to simulate low level aquatic environmental exposures. Following 32P-postlabelling analysis of the liver DNA of exposed fish, BP-DNA adducts were not detected. In the second procedure, fish were exposed to a constant low level of BP (ca. 0.5 micrograms/l) for 15 days then to a pulse (60 micrograms/l) which was allowed to naturally decline (to ca. 2 micrograms/l) during a further 15 days. Following this exposure, significant levels of BP-DNA adducts were detected in livers of trout. The effect of dietary exposures was investigated by feeding trout a diet containing either 58 micrograms or 288 micrograms BP per day for 6 days, equivalent to total doses of 43 mg/kg and 216 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)