Biological effect monitoring in dab (<Emphasis Type="Italic">Limanda limanda</Emphasis>) using gene transcript of CYP1A1 or EROD—a comparison

BACKGROUND, AIM, AND SCOPE: Gene expression analyses with real-time (RT)-polymerase chain reaction (PCR) gains importance in marine monitoring. This new technique has to be compared to the classical approaches like the well known biomarker ethoxyresorufin-O-deethylase (EROD) to test their suitability for monitoring programmes. The goal of the present study is to compare EROD activity and CYP1A1 mRNA expression in the important monitoring fish species dab (Limanda limanda) and to answer the question of whether these parameters reflect the polycyclic aromatic hydrocarbon (PAH) contamination of the fish. Further on, glyceraldehyd-3-phosphate dehydrogenase (GAPDH) was investigated as a potential housekeeping gene. MATERIALS AND METHODS: Female dab were caught in the summer of 2004 in the North Sea and in the Baltic. EROD activity was determined in liver samples by a kinetic fluorimetric assay according to a standard protocol. The gene expression of CYP1A (cytochrome P450 1A) and GAPDH were determined by means of RT-PCR. Results were compared to gonado somatic index and to the concentration of PAH metabolite 1OHPyr (1-hydroxypyrene) analysed in the bile fluids of the fish, respectively. RESULTS: Dab from all stations showed a considerable individual variation in the levels of both CYP1A mRNA and EROD. Highest mean values for CYP1A mRNA and EROD were detected in the northern part of the sampling area. In contrast, the PAH metabolite 1OHPyr was found at the highest concentration in fish caught near the German coast. CYP1A mRNA and EROD showed only a minor but significant correlation (r = 0.32, p < 0.05, n = 123). 1OHPyr in bile correlated significantly (p < 0.05) with the amount of GAPDH mRNA content in the liver. DISCUSSION: The significant but low correlation of CYP1A mRNA and EROD activity on an individual basis illustrates that these two parameters are apparently not closely linked. However, maximum EROD values correspond with maximum CYP1A mRNA concentrations when station means are regarded. Because EROD and CYP1A mRNA in dab follow different physiological principles, their application will lead to related but not identical monitoring results. This should be taken into account when future marine monitoring programmes are designed. The results also indicate that PAH are not the crucial factor for CYP1A and EROD levels in dab from the off-shore areas in the North Sea. This is remarkable because the PAH metabolism is known to be CYP1A-dependent and the widely used biomarker EROD has been recommended for monitoring PAH-related effects in fish from the North Sea. Due to a correlation between GAPDH and 1OHPyr, GAPDH was not suitable as housekeeping gene for dab. CONCLUSIONS: Neither the results from EROD nor from CYP1A1 mRNA measurements in dab reflected their exposure to PAH as measured by the PAH metabolite 1OHPyr. Thus, the question arises of whether EROD or CYP1A mRNA is a suitable biomarker at all to indicate PAH exposure in dab from the open North Sea. RECOMMENDATIONS AND PERSPECTIVES: For future biological effect monitoring, it is advisable to measure more and predominately independent parameters by RT-PCR and to incorporate more components of the detoxification system.     

EROD activity measured in flatfish from the area of the Sea Empress oil spill

Dab (Limanda limanda) and plaice (Pleuronectes platessa) were collected at five stations near to the site of the Sea Empress oil spill within two weeks of the incident and a further fourteen stations three months after the spillage. Ethoxyresorufin-O-deethylase (EROD) activity was determined in the livers of the specimens to determine whether induction could be detected. Statistically significant inter-site differences in EROD levels in both species were demonstrated. Elevated levels of EROD activity in dab were found at the two stations nearest to the incident up to three months after the spill but no clear relationship to putative contaminant levels was determined. EROD levels in plaice showed a generally similar pattern of induction as in dab. Correlation of EROD levels with other variables showed that sexual maturity had the greatest influence on dab during the study period. The plaice specimens were sexually immature and, therefore, did not demonstrate a corresponding relationship. It was concluded that, for EROD monitoring purposes, fish should be sampled during their sexually inactive phase and that close attention needs to be paid to other variables (depth, temperature, GSI, length, influential contaminants etc.) when interpreting the results.     

PAH Metabolites in Bile Fluids of Dab (Limanda limanda) and Flounder (Platichthys flesus): Spatial Distribution and Seasonal Changes (7 pp)

Background, Aim and Scope Polycyclic aromatic hydrocarbons (PAH) are important environmental contaminants which may lead to increased levels of neoplastic aberrations or tumours in fish liver. Therefore, monitoring of PAH and their effects are part of several international environmental programmes. The aim of the present field study was to investigate the concentrations of the PAH metabolites in fish bile, to elucidate spatial, seasonal and species differences as well as to discuss different strategies of normalisation with regard to environmental monitoring. Materials and Methods: PAH metabolites were determined in the bile fluid of dab (Limanda limanda) and flounder (Platichthys flesus) caught in the North Sea and Baltic Sea between 1997 and 2004. After enzymatic deconjugation, two metabolites were determined by means of HPLC. The limit of detection and the limit of quantification were calculated. The accuracy of the method was tested with a standard reference material. Results were referred to bile volume as well as to biliverdin. Results: The main metabolite, 1-hydroxypyrene, was determined in concentrations from <0.7 to 838 ng/ml in bile of dab (Limanda limanda) and flounder (Platichthys flesus) caught between 1997 and 2004. The values for 1-hydroxyphenanthrene in fish bile were considerably lower (<0.4 – 87 ng/ml). Significant differences in the 1-hydroxypyrene levels were found between summer and winter surveys as well as between the sampling sites in the data set from 2004 (383 dabs and 62 flounders): Highest levels of PAH contamination were found in dab from the German Bight and in flounder from the Baltic Sea. Discussion: Spatial differences in 1-hydroxypyrene concentrations between North Sea and Baltic Sea were discussed, as well as differences in relation to season, sex and species. Three parameters of normalisation (biliary protein, biliverdin and bile pigments) were discussed. Biliverdin was identified as a suitable parameter for the normalisation of PAH metabolites in field samples. Conclusions: Spatial differences in 1-hydroxypyrene concentrations of dab demonstrate the usefulness of PAH metabolites in fish bile as a monitoring parameter in marine regions. Significant differences in 1-hydroxypyrene concentrations were found between summer and winter sampling campaigns. This may be linked to an annual cycle of 1-hydroxyprene in dab. It is also possible that bile synthesis/release in dab differs between the seasons. There is no indication for a time trend from 1997 to 2004. Recommendations and Perspectives: It is recommended to relate PAH metabolites in fish bile to biliverdin concentrations. Although the concentrations are low in offshore regions and bile volumes are small, the method presented here allows one to measure PAH metabolites on an individual level which is a crucial prerequisite for meaningful monitoring studies.     

Cytochrome P4501A induction and testosterone hydroxylation in cultured hepatocytes of four fish species

Primary hepatocytes of the rainbow trout (Oncorhynchus mykiss), flounder (Platychthis flesus), dab (Limanda limanda) and lemon sole (Microstomus kitt) were exposed to 3,3'4,4'5 pentachlorobiphenyl (PCB 126) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for two days. This resulted in a dose-dependent induction of cytochrome P4501A (CYP1A) activity, measured as ethoxyresorufin O-deethylase (EROD), or methoxyresorufin O-deethylase (MROD) activity. In all species, a linear relationship was observed between EROD and MROD activities, suggesting that the same CYP1A enzyme metabolizes the two alkoxy-resorufin substrates. Exposures of hepatocytes of flounder or dab to TCDD, resulted in a 59-fold and 8.2-fold induction of EROD activity, respectively. This did not concur with a change in the in vitro testosterone hydroxylation profiles of both species. These and other in vitro data indicate that TCDD exposure does not influence monooxygenase activities involved in testosterone hydroxylation. Furthermore, CYP1A is of minor importance for testosterone hydroxylation in these fish species.     

Temporal induction pattern of hepatic cytochrome P450 1A in thermally acclimated dab (Limanda limanda) treated with 3,3′,4,4′-Tetrachlorobiphenyl (CB77)

Mature male dab (Limanda limanda) acclimated at 10° and 16°C were orally administered a single dose of 0.5 mg/kg 3,3′,4,4′-tetrachlorobiphenyl (CB77). At both temperatures, levels of cytochrome P450 1A (CYP1A) protein and 7-ethoxyresorufin O-deethylase (EROD) activity showed a two to six fold induction 40 days after CB77 treatment compared to control groups. Maximum responses of both EROD activity and CYP1A protein for the warm-acclimated fish were observed at 5 days after treatment. For the cold-acclimated fish a slow, progressive elevation for both EROD activity and CYP1A protein was observed and maximum responses were measured 40 days after treatment. Absolute EROD activity and CYPIA protein levels of fish from both temperatures were equally high at 40 days after treatment. Since in the control groups EROD activity and CYP1A protein levels were higher in the cold-acclimated fish, the magnitude of induction was higher in the warm acclimated ones. The highest concentrations of CB77 in muscle of fish from both temperatures were found at 5 and 10 days after treatment. The liver somatic index (LSI) showed 1.5 fold significantly higher values for the fish acclimated at 10°C.     

Comparision of the waterborne and dietary routes of exposure on the effects of Benzo(a)pyrene on biotransformation pathways in Nile tilapia (Oreochromis niloticus)

BaP is one of the most studied PAH, due to its ubiquitous presence in aquatic environments and toxicity to aquatic organisms. The main goal of this study was to assess BaP effects in Nile Tilapia after waterborne and dietary exposures, through the evaluation of EROD and GST activities in liver, gills and intestine, and BaP metabolites in bile; and also to evaluate the usefulness of these commonly used biomarkers after two different routes of exposure. Waterborne exposure to BaP led to a significant induction of EROD in all tissues analyzed (644%, 1640% and 2880% in relation to solvent in liver, gill and intestine respectively) while in dietary exposures EROD was induced only in intestine (3143%) after exposure to high BaP concentrations. GST activities with CDNB were slightly induced in liver (40%) and in gill (66%) after water exposure to BaP, and in intestine after dietary exposure to low BaP concentrations (182%). BaP metabolites in bile increased after both exposure routes, and were highly correlated with EROD activity after water exposure. In summary, this work has shown that the effects of BaP on biotransformation pathways depend on the route of exposure. Moreover, barrier tissues like gills and intestine also have an important role in the first-pass metabolism of BaP, reducing the amount of parent compound that reaches the liver to be metabolized. For that reason, EROD activity as a biomarker of exposure should also be applied in extrahepatic organs, like gills and intestine, in monitoring studies. Biliary BaP type metabolites are good reflectors of contamination levels under both exposure routes, while GST activity with CDNB as substrate, as a phase II enzyme, does not seem a reliable biomarker of exposure to BaP regardless the route of exposure.     

Induced alkoxyresorufin-O-dealkylases in tilapias (Oreochromis niloticus) from Guandu river, Rio de Janeiro, Brazil

The activity of fish monooxygenases has been extensively used as a monitoring tool to detect contamination of water bodies by cytochrome P450-inducing agents. In this study we evaluated the activities of ethoxy- (EROD), methoxy- (MROD) and pentoxy- (PROD) resorufin-O-dealkylases in the liver of Nile tilapias (Oreochromis niloticus) collected at the Guandu river, at a reference clean site (Lake 1) and at two other sampling sites (Lakes 2 and 3) in Rio de Janeiro state, Brazil. Alkoxyresorufin-O-dealkylases were measured fluorimetrically in the hepatic S9 fraction. EROD (17.7-fold), MROD (14.2-fold) as well as PROD activities were considerably higher in tilapias from Guandu river. A moderate increase of EROD (5.0-fold) and MROD (5.4-fold) was also found in tilapias from Lake 3. These findings suggest that Guandu river watershed, the main source of urban drinking water supply in Rio de Janeiro, is polluted with CYP1A-inducing xenobiotics. Furthermore, we also found a good linear relationship between EROD and MROD, a finding that agrees with the hypothesis that the two reactions are catalysed by the same CYP1A isoform in O. niloticus.     

Impact of chemical exposure on the fish Pomatoschistus microps Krøyer (1838) in estuaries of the Portuguese Northwest coast

Juveniles of the estuarine fish Pomatoschistus microps were collected from autumn 2001 to summer 2002 in five stations along the Portuguese Northwest coast with different types and/or levels of environmental contamination: two reference sites with low levels of contamination (R1 and R2) and three differently impacted areas with higher levels of contamination. UI is located in an estuary under the influence of urban and industrial effluents, AA in a channel that receives intensive agriculture run-off and IE in a highly impacted industrial area. The activity of the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH), 7-ethoxyresorufin O-deethylase (EROD) and glutathione S-transferases (GST) were used as environmental biomarkers on P. microps. A significant seasonality effect on all the enzymatic activities was found, lower levels being registered in winter and spring on AChE, in autumn on LDH, and in winter on GST and EROD. The battery of biomarkers used was capable of discriminating sites with different types and/or levels of contamination, R1 and UI being the highest discriminated (91.7% and 66.7%, respectively). At R1 significantly lower levels of AChE and LDH were found, and EROD was significantly inducted at UI. Furthermore, IE presented higher levels of GST, and R2 and AA an inhibition of AChE in winter and spring. The results indicated that the battery of biomarkers used in this study seems to be a useful tool to distinguish between different types of environmental contamination in estuarine systems, and that P. microps is a suitable species to be used as bioindicator.     

Microsomal monooxygenase activity in Tilapia (Oreochromis mossambicus) exposed to a bleached kraft mill effluent using different exposure systems.

Bleached kraft pulp and paper mill effluents (BKMEs) are known to have adverse effects on aquatic organisms. One of the effects of BKMEs is its ability to induce cytochrome P4501A activity in exposed fish. 7-Ethoxyresorufin O-deethylase (EROD) activity is the most common biomarker used to measure the mixed-function monooxygenase activity. In this study, Tilapia were exposed to BKMEs using different exposure systems and their hepatic EROD activity, as well as liver/somatic index (LSI), were determined. In the Phase I study, Tilapia treated with betaNF and a whole (100%) BKME using a static, non-renewal system exhibited statistically significant EROD induction, but LSI values were not altered. In the Phase II study, fish were either caged in the mill's fishpond with the whole effluent passing through or cultured in tanks receiving 100% of the BKME continuously using a flow-through system in the laboratory. Their EROD activities were then compared with the non-exposed fish (control). The EROD activities in both groups of fish were elevated significantly with the greatest induction being observed in the field-exposed group. The LSI values in all of the field-exposed fish were significantly greater than the control Tilapia. The EROD assay was sensitive in detecting biological changes in fish exposed to the BKME. Further studies are warranted to better understand the impacts of BKMEs on aquatic organisms in Taiwan.     

Monitoring contaminants from oil production at sea by measuring gill EROD activity in Atlantic cod (Gadus morhua)

An ex vivo gill EROD assay was applied in Atlantic cod (Gadus morhua) as a biomarker for waterborne CYP1A-inducing compounds derived from oil production at sea. Exposure to nominal concentrations of 1 ppm or 10 ppm North Sea crude oil in a static water system for 24 h caused a concentration-dependent gill EROD induction. Further, exposure of cod for 14 days to environmentally relevant concentrations of produced water (PW, diluted 1:200 or 1:1000) from a platform in the North Sea using a flow-through system resulted in a concentration-dependent induction of gill EROD. Crude oil (0.2 ppm) from the same oil field also proved to induce EROD. Finally, gill EROD activity in cod caged for 6 weeks at 500-10 000 m from two platforms outside Norway was measured. The activities in these fish were very low and did not differ from those in fish caged at reference sites.     

EROD activity and biliary fluorescence in Schroederichthys chilensis (Guichenot 1848): biomarkers of PAH exposure in coastal environments of the South Pacific Ocean

Schroederichthys chilensis is a common shark that lives in Chilean coastal environments. In this work, the relationship between liver 7-ethoxyresorufin-O-deethylase dealkylation (EROD) activity and Fluorescent Aromatic Compounds (FAC) in bile of S. chilensis sampled in three bays with different degrees of pollution were performed including a reference area. Sixty individuals were collected, 20 for each site; (10 males and 10 females per site) livers and bile samples were obtained and immediately frozen. EROD activity and FAC were measured according to three standard methods. EROD activity and FAC were higher in polluted areas than in the reference area. Synchronous Fluorescence Spectra of the bile from the fish collected at the most polluted area showed a peak at 347nm representing a metabolite corresponding to 1-hydroxypyrene. The low EROD activity in the reference area is likely related to the low level of PAH in sediments. We propose that this species is a good indicator of exposure to FACs, since it presents a series of characteristics that make it suitable for monitoring PAH exposure in coastal zones.     

PAH metabolites,GST and EROD in European eel (Anguilla anguilla) as possible indicators for eel habitat quality in German rivers

The stock of the European eel (Anguilla anguilla L.) continues to decline and has reached a new minimum in 2011. Poor health status of the spawners due to organic contaminants is one of the possible causes for this dramatic situation. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants, which are rapidly metabolized in vertebrates. EROD (ethoxyresorufin-O-deethylase) and GST (glutathione-S-transferase) are two enzymes involved in PAH detoxification in fish. In this study, PAH metabolites as well as EROD and GST activity in a large, comprising dataset of more than 260 migratory and pre-migratory eels from five large German river basin districts were used to describe PAH exposure and its metabolism as possible indicators for the habitat quality for eels. Eel from the river Elbe appear to be moderately contaminated with PAH. Highest mean values of PAH metabolites were analysed in fish from the river Rhine. However, the results suggest that contaminants such as PAH are metabolized in the fish and may have contributed to EROD activity in eels caught from the Elbe estuary to 600 km upstream. Since the eel’s onset of cessation of feeding is closely linked to maturation and migration, we propose bile pigments as new indicators contributing to identify the proportion of migratory eel, which is crucial information for eel management plans. We showed that PAH metabolites normalized to bile pigments as well as EROD could be used to describe the habitat quality and might be suitable parameters in search for suitable stocking habitats.     

Evaluation of biomarkers in caged fishes and mussels to assess the quality of waters in a bay of the NW Mediterranean Sea

Specimens of sea bass (Dicentrarchus labrax) were placed in cages for 1 month in spring and autumn at different locations in the Bay of Cannes (NW Mediterranean). Biochemical markers evaluated were: ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities in fish livers and acetylcholinesterase (AChE) activity in fish muscle. EROD and GST activities were higher in front of the outlet for the wastewater plant of Cannes and in the harbour than outside the marina. High EROD and GST activities may be induced by petrol hydrocarbons and/or polychlorinated biphenyls (PCBs). AChE was low in the muscles of the fish caged in the harbour compared with samples from the other cages. Low AChE activity could suggest the presence of organophosphorus and carbamate compounds in seawater from the harbour. Mussels (Mytilus galloprovincialis) were caged off Cannes for the same periods as the fishes. Heavy metal, metallothionein (MT) concentrations and lysosomal membrane stability were evaluated in the digestive gland of the mussels. Results show low heavy metal and MT concentrations, implying low metal concentrations in the surrounding waters. High lysosomal membrane stability revealed a good physiological status of these animals after caging. The whole set of data indicates that seawater in the Bay of Cannes appeared to be unpolluted as regards pollutants which may induce the measured biomarkers, except in restricted areas.     

Effects of complex waste mixtures on hepatic monooxygenase activities in brown bullheads (Ictalurus nebulosus)

Hepatic MFO components (cytochrome P-450, cytochrome b(5), and ethoxyresorufin O-deethylase, EROD) were measured in brown bullheads (Ictalurus nebulosus) inhabiting a creek receiving a complex mixture of organics and trace metals. The activities of these same enzymes were also measured in bullheads from an uncontaminated reference site to assess the relative ability of MFO parameters to serve as a biomarker of aquatic pollution. Bullheads analyzed from the polluted site had lower hepatic microsomal P-450 (p < 0.01) concentrations and similar EROD activities per mg protein as compared to bullheads from the reference site. However, analysis of enzyme turnover ratios revealed greater EROD activity per mg cytochrome P-450 (p < 0.05) in the fish from the polluted site. No difference in cytochrome b(5) activities were observed between the two groups. As compared to the reference site, bullheads collected from the polluted creek had an increased occurrence of lip and lower jaw lesions and liver damage, including elevated liver/body weight ratios. Accordingly, the monooxygenase activities measured in this study were not reliable indicators of chemical pollution or contaminant stress in bullheads in the polluted creek. Further research is needed concerning contaminant interactions, particularly among organic pollutants and metals and their effects on monooxygenase activities.     

EROD and CYP1A protein in channel catfish (Ictalurus punctatus) from an urban estuary relative to that in benzo[a]pyrene-exposed hatchery specimens

Bottom-feeding fish such as flounder and killifish have been widely used in monitoring hepatic monooxygenase induction in polluted water bodies. While channel catfish are often utilized in tissue monitoring of fresh and estuarine water bodies, few data are available on their use in environmental monitoring of hepatic monooxygenase activity. In this project, the presence of CYP1A protein was verified in channel catfish through recognition by Mab 1-12-3, an antibody which recognizes the CYP1A homologue in a variety of teleost species. CYP1A protein levels and 7-ethoxyresorufin-o-deethylase (EROD) activity in laboratory control and benzo-a-pyrene (BaP)-challenged channel catfish were compared to those in feral channel catfish from Back River, an urban estuarine tributary to Chesapeake Bay. Though more variable, mean CYP1A protein levels in the field-collected fish were similar to those of the BaP-induced laboratory fish. However, EROD activity of the Back River fish was less than one half that observed in the BaP-induced laboratory fish. When normalized to CYP1A protein levels, EROD activity was slightly lower in the Back River fish than either the laboratory control or BaP-treated fish. This finding may indicate possible inhibition or inactivation of the CYP1A protein in the feral fish.     

Ethoxyresorufin-O-deethylase (EROD) activity and bile metabolites as contamination indicators in Baltic Sea perch: determination by HPLC

Exposure of Baltic Sea perch (Perca fluviatilis) to organic contaminants was investigated by means of liver enzyme activity, measured as ethoxyresorufin-O-deethylase (EROD) activity, and PAH metabolites excreted to bile. Female perch used in the study were caught in coastal waters of the western Gulf of Finland. Reaction conditions were optimised for determination of EROD activity in liver. A high-performance liquid chromatography (HPLC) method with fluorescence detection was developed to separate the interfering fluorescent signal from the signal due to EROD activity. EROD activity in perch varied within a concentration range of 0.30-14 pmol min(-1)mg(-1) protein. Recent PAH exposure was indicated in enhanced levels of the bile metabolite 1-hydroxypyrene, which varied between 213 and 1149 microg kg(-1). No correlation was indicated between hepatic EROD activity and concentration of 1-hydroxypyrene.     

Comparison of biomarker and pathological responses in flounder (Platichthys flesus L.) induced by ingested polycyclic aromatic hydrocarbon (PAH) contamination

This study investigated the response of biomarker measurements and histopathological indicators of polycyclic aromatic hydrocarbon (PAH) exposure in the flounder (Platichthys flesus L.). Flounder were fed food spiked with a mixture of four PAHs at an environmentally relevant range of concentrations for either one or six months. Ethoxyresorufin-O-deethylase (EROD) activity was elevated following 1 month exposure to PAH concentrations up to 50 mgkg(-1) in food. Bile metabolite concentrations were found to increase with PAH concentration, up to 500 mgkg(-1) PAH. By comparison, no DNA adducts were detected and there were no significant histopathological changes observed. After 6 months exposure, EROD levels were not elevated but bile metabolites showed a similar dose dependent relationship as in the 1 month experiment, while DNA adducts were only detected in the highest PAH exposure groups. No significant histopathological changes were observed. The results are discussed with respect to the implications for the use of these methods in environmental monitoring studies.     

Endocrine effects of sublethal exposure to persistent organic pollutants (POPs) on silver carp (Hypophthalmichthys molitrix)

Silver carp (Hypophthalmichthys molitrix) samples were collected from five selected sites that represent diverse levels of downgraded persistent organic pollutants (POPs) contamination in Ya-Er Lake in October 1999. Hepatic ethoxyresorufin-O-deethylase (EROD) and UDP glucuronosyltransferase (UDPGT) activities, hepatosomatic index (HSI), hepatic retinoids, serum thyroid hormones were measured. It was found that hepatic retinol and serum free 3,5,3'- tetraiodothyronine (FT3) significantly increased (P < 0.01) when both hepatic EROD and UDPGT activities significantly declined (P < 0.01) from pond 1 to 5 with decrease in the degree of pollution. This significant negative correlation (P < 0.01) suggests that the persistent organochlorinated contaminants could induce hepatic EROD and UDPGT activities, alter retinoid and thyroid hormone homeostasis, and finally lead to the reduction of retinol and FT3, the two biologically active forms of retinoids and thyroid hormone in silver carp of Ya-Er Lake.     

Nonylphenols, nonylphenol-ethoxylates, linear alkylbenzenesulfonates (LAS) and bis (4-chlorophenyl)-sulfone in the German Bight of the North Sea.

Nonylphenols and nonylphenol-ethoxylates were detected in the water and sediment samples from the German Bight of the North Sea. Additionally bis (4-chlorophenyl)-sulfone and linear alkylbenzenesulfonates (LAS) were detected in marine waters. Proof of identification is given by comparison of spectral and chromatographic data from the compounds in sample extracts to those obtained from pure standards. In extracts obtained from water samples taken in 1990 and 1995 the concentrations of nonylphenols and bis-(4-chlorophenyl)-sulfone were compared for each year. The concentrations of nonylphenols in seawater varied from 0.7 to 4.4 ng/l while in the Elbe estuary about 33 ng/l were found. In water samples taken in 1998 nonylphenol-polyethoxylates could not be determined, whereas LAS concentrations of 30 ng/l were confirmed by HPLC-MS/MS. The concentrations of bis (4-chlorophenyl)-sulfone ranged from 0.18 to 2.2 ng/l. In sediment samples LAS concentrations of 39-109 ng/g dry weight were determined.     

Inhibition of ethoxyresorufin-O-deethylase (EROD) activity in mixtures of 2,3,7,8-tetrachlorodibenzo-p-dioxin and polychlorinated biphenyls

Induction of ethoxyresorufin-O-deethylase (EROD) activity and porphyrin accumulation shows different structure-activity relationships for different polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Interactions between the two responses can strongly influence the induction and activity of EROD. The results support the conclusion that there are nonadditive interactions between nondioxin-like PCBs and dioxin-like compounds. The interaction between EROD activity and the porphyrin biosynthesis makes the prerequisite of additivity in the toxic equivalency factor concept for environmental mixtures highly spurious. Inhibition of EROD activity caused by non-dioxin like compounds could have a significant impact on the value of EROD activity as a biomarker in the present methods of risk assessment for these compounds.