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1.
Newark Bay (NB) killifish (Fundulus heteroclitus) have been chronically exposed to environmental contaminants that activate the aryl hydrocarbon receptor (AHR) and are tolerant to toxic effects and CYP1A induction provoked by AHR ligands. Resistance to CYP1A induction could be due to an epigenetic mechanism such as DNA methylation. We measured in-ovo CYP1A catalytic activity (ethoxyresorufin-O-deethylase, EROD) in NB and reference site killifish embryos aqueously exposed to various concentrations of the de-methylating agent 5-azacytidine, 5-AC (5, 50 and 500 μ(micro)M) with or without 0.2 μ(micro)g/l of the CYP1A inducer 3,3′,4,4′,5 pentachlorobiphenyl (IUPAC PCB126). Neither PCB126 alone, nor PCB126 plus 5-AC, induced EROD above levels in vehicle treated Newark Bay fish. In reference site fish, the same PCB126 dose provoked a 7.4-fold EROD induction relative to controls. We conclude that Newark Bay killifish are resistant to CYP1A induction by co-planar PCBs during early embryological development and our data suggests that DNA methylation does not play a critical role in resistance to CYP1A induction in this model.  相似文献   

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3.
Freshwater sculpin were taken from various locations in the Kenai River to determine their in-vivo response to pollution exposure. The specific activity of cytochrome P4501A1 was determined using fluorescence detection of the 7-ethoxyresorufin-O-dealkylase (EROD) reaction. The EROD specific activity was found to be independent of river miles but appeared to relate to specific sites of urban runoff. Glutathione-S-transferase (GST) activities were also measured but showed no significant difference between sites. Cytochrome P450 laboratory induction studies were carried out on individuals collected from a pristine site. Five groups of 10 fish were dosed from 10–150 mg β-Naphthoftavone (βNF)/kg body weight. The response was linear from 10–50 mg βNF/kg body weight. Sculpin appear to have excellent potential as a sensitive indicator of xenobiotic exposure in a freshwater benthic habitat.  相似文献   

4.
The use of oil-based drilling muds has been discouraged in hydrocarbon exploration and production in the marine environment but these muds are presently being used to a considerable degree in the United Kingdom and Norwegian sectors of the North Sea. Field studies in the North Sea have demonstrated only localized impacts around individual drilling sites,1,2 even including those sites where ‘toxic’ diesel oils were employed as base fluids in drilling muds. Yet the question of disposal of cuttings contaminated with oil from drilling muds remains somewhat controversial. The induction of mixed-function oxygenases (MFO) has been validated on a number of occasions in the field as a sensitive index of low level hydrocarbon exposure (reviewed by Payne),3 including sites in the North Sea where diesel-based muds were used.4 The present study demonstrates that any potential for induction by hydrocarbon contaminated cuttings will probably be reduced by substitution of low-aromatic base oils for diesel in drilling mud formulations.  相似文献   

5.
The present study clarifies the enzymatic properties of two avian cytochrome P4501A (CYP1A) paralogs, CYP1A4 and 1A5, using a yeast-based vector system. Recombinant CYP1A4 and 1A5 proteins from common cormorant (Phalacrocorax carbo) were expressed in yeast cells, and showed typical reduced CO-difference spectra with a peak at 446 nm. Kinetic analysis of O-dealkylase of methoxy-, ethoxy-, pentoxy- and benzyloxyresorufin catalyzed by the CYP1A enzymes revealed that Vmax value for ethoxyresorufin-O-deethylase (EROD) activity was much higher than that for the other three O-dealkylase activities for both isozymes. Interestingly, remarkable substrate specificity of the CYP1As was observed for O-dealkylation of benzyloxyresorufin and methoxyresorufin; CYP1A4 was highly specific for catalyzing benzyloxyresorufin-O-debenzylase activity, whereas CYP1A5 was more efficient in catalyzing methoxyresorufin-O-demethylase activity. The present study also measured CYP1A-dependent EROD activity in the presence of 2,3,7,8-tetrachlorodibenzofuran (TCDF) to evaluate the ability of this dioxin-like congener to inhibit the EROD activity. One hundred nanomolar TCDF noncompetitively inhibited CYP1A5-dependent EROD activity, although no inhibitory effect was detected for CYP1A4-dependent EROD activity. These results indicate that the avian CYP1A paralogs have different affinities for substrate and inhibitor, thus suggesting their distinct physiological and toxicological roles.  相似文献   

6.
The degree of induction of hepatic mixed function oxidase (MFO) enzymes in fish is modulated by environmental conditions. This study was designed to investigate the influence of water temperature, presence or absence of food, and exposure to benzo(a]pyrene (BaP) on the inductive response of bluegill sunfish (Lepomis macrochirus). The results show an increase in 7-ethoxyresorufin O-deethylase (EROD) activity with an increase in acclimation temperature and dose. This activity appears to be associated with a very small fraction of the total cytochrome P-450 induced. Major changes were observed in the 53- and 57-kilodaltons (kDa) electrophoretic bands.  相似文献   

7.
Our experience in DNA alteration assessment tells us that aquatic vertebrates, in general, and also some of the invertebrates, by living in polluted areas acquire altered DNA; DNA alterations being defined either as single-strand breaks, and/or alkali sensitive or single-strand specific nuclease-cleavable sites (sse). This can be shown by several methods: (i) Alkaline filter elution;1 (ii) fluorescence analysis of DNA unwinding;2 (iii) alkaline sucrose density gradient centrifugation;3 (iv) alkaline unwinding analysis with hydroxyapatite differentiation;4 (v) nucleoid sedimentation analysis;5 (vi) supercoiled DNA relaxation detection by electrophoresis;6 and (vii) measurement of DNA molecular weight distributions with the electron microscope.7 The amount of sse per DNA mass can be a function of either an increased activity of DNA damaging agents or agents that inhibit DNA repair. Among DNA damaging agents are polycyclic aromatic hydrocarbons (PAH), that can cause sse by the ‘fast effect’8 or after induction upon uptake, through the action of mixed function oxygenase (MFO). Since MFO induction within certain limits is a function of PAH concentration measurement of this enzyme activity enables at least partial interpretation of the DNA alteration status, which can be a two-phase process.  相似文献   

8.
The aim of this study was to determine the detoxication capacity and the sensitivity to pollutants of fish living in a pristine environment such as the Antarctic Ocean. Forty specimens of Pagothenia bernacchii collected during the Antarctic summer of 1991–1992 were divided into three groups, and were treated with 10 mg/kg of B(α)P, 50 mg/kg of PCBs and corn oil and sacrificed after 2, 4 and 10 days. The mixed function oxidase activity measured in these fish through the test of BPMO, EROD and BROD activities revealed that both B(α)P and PCBs are effective in inducing this enzyme system. Owing to the slow metabolic rate of this species, related to the low ambient temperature of its natural habitat, the highest level of induction was monitored after 10 days i.e. much later than in fish of temperate seas.  相似文献   

9.
In fish, as well as in mammals, it is well known that the cytochrome P450-dependent oxidative metabolism of xenobiotics can generate DNA-reactive species. Moreover, this metabolism is known to be inducible by several compounds of environmental significance, such as polychlorobiphenyls, polycyclic aromatic hydrocarbons (PAHs) and dioxins. Consequently, we studied the relationship between the degree of induction of the cytochrome P4501A, expressed as that of 7-ethylresorufin O-deethylase (EROD) activity, and the level of DNA-adducts, using the post-labelling assay, in the liver of rainbow trout exposed to benzo(a)pyrene (a representative PAH). The results showed a significant 2- to 4-fold increase in EROD activity 2, 4 and 8 days after treatment, paralleled by an increase in DNA-adduct levels. This work further emphasizes the involvement of cytochrome P4501A in the metabolism of benzo(a)pyrene into genotoxic metabolites in rainbow trout.  相似文献   

10.
The degree of induction of hepatic cytochrome P-450 monooxygenases in fish by various chemicals may vary owing to many factors such as sex, sexual maturity, age, season and environmental temperature. In the present investigation the influences of gonadal steroids and water temperature on the inductive response were studied. The data indicate that gonadal steroids and water temperature modulate the response of the cytochrome P-450 system in rainbow trout to PCB and β-naphthoflavone.  相似文献   

11.
The occurrence of imposex, imposition of male sex characteristics on female snails, has been extensively documented throughout the world. Tributyltin (TBT) and other organotins have been causally linked to imposex induction at levels as low as 2 ng/l. There are several proposed mechanisms of action. First, TBT has been shown to be neurotoxic and to accumulate in snail ganglia. Peptide hormones control sexual differentiation in gastropods, and one hypothesis is that TBT acts as a neurotoxin to abnormally release the peptide hormone Penis Morphogenic Factor (PMF). However, PMF has not been characterized to date. The neuropeptide APGWamide significantly induces imposex in the mud snail, Ilyanassa obsoleta, at 10−16 moles sub-cutaneous (SQ) injection over 2 weeks, and could be the PMF in this species. A second hypothesis is that TBT inhibits aromatase activity leading to increased testosterone levels and decreased estradiol. In vitro studies with snail digestive gland microsomes showed that TBT-dosed snails not exhibiting imposex had a 52% reduction in aromatase activity. Although the role of vertebrate sex steroids is not known in gastropods, it is possible that the combination of changes in peptide and steroid hormones may lead to imposex induction at extremely low doses of TBT.  相似文献   

12.
Wet atmospheric deposition of dissolved N, P and Si species is studied in well-mixed coastal ecosystem to evaluate its potential to stimulate photosynthetic activities in nutrient-depleted conditions. Our results show that, during spring, seawater is greatly depleted in major nutrients: Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP) and Silicic acid (Si), in parallel with an increase of phytoplanktonic biomass. In spring (March–May) and summer (June–September), wet atmospheric deposition is the predominant source (>60%, relative to riverine contribution) for nitrates and ammonium inputs to this N-limited coastal ecosystem. During winter (October–February), riverine inputs of DIN predominate (>80%) and are annually the most important source of DIP (>90%). This situation allows us to calculate the possibility for a significant contribution to primary production in May 2003, from atmospheric deposition (total input for DIN ≈300 kg km−2 month−1). Based on usual Redfield ratios and assuming that all of the atmospheric-derived N (AD-N) in rainwater is bioavailable for phytoplankton growth, we can estimate new production due to AD-N of 950 mg C m−2 month−1, during this period of depletion in the water column. During the same episode (May 2003), photosynthetic activity rate, considered as gross primary production, was estimated to approximately 30 300 mg C m−2 month−1. Calculation indicates that new photosynthetic activity due to wet atmospheric inputs of nitrogen could be up to 3%.  相似文献   

13.
The acute lethality and sublethal heavy metal contamination potential to marine organisms of a waste brine solution from a potash mining operation were determined. The brine was acutely lethal to marine organisms of the Bay of Fundy, Canada, at concentrations between 47 and 55‰ salinity (96-h LC50 values: threespine stickleback, Gasterosteus aculeatus, 47·7‰; polychaete worm, Nephtys incisa, 52·5‰; blue mussel, Mytilus edulis, lethal to whole animal and reduced ciliary activity of gills above 55‰).The brine diluted to sublethal concentrations (≤40‰) contained manganese (≤ 49·5 ×), copper and zinc (≤ 5·2 ×), lead (≤ 2·6 ×) and cadmium (≤ 0·7 ×) in decreasing order of enrichment relative to control seawater. Copper was accumulated in mussels exposed to these solutions over 44 days to the greatest degree (4 ·4 ×), followed by manganese and lead. Tissue lead concentration reached a steady value within 44 days and cadmium was not accumulated.  相似文献   

14.
Our previous studies indicated that sea anemone microsomes contain cytochrome P450 (CYP) and have ethoxyresorufin O-dealkylation (EROD) activity. Other marine invertebrates have discrete organs which concentrate cytochromes P450, whereas cnidarians have evolved only to the tissue level of development. To examine the distribution of CYP in sea anemones, microsomes were prepared from the following tissue regions of two sea anemones, Anthopleura xanthogrammica: outer (heavy muscular wall), inner (imperfect and perfect mesentery, and retractor muscle), soft (digestive sac, gonads, and mesentery filaments), and tentacular (including algal/diatom symbiont). The cytochrome P450 content was distributed relatively evenly among the tissue regions. In contrast, the 418-nm CO-binding chromophore was approximately 10 times greater in the outer region than in any other region. Further, the 490-nm peak (which interferes with quantification of CYP in sea anemones) was greater in the outer region. In general, the EROD activity was comparable in the inner and soft regions and highest in the tentacles. However, the EROD results may have been complicated by the presence of the algal/diatom symbiont.  相似文献   

15.
Gonadally mature fish display strong sex-related differences in the content and activity of P4501A, the major polynuclear aromatic hydrocarbon-inducible P450 form in teleosts. Such differences appear related to plasma levels of the female sex steroid, estradiol (E2); however, neither the mechanism of estradiol suppression of P4501A nor the capacity for hormonal regulation to overcome P4501A induction by high concentrations of potent inducers are known. Gonadally mature flounder (Pseudopleuronectes americanus) were collected from Fox Island (FI), Rhode Island, a reference site, and New Bedford Harbor (NB), Massachusetts, a site highly contaminated with polychlorinated biphenyls (PCBs). Differences in flounder P4501A expression were determined at the level P4501A catalytic activity (measured as ethoxyresorufin-O-deethylase, EROD), P4501A protein content (immunoquantitated), and P4501A mRNA content (by Northern blot) as they relate to sex, reproductive status, and hepatic PCB content. Our results confirm that suppression of P4501A in gonadally mature female fish is probably due, at least in part, to elevated E2 titers, and demonstrate that such suppression occurs at a pretranslational level and, further, that endogenous regulation of P4501A expression can ‘override’ exogenous regulation by even high concentrations of P4501A inducers.  相似文献   

16.
Long term effects of sublethal concentrations of oil on the marine environment have become of general concern. Cytochrome P4501A activity (EROD) in liver and fixed wavelength fluorescence detection of PAHs metabolites (FF) have in this study been used as biomarkers for dispersed oil exposure on a long term period of juvenile turbot (Scophthalmus maximus L.). A Continuous Flow System was used to carry out the study. The fish were continuously exposed to 0.125, 0.5 or 2.0 mg litre−1 dispersed topped crude oil for 6, 15, 24 h, 4 and 21 days followed by a 9 days recovery period in clean seawater. No induction of the cytochrome P4501A was measured. A maximum level in bile metabolites (4- to 5-fold) was recorded after 24 h of exposure revealing thereby a detoxification process, but a decline occurred from day 4 to day 21. This study demonstrated that FF detection of PAHs metabolites in bile could be a more sensitive biomarker than EROD activity in a long term exposure to sublethal concentration of oil.  相似文献   

17.
Copper (Cu) is an essential element for biological systems, however, when present in excess, is toxic. Metallothioneins can play an important role in Cu homeostasis and detoxification. Moreover, Cu can catalyse the production of toxic hydroxyl radicals that cause lipid peroxidation but defence systems in the cells can limit the oxidative damage. The present study was performed to investigate the effect of three Cu concentrations (0.5, 2.5 and 25 μg l−1) on the response of antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathion peroxidase and total glutathion peroxidase), total proteins, metallothioneins (MT), malondialdehyde (MDA) concentrations in the gills of the clam, Ruditapes decussatus. The activity of antioxidant enzymes and total proteins, MT and MDA concentrations were measured in the gills of the clams after 1, 3, 7, 14, 21 and 28 days of Cu exposure. Results indicate that Cu only induces an imbalance in the oxygen metabolism during the first week of Cu exposure due to a decrease in mitochondrial SOD and CAT, selenium-dependent and total glutathion peroxidase activities. Cu also causes lipid peroxidation, measured by the MDA formation, that was Cu dependent. In the gills of clams exposed to 25 μg Cu/l, the excess of Cu triggers the induction of MT synthesis after 3 days of exposure.  相似文献   

18.
Effects on the hepatic cytochrome P450 1A1 system were investigated in juvenile rainbow trout i.p. injected with three different aromatic containing fractions: kerosene, light gas oil or heavy gas oil, originated from distilled North Sea crude oil. Kerosene treatment resulted in no effect on the P450 1A1 system, light gas oil injection caused a weak induction of EROD activities and heavy gas oil treatment resulted in a prominent induction of EROD activities as well as accumulation of CYP1A1 mRNA and P450 1A1 protein levels. The effects of heavy gas oil were compared with effects of β-napthoflavone (β-NF) on the P450 1A1 system. It was obvious that important discrepancies seemed to exist between EROD activities and corresponding CYP1A1 mRNA and P450 1A1 levels in rainbow trout treated with either heavy gas oil or β-NF i.e. heavy gas oil treatment resulted in higher specific EROD activities (EROD/P450 1A1) compared to β-NF. GC-MS analyses revealed that liver and bile from heavy gas oil treated rainbow trout in addition to naphthalene also contained polycyclic aromatic hydrocarbons such as phenanthrenes, anthracene, pyrenes, fluoranthene benz(a)anthracene and chrysene, while none of these compounds were detected in control trout.  相似文献   

19.
Few phosphorus-depleted coastal ecosystems have been examined for their ability to hydrolyze phosphomonoesters. We examined seasonal (August 2006–April 2007) alkaline phosphatase activity in Florida Bay, a phosphorus-limited shallow estuary, using fluorescent substrate at low concentrations (≤2.0 μM). In situ dissolved inorganic and organic phosphorus levels and phosphomonoester concentrations were also determined. Water column alkaline phosphatase activity was partitioned into two particulate size fractions (>1.2 and 0.2–1.2 μm) and freely dissolved enzymes (<0.2 μm). Water column alkaline phosphatase activity was also compared to leaf and epiphyte activity of the dominant tropical seagrass Thalassia testudinum. Our results indicate: (1) potential alkaline phosphatase activity in Florida Bay is high compared to other marine ecosystems, resulting in rapid phosphomonoester turnover times (2 h). (2) Water column alkaline phosphatase activity dominates, and is split equally between particulate and dissolved fractions. (3) Alkaline phosphatase activity was highest during cyanobacterial blooms, but not when normalized to chl a. These results suggest that dissolved, heterotrophic and autotrophic alkaline phosphatase activity is stimulated by phytoplankton blooms. (4) The dissolved alkaline phosphatase activity is relatively constant, while the particulate activity is seasonally and spatially dynamic, typically associated with phytoplankton blooms. (5) Phosphomonoester concentrations throughout the bay are low, even though potential hydrolysis rates are high. We propose that bioavailable dissolved organic P is hydrolyzed by dissolved and microbial alkaline phosphatase enzymes in Florida Bay. High alkaline phosphatase activity in the bay is also promoted by long hydraulic residence times. This background activity is primarily driven by carbon and phosphorus limitation of microorganisms, and regeneration of enzymes associated with cell lysis. Pulses of inorganic phosphorus and labile organic phosphorus and nitrogen may stimulate autotrophs, particularly cyanobacteria, which in turn promote biological activity that increase alkaline phosphatase activity of both autotrophs and heterotrophs in the bay.  相似文献   

20.
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