首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
These studies were designed to determine the metabolic capability of the microsomal cytochrome(s) P-450 in spiny lobster hepatopancreas, and to determine how chemicals which selectively modify mammalian monooxygenase activity catalyzed by different cytochrome P-450 isozymes affect the spiny lobster cytochrome P-450. We used a washing procedure to concentrate the hepatopancreas microsomal cytochrome P-450 and remove the inhibitors of monooxygenase activity which are normally present in microsomes. The resulting reparation (MI fraction) was used to determine monooxygenase activity towards benzo[a]pyrene, benz-phetamine, 7-ethoxyresorufin in the presence of either cumene hydroperoxide or NADPH and vertebrate liver cytochrome P-450 reductase. Benzphetamine was the best substrate for the lobster cytochrome P-450, whereas 7-ethoxyresorufin was metabolized very slowly. Studies with chemical modifiers showed that the responses of the lobster cytochrome(s) P-450 were not similar to those of any of the well-characterized cytochrome P-450 isozymes purified from mammalian liver.  相似文献   

2.
Monooxygenase reactions catalyzed by cytochromes P-450 are paramount in the oxidative metabolism of many xenobiotics, determining both the persistence and effects of numerous types of compounds. Immunological probes are proving useful in evaluating the functions of P-450 isozymes in microsomal preparations from many species. The regulation of specific isozymes by endogenous and exogenous factors can also be evaluated with such probes. Here we describe studies on the activities apparently catalyzed by induced P-450 in fish, evaluated with both polyclonal and monoclonal antibodies to cytochrome P-450E, the apparent major β-naphthoflavone(BNF) or methylcholanthrene(MC)-inducible isozyme purified from scup (S. chrysops) liver.  相似文献   

3.
Increasing anthropogenic pollution of the environment can have adverse consequences for organisms which are more subtle than direct toxicity. Detectable levels of persistent pollutants remain even if the substance is no longer used. An example is atrazine, a herbicide in common use throughout the world but one which has been banned in Germany since 1992. As a lipophilic substance, atrazine is bioconcentrated which may lead to chronic intoxication or physiological stress. In order to withstand chemical stressors, many organisms possess detoxication enzymes, for example certain P-450 monoxygenases and glutathione S-transferases. But detoxication demands cellular energy, and in developing organisms, such as fish embryos which have particularly high energy needs for sustaining growth and organogenesis, the additional energy needs of detoxication may present additional stress. In this study, uptake of atrazine, cytochrome P-450 binding spectra, effects on microsomal and soluble glutathione S-transferase activities, and the initial detoxication steps of atrazine via microsomal and soluble glutathione S-transferases were studied using early life stages of zebrafish.  相似文献   

4.
Monoclonal antibody directed against a major β-naphthoflavone (BNF)-induced form of teleost cytochrome P-450, P-450E (equivalent to P-450c in rat) was used to immunolocalize this enzyme in liver, gill and heart of scup and trout. Liver sections from both species showed P-450E in the cytoplasm of hepatocytes. No regional differences were observed which might indicate zonation of cytochrome P-450E within subpopulations of hepatocytes. Scup exocrine pancreatic cells were only weakly positive. In the gill of both fish, cytochrome P-450E was restricted to the endothelium (pillar cells) of secondary lamellae, where fluorescence appeared as a chain in longitudinal sections through lamellae and as star-shaped clusters in en face views. Sections of ventricular wall in both species revealed P-450E was restricted to endothelium at margins of muscle bands limiting heart ventricular lumen. Localization in the specific cells of these and other organs may be fundamentally important in understanding the role of cytochrome P-450E.  相似文献   

5.
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   

6.
Purification of cytochromes P-450 from liver microsomes of β-naphthoflavone (BNF)-fed rainbow trout yielded three apparently homogeneous forms. The major form (LM4b)* appears to be a P-448 type of cytochrome. A minor form (LM4a), having properties very similar to LM4b, was also obtained. In addition, a P-450 form (LM2) was isolated, with properties quite different from LM4a or LM4b, including a high rate of aflatoxin B1 (AFB1) metabolism (Williams & Buhler, 1983c). Antibodies to all three forms were obtained from rabbits. The IgGs prepared against LM4a and LM4b both cross-reacted (forming lines of identity) equally well with both antigens on Ouchterlony plates. Rat P-448 cross-reacted (without lines of identity) with both LM4a- and LM4b-IgG. LM4b-IgG was much more effective than LM4a-IgG for inhibition of LM4a or LM4b reconstituted benzo[a]pyrene (BP) hydroxylase, suggesting that these two antibodies recognize different antigenic sites. The LM2-IgG did not cross-react with any of the other rat or trout cytochromes P-450 examined. Levels of LM2 and LM4b in microsomes from untreated, polychlorinated biphenyl (PCB), phenobarbital (PB) or BNF-treated trout were estimated with an immunological technique involving electrophoresis on SDS-PAGE, followed by transfer to nitrocellulose and staining with either LM 2 - or LM4b -IgG. The ratio of in microsomes from PCB- or BNF-treated rainbow trout was much higher than 1, whereas the reverse was true with microsomes from untreated rainbow trout. These results are consistent with previous observations (Vodicnik et al., 1982) that pretreatment with BNF induced the synthesis of a P-448 type cyytochrome, presumably responsible for the great increase in the metabolism and activation of BP seen in these fish. Conversely, pretreatment with PB did not affect the levels of either LM2 or LM4b. This specific immunological technique should make it possible to assay the levels of these P-450 and P-448 isozymes in various strains of rainbow trout and other species of fish. In addition, the effect of age, sex, diet and exposure to P-450 and P-448 inducers could be examined and, perhaps, utilized to predict the relative risk of certain populations to pollutants activated by these different isozymes.  相似文献   

7.
Cytochrome P-450 monooxygenases catalyze the biotransformation of a great variety of foreign, as well as endogenous, lipid-soluble compounds to more water-soluble products. As in mammals, highest concentration of cytochrome P-450 in fish is found in the liver. However, previous studies have indicated that fish kidney contains relatively high cytochrome P-450-mediated activities.1,2 We have therefore prepared and characterized subcellular fractions from the kidney of rainbow trout suitable for studies on cytochrome P-450-dependent reactions. Furthermore, as in the liver, several cytochrome P-450-mediated reactions in the kidney were induced following treatment of the fish with β-naphthoflavone.  相似文献   

8.
The incidence of hepatoma, epidermal and other forms of cancerous growths in fish is well documented (Halver, 1967; Matsushima & Sugimura, 1976; Dawe et al., 1964). In fish, as in mammals, cancer may be a result of metabolically activated carcinogens. In mammals the primary enzyme system involved in the activation of environmental carcinogens is the cytochrome P-450 linked mixed-function oxidase (MFO). The hepatic microsomes of the species offish studied contain variable levels of cytochrome P-450. Liver microsomes of the trout Salmo trutta lacustris are surprisingly active in metabolising benzo-[a]pyrene (BP) and other compounds preferentially metabolised by polycyclic aromatic hydrocarbon (PAH)-specific cytochrome P-450. This finding may be significant, because it is apparent that the detrimental effects of PAHs require metabolic activation.We have studied the production of reactive intermediates of BP by following their binding to DNA and by measuring the specific nucleotide-BP metabolite complexes by chromatography. Untreated S. trutta liver microsomes catalyse the production of reactive intermediates of BP which bind to nucleotides of DNA at a rate that is 3–4 times higher than that catalysed by control rat liver microsomes. The most prominent DNA-BP metabolite adducts produced by trout liver microsomes are the nucleoside adduct of BP-7, 8-diol-9,10-epoxide and 9-OH-BP-4,5-oxide and other phenol oxides. In contrast to the trout, another fish species, roach (Rutilus rutilus), has extremely low activity. Although the in vitro binding of BP to DNA is not strictly correlated to in vivo binding or biological effects, our results show that reactive intermediates are formed by trout liver and thus the prerequisite for chemical carcinogenesis or mutagenesis is ful filled. This is further supported by the fact that in Ames's test, trout liver preparations produce mutagenic products from promutagens.  相似文献   

9.
The capacity of the mammalian liver microsomal P-450-dependent systems to metabolize a wide variety of endogenous and exogenous compounds is thought to reflect the presence of multiple forms of P-450 haemoproteins with broad and overlapping substrate specificity. In plants, the functions and specificity of cytochrome P-450 systems are less well known.This study was designed to prepare and characterize subcellular fractions from fresh sheaths (basal parts of leaves) of a mediterranean seagrass Posidonia oceanica (Linnaeus) Delile, the aim being the preparation of a microsomal fraction suitable for studying xenobiotic metabolism. The purity of the different fractions obtained by centrifugation, as well as the recovery of different organelles, was determined using enzyme markers (cytochrome c oxidase, alkaline phosphatase, glucose-6-phosphatase) and morphological examination by transmission electron microscopy. Some assays of enzymes involved in xenobiotic metabolism (cytochrome c reductase, laurate hydroxylase, ethoxyresorufin O-deethylase and glutathione-S-transferase) were also performed on different fractions of the preparation. The subcellular distribution for drug metabolism and marker enzymes showed a loss of endoplasmic reticulum in the pellet obtained after the first centrifugation, but the microsomal fraction was relatively free of mitochondria and fragments of the plasma membrane.Some assays are still being performed to avoid the small loss of endoplasmic reticulum experienced with the first pellet. However, the microsomes prepared in this study from sheaths of Posidonia oceanica appear suitable for further investigation of xenobiotic metabolism.  相似文献   

10.
The hepatic cytochrome P-450-dependent monooxygenase system of the marine fish plaice has been characterised by i.p. injection with chemical inducing agents, followed by measurement of a variety of monooxygenase activities. The results suggest that more than one isozyme is present in these fish. The response to oil-based drilling fluids, a major contaminant of the North Sea, has also been examined and indicates that more than one isozyme is responsive to these products.  相似文献   

11.
In this study we have used cloned gene probes for human glutathione peroxidase (GPX), rat cytochrome P-450IVA1 and rat cytochrome P-450IIE1 to detect homologous sequences in RNA from the hepato-pancreas of Mytilus edulis. The presence of sequences hybridising to the GPX and P-450IVA1 probes, but not to the P-450IIE1 probe, confirms the ancient origin of the former genes and indicates that conserved-sequence DNA probes from higher organisms can be used to examine the structure and function of genes of environmental interest in marine organisms.  相似文献   

12.
The possible utility of glutathione S-transferase isoenzymes in affinity purified extracts of digestive gland from Mytilus galloprovincialis as indicators of exposure to organic pollution has been assessed by fast protein liquid chromatography (FPLC) using a Mono-Q ion exchange column. Four main peaks of protein (isoenzymes 1–4) were detected in these chromatographic studies all of which displayed detectable catalytic activity with 1-chloro-2,4-dinitrobenzene and glutathione as substrates. The bulk of the activity with these substrates was associated with isoenzyme 1. The specific activity of cytosolic extracts from six sites in Venice Lagoon and the Adriatic Sea (UNESCO-MURST Venice Lagoon Ecosystem Project) decreased slightly with increasing tissue levels of chemical contaminants (hydrocarbons, PCBs and organochlorines). FPLC of affinity purified extracts from three of these sites was used to assess the possible variation in the levels of individual isoenzymes relative to pollution status. No difference was observed in the levels of these isoenzymes.  相似文献   

13.
Activities of the cytochrome P450 monooxygenase (MO) system and GSH-transferase (GST) were monitored about every 2 weeks in sockeye salmon during their sexual migration and ultimate death. Liver cytosol and microsomes were prepared from the tissue of 50 individuals, five males and five females at each collection. The activities observed were not significantly different between the sexes. Substantial changes occurred in cytochrome P450, cytochrome b5 and the monitored activities during the migration. The most dramatic changes occurred at the spawning grounds and were evident even before spawning occurred. The cytochrome P450 and cytochrome b5 contents increased while the MO and GST activities decreased. Pre-spawning MO and GST activities were similar to those reported for other species undergoing sexual maturation. Migrating salmon offer an interesting model for studying the regulation of sex-dependent and terminal forms of cytochromes P450, MO and phase II activities.  相似文献   

14.
Bivalve and gastropod molluscs readily accumulate polynuclear aromatic (PNAH) and other hydrocarbons from the environment and are widely used in environmental monitoring programmes.1 The response of the cytochrome P-450 monooxygenase or mixed function oxidase (MFO) system to organic xenobiotics is of interest from the comparative viewpoint and in biological effects monitoring.2 We have studied the bivalves Mytilus edulis (mussel) and Cardium edule (cockle) and the gastropod Littorina littorea (periwinkle) exposed to hydrocarbons, experimentally or naturally in the field. The general trend of response in digestive gland microsomes was an increase in cytochrome P-450 content and NADPH-cytochrome c reductase (NADPH-CYTCRED) activity but no increase in benzo[a]pyrene hydrolyase (BPH) activity. Sex and seasonal interactions were evident. We conclude that aspects of the responses may be peculiar to the Mollusc and that NADPH-CTYCRED possibly offers potential for this phylogenetic group as a specific indicator of biological impact by organic pollution.  相似文献   

15.
The effect of environmental pollutants present in sediments obtained from Bahía de Chetumal, a bay on the border between Mexico and Belize, was studied in nile tilapia (Oreochromis niloticus) intraperitoneally injected with sediment extracts from six different sites of the Bay. Sediment samples used for the study contained a variety of organic chemicals such as organochlorine pesticides, polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs). Total cytochrome P-450 and EROD activity were measured in fish liver. Haematological and histological analyses were also carried out. Hepatic P-450 content in treated fish increased from 43 to 240%, and EROD activity from 85 to 160% compared to controls. Extracts from two sampling sites inhibited EROD activity. There were positive significant correlations between P-450 content and the levels of PCBs 44 and 128. EROD activity correlated to HCB, op'-DDE, pp'-DDE, pp'-DDD, mirex and PCB 18 concentrations. Blood examination showed cell degeneration and binucleated leukocytes with abnormal chromatin. Extract treatment also resulted in foci of hyperplasia on the basement of gill lamellae, hypertrophy and oedema in gills and liver necrosis. Control fish showed no abnormalities. The results demonstrate that sediments from Bahía of Chetumal have the potential to cause histopathological, haematological and biochemical alterations in fish. The administration of sediment extracts to fish may serve as a useful test to screen the toxicity of sediments from different areas.  相似文献   

16.
The metabolism of some xenobiotics can lead to the formation of reactive intermediates with mutagenic/carcinogenic properties. With the carcinogenic PAH these have been identified as bay-region diol-epoxides.1 Phenanthrene, a non-carcinogenic, bay-region containing model PAH, is metabolised in vivo by bony fish at the proximate bay-region position, whereas mammals and other marine organisms mainly form the K-region metabolite 9,10-dihydro-9,10-dihydroxy-phenanthrene.2 We wanted to investigate this difference more closely by studying the regiospecificity of phenanthrene metabolism in vitro both with microsomes from differently pretreated cod and with isolated cytochrome P-450 isozymes from BNF-induced cod.3 Secondly, by preparing antibodies to the major isozyme isolated (called cod P-450c), we investigated the immunochemical properties of the variously treated cod liver microsomes.  相似文献   

17.
The hepatic mixed function oxidase system in the fish differs from that in mammals in its responses to the two classic mammalian inducers. The cytochrome P-448-type inducers (polycyclic aromatic hydrocarbons) stimulate monooxygenase activity, but phenobarbital, a P-450-type inducer, does not.1 We have compared the effects of phenobarbital (PB) and polychlorinated biphenyls (PCB) on the turnover of hepatic microsomal hemoproteins in trout (PCB's are P-448- and P-450-type inducers in mammals, which in fish induce only cytochrome P-448). We show here that neither PCB nor PB treatment changed the turnover rate. However, both the rates of synthesis and degradation were much slower than in the rat.  相似文献   

18.
Hepatic monooxygenase enzyme activities and relative cytochrome P4501A protein content were measured to evaluate the time-course alterations in rainbow trout after change in living habitat. Fish were transferred from one fish farm to the tanks of another hatchery and/or into cages kept in a lake. In the new habitats, cytochrome P450-dependent enzyme activities in rainbow trout decreased, and were at their lowest levels after two or three weeks in the summer. Later the activities partly reversed. The immunodetection of cytochrome P4501A protein expressed a similar trend as for catalytic monooxygenase activities.  相似文献   

19.
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   

20.
Paralytic shellfish poisoning (PSP) toxins have been implicated as the causative agent of a number of fish kills. Exposure experiments indicate that fish are susceptible to PSPs by intraperitoneal (i.p.) and oral administration, while sampling of fish affected by toxic blooms reveals that these toxins can be accumulated. In spite of the potential impact to marine fisheries, little research has been conducted on the potential metabolism and detoxification of PSPs in marine fishes. Previous work by this group has shown that the xenobiotic metabolising enzyme (XME) cytochrome P-450 (CYP1A) is induced in Atlantic salmon (Salmo salar) following i.p. exposure to saxitoxin (STX). Salmon injected i.p. with sub-lethal doses of STX show a four- to eight-fold induction of hepatic CYP1A (as shown by ethoxyresorufin-O-deethylase activity) over controls after 96 h. Results presented here show that the phase II XME glutathione S-transferase (GST) is also induced in salmon following PSP exposure. Post smolts were exposed to three injections of PSPs (2 micrograms STXeq/kg) over 21 days. Injection of both STX and PSPs extracted from a toxic strain of dinoflagellate (Alexandrium fundyense, CCMP 1719) resulted in induction of hepatic GST, as measured by activity for 1-chloro 2,4-dinitrobenzene. Such inductions indicate a potential role for XMEs in PSP metabolism. Possible roles for other enzymes are also discussed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号