共查询到20条相似文献,搜索用时 46 毫秒
1.
E. Agradi T. A.L. Brevini M. Bolla R. Baga L. A. Favetta 《Zeitschrift fur angewandte Ichthyologie》1999,15(4-5):96-98
The cytochrome P-450 enzyme system was studied in juvenile Acipenser naccarii (317.6±77 g initial live weight) reared at 23°C and at a standard diet over a period of two month before using for experiments (final weight 546.3±148.8 g). While determining normal levels of cytochrome P-450 in liver tissue its induction was also studied under exposure to P-naphthoflavone (BNF; single dose at 80 mg/Kg body weight 52 hrs prior to sampling). Control fish showed total cytochrome P-450 levels in liver microsomes around 0.40±0.12 nmoles/mg proteins (n=12) while in BNF exposed fish the values increased significantly (0.55±0.11nmoles/mg proteins; n=12). Ethoxyresorufin-O-deethylase (EROD) in control fish was 0.015±0.02 nmoles/mg proteins/min (n=12); it was found to be NADPH dependent and inducible by BNF. Western Immunoblotting and enzyme-linked-immunosorbent (ELISA) analyses of liver microsomes from untreated and BNF-exposed fish, using an antibody to rat cytochrome P-450 1A1 isoform (P-450 1A1) (Nelson et al.,1996) suggested the presence of a constitutive and BNF-inducible cytochrome P-450 homologous to rat P-450 protein.
Measurement of cytochrome P-450-dependent EROD activity and P-450 1A1 expression levels in A. naccarii may be a useful parameter in monitoring environmental pollution. 相似文献
Measurement of cytochrome P-450-dependent EROD activity and P-450 1A1 expression levels in A. naccarii may be a useful parameter in monitoring environmental pollution. 相似文献
2.
In order to define the site of bioactivation of CCl4, CHCl3 and CBrCl3 in the NADPH cytochrome reductase-cytochrome P-450 coupled systems of liver microsomes, the 14C-labeled hepatotoxins were incubated with isolated rat liver microsomes and a NADPH-generating system. The covalent binding of radiolabel to microsomal protein was used as a measure of the conversion of the hepatotoxins to reactive intermediates. Omission of NADPH, incubation under CO:O2 (8:2) and addition of a cytochrome reductase specific antisera mardedly reduced the covalent binding of all three compounds. When cytochrome P-450 was reduced to less than 25% of normal by pretreatment of rats with allylisopropylacetamide (AIA), but cytochrome reductase activity was unchanged, the covalent binding of CCl4, CHCl3, and CBrCl3 was decreased by 63, 83, 70%, respectively. Incubation under an atmosphere of N2 enhanced the binding of CCl4, inhibited the binding of CHCl3 and did not influence the binding of CBrCl3. It is concluded that cytochrome P-450 is the site of bioactivation of these three compounds rather than NADPH cytochrome reductase and that CCl4 bioactivation proceeds by cytochrome P-450 dependent reductive pathways, while CHCl3 activation proceeds by cytochrome P-450 dependent oxidative pathways. 相似文献
3.
Lance R. Pohl John W. George 《Biochemical and biophysical research communications》1983,117(2):367-371
Although indirect evidence has suggested that liver microsomal cytochrome P-450 can reductively dehalogenate several compounds to carbene metabolites, there has been no direct proof for the formation of these reactive species. We report in this paper that carbenes can be chemically trapped and identified as metabolites. For example, 1,1-dichloro-2,2,3,3-tetramethylcyclopropane was identified as a metabolite by gas chromatography mass spectrometry when carbon tetrachloride (CCl4) was incubated anaerobically with rat liver microsomes, NADPH and 2,3-dimethyl-2-butene. The reaction required NADPH and was inhibited by carbon monoxide. These findings show that cytochrome P-450 in rat liver microsomes can reductively metabolize CCl4 to dichloromethyl carbene (:CCl2) which can be trapped with 2,3-dimethyl-2-butene to form 1,1-dichloro-2,2,3,3-tetramethylcyclopropane. A similar approach may be used for the identification of carbene metabolites of other compounds. 相似文献
4.
E G de Toranzo M I Gomez J A Castro 《Biochemical and biophysical research communications》1975,64(3):823-828
Prior administration of aminotriazole (3-amino-1,2,4-triazole) or pyrazole to rats resulted in a significant prevention of the CCl4-induced decrease in the liver microsomal P-450 content. In A/J mice the CCl4 activation and P-450 destruction occurred in absolute absence of lipid peroxidation as determined by uv absorption. The data suggest that P-450 destruction is mainly mediated by direct attack of CCl4 metabolites rather than by CCl4-induced lipid peroxidation. 相似文献
5.
Harihara M. Mehendale Kashyap N. Thakore C. Vaman Rao 《Journal of biochemical and molecular toxicology》1994,9(3):131-139
Autoprotection is a phenomenon whereby prior exposure to a small dose of a chemical results in protection against a subsequently administered lethal dose of the same compound. While CCl4 autoprotection has been studied the most, it has also been demonstrated for other chemicals. Recent studies indicate that the prevailing concept of decreased bioactivation of the normally lethal dose of CCl4 owing to decreased hepatic microsomal cytochrome P-450 1 Abbreviations used: CD, chlordecone; cyt. P-450, cytochromes P-450; M, mirex; N, normal diet; PB, phenobarbital. content can not be supported by direct end points of liver injury such as necrosis. These findings suggest a pivotal role for hepatocellular division and tissue healing processes stimulated by the protective dose in the mechanism of autoprotection. Augmentation of hepatocellular regeneration and tissue repair, stimulated by the protective dose, appears to permit timely recovery and restoration of hepatic structure and function. In the absence of the protective dose, hepatocellular division is substantially deficient and it occurs too late to tip the delicate balance between recovery from injury and progression of massive injury in favor of recovery. Abolition of autoprotection by colchicine antimitosis, under conditions where metabolism and disposition of CCl4 are not altered, is supportive of this concept. Selective colchicine antimitotic suppression of the early phase of hepatocellular division and tissue repair induced by a low dose of CCl4 results in progression of toxic liver injury, leading to hepatic failure and mortality. Studies have shown that pretreatment with phenobarbital results in postponed low-dose CCl4-stimulated cell division by 24 hours, which accordingly postpones the optimal autoprotection. These findings provide discrete evidence to suggest that the protective dose-stimulated hepatocellular division and tissue repair underlies the mechanism of autoprotection. These new insights reveal that in contrast to the widely held concept, the ultimate outcome of toxic injury is determined by whether a prompt stimulation of sustainable tissue repair can occur rather than by the magnitude of the injury inflicted by a toxic chemical. 相似文献
6.
J A Castro C R De Castro N D'Acosta M I Diaz Gomez E C De Ferreyra 《Biochemical and biophysical research communications》1973,50(2):273-279
The irreversible binding of14C from14CCl4 to microsomal lipids is decreased in animals treated with 3-methylcholantrene (3-MC), while it is increased in animals induced with phenobarbital (PB). CCl4-induced lipid peroxidation in 3-MC treated rats is as intense as in controls. Destruction of glucose 6-phosphatase (G6P-ase) by CCl4 is smaller in 3-MC treated rats than in controls. Destruction of total cytochrome P-450 (P-450 + P1-450) by CCl4 is smaller in 3-MC treated than in PB treated rats but similar to that obtained in controls. Results would indicate that P-450 would participate in CCl4 activation much more effectively than P1-450. 相似文献
7.
E C Castro JA Diaz GomezDe Ferreyra C R De Castro N D'Acosta C M De Fenos 《Biochemical and biophysical research communications》1973,50(2):337-343
There is a higher activity of ethyl morphine N-demethylase (EM-ase) and cytochrome P-450 (P-450) reductase as well as higher P-450 content in the smooth endoplasmic reticulum (SER) than in the rough endoplasmic reticulum (RER). The extent of the irreversible binding of the14C from14CCl4 to lipids and proteins, as well as the CCl4-induced destruction of P-450 is more intense in SER than in RER while the opposite was found for glucose 6-phosphatase (G6P-ase) destruction. CCl4-induced lipid peroxidation is as intense in SER as is in RER.14C from14CCl4 gets irreversibly bound to ribosomal proteins. 相似文献
8.
《Bioscience, biotechnology, and biochemistry》2013,77(4):656-661
This study elucidated the effects of cornuside on carbon tetrachloride (CCl4)-induced hepatotoxicity. Rats were treated intraperitoneally with 0.5 mL/kg of CCl4. Sixteen h after CCl4 treatment, the levels of serum aminotransferases, tumor necrosis factor-α (TNF-α), and lipid peroxidation were significantly elevated, whereas the hepatic antioxidative enzyme activities were decreased. These changes were attenuated by cornuside. Histological studies also indicated that cornuside inhibited CCl4-induced liver damage. Furthermore, the contents of hepatic nitrite, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) were elevated after CCl4 treatment, while cytochrome P450 2E1 (CYP2E1) expression was suppressed. Cornuside treatment inhibited the formation of liver nitrite, and reduced the overexpression of iNOS and COX-2 proteins, but restored the liver CYP2E1 content as compared with the CCl4-treated rats. Our data indicate that cornuside protects the liver from CCl4-induced acute hepatotoxicity, perhaps due to its ability to restore the CYP2E1 function and suppress inflammatory responses, in combination with its capacity to reduce oxidative stress. 相似文献
9.
Administration of allylisopropylacetamide (AIA) or CCl4 to rats previously treated with phenobarbital leads to a rapid decrease in cytochrome P450 within 1 hr. The amount of cytochrome b5 and NADPH cytochrome c reductase in liver microsomes remains unchanged following AIA treatment. In contrast, CCl4 administration causes a decrease in total microsomal protein thus leading to a net loss in cytochrome b5 and NADPH cytochrome c reductase. By using 3H-δ-aminolevulinic acid to label microsomal cytochrome P450 heme, the effect of AIA and CCl4 on this cytochrome was shown to be caused by destruction of preexisting CO-binding pigment and not from inhibition of synthesis. In addition, the breakdown products of cytochrome P450 heme accumulate in the liver after AIA or CCl4 treatment. 相似文献
10.
R E Ebel 《Biochemical and biophysical research communications》1989,161(2):615-618
Rats were treated with pyrazole to increase the liver content of the "alcohol-inducible" form of cytochrome P-450. This treatment increased the sensitivity of these animals to CCl4-hepatotoxicity assessed by increases in SGPT and SGOT levels and decreases in microsomal cytochrome P-450 and aniline p-hydroxylase activity. However, the hepatotoxicity of CHCl3 was not increased by pyrazole-treatment. These data are consistent with the hypothesis that the "alcohol-inducible" form of cytochrome P-450 is capable of CCl4- but not CHCl3-activation. 相似文献
11.
Previous work has established the marked potentiation of CCl4 hepatoxicity by prior exposure to chlordecone (CD). This study was conducted to determine if prior exposure to CD results in enhancement of CCl4-induced destruction of the hepatic microsomal mixed-function oxygenase (MFO) system. Male Sprague-Dawley rats received a single oral dose of CD (10 mg/kg) or corn oil vehicle alone (1 ml/kg) 24 hr prior to a single ip injection of CCl4 (0-100 microliter/kg). Mirex (M; 10 mg/kg) and phenobarbital (PB; 80 mg/kg/day for two days) were used as negative and positive controls respectively for the potentiation of CCl4 hepatotoxicity. Hepatotoxicity was evaluated 24 hrs after CCl4 administration by elevations of three serum enzymes (GPT, GOT, and ICD). The key hepatic microsomal MFO parameters measured were microsomal protein, cytochrome P-450 content, glucose-6-phosphatase (G-6-Pase), and aminopyrine demethylase (APD). As previously demonstrated using a subchronic dietary pretreatment protocol, CD potentiated CCl4 hepatotoxicity over a range of CCl4 doses to a greater extent than PB or M, as judged by elevations in serum enzymes. PB caused the greatest increase in total P-450 content and the greatest increase in CCl4-mediated destruction of microsomal protein and APD activity. M caused the least destruction of total hepatic cytochrome P-450, despite the same level of cytochrome P-450 as in the PB group. CD treatment caused the greatest decrease in G-6-Pase activity in comparison to PB or M pretreatments and a similar degree of P-450 destruction as observed with the PB group. These findings suggest that in general, CCl4-induced destruction of hepatic MFO parameters measured in this study is disproportional to the known degree of potentiated hepatotoxicity by the pretreatments and does not accurately reflect the potentiation of CCl4 hepatotoxicity by CD. 相似文献
12.
The relation between the delta-aminolevulinate-synthase and heme-oxygenase activities and the contents of cytochromes b5 and P-450 in rat liver after phenobarbital and CoCl2 injections was studied. Two hours after a single injection of phenobarbital the delta-aminolevulinate-synthase activity is increased, showing a further rise after 24 hrs. The content of cytochrome b5 is not changed, while that of cytochrome P-450 is increased 24 hrs after the injection. The heme-oxygenase activity remains unaffected thereby. The increase in the enzyme activity and cytochrome P-450 content induced by phenobarbital is eliminated by a preliminary administration of actinomycin D. The administration of CoCl2 is accompanied by a decrease in the delta-aminolevulinate-synthase activity after 2 hrs and its further increase after 24 hrs. The heme-oxygenase activity shows a sharp rise 24 hrs after the injection. The rise in the delta-aminolevulinate-synthase activity induced by CoCl2 is removed by actinomycin D. CoCl2 decreases the content of cytochromes b5 and P-450 24 hrs after the injection. It is assumed that the correlation between the delta-aminolevulinate-synthase activity and cytochrome P-450 content is observed only in the case when the heme-oxygenase activity is not increased. The cytochrome b5 content is independent of the changes in the activity of the key enzyme of heme synthesis and depends to a certain extent on the rate of heme degradation by heme-oxygenase. 相似文献
13.
Masayuki Katagiri Katsuko Suhara Masahiro Shiroo Yoshiyuki Fujimura 《Biochemical and biophysical research communications》1982,108(1):379-384
The cytochrome P-450 (P-450sccII) and its reductase, NADPH-cytochrome reductase [EC 1.6.2.4], associated with conversion of progesterone to 4-androstene-3,17-dione, were extensively purified from pig testis microsomes. Higher lyase activity (turnover number of 15 mol of the product formed/min/mol of P-450) could be restored by mixing the P-450sccII, its reductase, pig liver cytochrome b5 and cytochrome b5-reductase [EC 1.6.2.2], and phospholipid in the presence of NADPH, NADH, and O2. Omission of either cytochrome b5 or NADH resulted in a significant loss of the lyase activity indicating actual participation of cytochrome b5 in this P-450-mediated steroidogenic system in the testis. 相似文献
14.
Annika Brunström Magnus Ingelman-Sundberg 《Biochemical and biophysical research communications》1980,95(1):431-439
The roles of rabbit liver cytochrome b5, epoxide hydrase and various forms of cytochrome P-450 in the NADPH-dependent metabolism of benzo(a)pyrene were examined. After incorporation of the purified enzymes into phospholipid vesicles, using the cholate gel filtration technique, the various types of cytochrome P-450 did exhibit different stereospecificities in the oxygenation of the substrate. Cytochrome P-450LM2 was found to efficiently convert benzo(a)pyrene in the presence of epoxide hydrase to 4,5-dihydroxy-4,5-dihydrobenzo(a)pyrene whereas cytochrome P-450LM4 primarily participated in the formation of 9,10-dihydroxy-9,10-dihydrobenzo(a)pyrene. By contrast, benzo(a)pyrene was not metabolized by cytochrome P-450LM3. Cytochrome b5 enhanced cytochrome P-450LM2-catalyzed oxygenations 5-fold, whereas cytochrome P-450LM4-dependent oxygenations proceeded at a 3 times higher rate when cytochrome b5 was present in the membrane. 相似文献
15.
William L. Dean Robert D. Gray 《Biochemical and biophysical research communications》1982,107(1):265-271
Sedimentation equilibrium and sedimentation velocity measurements were carried out on cytochrome P-450LM2 from phenobarbital-treated rabbit liver and on cytochrome P-450LM4 from 5,6-benzoflavone-treated rabbit liver in the presence of the nonionic detergent . P-450LM2 was monomeric with a molecular weight of 48,800 and a Stokes radius of 3.1 nm in 7 g/l detergent and P-450LM4 was monomeric with a molecular weight of 49,800 and a Stokes radius of 2.6 nm at 5 g/l detergent. Both particles were spherical in shape under these conditions. Neither cytochrome was irreversibly denatured at these detergent concentrations as indicated by the ability to form substantial amounts (>60%) of the CO adduct with an absorption maximum at 451 nm (P-450LM2) or 448 nm (P-450LM4) when diluted into detergent-free buffer containing CO and sodium dithionite. 相似文献
16.
J. F. Ghersi-Egea A. Minn J. L. Daval Z. Jayyosi V. Arnould H. Souhaili-El Amri G. Siest 《Neurochemical research》1989,14(9):883-887
NADPH:cytochrome P-450 (c) reductase is a microsomal enzyme which is involved in the cytochrome P-450-dependent biotransformation of many exogenous agents as well as of some endogenous molecules. Using cytochromec as a substrate, the kinetic parameters of this enzyme were determined in brain microsomes. The comparison of the NADPH:cytochrome P-450 reductase's Vmax values and cytochrome P-450 contents in both fractions, suggests a role of cerebral NADPH:cytochrome P-450 reductase in cytochrome P-450 independent pathways. This is also supported by the different developmental pattern of brain enzyme as compared to the liver enzyme, and by the presence of a relatively high NADPH:cytochrome P-450 reductase activity in immature rat brain and neuronal cultures, while cytochrome P-450 was hardly detectable in these preparations. The enzyme activity was not induced by a phenobarbital chronic treatment neither in the adult brain nor in cultured neurons, suggesting a different regulation of the brain enzyme expression. 相似文献
17.
George M. Padilla Michelle W. Kloss Elmer J. Rauckman Gerald M. Rosen 《Cell proliferation》1984,17(2):153-159
ABSTRACT Experiments were undertaken to investigate the hepatic, temporal and spatial sequence of events following a single injection of cocaine, a known hepatotoxin. Centrilobular necrosis was induced in male mice (DBA/2Ha) 24 hr post-injection (PI). the time course of hepatic damage was monitored by assaying microsomal cytochrome P450 content, the activity of microsomal FAD-containing monooxygenase (FAD-M) and by determining the levels of serum glutamic pyruvic transaminase (SGPT). Kinetics of the onset of DNA synthesis were determined by autoradiography of thin liver sections and the incorporation of 3H-methyl thymidine into perchloric-acid-precipitable material. There was no increase in the labelling index (LI) and thymidine (TdR) incorporation in the first 24 hr PI. the LI rose to 14.6% and TdR incorporation showed a 5-fold increase over control values 48 hr PI. Both indices declined slightly at 72 hr PI and returned to control values by 96 hr PI. In contrast, the cytochrome P450 content declined by 69%, the FAD-M activity dropped by 40% and the SGPT levels showed an 18-fold increase at 24 hr PI, coincident with cytological signs of necrosis. Although the patterns of recovery differed between these selected enzymes, normal values were attained by 96 hr PI. These results demonstrate that cell damage and hepatic dysfunction precede the onset of DNA synthesis and subsequent proliferation. 相似文献
18.
T. Takano Y. Miyazaki Y. Motohashi K. Yamada 《International journal of biometeorology》1986,30(3):239-247
Changes in the hepatic cytochrome P-450-dependent drug-metabolizing system were studied in perfused livers obtained from cold-acclimated male Wistar rats after 30 days of cold exposure (4C) when using hexobarbital as a substrate. In fasted animals the cold-acclimated rats showed higher levels of hexobarbital metabolic rates compared to control rats, but there was no significant difference in fed animals. The maximum rates of hexobarbital metabolism produced by xylitol perfusion were also significantly higher in the perfused liver of cold-acclimated rats. It was concluded that the function of the cytochrome P-450 system for hexobarbital in cold-acclimated rats changed due to both an increase in the activity of the cytochrome P-450 system and to changes in regulation of the cytochrome P-450 system by the supply of reducing equivalents. 相似文献
19.
The cytotoxic effect of aflatoxin B1 on cultures of a differentiated rat hepatoma cell line, Faza 967, has been evaluated by scoring the surviving colonies two weeks after briefly exposing the freshly plated cells to the mycotoxin. At the lowest concentration, aflatoxin B1 exhibits no toxicity, unless the cultures have been pretreated with dexamethasone. HF-1, an hepatoma hybrid cell line exhibiting extinction of the hepatic functions and HF1-4, its subclone, that reexpresses all of these functions, have been compared. A 6hrs exposure to 60ng/ml aflatoxin B1 is not toxic for HF1 even after an hormonal treatment, while dexamethasone enhances the effect on HF1-4. Glucocorticoïds have been shown previously to induce, in the differentiated clones, the hydroxylation of bile acid - a cytochrome P-450-mediated reaction ; in contrast, 3-methylcholanthrene, an inducer of benzopyrene hydroxylase in hepatoma cultures, is without effect on bile acid metabolism and on aflatoxin B1 cytotoxicity. These results suggest that in the differentiated hepatoma cells, aflatoxin B1 is converted into a cytotoxic metabolite by a glucocorticoïd-induced monooxygenase belonging to the cytochrome P-450-related group. 相似文献
20.
V M Mishin E L Peregoedova D V Mishina V V Liakhovich 《Biokhimii?a (Moscow, Russia)》1989,54(7):1163-1169
Cytochrome P-450d was isolated from isosafrol-induced rat liver microsomes by affinity chromatography on 1.8-diaminooctyl-Sepharose 4B and chromatography on hydroxylapatite using a linear potassium phosphate gradient (45-250 mM). The enzyme has a molecular mass of 54 kDa, CO-maximum 448 nm is characterized by a high spin state; the rate of 4-aminobiphenyl hydroxylation is 54 nmol/min/nmol of cytochrome P-450d (37 degrees C), those, of 7-ethoxyresorufin O-deethylation and benz (a) pyrene oxidation are 1 nmol/min/nmol of cytochrome P-450d (22 degrees C) and 2 nmol/min/nmol of cytochrome P-450d (37 degrees C), respectively. The properties of cytochrome P-450d were compared to those of cytochrome P-450c isolated from 3-methylcholanthrene-induced rats. The yield of these cytochromes under the conditions used (10% P-450d from isosafrol-induced microsomes and 15% P-450c from 3-methylcholanthrene-induced microsomes) was relatively high. Antibodies to cytochromes P-450d and P-450c were obtained. Using rocket immunoelectrophoresis the percentage of these hemoprotein forms in 3-methylcholanthrene-induced (P-450d-20%, P-450c-70%) and isosafrol-induced rat liver microsomes (P-450d-50%, P-450c-15%) was determined. 相似文献