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PubMed1981

Studies on the mechanism of stimulation of microsomal H2O2 formation and benzo(a)pyrene hydroxylation by substrates and flavone.

The addition of activators like flavone and hexobarbital to hepatic microsomes markedly stimulates H2O2 formation. The similar increase observed with flavone of microsomal hydroxylation of benzo(a)pyrene and its inhibition by catalase and methanol suggests but does not prove a necessary interaction of microsomal H2O2 production with benzo(a)pyrene hydroxylation. Hexobarbital and flavone-stimulated H2O2 formation is optimal at a stoichiometric relationship of these activators and NADPH. This implies either their direct participation as electron donors or their indirect involvement in electron transport by facilitation of stoichiometric substrate cytochrome P-450/NADPH flavoprotein interactions. Steady state kinetics data are consistent with a scheme in which the formation in microsomes of a complex of 1 mole of NADPH with NADPH-cytochrome P-450 reductase and 1 mole hexobarbital with cytochrome P-450 regulates H2O2 formation.

Animals↗
PubMed1992

Reactions in lipid vesicles. Pyrene excimer formation in restricted geometries. Effect of temperature and concentration.

The decay of pyrene in the presence of excimers in small unilamellar vesicles of 3-sn-phosphatidyl glycerol, dipalmitoyl and 3-sn-phosphatidylglycerol from egg yolk has been analyzed with the use of models appropriate for reactions in restricted geometries. Results are presented with emphasis on probe concentration and temperature. The reaction rate in an organized lipid phase is redefined in a simple manner which allows for a simple treatment of any reaction in such environments. The analysis allows detection of pyrene aggregation in the vesicle lipidic core.

Biophysical Phenomena↗
PubMed1979

Temperature dependence of the fluorescence of pyrene labeled crab nerve membranes.

A method, using albumin-pyrene complexes, has been developed for labeling, in a controlled manner, crab leg nerves whose excitability was preserved. The excimer-to-monomer fluorescence intensity ratio of pyrene, embedded in nerve membrane lipids and in their crude lipid extracts, is a fluidity parameter which displayed the following features with temperatures. a--a temperature-dependent increase of fluidity b--three breaks (6 degrees, 19 degrees and 37 degrees C) in the physiological medium c--In Ca++-depleted sea water, the 37 degrees characteristic temperature vanished. These breaks may reflect some lateral phase separations of the lipid components of nerve membranes. The calcium dependent temperature break may involve a segregation of acidic phospholipids while the other two breaks (6 degrees and 19 degrees C) may be due to neutral lipids phase separation. The relationship of these findings to nerve function is discussed.

Animals↗
PubMed1992

Benzo(a)pyrene-blood protein adducts in wild woodchucks used as biological sentinels of environmental polycyclic aromatic hydrocarbons contamination.

Levels of benzo(a)pyrene-diolepoxide (BaPDE)-albumin and BaPDE-hemoglobin adducts in wild woodchucks (Marmota monax) have been measured to evaluate the potential usefulness of these parameters in the assessment of environmental contamination by polycyclic aromatic hydrocarbons (PAHs). Blood was obtained from nine woodchucks living near an aluminum electrolysis plant, contaminated area (Saguenay region, Québec, Canada), and from eight living in a control area (Saint-Roch-des-Aulnaies, Québec, Canada). Blood samples were collected and plasma separated from red blood cells by centrifugation on site. Isolation of albumin (Alb) and hemoglobin (Hb) was performed in our laboratory and each protein fraction was subjected to mild acid hydrolysis yielding free benzo(a)pyrene (BaP) tetrol from the adducts. The analysis was performed by high performance liquid chromatography (HPLC) using fluorescence detection. For the control and contaminated areas geometric mean (interval) Alb adduct levels were 7.6 (0.8-29.3) and 69.6 (10.0-1,103) pmol tetrol/g protein (p less than 0.01) while the corresponding figures for Hb adduct levels were 0.40 (0.01-2.72) and 1.18 (0.02-12.8) pmol/g protein (p greater than 0.01). Alb but not Hb adduct levels were associated with the measured concentration of BaP in the vegetation samples collected on the site where each animal was found. This is compatible with the short half-life of Alb adducts and with the instantaneous image provided by BaP measurements in the collected vegetation samples. BaPDE-blood protein adducts measured in wild animals appear to be good biomarkers of environmental contamination by PAHs.

Animals↗
PubMed1986

Oxidative biotransformation in primary cultures of chick embryo hepatocytes: induction of cytochrome P-450 and the metabolism of benzo(a)pyrene.

Primary cultures of chick embryo hepatocytes are known to maintain their initial level of cytochrome P-450 for a number of days. To explore the possibilities of chick embryo hepatocyte cultures as a tool in drug metabolism, induction profiles of cytochrome P-450 were determined and the metabolism of benzo(a)pyrene as a model substrate was studied. Maximum induction by phenobarbitone and Aroclor 1254 is reached after 21 h and 18 h, respectively, both in the presence and absence of serum. For beta-naphthoflavone induction is maximal after 31 h in the presence and 43 h in the absence of serum. The levels of P-450 after induction are comparable to those found in vivo in rats: increases of 200% for phenobarbitone, 200% for beta-naphthoflavone and 210% for Aroclor 1254. Ethoxyresorufin-O-deethylase activities are induced by beta-naphthoflavone and Aroclor 1254, but as expected only slightly by phenobarbitone. In the absence of serum in the culture medium, for the control as well as the induced cells a plateau of activity is maintained for at least 24 h. In the presence of serum a decline in P-450 levels is observed. Especially in the case of Aroclor, an increase in porphyrin content of 320% of control values is seen at the same time. A number of representative metabolites of benzo(a)pyrene were quantitated during a 4-h incubation. Relative amounts are comparable to those observed with rat liver microsomes. As expected, beta-naphthoflavone and Aroclor induce the rate of metabolism (by 500% and 400%, respectively, in the absence of serum), but phenobarbitone has no or very little effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland of fluorinated derivatives of benzo[a]pyrene and 3-methylcholanthrene.

Comparative studies of tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland were conducted with benzo[a]pyrene (BP) and 3-methylcholanthrene (MC) derivatives. SENCAR mice were initiated with BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-methylBP, 7-FBP, 8-FBP, 9-FBP, 10-FBP, or 10-azaBP and promoted with tetradecanoyl phorbol acetate. The same compounds plus BP 7,8-dihydrodiol were tested by intramammillary injection in female Sprague-Dawley rats. Tumor-initiating activity in mice and/or carcinogenicity in rats were observed for BP, 6-methylBP, 6-, 7-, 8-, and 10-FBP, whereas 9-FBP was inactive in both experiments and 10-azaBP was only marginally active in the mammary gland. BP 7,8-dihydrodiol was carcinogenic in rat mammary gland, although it was less potent than BP. MC, 8-FMC, 10-FMC, and 3-methylcholanthrylene were also tested in Sprague-Dawley rats by intramammillary injection. All compounds were carcinogenic, with MC displaying the most potent activity. The less potent carcinogenic activity of BP 7,8-dihydrodiol in the mammary gland, compared with BP, and the moderate-to-weak tumor-initiating and/or carcinogenic activity of 7-, 8-, and 10-FBP suggest that the bay-region diol-epoxide pathway does not play a significant role in the activation of BP in these two target tissues. Similarly, the carcinogenic activity of 8-FMC and 10-FMC, in which the bay-region diol-epoxide pathway is blocked, suggests that this mechanism of activation is not important in the carcinogenicity of MC in rat mammary gland.

Animals↗
PubMed1989

Oxygen diffusion-concentration in erythrocyte plasma membranes studied by the fluorescence quenching of anionic and cationic pyrene derivatives.

Fluorescence quenching by oxygen of cationic [pyrene-(CH2)nN(CH3)3+; n = 1, 4, and 11] and anionic [pyrene-(CH2)nCO2-, n = 3, 8, 11, and 15] probes was investigated in erythrocyte plasma membranes (leaky) in order to assess the ability of oxygen molecules to interact with solutes located at different positions in the membrane. The pseudounimolecular quenching rate constants measured increase, both for cationic and anionic probes, when n increases. These results are interpreted in terms of an increased oxygen solubility toward the center of the membrane interior, and imply that lateral diffusion contributes more than transverse diffusion to total oxygen mobility. For all of the probes considered, quenching rates increase when n-alkanols are added. The effect observed increases when n decreases and when the size of the n-alkanol alkyl chain increases. Arrhenius-type plots for the quenching rate constants show noticeable downward curvatures. Average (0-40 degrees C) activation energies are approximately 6 kcal/mol.

Animals↗
PubMed1987

Comparison of benzo(a)pyrene metabolism in isolated perfused rat lung and liver.

The metabolism of 1 mM benzo(a)pyrene was studied in isolated perfused lung and liver of 5,6-benzoflavone-pretreated rats. Benzo(a)pyrene metabolism by the liver was more rapid than by the lung, but total metabolite formation in the lung at the end of a 120-min perfusion period was comparable to that in the liver. Lung perfusate was characterized by high concentrations of free metabolites, with diols outweighing phenols; in liver perfusate free metabolite concentrations were low, and large quantities of metabolites were found as conjugates in the bile at the end of perfusion. The tissue concentrations of free diols and phenols including the precursors of the main DNA-binding secondary metabolites were higher in the lung than in the liver. These findings explain the similar level of covalent binding in perfused lung and liver previously described (Klaus et al. 1982).

Animals↗
PubMed1991

Effects of smoking on benzo(alpha)pyrene- and glutathione-metabolizing enzymes in human lung tissue.

The influence of smoking on the metabolism of benzo(alpha)pyrene and glutathione was investigated in 190 patients with primary bronchial carcinoma and 20 patients with benign lung diseases. There were no significant differences in the activities of drug-metabolizing enzymes in the lung tissue of smokers, regardless of whether they smoked low- or high-tar and -nicotine cigarettes; former smokers; or nonsmokers; nor were there such differences between female and male patients. No significant differences existed between patients with squamous cell carcinoma and those with adenocarcinoma. Impaired detoxification due to decreased activity of glutathione S-transferases, rather induction of benzo(alpha)pyrene-metabolizing enzymes, may disturb the delicate balance between the generation and detoxification of reactive metabolites. This impairment may lead to the accumulation of these compounds in the cell.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1986

The protective effect of Thiola against the genotoxic action of benzo(a)pyrene.

The protective effect of Thiola against the genotoxicity, induced by benzo(a)pyrene, in vitro and in vivo, was investigated. By association of Thiola to benzo(a)pyrene a significant decrease of the numerical and structural chromosome aberrations and a reduction of the incidence of c-mitoses has been obtained in human diploid cells, i.e. human embryonic lung fibroblasts of the cell-line ICP-23, and C56B1/6 mouse bone marrow cells.

Amino Acids, Sulfur↗
PubMed1995

Long-lasting persistence of elevated sister-chromatid exchange frequencies induced by perinatal benzo(a)pyrene treatment in rat bone-marrow cells.

In this work the possibility that a mutagenic factor acting in utero or in the perinatal period might lead to elevated mutagenic rates in bone-marrow cells after a considerable period of time was examined. An aromatic hydrocarbon, benzo(a)pyrene was used as the test substance. Benzo(a)pyrene treatments resulted in significantly higher sister-chromatid exchange (SCE)-frequencies in both fetal and neonatal groups in both sexes, even four months after exposure. In a second experiment we examined whether mutagenic exposure suffered in utero could make the individual more susceptible to mutagenic effects in adulthood. Preliminary results indicate that such a possibility could exist.

Animals↗
PubMed1990

Hydrolysis of fluorescent pyrene-acyl esters by human pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase.

Fluorescent esters containing pyrenedecanoic acid (P10) or pyrenebutanoic (P4) acid (P4cholesterol, P10cholesterol, P4- and P10-containing triacylglycerols) were synthesized and used as substrates for human pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase from human milk. Both enzymes were purified by immunoaffinity chromatography. All fluorescent pyrene derivatives were hydrolyzed by pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase, but at different rates. The hydrolytic rates of the "short" acyl esters (P4-containing esters) were higher than those of the "long" ones (P10-containing esters). Conditions were optimized for sensitivity of the assay using fluorescent cholesteryl esters. The pH optimum was 7.5-8.0. Sodium cholate exhibited a stronger activating effect than taurocholate or taurodeoxycholate (maximal activation was achieved with 5 mmol/L cholate and with a molar ratio cholesteryl ester/cholate around 1:10). Both pancreatic carboxylic ester hydrolase and bile salt-stimulated lipase from milk were strongly inhibited by the other amphiphiles tested, namely phosphatidylcholine and Triton X-100, and were inactivated by low concentrations (10 mumol/L) of the serine-reactive diethyl-paranitrophenyl phosphate (E600). Both enzymes were strongly inhibited by relatively low concentrations of plasma low density lipoproteins. These studies indicate that the fluorescent esters containing pyrene fatty acids can be used as substrates for assaying and investigating the properties of pancreatic carboxylic ester hydrolase as well as bile salt-stimulated lipase from milk.

Animals↗
PubMed2002

Laser-induced fluorescence with an OPO system. Part I. Optimisation of the analytical system by use of experimental design methodology. Application to the direct quantification of traces of benzo[ a]pyrene.

This study deals with the optimisation and application of a method for direct analysis of trace pollutants in water by laser-induced fluorescence. The arrangement used consisted of an Nd:YAG Laser coupled with an optical parametric oscillator (LYOPO) and connected to a spectrophotometer and a high-sensitivity camera. Optimisation was achieved by developing an experimental design methodology to maximise the signal-to-noise ratio and reduce the limit of detection. The technique was then applied to the detection of benzo[ a]pyrene in water. The experimental results were evidence of its high sensitivity and time-resolution potential. The detection limit for benzo[ a]pyrene was 0.7 ng L(-1) in drinking water and 4 ng L(-1) in raw water containing 1 mg L(-1) humic acids.

Benzo(a)pyrene↗
PubMed2000

Benzo[a]pyrene toxicokinetics in rainbow trout (Oncorhynchus mykiss) acclimated to different salinities.

The effects of environmental salinity on the distribution, metabolism, and elimination of benzo[a]pyrene (B[a]P) were examined in mature rainbow trout. Trout acclimated to either fresh water (0 ppt, FW) or sea water (20 ppt, SW) for 3 weeks received a single 10 mg/kg intra-arterial injection of [(3)H]-benzo[a]pyrene (B[a]P) at their acclimation salinity or when subjected to an acute salinity change. Statistically significant differences in the percent body burden of B[a]P-derived radioactivity in various tissues were seen between fish in FW versus SW. Significant differences in the distribution of B[a]P and its metabolites were also noted when fish were subjected to an acute salinity change after chemical injection. Modulation of B[a]P metabolism by environmental salinity included: (1) significant differences in the proportions of Phase I metabolites in the bile of FW- (2.3%) versus SW-acclimated (14.1%) fish, and (2) alterations in the accumulations of specific metabolites (predominantly t-9, 10-dihydrodiol-B[a]P in FW fish, and 3-hydroxy-B[a]P in SW fish). The percentages of the [(3)H]-B[a]P dose eliminated by 48 h was similar in FW and SW fish, but decreased in fish subjected to an acute salinity change (FW 98.8% eliminated, FW:SW 90.4%, SW 98.1%, and SW:FW 93.1%). Pharmacokinetic modeling confirmed that acute salinity changes can result in longer terminal half-lives and slower total body clearances of B[a]P.

Adaptation, Physiological↗
PubMed2005

Degradation of anthracene and pyrene supplied by microcrystals and non-aqueous-phase liquids.

Polycyclic aromatic hydrocarbons (PAHs) are worldwide environmental pollutants. Their bioavailability is limited by a low aqueous solubility, which causes specific adaptations in degrading bacteria. To compare bacterial degrading behavior, a study was conducted on the mineralization, metabolization and formation of biomass from (14)C-anthracene by Sphingomonas sp. BA2 compared with those from (14)C-pyrene by Gordonia-like strain BP9 and Mycobacterium gilvum VF1. Different conditions of PAH supply were used in the medium: crystals <0.5 mm, microcrystals <<0.1 mm formed by sonication, or PAH solubilized in 2,2,4,4,6,8,8-heptamethylnonane (HMN) or silicone oil. Anthracene supply by crystals and silicone oil led to similar maximum mineralization rates 33 ng ml(-1) h(-1) and the same amount of mineralization (24%) after 168 h. Microcrystals increased the rates and amounts only slightly. HMN decreased the values to less than one-third. In comparison with crystals, microcrystals increased overall pyrene mineralization by strain BP9 from 53% to 58%, with maximum mineralization rates of 160 ng ml(-1) h(-1) and 166 ng ml(-1) h(-1). Silicone oil heavily increased the rate to 292 ng ml(-1) h(-1) and the amount mineralized to 71%, whereas HMN inhibited the degradation by one order of magnitude. A similar degradation behavior showing lower mineralization rates and extent was observed with strain VF1. However, inhibition by HMN was less pronounced. Sonication, leading to decreased PAH crystal size, increased the mass transfer and mineralization rates. PAH supply by silicone oil led to a much higher mass transfer, which may be due to emulsification of the oil, whereas such effects were not observed with HMN.

Alkanes↗
PubMed2000

Degradation of acenaphthene, phenanthrene and pyrene in a packed-bed biofilm reactor.

Biofilm reactors are particularly suitable for the treatment of large amounts of diluted effluent, such as groundwater contaminated with scarcely soluble pollutants. A packed-bed column reactor was tested for the degradation of acenaphthene, phenanthrene and pyrene provided at their aqueous solubility concentrations. Acenapthene and phenanthrene were removed to more than 99% efficiency from this reactor whilst pyrene was removed to 90%. Pollutant disappearance was also recorded in the control reactor and was probably caused by the adsorption of pollutants into the reactor. The measurement of oxygen consumption in both reactors confirmed that microbial degradation of the pollutants was indeed occurring in the inoculated reactor. Physical adsorption is not however unwanted, as it could help with the formation of a biofilm at an early stage of the treatment.

Acenaphthenes↗
PubMed2001

Microbial degradation of phenanthrene and pyrene in a two-liquid phase-partitioning bioreactor.

A study was conducted to determine the potential of two-liquid phase-bioreactors for the treatment of (polycyclic aromatic hydrocarbons) PAHs. Phenanthrene and pyrene were supplied two times at a concentration of 100 mg/l of reactor broth, either as crystals or dissolved in silicone oil. Complete phenanthrene biodegradation was achieved within 3 days after each addition to the biphasic-inoculated reactor. Its concentration in the monophasic reactors dropped by 93% within 4 days, but remained incomplete for the duration of the experiment. Pyrene removal occurred to a limited extent only in the presence of phenanthrene. Significant pollutant losses were recorded in the monophasic reactors, most likely caused by volatilization. Pollutant degradation was improved upon repeated phenanthrene amendment to the biphasic system. Biphasic reactors allow the fast and complete degradation of PAHs and prevent their hazardous disappearance. The use of biphasic reactors for the degradation of poorly soluble pollutants should become more beneficial when the substrate-interface uptake mechanism is operating. Thus, biphasic reactors should be integrated into the microbial enrichment procedure.

Bacteria↗
PubMed2005

Effect of benz(a)pyrene and constant light exposure on rat liver lysosomes and biliary excretion of lysosomal enzymes.

Threefold administration of benz(a)pyrene in a dose of 20 mg/kg markedly stimulated biliary excretion of lysosomal enzymes from rat liver without signs of lysosomal damage. Constant light exposure induced changes attesting to functional activation of the lysosomal apparatus in liver cells and inhibited constitutive biliary excretion of lysosomal enzymes. Combined treatment decreased, but not abolished the stimulatory effect of benz(a)pyrene on vesicular transport of lysosomal enzymes to the bile.

Acetylglucosaminidase↗