摘要:

AbstractThe aromatic hydrocarbon responsiveness (Ah) locus has been correlated with genetic differences in the risk of drug toxicity, teratogenesis, chemical carcinogenesis, and mutagenesis. Hepatic cytosolic Ah receptor levels, 2‐amino‐5‐chlorobenzoxazole (zoxazolamine) paralysis time following β‐naphthoflavone treatment and aryl hydrocarbon hydroxylase (AHH),3acetanilide 4‐hydroxylase (Ac4H), and NAD(P)H:menadione oxidoreductase (NMOR);4induction by 3‐methylcholanthrene were studied in (a) the progenitors C57BL/6J (Ahb/Ahb) and DBA/2J (Ahd/Ahd) and 25 BXD recombinant inbred lines, (b) the progenitors C57BL/6N and C3H/HeN and 14 B6NXC3N recombinant inbred lines, and (c) the progenitors C57BL/6J and C3H/HeJ and 12 BXH recombinant inbred lines. TheAhbphenotype exhibits>5 femtomole receptor/mg of cytosolic protein, ≤15 minutes zoxaxolamine paralysis time, and twofold to 15‐fold induction of these three hepatic enzyme activities; theAhdphenotype exhibits ≤2 fmol receptor/mg protein,>15 minutes zoxazolamine paralysis time, and<30% induction of these three activities. Among the BXD lines but especially among the B6NXC3N and BXH lines, high frequencies of recombination were found; the phenotype of each of the five parameters did not segregate with the phenotype of each of the other parameters in four or more recombinant lines. This report shows for the first time that AHH induction by 3‐methylcholanthrene can occur in theAhdphenotype mouse. These data underline the complexity of this genetic system when genes from C57BL/6 and DBA/2 are combined and particularly when genes from C57BL/6 and C3H/He inbred mouse

ISSN:0887-2082    

DOI:10.1002/jbt.2570010103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractHomogenates of all rat tissues examined, except brain, catalyze reduction ofN,N‐dimethyl‐p‐aminoazobenzeneN‐oxide (DMABN‐oxide) toN,N‐dimethyl‐p‐aminoazobenzene by NADPH. Liver is the most active, and about one third of the homogenate activity of this tissue is recovered in the cytosol fraction. The purified cytosol enzyme has the properties of a tetrameric protein (Mr 370,000) consisting of identical subunits free from chromophores that absorb in the visible spectrum and from metals or other detectable prosthetic groups. The purified reductase is also free from NADPH oxidase and from cytochromecor azo reductase activities. The enzyme is quite specific for NADPH as reductant and DMABN‐oxide as the electron acceptor. Reduction of otherN,N‐dimethyl‐arylamine or alkylamine oxides as well asN‐methylheterocyclicamine oxides could not be detected. Analysis of kinetic data indicate that, at saturating concentrations of the other substrate, 21 μM NADPH and 700 μM DMABN‐oxide are required for half maximal velocity. At infinite concentrations of both substrates the tu

ISSN:0887-2082    

DOI:10.1002/jbt.2570010104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe incubation of isolated rat hepatocytes with extracellular adenosine 5′‐trihosphate (ATP) resulted in an inhibition of Ca2+efflux. The ATP‐induced Ca2+accumulation as determined by the increase in phosphorylaseaactivity and the Ca2+‐sensitive fluorescent indicator (2‐[(2‐bis‐[carboxymethyl]‐amino‐5‐methylphenoxy)‐methyl]‐6‐methoxy‐8‐bis‐[carboxymethyl] aminoquinoline‐tetrakis‐[acetoxymethyl]ester) (Quin 2‐AM) was associated with both the hydrolysis of ATP and the phosphorylation of a 110 kDa protein. No significant alteration in the intracellular ATP level was observed.The appearance of surface blebs and cytotoxicity followed the rise in cytosolic Ca2+, suggesting that the increased free Ca2+may be responsible for the loss of viability. When a calmodulin inhibitor, 1‐[bis(4‐chlorophenyl)methyl]‐3‐[2‐(2,4‐dichlorophenyl)‐2‐[(2,4‐dichlorophenyl)methoxy]ethyl]‐1H‐imidazolium chloride (calmidazolium), was included in the medium prior to ATP addition, bleb formation was reduced and the loss of viability was completely prevented, indicating that a Ca2+‐calmodu

ISSN:0887-2082    

DOI:10.1002/jbt.2570010105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe enzyme systems in rat liver and lung responsible for the oxidative metabolism of hydrazine derivatives were studied to determine whether these enzymes, cytochrome P‐450 and monoamine oxidase, were responsible for metabolically activating hydrazines to carcinogenic/toxic metabolites. Cytochrome P‐450 preferentially oxidized the nitrogen to nitrogen bond of 1,2‐disubstituted hydrazines and hydrazides, while monoamine oxidase oxidized the nitrogen to nitrogen bond of all the classes of hydrazine derivatives that were tested. Oxidation of the nitrogen to nitrogen bond led to the formation of stable azo intermediates in the case of 1,2‐disubstituted hydrazines and to unstable monoazo (diazene) metabolites in the case of monosubstituted hydrazines and hydrazides. In addition, cytochrome P‐450 preferentially oxidized the carbon to nitrogen bond of monoalkylhydrazines; this reaction resulted in the formation of aldehyde metabolites (via hydrazone intermediates).Monosubstituted hydrazines were shown to be potent, irreversible inhibitors of mitochondrial monoamine oxidase. In contrast, the 1,2‐disubstituted hydrazines appeared to be good substrates for the monoamine oxidase and served as competitive inhibitors at high concentrations. There did not appear to be any monoamine oxidase isozyme (form A or B) specificity in the metabolism of either the 1,2‐disubstituted hydrazines or the monoalkylhydrazines, ethyl‐ andn

ISSN:0887-2082    

DOI:10.1002/jbt.2570010106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe oxidation of mercury vapor (Hg°) to divalent inorganic mercury (Hg2+) was studied in rat brain homogenates. By using a “degassing” method, it was possible to speciate the mercury present in the homogenate and, for the first time, to measure the rate of oxidation as a function of the substrate (Hg°) concentration. Mercury oxidation was first‐order with respect to substrate concentration at all concentrations tested, and the first‐order rate constant for the oxidation process was proportional to homogenate concentration. The role of catalase compound I in mercury vapor oxidation by brain homogenate was examined by observing the effects of two inhibitors of catalase (catalase compound I) on homogenate mercury‐oxidizing activity and catalase activity. Sodium azide (50 mM) completely inhibited both mercury‐oxidizing activity and catalase activity. Aminotriazole (3‐amino‐1H‐1,2,4‐triazole) (50 mM) completely inhibited only mercury‐oxidizing activity; some residual catalase activity was found in the aminotriazole‐treated homogenate. It was concluded that catalase compound I plays a major role in the oxidation of Hg°, but the possibility that catalase‐independent pathways make a minor con

ISSN:0887-2082    

DOI:10.1002/jbt.2570010107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe interaction of avermectin B1a(AVM) with the γ‐aminobutyric acid (GABA) receptor of rat brain was studied using radioactive ligand binding and tracer ion flux assays. Avermectin potentiated the binding of [3H]flunitrazepam and inhibited the binding of both [3H]muscimol and [35S]t‐butylbicyclo‐phosphorothionate to the GABAAreceptor. Inhibition of muscimol binding by AVM suggested competitive displacement. Two kinds of36chloride (Cl) flux were studied. The36Cl efflux from preloaded microsacs was potentiated by AVM and was highly inhibited by the Cl‐channel blocker 4,4′‐diisothiocyano‐2,2′‐stilbenedisulfonic acid (DIDS). However, it was not potentiated by GABA nor was it sensitive to the convulsants picrotoxin or bicuculline. On the other hand,36Cl‐influx measurement in a different microsac preparation of rat brain was very sensitive to GABA and other GABA‐ergic drugs. Avermectin induced36Cl influx into these microsacs in a dose–dependent manner, but to only 35% of the maximal influx induced by GABA. The AVM‐induced36Cl influx was totally blocked by bicuculline. It is suggested that AVM opens the GABAA‐receptor Cl channel by binding to the GABA recognition site and acting as a partial receptor agonist, and also opens a voltage–dependent Cl channel which is totally insensitive to GABA

ISSN:0887-2082    

DOI:10.1002/jbt.2570010108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractCollagen cross‐linking was analyzed in lungs of rats two, four, and ten weeks after intratracheal instillation of 1.5 units of bleomycin. Similar analyses were performed on lungs of mice 18 months after intratracheal instillation of bleomycin with or without subsequent exposure to 70% oxygen (O2) for 72 hours. Lungs were analyzed to determine the content of the reduced difunctional cross‐links dihydroxylysinonorleucine (DHLNL) and hydroxylysinonorleucine (HLNL) and of the nonreducible trifunctional cross‐link hydroxypyridinium (OHP). Ratios of DHLNL:HLNL were elevated in the rat lungs at two and four weeks, due to increased levels of DHLNL. There were no changes in the difunctional cross‐links in any of the mouse lungs. Hydroxypyridinium content was elevated in the rat lungs at ten weeks and in the mouse lungs exposed to bleomycin and oxygen. We conclude that increases in DHLNL may serve as an early indicator that potentially “fibrotic collagen” is being synthesized in lungs acutely exposed to fibrogenic stimuli, while increases in OHP may serve as a permanent marker of a fibrogenic event that could have occurred months to ye

ISSN:0887-2082    

DOI:10.1002/jbt.2570010109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThiobarbituric acid (TBA) assays which have been modified for detection of lipid hydroperoxides appear to be useful for demonstration of in vivo lipid peroxidation. Since these methods require heating tissue membranes with the buffered TBA, there is a possibility of interference from the detection of autoxidation that occurs during heating. These studies were undertaken to investigate conditions which favor TBA color production from hydroperoxide while limiting autoxidation during the assay. An acetic acid‐sodium acetate buffered (pH 3.6) TBA assay was used. Heating linoleic acid hydroperoxide with 50 μM ferric iron or under nitrogen nearly doubled color production compared to heating it with no added iron or under air. The lipid antioxidant butylated hydroxytoluene inhibited color production from fatty acid hydroperoxides. When tissue fractions, including liver and lung microsomes and lung whole membranes, were heated in the assay, color production was greater under air than under nitrogen and was much greater under oxygen. When liver microsomes from carbon tetrachloride‐exposed rats were used, color was increased only when oxygen was present in the heating atmosphere. The results with tissue fractions appear to demonstrate autoxidation during color development rather than the presence of preformed hydroperoxides. Finally, it was found that color production from membrane fractions was dependent on the vitamin E content of the membranes. It appears that autoxidation during heating should be limited by heating under nitrogen and not by adding antioxidants, which inhibit color production from hydroperoxides. As the vitamin E effect demonstrates, antioxidant status must be considered, since a change in color production could result from a change in antioxidant content without the accumulation of lipid hydroperox

ISSN:0887-2082    

DOI:10.1002/jbt.2570010110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe potentials of octachlorostyrene (OCS) and hexachlorobenzene (HCB) to induce liver microsomal ethoxyphenoxazone deethylation (an indicator of induction of 3‐methylcholanthrene and β‐naphthoflavone–like cytochrome P‐450 monoxygenase activity) and cause porphyria in male C57BL/6 and C57BL/10 mice and female F344 rats were compared. Ethoxyphenoxazone deethylation was induced much more by HCB than by OCS in both of these strains of mice (although neither OCS nor HCB greatly induced deethylation in the DBN/2 strain). In rats ethoxyphenoxazone deethylase was induced 26‐fold by HCB but only four‐fold by OCS, whereas dealkylation of pentoxyphenoxazone (an indicator of phenobarbital‐like induction) increased 43‐and 36‐fold, respectively. Both chemicals were poor inducers of dealkylation of pentoxyphenoxazone in mice. When fed HCB continuously but not when given OCS, C57BL/6 and C57BL/10 mice (both after pretreatment with iron) and F344 rats developed porphyria with a depression of hepatic uroporphyrinogen decarboxylase activity. The results illustrate that in these species OCS and HCB cannot be considered as equally efficient agents for inducing ethoxyphenoxazone deethylation or causing porphyria. If these effects are mediated through binding to the aromatic hydrocarbon responsiveness (Ah) receptor, HCB would appear to have a much greater affinity than OCS despite the face that neither chemical possesses a structure currently considered to be necessary for

ISSN:0887-2082    

DOI:10.1002/jbt.2570010111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0887-2082    

DOI:10.1002/jbt.2570010102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY