摘要:

AbstractThe purpose of this study was to determine the effects of diamide, a reversible sulfhydryl oxidizing agent, on the transport of serotonin (5‐HT) by mouse platelets. Diamide produced a concentration‐dependent (10–200 μM) stimulation of 5‐HT transport that was rapid and sustained over 0–10 minutes of incubation. When platelets were incubated with diamide (10–200 μM) in the presence of glucose, the content of reduced glutathione was significantly decreased only at a final concentration of 200 μM, while washed platelets incubated with diamide (10–200 μM), in the absence of glucose, had a significant concentration‐dependent decrease in their content of reduced glutathione. Fluoxetine, an inhibitor of the platelet 5‐HT transporter, blocked diamide‐induced stimulation of 5‐HT transport. The kinetics of 5‐HT transport showed that diamide caused a marked increase in the maximal rate of transport (Vmaxcontrol = 28.4 ± 1.4 vs.Vmaxdiamide = 60.9 ± 4.1 pM/108platelets/4 min) but did not significantly alter the Kmvalues. Ouabain, an inhibitor of platelet Na+‐K+ATPase, blocked the stimulation by diamide in a concentration‐dependent manner. Dithiothreitol, a disulfide reducing agent, was able to partially reverse the stimulation of platelet 5‐HT transport caused by diamide. This study has shown that diamide can stimulate the active transport of 5‐HT by mouse platelets and suggests a possible role for free sulfhydryl gro

ISSN:0887-2082    

DOI:10.1002/jbt.2570070302

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe toxicity of polycyclic aromatic hydrocarbons such as benzo(a)pyrene, 7,12‐dimethylbenz(a)anthracene, and 3‐methylcholanthrene has been associated with alterations in the proliferation of vascular smooth muscle cells and the development of lesions of mesenchymal origin. Because phosphorylation of endogenous substrates plays a central role in the regulation of smooth muscle cell growth, the present studies were conducted to evaluate the phosphorylation pattern of medial aortic protein upon repeated in vivo exposure of Japanese quail to benzo(a)pyrene (BaP). Medial aortic homogenates from quail treated for 10 weeks with 10 mg/kg benzo(a)pyrene or vehicle were processed for in vitro measurements of protein phosphorylation. In vitro phosphorylation of endogenous or exogenous proteins stimulated in vitro by phorbol myristate acetate/phosphatidyl‐serine or cyclic AMP, known activators of protein kinase C and cyclic AMP‐dependent protein kinase, respectively, was examined in the cytosolic and particulate fractions of homogenates from control and treated animals. Benzo(a)pyrene treatment significantly enhanced the basal phosphorylation of Mr 113, 35, and 23 kDa proteins in the cytosolic fraction. Modest increases in the phosphorylation of Mr 71, 52, and 38 kDa were also observed under basal conditions. No changes in the basal phosphorylation of particulate proteins were observed. Phosphorylation of endogenous protein substrates by protein kinase C in the cytosolic fraction was not altered by benzo(a)pyrene treatment. In contrast, inhibition of C‐kinase‐mediated phosphorylation of endogenous Mr 272, 72, and 45 kDa proteins was observed in the particulate fraction of aortic homogenates from benzo(a)pyrene‐treated quail relative to controls. Exogenous histone phosphorylation by PKC in the particulate, but not cytosolic fraction, was decreased by benzo(a)pyrene treatment. The effects of benzo(a)pyrene on the C‐kinase system were specific, since cAMP‐mediated phosphorylation of endogenous proteins, as well as exogenous histone, was not altered by benzo(a)pyrene. Interestingly, benzo(a)pyrene treatment was associated with a selective increase of Mr 200, 80, and 67 kDa proteins in the cytosolic fraction. Collectively, these data are consistent with the hypothesis that medial protein phosphorylation is a significant molecular target of benzo(a)pyrene within

ISSN:0887-2082    

DOI:10.1002/jbt.2570070303

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe in vitro toxicity of multiple hydrophobic compounds was the focus of this study. A mitochondrial respiratory assay, sensitive to perturbations caused by hydrophobic chemicals, was utilized to measure the effects of individual aromatic hydrocarbon pollutants and their mixtures on mitochondrial respiratory function. Benzene, naphthalene, acenaphthene, and 1‐chloronaphthalene, common industrial solvents shown to interact additively in vivo, were evaluated using this in vitro assay system. Mitochondrial respiration was inhibited 50% (EC50) by 525 ppm (6.7 mM) benzene, 15 ppm (117 μM) naphthalene, 3.9 ppm (25.5 μM) acenaphthene, or 3.8 ppm (23.4 μM) 1‐chloronaphthalene. NADH:O2oxidoreductase (NADH → O2), NADH: ubiquinone oxidoreductase, and ubiquinol:O2oxidoreductase activities were inhibited by all four compounds, whereas succinate:O2oxidoreductase, cytochrome c oxidase, and duroquinol: O2oxidoreductase activities were not inhibited. Inhibition of mitochondrial respiration occurred at the level of ubiquinone (coenzyme Q10) for all four aromatic hydrocarbons. The ultraviolet absorbance spectrum of isolated Q10was also altered by naphthalene, acenaphthene, or 1‐chloronaphthalene, suggesting a specific interaction between that component of the respiratory chain and these aromatic hydrocarbons. Inhibition by a mixture of 2, 3, or 4 of the compounds tested was additive, reflecting a summation effect of each compound present in the mixture. This additive nature is consistent with previously reported effects of these compounds in vivo and with compounds having similar modes of action. The similar mode of action in vitro is a specific interaction with coenzyme Q10, not a generalized membrane perturbation as speculated to occur in vivo, and is the likely mechanism for the observed additiv

ISSN:0887-2082    

DOI:10.1002/jbt.2570070304

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe flavin‐containing monooxygenase (FMO) was purified from mouse lung microsomes. On SDS‐PAGE, the purified enzyme separated as two bands, a major band of 58,000 daltons and a minor band of 59,000 daltons. Antibodies to mouse liver FMO cross‐reacted with both bands in the purified preparations, whereas antibodies to rabbit lung FMO cross‐reacted only with the major band. In microsomal preparations the major band was recognized by both antibodies, but neither antibody detected the minor band in microsomes. A cDNA encoding the pig liver FMO hybridized with mRNA isolated from mouse liver, kidney, and lung, whereas cDNA encoding the rabbit lung FMO hybridized only with mouse lung and kidney mRNA. Thermal stability studies showed that the FMO preparation purified from mouse lung consisted of a heat‐stable and a heat‐labile component. The heat‐labile component of lung FMO was inhibited competitively by imipramine, whereas the heat‐stable component was insensitive to the presence of imipramine. Immunoprecipitation of purified mouse lung FMO with anti‐rabbit lung FMO completely removed the protein band reactive to anti‐rabbit lung FMO while leaving reactivity to anti‐liver FMO. The catalytic and immunochemical differences seen between FMO from rabbit lung and mouse lung appear to result from the expression of at least two forms of FMO in the mouse lung, one similar to the rabbit pulmonary form and one similar to the major mo

ISSN:0887-2082    

DOI:10.1002/jbt.2570070305

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

年代:1992

数据来源: WILEY

摘要:

AbstractCarbon disulfide, a volatile solvent, is widely used in industry. It has been demonstrated that it causes several neuropsychological symptoms. However, the neurochemical basis of its neurotoxic effect is relatively unknown. In this paper we have measured the effect of subacute i.p. administration on neutral and basic aminopepti‐dase activities in discrete zones of the rat brain using lysine‐ and leucine‐2‐naphtylamides as substrates. Neutral aminopeptidase activity showed a significant decrease in the thalamus and cerebellum with marked (not significant) changes in the hypothalamus, hippocampus, medulla, and occipital cortex. There were no changes in basic ami‐nopeptidase activity. It is suggested that amino‐peptidase activity could play a role in carbon disulfide neurotoxic action in the aforementioned regions by generating changes in several neuropep

ISSN:0887-2082    

DOI:10.1002/jbt.2570070306

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

年代:1992

数据来源: WILEY

摘要:

AbstractSeveral vitamin A compounds have been tested for their ability to suppress formation of DNA adduct by the carcinogen benzo[a]pyrene (B[a]P) in an in vitro reaction catalyzed by rat liver microsomes. Retinol, retinal, 3‐dehydroretinol and 3‐hydroxyretinol were found to be effective inhibitors of adduct formation. Certain carotenoids that are precursors of these retinoids also displayed considerable inhibitory capacity. Carotenoids and the 3‐substituted retinoids appeared to modulate the DNA adduct formation exclusively through their action on microsomal enzymes, since an effective inhibition in each case was observed on the formation of B[a]P‐7,8‐diol, a proximate carcinogenic metabolite of B[a]P. Unsubstituted retinoids, on the other hand, had marginal effect on enzymes but were found effective in accelerating inactivation of B[a]P‐7,8‐diol‐9,10‐epoxide, the ultimate carcinogenic metabolite

ISSN:0887-2082    

DOI:10.1002/jbt.2570070307

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

年代:1992

数据来源: WILEY

摘要:

AbstractSix species (CD‐1 mouse, Fischer 344 rat, Syrian golden hamster, Duncan‐Hartley guinea pig, half‐lop rabbit and marmoset monkey) were treated orally with ciprofibrate, a potent oxyisobutyrate hypolipidaemic drug for 14 days. A dosedependent liver enlargement was observed in the mouse and rat and at the high dose level in the hamster. A marked dose‐dependent increase in the 12‐hydroxylation of lauric acid was observed in the treated mouse, hamster, rat, and rabbit, associated with a concomitant elevation in the specific content of cytochrome P‐450 4A1 apoprotein, determined by an ELISA technique. Similarly, in these responsive species, an increase in mRNA levels coding for cytochrome P450 4A1 was observed. Lauric acid 12‐hydroxylation was unchanged in the guinea pig and marmoset after ciprofibrate pre‐treatment, and cytochrome P‐450 4A1 was not detected immunochemically in liver microsomes from these latter species. In the untreated mouse, hamster, rat, and rabbit, the 12‐hydroxylation of lauric acid was more extensive than the 11‐hydroxylation, whereas in the guinea pig and marmoset the activity ratios were reversed, with 11‐hydroxylation predominating. Peroxisomal fatty acid β‐oxidation was markedly induced in the mouse, hamster, rat, and rabbit on treatment at the higher dose level (39‐, 3‐, 13‐ and 5‐fold, respectively) and was slightly increased in the marmoset (2‐fold), yet was unchanged in the guinea pig following treatment. In the marmoset the increase in peroxisomal β‐oxidation was 3‐ to 4‐fold at the high dose level; however, the dose levels used in the marmoset were 20 and 100 mg/kg as opposed to 2 and 20 mg/kg in the other species. The differences in the foregoing hepatic enzyme responses to ciprofibrate between the species examined in our studies indicate a specific pattern of enzyme changes in responsive species. In the responsive species (rat, mouse, hamster, and rabbit), cytochrome P‐450 4A1 specific content and related enzyme activity were increased concomitant with elevated peroxisomal β‐oxidation. By contrast, the marmoset and guinea pig lack the coordinate hepatic induction of peroxisomal and microsomal parameters and may be categorized as less responsive species. Accordingly, the rat hepatic responses to peroxisome proliferators cannot confidently be used to predict biological responses in primates, with obvious implicat

ISSN:0887-2082    

DOI:10.1002/jbt.2570070308

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe influence of both single and concurrent administration of phenobarbital and clofibrate on hepatomegaly, cytochrome P450‐depen‐dent mixed function oxidase activities, and peroxisome proliferation in male rat liver have been studied. Both xenobiotics separately increase the liver :body weight ratio and their combined administration results in greater hepatomegaly than either compound alone. Both compounds induce NADPH‐cytochrome c(P450) reductase activity and laurate ω‐ and ω‐1‐hydroxylase activities, but only phenobarbital induces pentoxyresorufin‐O‐de‐alkylase. None of the drug treatments induced microsomal cytochrome b5. Phenobarbital did not cause peroxisome proliferation and inhibited the corresponding clofibrate‐dependent proliferation. Taken collectively, our studies have demonstrated that concomitant treatment with phenobarbital and clofibrate are largely permissive with respect to the hepatic mixed function oxidase system but have opposing effects on the phenomenon of peroxisome proliferati

ISSN:0887-2082    

DOI:10.1002/jbt.2570070309

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

年代:1992

数据来源: WILEY

ISSN:0887-2082    

DOI:10.1002/jbt.2570070301

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

年代:1992

数据来源: WILEY