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ХРОНИКА
Toxicology and Applied Pharmacology, Mepanipyrim, a New Fungicide, Inhibits Intracellular Transport of Very Low Density Lipoprotein in Rat Hepatocytes Megumi Terada, Fukutaro Mizuhashi, Kyoji Murata, Takako Tomita We have previously reported that ingestion of mepanipyrim induces fatty liver in rats due to the inhibitory effect on the synthesis or secretion of hepatocytic very low density lipoproteins (VLDL). To clarify the mechanism by which mepanipyrim induces fatty liver, morphological and biochemical effects of mepanipyrim on the movement of VLDL in rat liver and in the primary culture of rat hepatocytes were investigated. In in vivo experiments, rats were fed for 4 days a diet containing mepanipyrim at 4,000 ppm. VLDL accumulation in the Golgi apparatus of the liver, especially in the secretory vacuoles, was observed in the treated rats and in the hepatocytes treated for 2 hr with 25 µg/ml mepanipyrim. Using 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]caproyl-sphingosine (C6-NBD-ceramide), a selective staining agent for the Golgi apparatus, it was found that mepanipyrim inhibited C6-NBD-ceramide transport from the Golgi to the cell surface of cultured hepatocytes. The density of the VLDL-loaded secretory vacuoles isolated from the Golgi fractions was greater in mepanipyrim-treated rat livers compared with that in the control. Immunofluorescence micrograph of rat hepatocytes stained with anti--tubulin monoclonal antibody demonstrated that mepanipyrim neither affected microtubule network nor changed the intracellular ATP level. These results together suggested that fatty liver induced by mepanipyrim results mainly from the inhibition of the transport of hepatic VLDL from the Golgi to the cell surface. The inhibition of the transport of hepatic VLDL appears to result from qualitative changes in VLDL such as alteration of the apoprotein composition and/or insufficient lipidation of VLDL. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p1-11 (ID taap.1998.8551) Pulmonary Vascular Stress from Carbon Monoxide Stephen R. Thom, S. Tsuyoshi Ohnishi, Donald Fisher, Y. Anne Xu, Harry Ischiropoulos Studies were conducted with rats to investigate whether exposure to carbon monoxide (CO) at concentrations frequently found in the environment caused lung injury mediated by nitric oxide (NO)-derived oxidants. Lung capillary leakage was significantly increased 18 h after rats had been exposed to CO at concentrations of 50 ppm or more for 1 h. An elevation of NO during CO exposure was demonstrated by electron paramagnetic resonance spectroscopy. There was a 2.6-fold increase of NO over control in the lungs of rats exposed to 100 ppm CO. A qualitative increase in the concentration of H2O2 was also detected in lungs during CO exposure, and this change was caused by NO as it was inhibited in rats pretreated with the nitric oxide synthase inhibitor, N nitro-l-arginine methyl ester (l-NAME). Production of NO-derived oxidants during CO exposure was indicated by an elevated concentration of nitrotyrosine in lung homogenates. The CO-associated elevations in lung capillary leakage and nitrotyrosine concentration did not occur when rats were pretreated with l-NAME. CO exposure did not change the concentrations of endothelial or inducible nitric oxide synthase in lung and leukocyte sequestration was not detected as a consequence of CO exposure. CO-mediated lung leak and nitrotyrosine elevation were not affected by neutropenia. We conclude that CO exposure elevates the steady-state concentration of NO in lungs. Consequences from this change include increases in the concentration of reactive oxygen species, production of NO-derived oxidants such as peroxynitrite, and physiological evidence of lung injury. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p12-19 (ID taap.1998.8553) Effects of Cadmium on Metallothionein-I and Metallothionein-II mRNA Expression in Rat Ventral, Lateral, and Dorsal Prostatic Lobes: Quantification by Competitive RT-PCR Kai-Fai Lee, Kin-Mang Lau, Shuk-Mei Ho Highly sensitive, sequence-specific competitive reverse transcriptase-polymerase chain reaction (RT-PCR) protocols were established for the detection and quantification of metallothionein (MT)-I and MT-II messages, in absolute values, in rat tissues. Detection limits for these protocols were in the range of 5 to 10 amol per µg total RNA. Levels of MT-I and MT-II transcripts in the three major prostatic lobes, kidney, and testis were measured in untreated and cadmium (Cd)-treated rats. The dorsal prostate (DP), lateral prostate (LP), kidney, and testis expressed substantial levels of MT-I and MT-II mRNA while the ventral prostate (VP) had extremely low levels of the transcripts. Cd treatment induced higher levels of MT-I and/or MT-II mRNA expression in all tissues studied with the exception of LP. In the LP, Cd treatment caused reductions of MT-I and MT-II mRNA levels. The Cd-induced levels attained in the VP following Cd exposure were still markedly lower than those found in the kidney, testis, LP, and DP of untreated animals. These findings contradict previous claims that the MT genes in rat VP are unresponsive to Cd activation. The susceptibility of VP to Cd toxicity/carcinogenicity may therefore be explained by low levels of Cd-induced expression rather than lack of induction of MTs. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p20-27 (ID taap.1998.8556) Interactive Effects of TCDD and p,p’-DDE on Male Reproductive Tract Development in in Utero and Lactationally Exposed Rats I. Kati Loeffler, Richard E. Peterson Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p28-39 (ID taap.1998.8572) Age-Related Changes on Parameters of Experimentally-Induced Liver Injury and Regeneration Nuria Sanz, Carmen Dнez-Fernбndez, Alberto M. Alvarez, Lourdes Fernбndez-Simуn, Marнa Cascales Age-dependent changes related to liver injury and regeneration were studied in rats aged 2, 12, and 30 months in a time period of 96 hr following a sublethal dose of thioacetamide (6.6 mmoles/kg body wt). Serum aspartate aminotransferase activity increased earlier in young rats, but the severity of injury was higher in those aged 12 months when compared to young and to old. Microsomal hepatocyte FAD monooxygenase activity was induced earlier in 2-month-old rats following intoxication and the increase was significantly lower both in the youngest and in the oldest groups when compared to adults. As a parameter of hepatocellular postnecrotic regeneration, DNA synthesis (2C --> 4C) was evaluated. The population of hepatocytes in S phase peaked more sharply and earlier in young rat hepatocytes, and was 8 to 12 times higher than the initial in hepatocytes from 2- and 12-month-old rats, while the rise was only 3 times in the oldest group. At 96 hr of intoxication the restoration towards normal in all these parameters was complete in young, incomplete in adult, and slightly detected in the oldest. Serum proliferative activity, assayed on mouse NIH 3T3 fibroblast cultures, increased preceding the necrosis and this increase was higher in 2- and 12-month-old (171% and 224%, respectively), while in the oldest the increase was only 110%. This mitogenic activity decreased in all groups during necrosis, showing a second peak, nondetectable in rats aged 30 months, parallel to regeneration. Serum TNF level was absent in untreated animals and increased markedly following intoxication, the highest values being recorded at 72 hr of intoxication in serum from rats aged 12 months (347 ± 30 pg/ml) and the lowest at 30 months (4.1 ± 0.3 pg/ml). The serum ability to induce nitric oxide synthase activity on peritoneal macrophages ex vivo showed significant time- and age-dependent changes in nitric oxide release: a decrease throughout necrosis and an increase during regeneration. We conclude that the main age-related changes in the sequenced process of liver injury and regeneration are the delayed response in the development of cell killing and regeneration and the decreased regenerative ability, which significantly delays the restoration of liver function. Copyright 1999 Academic Press Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p40-49 (ID taap.1998.8541) Modulation of Phase II Enzymes by Organosulfur Compounds from Allium Vegetables in Rat Tissues D. Guyonnet, M.-H. Siess, A.-M. Le Bon, M. Suschetet Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p50-58 (ID taap.1998.8574) Cytotoxicity of Cadmium and Characteristics of Its Transport in Cardiomyocytes Dnyanesh A. Limaye, Zahir A. Shaikh Cadmium (Cd) is reported to produce cardiotoxicity at doses and exposure conditions that cause no effect in kidney or liver. The purpose of the present investigation was to examine the cytotoxicity of Cd to neonatal rat cardiomyocytes in primary culture and to elucidate the transport characteristics of Cd in these cells at a nontoxic concentration. Cd concentrations of 0.1 µM and higher that are well tolerated by hepatocytes and renal cortical epithelial cells were toxic to the cardiomyocyte. The plot of initial uptake rate of Cd at various concentrations was nonlinear suggesting that, in addition to simple diffusion, other processes may also be involved. These processes required metabolic energy as pretreatment with dinitrophenol or sodium fluoride inhibited 58 and 59% of the Cd uptake, respectively. The uptake of Cd was also affected by the incubation temperature and lowering the temperature from 37 to 4°C reduced Cd uptake over 30 min by 61%. Cd uptake required interaction with membrane sulfhydryl groups; pretreatment with p-chloromercuribenzenesulfonic acid or mercuric chloride reduced Cd uptake by 46 and 58%, respectively. Cd utilized the transport pathways for calcium (Ca), zinc (Zn), and copper (Cu). Coincubation with 1.26 mM Ca competitively inhibited Cd uptake by 77%. In the presence of Ca, 30 µM Zn or Cu further inhibited Cd accumulation competitively by as much as 63 and 32%, respectively. Cd could enter the cardiomyocytes through Ca channels and Ca channel blocker, verapamil, inhibited up to 76% of Cd uptake. From the above results it can be concluded that Cd is highly toxic to the cardiomyocytes. A majority of Cd enters these cells through transport processes that exist for Ca, Zn, and Cu. The transport processes utilized by Cd are temperature sensitive and dependent on metabolic energy. Furthermore, these involve membrane sulfhydryl groups and include Ca channels. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p59-66 (ID taap.1998.8575) Absorption and Retention of Nickel from Drinking Water in Relation to Food Intake and Nickel Sensitivity Gitte Dalsgaard Nielsen, Ulla Sшderberg, Poul J. Jшrgensen, Douglas M. Templeton, Sшren N. Rasmussen, Klaus E. Andersen, Philippe Grandjean Two studies were performed to examine the influence of fasting and food intake on the absorption and retention of nickel added to drinking water and to determine if nickel sensitization played any role in this regard. First, eight nonallergic male volunteers fasted overnight before being given nickel in drinking water (12 µg Ni/kg) and, at different time intervals, standardized 1400-kJ portions of scrambled eggs. When nickel was ingested in water 30 min or 1 h prior to the meal, peak nickel concentrations in serum occurred 1 h after the water intake, and the peak was 13-fold higher than the one seen 1 h after simultaneous intake of nickel-containing water and scrambled eggs. In the latter case, a smaller, delayed peak occurred 3 h after the meal. Median urinary nickel excretion half-times varied between 19.9 and 26.7 h. Within 3 days, the amount of nickel excreted corresponded to 2.5% of the nickel ingested when it was mixed into the scrambled eggs. Increasing amounts were excreted as the interval between the water and the meal increased, with 25.8% of the administered dose being excreted when the eggs were served 4 h prior to the nickel-containing drinking water. In the second experiment, a stable nickel isotope, 61Ni, was given in drinking water to 20 nickel-sensitized women and 20 age-matched controls, both groups having vesicular hand eczema of the pompholyx type. Nine of 20 nickel allergic eczema patients experienced aggravation of hand eczema after nickel administration, and three also developed a maculopapular exanthema. No exacerbation was seen in the control group. The course of nickel absorption and excretion in the allergic groups did not differ and was similar to the pattern seen in the first study, although the absorption in the women was less. A sex-related difference in gastric emptying rates may play a role. Thus, food intake and gastric emptying are of substantial significance for the bioavailability of nickel from aqueous solutions. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p67-75 (ID taap.1998.8577) New Screening Methods for Chemicals with Hormonal Activities Using Interaction of Nuclear Hormone Receptor with Coactivator Jun-ichi Nishikawa, Koichi Saito, Jun Goto, Fumi Dakeyama, Masatoshi Matsuo, Tsutomu Nishihara The endocrine system exerts important functions in a multitude of physiological processes including embryogenesis, differentiation, and homeostasis. Xenobiotics may modify natural endocrine function and so affect human health and wildlife. It is necessary, therefore, to understand the degree to which xenobiotics can disrupt endocrine systems. The key targets of endocrine disruptors are nuclear hormone receptors, which bind to steroid hormones and regulate their gene transcription. We have developed relevant assay systems based on the ligand-dependent interaction between nuclear hormone receptor and coactivator. The coactivators used in this study contained CBP, p300, RIP140, SRC1, TIF1, and TIF2. By two hybrid assay in yeast, the interactions of estrogen receptor with RIP140, SRC1, TIF1, and TIF2 were detected and they were completely dependent on the presence of estrogen. Specificity of this assay was assessed by determining the effect of steroids, known estrogen receptor agonists, and phytoestrogens. The pattern of response to chemicals were consistent with estrogenic activity measured by other assay systems, indicating that this assay system is reliable for measuring estrogenic activity. In addition, we carried out in vitro binding studies: GST pull-down assay and surface plasmon resonance analysis. The estrogen receptor also bound to coactivator in response to chemicals depending on their estrogenic activity in vitro. These data demonstrate that the measurement of interaction between steroid hormone receptor and coactivator serves as a useful tool for identifying chemicals that interact with steroid receptors. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p76-83 (ID taap.1998.8557) TA1 Oncofetal Rat Liver cDNA and Putative Amino Acid Permease: Temporal Correlation with c-myc during Acute CCl4 Liver Injury and Variation of RNA Levels in Response to Amino Acids in Hepatocyte Cultures Valerie D. Shultz, William Campbell, Shannon Karr, Douglas C. Hixson, Nancy L. Thompson TA1 is a rat liver oncofetal cDNA and a member of an emerging family of evolutionarily conserved molecules with homology to amino acid transporters and permeases. The aim of these studies was to characterize the regulation and role of TA1 in acute rat liver injury by examining its relation to regeneration and metabolic stress. Following a single dose of CCl4, TA1 message was expressed 3-48 h. The major 3.3-kb TA1 transcript correlated temporally with c-myc expression. A novel 2.9-kb TA1 transcript was expressed more variably 24-48 h. TA1 protein was restricted to hepatocytes in G0 and G1 phases of the cell cycle. Relative to CCl4, a much smaller increase in TA1 was noted after partial hepatectomy and TA1 preceded the peak of c-myc expression. In vitro TA1 was not induced in hepatocytes by EGF or the acute-phase cytokines IL-6 and TNF-, but was found to be modulated in response to amino acid availability. TA1 expression increased in media without arginine and glutamine and was repressed by total amino acid levels 5-fold over basal MEM. Together, these results contrast with the constitutive expression observed in transformed cells and suggest an adaptive role for TA1 during liver injury. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p84-96 (ID taap.1998.8555) Additive Toxicity of Binary Mixtures of Phototoxic Polycyclic Aromatic Hydrocarbons to the Oligochaete Lumbriculus variegatus Russell J. Erickson, Gerald T. Ankley, David L. DeFoe, Patricia A. Kosian, Elizabeth A. Makynen Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p97-105 (ID taap.1998.8563) Particulate Matter Initiates Inflammatory Cytokine Release by Activation of Capsaicin and Acid Receptors in a Human Bronchial Epithelial Cell Line B. Veronesi, M. Oortgiesen, J. D. Carter, R. B. Devlin Toxicology and Applied Pharmacology, v 154, n 1, January 1, 1999, p106-115 (ID taap.1998.8567)
Toxicology and Applied Pharmacology, The Mitochondrial Permeability Transition Mediates Both Necrotic and Apoptotic Death of Hepatocytes Exposed to Br-A23187 Ting Qian, Brian Herman, John J. Lemasters A23187 and related Ca2+ ionophores are widely used to study Ca2+-dependent cell injury. Here, using laser scanning confocal microscopy and parameter-indicating fluorophores, we investigated the role of the mitochondrial permeability transition (MPT) in Br-A23187 toxicity to cultured rat hepatocytes. After 10 µM Br-A23187, over 60% of hepatocytes lost viability within 1 h. This necrotic cell killing was preceded by increased mitochondrial free Ca2+, mitochondrial depolarization, and onset of the MPT. Cyclosporin A (CsA), a blocker of the permeability transition pore, prevented the MPT and cell killing but had no effect on increased mitochondrial free Ca2+ and depolarization after Br-A23187. To determine whether Br-A23187-induced cell killing was linked to loss of cellular ATP supply, hepatocytes were incubated with fructose and oligomycin, a source of glycolytic ATP and an inhibitor of the uncoupler-stimulated mitochondrial ATPase, respectively. Fructose plus oligomycin prevented cell killing after Br-A23187 but not the MPT. When fructose plus oligomycin prevented necrotic cell killing, apoptosis developed after 10 h. When cells were treated additionally with CsA, these apoptotic changes were prevented. In conclusion, the MPT mediates Br-A23187 cytotoxicity. Acutely, the MPT causes mitochondrial uncoupling and profound ATP depletion, which leads to necrotic cell death. However, when glycolytic ATP generation is available, the MPT induces apoptosis. CsA blocks the MPT and prevents both necrotic and apoptotic cell killing after Br-A23187. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p117-125 (ID taap.1998.8580) Nitroarene Reduction and Generation of Free Radicals by Cell-Free Extracts of Wild-Type, and Nitroreductase-Deficient and -Enriched Salmonella typhimurium Strains Used in the umu Gene Induction Assay Caroline A. Metosh-Dickey, Ronald P. Mason, Gary W. Winston Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p126-134 (ID taap.1998.8573) Disposition of Inorganic Mercury Following Biliary Obstruction and Chemically Induced Glutathione Depletion: Dispositional Changes One Hour after the Intravenous Administration of Mercuric Chloride Rudolfs K. Zalups, Delon W. Barfuss, Lawrence H. Lash Influences of biliary obstruction and systemic depletion of glutathione (GSH) on the disposition of a low nontoxic iv dose of inorganic mercury were evaluated in rats in the present study. Specifically, the disposition of mercury in the kidneys, liver, small and large intestines, and blood was assessed 1 h after the injection of 0.5 µmol/kg mercuric chloride in control rats and rats pretreated with acivicin, buthionine sulfoximine (BSO), or diethylmaleate (DEM) that did or did not undergo acute biliary ligation prior to the injection of mercury. Among the groups that did not undergo biliary ligation, the pretreatments used to alter GSH status systemically had varying effects on the disposition of inorganic mercury in the kidneys, liver, intestines, and blood. Biliary ligation caused the net renal accumulation of mercury to decrease under all pretreatment conditions. By contrast, biliary ligation caused significant increases in the hepatic burden of mercury in all pretreatment groups except the acivicin-pretreated group. Blood levels of mercury also increased as a result of biliary ligation, regardless of the type of pretreatment used. Evidence for a secretory-like movement of mercury into the lumen of the intestines is also provided in the animals that underwent biliary ligation. The present findings indicate that biliary ligation combined with methods used to alter GSH status systemically have additive effects with respect to causing reductions in the net renal accumulation of mercury. In addition, the findings indicate that at least some fraction of the renal accumulation of inorganic mercury is linked mechanistically to the hepatobiliary system. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p135-144 (ID taap.1998.8562) Reversible Long-Term Toxicity of Epristeride in Beagle Dogs Zu-Yue Sun, Jie Feng, Xiao-Dong Qi, Hong-Yan Wu, Wei-Jun Zheng, Zeng-Hong Tu Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p145-152 (ID taap.1998.8579) Propanil Affects Transcriptional and Posttranscriptional Regulation of IL-2 Expression in Activated EL-4 Cells Wei Zhao, Rosana Schafer, John B. Barnett The amide-class herbicide, propanil, causes numerous immunomodulary effects in animal models. In the present study, we investigated the effect of propanil on IL-2 expression and production in the murine lymphoma T cell line, EL-4. When supernatants of cells stimulated with phorbol 12-myristate 13-acetate in the presence of propanil were assessed by enzyme-linked immunosorbent assay, IL-2 levels were dose-dependently decreased by 20 and 50 µM of propanil but not at 10 µM. Quantitative Northern blot analysis of peak IL-2 message levels also showed a dose-dependent decrease. The kinetic pattern of message production, however, was unaffected. To determine if the reduced message production was due to reduced signaling or message stability, nuclear run-on and mRNA stability assays were performed. Nuclear run-on assays determined that the transcription rate of the IL-2 gene was decreased approximately 50% in the presence of 20 µM propanil, indicating that it was able to interfere with signal transduction. IL-2 message stability assays also demonstrated a reduction in message stability. Thus, propanil appears to reduce IL-2 production by affecting the signal transduction pathway and IL-2 message stability. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p153-159 (ID taap.1998.8545) Lactational Exposure and Neonatal Kinetics of Methylmercury and Inorganic Mercury in Mice Johanna Sundberg, Siv Jцnsson, Mats O. Karlsson, Agneta Oskarsson The concentration of mercury in milk and the distribution pattern in the sucking pup was followed over time after administration of a single iv injection of 0.5 mg/kg body wt of 203Hg-labeled methylmercuric chloride or mercuric chloride to lactating mice on Day 10 of lactation. Mercury concentrations in milk of the dams and in whole body, blood, plasma, GI-tract, liver, kidneys, and brain of the offspring were followed up to 11 days after dosing (until lactational Day 21). Following the inorganic mercury dose to the dams, most of the mercury in milk was delivered to the pups during the first 24 h, but the maximum mercury concentration in plasma and tissues of pups was not reached until 7 days after dosing, indicating a prolonged absorption of inorganic mercury in the sucking pup. Pups of dams given methylmercury were exposed to a much lower and constant mercury concentration in milk. The estimated accumulated mercury dose via milk per pup of dams given methylmercury was less than half of that estimated after the inorganic mercury dose. When the accumulated dose via milk from methylmercury-exposed dams was compared to the amount of mercury in pup’s carcass (whole body minus GI-tract including content), it was revealed that almost all mercury delivered via milk was absorbed, and that the suckling pups had a very low elimination of mercury until lactational Day 17. Lactational exposure following a maternal methylmercury or inorganic mercury dose resulted in almost similar mercury concentrations in liver, kidneys, and plasma of the suckling, but higher concentrations in brain (as most 14 times) and also twice as high mercury body burden in the methylmercury group. Thus, differences in kinetics indicate that lactational exposure of methylmercury is a greater hazard for the breast-fed infant than inorganic mercury. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p160-169 (ID taap.1998.8566) The Role of Glucuronidation in N-(3,5-Dichlorophenyl)succinimide (NDPS) Nephrotoxicity: Nephrotoxic Potential of NDPS and NDPS Metabolites in Gunn, Wistar, and Fischer 344 Rats Suk K. Hong, Dianne K. Anestis, Christopher Skaggs, Patrick I. Brown, Gary O. Rankin Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p170-180 (ID taap.1998.8554) Heavy Metals Mercury, Cadmium, and Chromium Inhibit the Activity of the Mammalian Liver and Kidney Sulfate Transporter sat-1 Daniel Markovich, Kristy M. James Heavy metal intoxication leads to defects in cellular uptake mechanisms in the mammalian liver and kidney. We have studied the effects of several heavy metals, including mercury, lead, cadmium, and chromium (at concentrations of 1 to 1000 µM), on the activity of the mammalian sulfate transporter sat-12 in Xenopus oocytes. sat-1 encodes a sulfate/bicarbonate anion exchanger expressed in the rat liver and kidney. Mercury (10 µM) strongly inhibited sat-1 transport by reducing Vmax by eightfold but not its Km for inorganic sulfate (Si). Lead (up to 1 mM) was unable to significantly inhibit sat-1 transporter activity. Cadmium (500 µM) showed weak inhibition of sat-1 transport by decreasing only sat-1 Vmax. Chromium (100 µM) strongly inhibited sat-1 transport by reducing Km for Si by sevenfold, most probably by binding to the Si site, due to the strong structural similarity between the CrO2-4 and SO2-4 substrates. This study presents the first characterization of heavy metal inhibition of the hepatic and renal sulfate/bicarbonate transporter sat-1, through various mechanisms, which may lead to sulfaturia following heavy metal intoxication. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p181-187 (ID taap.1998.8559) In Vitro Estrogenicity of the Catechol Metabolites of Selected Polychlorinated Biphenyls C. Edwin Garner, Wendy N. Jefferson, L. T. Burka, H. B. Matthews, Retha R. Newbold Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p188-197 (ID taap.1998.8560) Pyrrolizidine Alkaloids Crosslink DNA with Actin Roger A. Coulombe, Gail L. Drew, Frank R. Stermitz Pyrrolizidine alkaloids (PAs) are toxic constituents of hundreds of plant species, some of which people are exposed to in herbal products and traditional remedies. The bioactivity of PAs are related, at least in part, to their ability to form DNA-protein complexes (DPC). Previous studies from our laboratory indicated a possible role for actin in PA-induced DPCs. Nuclei prepared from Madin-Darby bovine kidney (MDBK) and human breast carcinoma (MCF-7) cells were treated with the pyrrolic PAs dehydrosenecionine (DHSN) and dehydromonocrotaline (DHMO). DPCs were purified and then analyzed by Western immunoblotting. Actin was found in DPCs induced by both DHSN and DHMO, but not in those from control nuclei. Actin was also present in DPCs induced by cisplatinum and mitomycin C, two bifunctional cross-linkers. In separate experiments, DHSN and DHMO were crosslinked to a mixture of HindIII digested phage with varying amounts of glutathione (GSH), cysteine, or methionine to identify the stoichiometry of competition between DNA and alternate nucleophiles for crosslink formation with pyrroles. GSH and cysteine, but not methionine, competed with phage for DNA crosslinking, indicating that reduced thiols may have a role in nucleophilic reactions with pyrroles in the cell. While actin involvement in cisplatinum-induced DPCs is documented, the discovery of actin crosslinking in PA or mitomycin C-treated cells or nuclei is, to our knowledge, novel. Pyrrole-induced DPC formation with actin, a protein with structural and/or regulatory importance proteins, may be a significant mechanism for PA toxicity and bioactivity. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 2, January 15, 1999, p198-202 (ID taap.1998.8552)
Toxicology and Applied Pharmacology, Methyl Mercury-Induced Autoimmunity in Mice Per Hultman, Helйn Hansson-Georgiadis Female SJL/N, A.SW, B10.S (H-2s), BALB/C, DBA/2 (H-2d), A.TL and B10.TL (H-2t1) mice were treated with sc injections of 1.0 mg CH3HgCl/kg body weight every third day for 4 weeks. Controls were given sterile, isotonic NaCl. CH3HgCl (MeHg) induced in SJL, A.SW and B10.S mice antinucleolar antibodies (ANoA) targeting the nucleolar 34-kDa protein fibrillarin. The susceptibility to develop ANoA in response to MeHg was linked to the mouse major histocompatibility complex (H-2), since H-2s but not H-2t1 mice sharing background (non-H-2) genes developed ANoA. However, the background genes decided the strength of the ANoA response in the susceptible H-2s mice, and the ANoA titer was in the order: A.SW > SJL > B10.S. Although MeHg as well as inorganic mercury induced ANoA, the two forms of mercury differed both quantitatively and qualitatively in their effect on the immune system. MeHg induced in H-2s mice a weaker general (polyclonal) and specific (ANoA) B-cell response than HgCl2, probably due to weaker activation of Th2 cells with lower IL-4 production, as indicated by the minimal increase in serum IgE. The A.TL strain with a susceptible genetic background, but a H-2 haplotype resistant to HgCl2, responded to MeHg with a modest polyclonal B-cell response dominated by Th1-associated Ig isotypes. H-2s mice treated with MeHg showed in contrast to HgCl2-treated mice no systemic immune-complex (IC) deposits, which may be due to the weaker immune activation after MeHg treatment. The increase in serum IgE concentration and ANoA titer 2-6 weeks after stopping treatment with MeHg is identical to reactions during the first 2-3 weeks of HgCl2 treatment. Therefore, demethylation of MeHg probably increased the concentration of inorganic mercury in the body sufficiently to reactivate the immune system. This reactivation indicated that genetically susceptible mice are not resistant to challenge with mercury, making them distinctly different from rats. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p203-211 (ID taap.1998.8576) Cadmium Binding and Sodium-Dependent Solute Transport in Renal Brush-Border Membrane Vesicles Do Whan Ahn, Young Mook Kim, Kyoung Ryong Kim, Yang Saeng Park Exposure to cadmium (Cd) impairs renal transport systems for glucose, amino acids, phosphate, and dicarboxylates. To investigate if these changes are directly related to a Cd binding to the renal brush-border membrane, Cd binding and the Na+-dependent uptakes of d-glucose, l-alanine, phosphate, and succinate were determined in rat renal brush-border membrane vesicles (BBMV) exposed to CdCl2. Cd uptake by BBMV showed time and concentration dependence. Changes in medium osmolality had no effect on Cd uptake, indicating that the process primarily involves binding of Cd to the membrane. Scatchard analysis indicated the presence of two types of Cd binding sites, differing in affinity and number. Increasing the medium Cd concentration from 50 to 200 µM resulted in a progressive increase in Cd binding to the membrane and decrease in Na+-dependent transport of d-glucose, l-alanine, inorganic phosphate, and succinate. In all cases, the inhibition of transport was directly proportional to the total amount of Cd binding to the membrane. These results suggest that, during chronic exposure to Cd, free Cd ions liberated in renal tubular cells may directly interact with brush-border membranes and impair Na+-dependent solute transports. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p212-218 (ID taap.1998.8581) Activation of NF-kappaB in Normal Rat Kidney Epithelial (NRK52E) Cells Is Mediated via a Redox-Insensitive, Calcium-Dependent Pathway James S. Woods, Maureen E. Ellis, Francisco J. Dieguez-Acuсa, Jeannette Corral Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p219-227 (ID taap.1998.8583) Molecular Genotoxicity Profiles of Apoptosis-Inducing Vanadocene Complexes Jiri Aubrecht, Rama Krishna Narla, Phalguni Ghosh, Jennifer Stanek, Fatih M. Uckun Metallocene complexes containing vanadium induce apoptosis in human cancer cells by an as yet unknown mechanism and may therefore be useful as a new class of cytotoxic anticancer drugs. Ultrastructural studies showing the formation of metallocene-DNA complexes prompted the hypothesis that their mechanism of action may resemble the DNA damage induced by cisplatin. Molecular genotoxicity testing provides insights into the mechanisms of action of new chemotherapeutic agents. Therefore, we determined the effects of three cytotoxic vanadocene complexes, vanadocene dichloride, vanadocene dithiocyanate, and vanadocene dioxycyanate, on genomic stability using the yeast DEL recombination assay and transcriptional activation of genotoxic stress-specific promoters in human HepG2 cells using the CAT-Tox(L) assay. Cisplatin caused an 11-fold increase of recombination frequency in yeast and induced transcriptional activation of the DNA damage-associated promoters such as the minimum promoter containing p53 response elements and the GADD45 promoter in addition to activating the promoters for c-fos, heat shock protein 70, metallothionine IIa, and the minimum promoter containing nuclear factor kappaB response elements. In contrast to cisplatin, vanadocene complexes did not increase the DEL recombination frequency in yeast nor did they activate any of the DNA damage-associated promoters in HepG2 cells. Vanadocene complexes triggered activation of the c-fos promoter without affecting the minimum promoter containing p53 response elements or the GADD45 promoter. These results indicate that the apoptotic signal of vanadocene complexes is not triggered by primary DNA damage and it does not require p53 induction, thereby disproving the hypothesis that it mechanistically resembles the cytotoxic action of cisplatin. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p228-235 (ID taap.1998.8592) Effects of the Antiestrogenic Environmental Pollutant 3,3’,4,4’,5-Pentachlorobiphenyl (PCB #126) in Rat Bone and Uterus: Diverging Effects in Ovariectomized and Intact Animals P. Monica Lind, E. F. Eriksen, L. Sahlin, M. Edlund, J. Цrberg Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p236-244 (ID taap.1998.8568) DNA-Protein Crosslinks Induced by Nickel Compounds in Isolated Rat Renal Cortical Cells and Its Antagonism by Specific Amino Acids and Magnesium Ion Saroj K. Chakrabarti, Chengjiang Bai, Kunnath S. Subramanian Suspensions of isolated renal cortical cells in modified Krebs-Henseleit buffer (pH 7.4) were incubated with nickel chloride, nickel acetate, nickel sulfate, and nickel subsulfide (0-2 mM) at 37°C for 2 h. A significant increase (63%) in DNA-protein crosslinks was observed at 2 mM nickel sulfate, whereas nickel subsulfide induced a significant increase in such crosslinks beginning at 0.5 mM concentration and a maximum increase of 200% of the control value reached at 2 mM concentration. No significant reduction in viability of renal cortical cells (as measured by trypan blue exclusion) was observed due to these nickel compounds at any concentration used. In the second series of experiments, coincubation of nickel subsulfide (2 mM) with l-histidine (8 or 16 mM), l-cysteine (4 or 8 mM), or l-aspartic acid (8 or 24 mM) significantly reduced the DNA-protein crosslinks induced by 2 mM nickel subsulfide. Similarly Mg2+ (24 mM), but not Ca2+ (24 mM), was able to antagonize nickel subsulfide-induced increase in DNA-protein crosslinks. High extracellular levels of Mg2+ and these amino acids significantly decreased the accumulation of Ni2+ from nickel subsulfide in renal cortical cells. Furthermore, these amino acids at high concentrations significantly inhibited the binding of Ni2+ from nickel subsulfide to deproteinized DNA from renal cortical cells, whereas such inhibition due to Mg2+ was close to significant (0.1 > p > 0.05). In vitro exposures of renal cortical cells to nickel subsulfide (0-2 mM) increased the formation of reactive oxygen species in concentration-dependent manner. Furthermore, coincubation of 2 mM nickel subsulfide with either catalase, dimethylthiourea, mannitol, or vitamin C at 37°C for 2 h resulted in a significant decrease of nickel subsulfide-induced formation of DNA-protein crosslinks, suggesting that nickel subsulfide-induced DNA-protein crosslink formation in isolated rat renal cortical cells is caused by the formation of reactive oxygen species. The potent protective effects of these specific amino acids and Mg2+ against nickel subsulfide-induced DNA-protein crosslink formation in isolated renal cortical cells are due to reduction of cellular uptake of Ni2+ and inhibition of the binding of Ni2+ to deproteinized DNA. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p245-255 (ID taap.1998.8584) Oxidative Stress as a Mechanism of Chronic Cadmium-Induced Hepatotoxicity and Renal Toxicity and Protection by Antioxidants Zahir A. Shaikh, Thanhtam T. Vu, Khalequz Zaman The role of oxidative stress in chronic cadmium (Cd) toxicity and its prevention by cotreatment with antioxidants was investigated. Adult female Sprague-Dawley rats were injected sc with 5 µmol CdCl2/kg/day, 5 times a week, for up to 22 weeks. Serum alanine amino transferase and lactate dehydrogenase activities were elevated after 9 weeks of Cd administration, indicating hepatic damage. Renal toxicity, indicated by elevation in urinary lactate dehydrogenase activity and protein, was also observed around this time. Chronic Cd administration resulted in a gradual rise in hepatic as well as renal cortex glutathione levels. In spite of this, lipid peroxidation increased in both tissues, particularly during the second half of the Cd exposure period. Depletion of glutathione following buthionine sulfoximine administration at the end of Week 5, or inhibition of catalase by aminotriazole at the end of Week 7, resulted in the development of acute nephrotoxicity within 6 h. Coadministration of antioxidants, N-acetylcysteine (50-100 mg/kg, sc), or vitamin E (100-150 mg/kg, sc) with Cd, starting from the early phases of Cd exposure, controlled Cd-induced lipid peroxidation and protected the animals against hepatic as well as renal toxicity. A Japanese hepatoprotective drug, Stronger Neo-Minophagen C, containing glycyrrhizin, glycine, and cysteine, was also effective in reducing the chronic Cd nephrotoxicity. In conclusion, oxidative stress appears to play a major role in chronic Cd-induced hepatic and renal toxicity since inhibition of components of the antioxidant defense system accelerated and administration of antioxidants protected against Cd toxicity. Copyright 1999 Academic Press. Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p256-263 (ID taap.1998.8586) Physiologically Based Pharmacokinetic Modeling of Inhaled Trichloroethylene and Its Oxidative Metabolites in B6C3F1 Mice Marc S. Greenberg, G. Allen Burton, Jeffrey W. Fisher Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p264-278 (ID taap.1998.8594) Characterization of the Dose-Response of CYP1B1, CYP1A1, and CYP1A2 in the Liver of Female Sprague-Dawley Rats Following Chronic Exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin Nigel J. Walker, Christopher J. Portier, Sigurd F. Lax, Frances G. Crofts, Ying Li, George W. Lucier, Thomas R. Sutter Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p279-286 (ID taap.1998.8595) Arsenite Methylation by Methylvitamin B12 and Glutathione Does Not Require an Enzyme Robert A. Zakharyan, H. Vasken Aposhian Toxicology and Applied Pharmacology, v 154, n 3, February 1, 1999, p287-291 (ID taap.1998.8587) |