thioacetamide and bromobenzene

In the field of gene expression analysis, DNA microarray technology has a major impact on many different areas including toxicogenomics, such as in predicting the adverse effects of new drug candidates and improving the process of risk assessment and safety evaluation. In this study, we investigated whether there is relationship between the hepatotoxic phenotypes and gene expression profiles of hepatotoxic chemicals measured by DNA microarray analyses. Sprague-Dawley rats (6 weeks old) were administered five hepatotoxicants: acetaminophen (APAP), bromobenzene, carbon tetrachloride, dimethylnitrosamine, and thioacetamide. Serum biochemical markers for liver toxicity were measured to estimate the maximal toxic time of each chemical. Hepatic mRNA was isolated, and the gene expression profiles were analyzed by DNA microarray containing 1,097 drug response genes, such as cytochrome P450s, other phase I and phase II enzymes, nuclear receptors, signal transducers, and transporters. All the chemicals tested generated specific gene expression patterns. APAP was sorted to a different cluster from the other four chemicals. From the gene expression profiles and maximal toxic time estimated by serum biochemical markers, we identified 10 up-regulated genes and 10 down-regulated genes as potential markers of hepatotoxicity. By Quality-Threshold (QT) clustering analysis, we identified major up- and down-regulated expression patterns in each group. Interestingly, the average gene expression patterns from the QT clustering were correlated with the mean value profiles from the biochemical markers. Furthermore, this correlation was observed at any extent of hepatotoxicity. In this study, we identified 17 potential toxicity markers, and those expression profiles could estimate the maximal toxic time independently of the hepatotoxicity levels. This expression profile analysis could be one of the useful tools for evaluating a potential hepatotoxicant in the drug development process.

Topics: Acetaminophen; Alkaline Phosphatase; Animals; Bromobenzenes; Carbon Tetrachloride; Dimethylnitrosamine; Gene Expression Profiling; L-Lactate Dehydrogenase; Liver; Male; Rats; Rats, Sprague-Dawley; Thioacetamide

The hepatic lesion produced as a result of oxidative stress is of wide occurrence. In the present study, the effect of tungsten on liver necrosis and fulminant hepatic failure (FHF) has been studied in rats treated with various compounds known to produce oxidative stress. Supplementation of animals with sodium tungstate for 7 weeks before the induction of liver injury by chemicals including thioacetamide (TAA), carbon tetrachloride (CCl(4)), or chloroform (CHCl(3)) could protect progression of hepatic injury. Various biochemical changes associated with liver damage and oxidative stress were measured. Hepatic malondialdehyde content, endogenous tripeptide, and reduced glutathione were measured as oxidative stress markers. The activity of xanthine oxidase, which generates reactive oxygen species (ROS) as a by-product, was also determined and found to be perturbed. Tungsten supplementation to rats caused a significant decrease in lipid peroxidation and lowered the levels of the biochemical markers of hepatic lesions produced by TAA, CCl(4) (CCl(4)), or CHCl(3). Tungsten could also cause an increase in the survival rate in rats receiving lethal doses of TAA, CCl(4), or CHCl(3). The protective effect of tungsten, however, is suggested to be limited to the conditions where the hepatic lesion is reported to be due to the generation of ROS. The progression of liver injury produced by the compounds causing oxidative stress without initiating the generation of free radicals such as bromobenzene (BB), or acetaminophen (AAP), could not be inhibited by tungsten. The possible mechanism explaining the role of oxyanionic form of tungsten in free radical-induced hepatic lesions is discussed.

Topics: Acetaminophen; Alkaline Phosphatase; Allopurinol; Animals; Bromobenzenes; Carbon Tetrachloride Poisoning; Chloroform; Dimethyl Sulfoxide; Female; Lethal Dose 50; Liver; Liver Failure; Necrosis; Oxidative Stress; Rats; Rats, Wistar; Thioacetamide; Transaminases; Tungsten Compounds

Syngenic fetal liver tissue suspensions were transplanted into the spleens of adult male Fisher 344 inbred rats. Four months after surgery, transplant recipients and age matched control rats were treated with different cytotoxins (allyl alcohol [AAL], bromobenzene [BBZ], carbon tetrachloride [CCl4], or thioacetamide [TAA]) or the respective solvents 24 or 48 hours before sacrifice. Effects of the cytotoxins on P450 mediated monooxygenase functions in liver and spleen 9,000 g supernatants were assessed by measuring the model reactions ethoxyresorufin O-deethylation (EROD), ethoxycoumarin O-deethylation (ECOD), pentoxyresorufin O-depentylation (PROD), and ethylmorphine N-demethylation (EMND). Additionally, the influence on the oxidative state was investigated by assessing the liver and spleen tissue content of lipid peroxidation (LPO) products and of reduced and oxidized glutathione (GSH;GSSG). The livers of both solvent treated transplant recipients and control rats displayed regular EROD, ECOD, PROD and EMND activities. After AAL treatment EROD and EMND activities within the livers were not affected, but ECOD and PROD activities were increased. BBZ administration caused a decrease in EROD and EMND activities, ECOD activity remained unaffected, and PROD activity was even increased. CCl4 and TAA administration caused a strong reduction in the activity of all four model reactions. Spleens of control rats displayed almost no P450 mediated monooxygenase functions, independent whether the rats had been treated with the cytotoxins or not. In the transplant containing spleens, however, significant EROD and ECOD, but hardly any PROD or EMND activities were seen. After AAL administration EROD activity was not affected in the transplant containing spleens, but ECOD activity was increased. BBZ treatment led to a decrease in EROD and an elevation in ECOD activity. CCl4 and TAA strongly reduced the activity of both of these model reactions. The tissue content of LPO products within livers and transplant containing spleens was significantly increased after BBZ and CCl4 treatment. An elevation in LPO products was also seen in the spleens of the control rats due to CCl4 administration. Tissue GSH and GSSG content in both livers and transplant containing spleens were strongly reduced after BBZ treatment. After CCl4 administration only a significant decrease in liver GSSG contents was seen. TAA treatment caused a reduction in the GSH and GSSG content in the spleens of both

Topics: 7-Alkoxycoumarin O-Dealkylase; Animals; Bromobenzenes; Carbon Tetrachloride; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP2B1; Cytochrome P-450 Enzyme System; Cytotoxins; Ethylmorphine-N-Demethylase; Female; Fetal Tissue Transplantation; Glutathione; Hepatocytes; Lipid Peroxidation; Male; Pregnancy; Propanols; Rats; Rats, Inbred F344; Spleen; Thioacetamide

Syngenic fetal liver tissue suspensions were transplanted into the spleens of adult male Fisher 344 inbred rats. Four months after surgery, transplant recipients and age matched control rats were treated with different cytotoxins (allyl alcohol [AAL], bromobenzene [BBZ], carbon tetrachloride [CCl4], or thioacetamide [TAA]) or the respective solvents 24 or 48 hours before sacrifice. Effects of the cytotoxins on the expression of three cytochrome P450 (P450) isoforms, 1A1, 2B1 and 3A2, within spleens and livers were assessed by immunohistochemistry. Additionally, effects on glycogen content within the hepatocytes were examined. In the livers AAL caused small lesions and fatty degeneration of hepatocytes only in some periportal areas. BBZ led to a perivenous necrosis of single cells only, whereas CCl4 and TAA caused complete necrosis of the centrilobular parenchyma. Treatment with each of the four cytotoxins led to necrosis and fatty degeneration of single or groups of hepatocytes within the intrasplenic transplants. This effect was most pronounced with CCl4 and TAA. The orthotopic livers of both solvent treated transplant recipients and control rats displayed only in few lobules a slight P450 1A1, but in all lobules a strong P450 2B1 and 3A2 expression, all mainly located in the hepatocytes around the central veins. AAL administration led to an increase in the P450 2B1 expression in the perivenous hepatocytes, whereas the staining for P450 1A1 was not affected and that for P450 3A2 in the periportal areas was even decreased. BBZ administration caused a P450 1A1 expression in the periportal hepatocytes but a decrease in this staining of the perivenous cells. The number of hepatocytes positively stained for P450 2B1 and 3A2 in the perivenous and intermediate zones was diminished in comparison to the livers of solvent treated rats. TAA and, more pronounced, CCl4 administration caused a strong reduction in the expression of all three P450 isoforms. Spleens of control rats displayed almost no P450 isoforms expression, independent of the treatment with the cytotoxins. Similar to adult liver, the hepatocytes in the transplant containing spleens showed nearly no P450 1A1, but a noticeable P450 2B1 and 3A2 expression. No staining was observed within the bile duct cells of the intrasplenic transplants. AAL administration slightly reduced the P450 2B1 and 3A2 expression in the transplants. BBZ and, much more pronounced, CCl4 and TAA treatment diminished the staining f

Topics: Animals; Bromobenzenes; Carbon Tetrachloride; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP2B1; Cytochrome P-450 Enzyme System; Fetal Tissue Transplantation; Hepatocytes; Liver Glycogen; Organ Size; Propanols; Rats; Rats, Inbred F344; Spleen; Steroid Hydroxylases; Suspensions; Thioacetamide; Transplantation, Heterotopic

A 24-hr oral pretreatment of rats with 1.6 g/kg acetaminophen potentiated hepatotoxicity of allyl alcohol, bromobenzene, carbon tetrachloride, 1,1-dichloroethylene, and thioacetamide, as assessed by elevation of serum alanine aminotransferase activity and histopathological examination. Doses, of these hepatotoxicants, which did not cause hepatocellular necrosis, became necrogenic after acetaminophen pretreatment with all toxicants except thioacetamide. Acetaminophen pretreatment did not decrease the threshold dose of toxicity for thioacetamide but did accentuate hepatotoxic doses. Acetaminophen pretreatment potentiated lethality of allyl alcohol and 1,1-dichloroethylene. Upon necropsy, these rats had congested livers and appeared to suffer from hypovolemic shock. We conclude that while acetaminophen was not necrogenic at the doses used in this study, it produced alterations that make hepatocytes much more susceptible to hepatotoxic insult.

Topics: 1-Propanol; Acetaminophen; Alanine Transaminase; Animals; Bromobenzenes; Carbon Tetrachloride; Dichloroethylenes; Drug Synergism; Liver; Male; Models, Biological; Propanols; Rats; Rats, Inbred Strains; Thioacetamide; Time Factors

Pretreatment of rats with zinc-protoporphyrin, which has shown to be a potent competitive inhibitor of heme oxygenase, resulted in the inhibition of bromobenzene-mediated induction of heme oxygenase and decreases of the cytochrome P-450 content, aminopyrine demethylase and aniline hydroxylase activities. Such an inhibitory effect of zinc-protoporphyrin on the induction of heme oxygenase and concomitant decreases of drug-metabolizing enzymes occurred in a dose-dependent manner with complete inhibition of these effects at a dose of 40 mumol/kg. The effects of zinc-protoporphyrin were also observed in thioacetamide- and BCG-treated rats and ascitic tumor AH 66-bearing rats. Likewise, a decrease of cytochrome b5 content observed under these experimental conditions was also restored significantly by zinc-protoporphyrin. These results strongly suggest that the induction of heme oxygenase is a primarily important early event which consequently leads to the decrease in cytochrome P-450 content and associated enzyme activities.

Topics: Aminopyrine N-Demethylase; Aniline Hydroxylase; Animals; Bromobenzenes; Cytochrome b Group; Cytochrome P-450 Enzyme System; Drug Interactions; Enzyme Induction; Female; Heme Oxygenase (Decyclizing); Male; Microsomes, Liver; Mixed Function Oxygenases; Neoplasms, Experimental; Porphyrins; Protoporphyrins; Rats; Rats, Inbred Strains; Thioacetamide

Sulphoxidation of cimetidine was investigated in male and female rats after pretreatment with the hepatotoxins allyl alcohol, dl-ethionine, thioacetamide and carbon tetrachloride. There was a marked sex difference in cimetidine sulphoxidation in response to the hepatotoxin pretreatment. All the hepatotoxins enhanced cimetidine sulphoxidation in the male rat (P less than 0.01). Carbon tetrachloride and thioacetamide inhibited cimetidine sulphoxidation in the female rat (P less than 0.01) but dl-ethionine and allyl alcohol had no effect on this metabolic pathway.

Topics: 1-Propanol; Animals; Bromobenzenes; Carbon Tetrachloride Poisoning; Chemical and Drug Induced Liver Injury; Cimetidine; Propanols; Rats; Rats, Inbred Strains; Sulfoxides; Thioacetamide

Topics: Acetonitriles; Amides; Benzene; Bromobenzenes; Cyanides; Liver; Liver Diseases; Necrosis; Tannins; Thioacetamide