• Toxicological Research
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• v.14 no.4
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• pp.525-533
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• 1998

The covalent interactions of toluenediisocyanate (TDI) with macromolecules were investigated both in vitro and in vivo. In vitro incubations of 2,4- and 2,6-TDI with DNA or proteins resulted in dose-dependent formation of TDI-protein and TDI-DNA adducts. TDI-treated DNA was highly resistant to enzymatic digestion and thermal hydrolysis, but was readily hydrolyzed under acidic conditions by releasing its corresponding toluenediamine (TDA), suggesting that TDI caused the crosslinking of DNA. Reaction of TDI with albumin and globin resulted in the formation of several adducts, and some adducts were formed in blood of TDI-treated rats in a dose-dependent fashion. Administration of TDI to rats resulted also in a dose-dependent binding of TDI to hepatic tissue. Levels of TDI-albumin adducts were 10 times higher than those of TDI-globin adducts; the biological half lives of TDI-albumin and TDI-globin adducts were 1.2 and 12.5 days, respectively. Globin adducts were detected up to 28 days after the treatment. Hepatic TDI protein adducts were persistent for a substantial period whereas the levels of hepatic TDI-DNA adduct were decreased rapidly. These results indicate that the isocyanato group of TDI is not readily hydrolyzed under physiological conditions, is transported to other organs, and is bound to DNA and/or proteins without further metabolic activation. As the adducted products degrade in the body, TDA is released and introduced to the liver. TDA may additionally bind to hepatic tissue after metabolic activation. Thus, the toxic effect of TDI exposure is considered to persist during the lifetime of the adducted biological macromolecules.

• Toxicological Research
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• v.13 no.3
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• pp.257-263
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• 1997

Pentachlorophenol(PCP) which ks widely used in wood preservation, pulp and paper mills, has led to a substantial envirortmental contamination. To get the reliable data for the effective health risk assessment with PCP, covalent binding potential of PCP to cellular macromolecules and glutathione(GSH) was investigated after intraperitoneal administration of $^{14}C-PCP$ to rats. PCP metabolites were able to bind covalently to serum albumin and hepatic protein in a dose- and time-dependent manner. Hepatic protein adducts of PCP metabolites were increased as a function of cytochrome P-450 activities, whereas, albumin adducts significantly decreased. Covalent binding of PCP metabolites with DNA or hemoglobin was not observed. GSH levels in liver tissue decreased over 12hrs, however, the level was recovered after 48hrs. Tetrachloro-1,4-benzoquinone (1,4-TCBQ), one of the most reactive PCP metabolites, conjugated with GSH very rapidly. Base on our results, we could conclude that PCP metabolized to reactive electrophilic metabolites by cytochrome P-450 isoenzymes and conjugated rapidly with neighboring protein or nonprotein sulfhydryl before reacting with DNA or hemoglobin. We propose that albumin adducts and mercapturic acids of PCP metabolites can be used good biomarker of recent PCP exposure.

• Proceedings of the Korean Society of Toxicology Conference
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• 2000.11a
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• pp.45-67
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• 2000

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) is a mutagenic and carcinogenic heterocyclic amino found in cooked meat. The in vivo mutagenicity and hepatocarcinogenicity of MeIQx were examined in mice harboring the lacZ mutation reporter gene ($Muta^{TM}$ Mice) and bitransgenic mice over-expressing the c-myc oncogene. C57B1/$\lambda$lacZ and bitransgenic c-myc (albumin promoter)/$\lambda$lacZ mice were bred and weaned onto an AIN-76 based diet containing $0.06\%$ (w/w) MeIQx or onto control diet. After 30 weeks on diet, only male bitransgenic mice on MeIQx developed hepatocellular carcinoma ($100\%$ incidence) indicating that there was synergism between c-myc over-expression and MeIQx. By 40 weeks, hepatic tumor incidence was $100\%$ ($17\%$) and $44\%$ ($0\%$) in male c-myc/$\lambda$lacZ and C57B1/$\lambda$lacZ mice given MeIQx (or control) diet, respectively, indicating that either MeIQx or c-myc over-expression alone eventually induced hepatic tumors. At either time point, mutant frequency in the lacZ gene was at least 40-fold higher in MeIQx-treated mice than in control mice of either strain. These findings suggest that MeIQx-induced hepatocarcinogenesis is associated with MeIQx-induced mutations. Elevated mutant frequency in MeIQx-treated mice also occurred concomitant with the formation of MeIQx-guanine adducts as detected by the $^{32}P$-postlabeling assay. Irrespective of strain or diet, sequence analysis of the lacZ mutants from male mouse liver showed that the principal sequence alteration was a single guanine-base substitution. Adenine mutations, however, were detected only in animals on control diet. MeIQx-fed mice harboring the c-myc oncogene showed a l.4-2.6-fold higher mutant frequency in the lacZ gene than mice not carrying the transgene. Although there was a trend toward higher adduct levels in c-myc mice, MeIQx-DNA adduct levels were not significantly different between c-myc/$\lambda$lacZ and C57B1/$\lambda$lacZ mice after 30 weeks on diet. Thus, it appeared that factors in addition to MeIQx-DNA adduct levels, such as the enhance rate of proliferation associated with c-myc over-expression, may have accounted for a higher mutant frequency in c-myc mice. In the control diet groups, the lacZ mutant frequency was significantly higher in c-myc/$\lambda$lacZ mice than in 057B1/$\lambda$1acZ mice. The findings are consistent with the notion that c-myc over-expression is associated with an increase in mutagenesis. The mechanism for the synergistic effects of c-myc over-expression on MeIQx hepatocarcinogenicity appears to involve an enhancement of MeIQx-induced mutations.

• Herbal Formula Science
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• v.19 no.1
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• pp.145-160
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• 2011

Objectives : Rehmannia glutinosa has been used extensively in Korean traditional medicine. Although thorough clinical trials are lacking, Various pharmacological actions for Rehmannia glutinosa has been identified newly using animal models. In addition, it was reported that reactive intermediates, potentially causing toxic effects, was isolated from one of components in Rehmannia glutinosa. In this article, it is purposed for explanation and introduction of new studies for Rehmannia glutinosa in terms of pharmacological action and toxicology. Methods : New studies for Rehmannia glutinosa were reviewed and summarized in terms of pharmacological action and toxicity. Results and Conclusions : Rhmannia glutinosa and its components including iridoids, saccharides, as well as amino acid, showed a variety of pharmacological actions on the blood system, immune system, endocrine system, cardiovascular system and the nervous system. In addition, it was identified that aucubin, one of major components of Rhmannia glutinosa was biotransformed to reactive intermediates by ${\beta}$-glycosidase and acid-hydrolysis, resulting in forming aucubigenin- albumin adduct. Even if a lot of new pharmacological actions has been identified, it should be considered for Rhmannia glutinosa to contain the material producing reactive intermediates which may induce the side effects.

• BMB Reports
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• v.31 no.2
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• pp.161-169
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• 1998

TThe reactive oxygen species oxidatively modify the biological macromolecules, including proteins, lipids, and nucleic acids. Iron- and heme-mediated Fenton-like reactions produce different pro-oxidants. However, these reactive products have not been clearly characterized. We examined the nature of the oxidizing species from the different iron sources by measuring oxidative protein modification and spectroscopic study. Hemoglobin (Hb) and methemoglobin (metHb) were oxidatively modified in $O{\array-\\\dot{2}}$ and $H_{2}O_{2}$ generating systems. Globin and bovine serum albumin (BSA) were also modified by iron, iron-EDTA, hematin, and Hb in an $O{\array-\\\dot{2}}$ generating system. In a $H_{2}O_{2}$ generating system, the iron- and iron-EDTA-mediated protein modifications were markedly reduced while the Hb-and hematin-mediated modifications were slightly increased. In the $O{\array-\\\dot{2}}$ generating system, the iron- and iron-EDTA-mediated protein modifications were strongly inhibited by superoxide dismutase (SOD) or catalase, but heme- and Hb-mediated protein modifications were inhibited only by catalase and slightly increased by SOD. Mannitol, 5,5-dimethyl-l-pyrroline-N-oxide (DMPO), deoxyribose, and thiourea inhibited the iron-EDTA-mediated protein modification. Mannitol and DMPO, however, did not exhibit significant inhibition in the hematin-mediated modification. Desferrioxamine (DFO) inhibited protein modification mediated by iron, but cyanide and azide did not, while the hematin-mediated protein modification was inhibited by cyanide and azide, but not significantly by DFO. The protein-modified products by iron and heme were different. ESR and UV-visible spectroscopy detected the DMPO spin adduct of the hydroxyl radical and ferryl ion generated from iron-EDTA and metHb, respectively. These results led us to conclude that the main oxidizing species are hydroxyl radical in the iron-EDTA type and the ferry I ion in the hematin type, the latter being more effective for protein modification.