vitamin-k-semiquinone-radical and phorone

Inducibility of oxidative stress in rat liver in vivo by menadione-associated redox cycling activation under redox enzyme modulating conditions was examined by monitoring hepatocyte injury and 8-hydroxydeoxyguanosine (8-OHdG) levels of liver DNA. In addition, the treatment-associated liver tumor initiating activity was assessed in terms of development of gamma-glutamyl-transpeptidase (GGT)- and glutathione S-transferase placental form (GST-P)-positive foci and hyperplastic nodules. With or without following menadione treatment (50 mg/kg, i.g.), redox enzyme modulations of increased cytochrome P450 reductase activity induced by phenobarbital (PB)-Na (100 mg/kg, i.p. for 5 days), inhibition of DT-diaphorase by dicumarol (25 mg/kg, i.p.) and depletion of glutathione by phorone (200 mg/kg, i.p.), with or without further supplement of iron EDTA-Na-Fe(III) (70 mg/kg, i.p.), caused both substantial hepatocyte necrosis and 8-OHdG production in Fischer 344 male rats. Subsequent feeding with a 0.05% PB diet for 64 weeks resulted in slightly increased development of GGT-positive foci but not GST-P positive lesions or hyperplastic nodules, suggesting a lack of tumor-initiating activity of the oxidative DNA damage associated with redox enzyme modulations with or without menadione.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Body Weight; Cytochrome Reductases; Deoxyguanosine; Dicumarol; DNA; DNA Damage; gamma-Glutamyltransferase; Glutathione; Iron; Ketones; Liver; Liver Neoplasms, Experimental; Male; NAD(P)H Dehydrogenase (Quinone); Necrosis; Neoplasms, Experimental; Organ Size; Oxidation-Reduction; Phenobarbital; Quinone Reductases; Rats; Rats, Inbred F344; Time Factors; Vitamin K

Metallothionein (MT) is a low-molecular-weight protein with a high cysteine content that has been proposed to play a role in protecting against oxidative stress. For example, MT has been shown to be a scavenger of hydroxyl radicals in vitro, and cells with high levels of MT are resistant to radiation. However, it is not known if compounds that cause oxidative stress affect MT levels. Therefore, mice were injected subcutaneously with 11 chemicals (t-butyl hydroperoxide, paraquat, diquat, menadione, metronidazole, adriamycin, 3-methylindole, cisplatin, diamide, diethyl maleate, and phorone) that produce oxidative stress by four main mechanisms. MT was quantitated in the cytosol of major organs (liver, pancreas, spleen, kidney, intestine, heart, and lung) by the Cd/hemoglobin radioassay 24 hr after administration of the chemicals. All agents significantly increased MT levels in at least one organ. Liver was the most responsive to these agents in that all 11 chemicals increased MT concentrations in liver, with diethyl maleate, paraquat, and diamide producing 20- to 30-fold increases. Pancreas and kidney were the next most responsive organs to these chemicals. The organ least responsive to these agents was the heart, as only 3 compounds caused significant increases in MT concentrations in heart. Diethyl maleate and diquat were the most general inducers of MT in that they increased MT in six of the seven organs examined. No treatment resulted in a significant decrease in MT concentration in any organ. In conclusion, chemicals that produce oxidative stress by one of four distinct mechanisms are very effective at increasing MT concentrations in a variety of organs. This suggests that MT might be involved in protecting against oxidative stress.

Topics: Animals; Cisplatin; Cytosol; Diamide; Diquat; Doxorubicin; Ketones; Liver; Male; Maleates; Metallothionein; Metronidazole; Mice; Mice, Inbred Strains; Organ Specificity; Paraquat; Peroxides; Skatole; tert-Butylhydroperoxide; Vitamin K

The aim of this study has been to define cytotoxic mechanisms that may cause clonal expansion in the liver of pre-carcinogenic cells. An in vitro model, which has been described previously, was used. Hepatocytes were isolated from carcinogen-treated rats and a high proportion of the cells were gamma-glutamyltranspeptidase (GGT)-positive. The cells were incubated in suspension and exposed to toxic agents in concentrations that induced a moderate increase in cellular leakage within 3 h. Samples were withdrawn and sampled cells were then allowed to attach to collagen-coated plates. Attached cells were stained and the ratio of GGT-positive/GGT-negative cells (GGT-ratio) was determined. The initial GGT-ratio was 10.4 +/- 4.7% and an increased ratio was taken as a sign of toxicity that resulted in a selection of GGT-positive cells. In a first series of experiments it was shown that hydroquinone and menadione increase the GGT-ratio, while diquat, sodium selenite, diethyl maleate or phorone do not. However, diethyl maleate in combination with diquat increased the GGT-ratio. Hydrogen peroxide (5 mM) increased the GGT-ratio as effectively as hydroquinone (0.3 mM). Lower concentrations of H2O2 (0.05 mM) increased the GGT-ratio in GSH-depleted cells. The changes induced by hydroquinone and H2O2 in low concentration were reversible. In another series of experiments, plates coated with antibodies against beta 1-integrin were used. An increase in the GGT-ratio was obtained with anti beta 1-integrin, but not with broad spectrum anti-rat hepatocyte or anti-rat beta 2-microglobulin antibodies as substrata. These data suggested an involvement of the beta 1-integrin in the selection. Taken together, these data indicate that GGT-positive hepatocytes are protected against GSH depletion and oxidative stress that may result in reversible receptor alterations.

Topics: Animals; Biomarkers, Tumor; Cell Transformation, Neoplastic; Cells, Cultured; Collagen; Diethylnitrosamine; Diquat; Female; gamma-Glutamyltransferase; Glutathione; Hydrogen Peroxide; Hydroquinones; Ketones; Kinetics; Liver; Maleates; Phenobarbital; Rats; Receptors, Cell Surface; Receptors, Collagen; Selenium; Sodium Selenite; Vitamin K

In perfused rat liver menadione elicits substantial oxidation in both the NADPH and GSH redox systems. Biliary excretion of GSSG is increased several-fold. Menadione derivatives appear in the bile predominantly as the menadione-S-glutathione conjugate, thiodione (60%), or as conjugates derived therefrom (17%). About 10% appear as menadione glucuronides. The excretion of taurocholate into bile is strongly inhibited upon menadione infusion. The inhibition of taurocholate excretion is small in livers with a low content of Se-GSH-peroxidase and in glutathione-depleted livers. In these livers intracellular GSSG and biliary GSSG release remain at low values, although menadione still imposes oxidative stress as indicated by an oxidation of intracellular NADPH. Under anoxic conditions menadione has little influence on both the NADPH and GSH redox systems and also on biliary taurocholate excretion. The amount of thiodione released into bile is similar to that found under normoxia, whereas the amount of glucuronidated products almost doubled. We conclude (a) that intracellular formation of GSSG by menadione occurs via the generation of hydrogen peroxide; (b) that the inhibition of biliary taurocholate excretion by menadione is related to the increased formation of glutathione disulfide; and (c) that menadione derivatives show little, if any, contribution to the inhibition of taurocholate excretion.

Topics: Adenosine Triphosphate; Animals; Bile; Dose-Response Relationship, Drug; Glutathione; Hypoxia; Ketones; Liver; Male; NADP; Perfusion; Rats; Rats, Inbred Strains; Selenium; Taurocholic Acid; Vitamin K

Treatment of male mice with the redox cycling compounds nitrofurantoin, paraquat, diquat or menadione failed to elicit in vivo lipid peroxidation as evidenced by ethane exhalation. The first three led to an enhanced ethane production, however, when the animals were pretreated with a low dose of Fe2+. While GSH-depletion by phorone pretreatment alone had no influence on the in vivo lipid peroxidation as evidenced by ethane expiration in the presence of either compound, the combined treatment with phorone, Fe2+ and nitrofurantoin, paraquat or diquat led to a further enhancement of ethane exhalation. These results indicate that redox cycling compounds do not initiate lipid peroxidation by themselves, but are well capable of stimulating the iron-induced LPO.

Topics: Animals; Breath Tests; Diquat; Ethane; Ferrous Compounds; Glutathione; Iron; Ketones; Lipid Peroxides; Male; Mice; Nitrofurantoin; Oxidation-Reduction; Paraquat; Vitamin K