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At least 1,135 records · Page 63Linked to original sources
PubMed1995

Differential induction of peroxisomal enzymes by hypolipidaemics in human (HepG2) and rat (MH1C1) hepatoma cell lines.

Human (HepG2) and rat (MH1C1) hepatoblastoma cells were incubated with different concentrations of the hypolipidaemics cetaben, clofibrate and thyroxine. The enzymatic activities of catalase, peroxisomal bifunctional enzyme, succinate dehydrogenase, and 3-oxoacyl-CoA thiolase were measured. In order to determine the point of regulation of the enzymatic activities Northern and Slot blot experiments with probes for peroxisomal bifunctional enzyme, catalase and fatty acyl CoA oxidase were performed on total RNA. Catalase activity was enhanced in HepG2 cells treated with 3 mmol/l clofibric acid to 135% of control and the mRNA value to 2.6 fold, whereas in cetaben treated cells the enhancement (up to 119% of control) was less pronounced. In MH1C1 cells catalase activity was not changed by any of the drugs. The activity of the peroxisomal bifunctional enzyme was not affected in HepG2 cells by clofibric acid and cetaben, whereas the mRNA level was elevated to 2.3 fold by 10 micromol/l cetaben. At high concentrations of cetaben all enzyme activities were decreased in both cell lines due to its high cytotoxicity. Our data show that, due to the differences in the genomic organisation, the regulation of the enzyme activities is different in human and rat, but the results from the human and rat hepatoblastoma cells correlate with the findings in whole man and rat, so that a human in vitro system is more suitable for pharmacological tests. These results suggest that the human hepatoma cell line HepG2 may be a useful model system for studies of the influence of hypolipidaemics on the peroxisomal enzyme system.

4-Aminobenzoic Acid↗
PubMed1992

Purification and molecular properties of 2-carboxybenzaldehyde (CBA) reductase from phenobarbital-treated rat liver.

1. A rat liver cytosol enzyme, tentatively named CBA reductase, catalyses the conversion of 2-carboxybenzaldehyde (CBA) to 2-hydroxymethyl benzoic acid in the presence of NADH (or NADPH). CBA reductase is useful for exploring the mechanism of in vitro enzyme induction, as the enzyme can be induced by phenobarbital (PB) both in vivo and in vitro. 2. Possible involvement of glutathione (GSH) in gene expression was suggested by a recent study with cultured rat hepatocytes. 3. CBA reductase was purified about 200-fold by a combination of column chromatography and isoelectric focusing in the presence of mercaptoethanol. 4. The ability to form 2-hydroxymethyl benzoic acid was lost when the enzyme was chromatographed on a hydroxylapatite column in the absence of mercaptoethanol; however, it was restored if sulphydryl compounds or bovine serum albumin was added to the eluate from the column. 5. Gel filtration showed the molecular sizes of CBA reductase from the 105,000g supernatant fraction of rat liver extracts and the purified preparation were 64 kDa and 49 kDa, respectively. 6. The results suggest that sulphydryl substances and some proteins play important roles in preserving the molecular and catalytic properties of CBA reductase.

Alcohol Oxidoreductases↗
PubMed1976

Effect of adenosine 3',5'-monophosphate on serine metabolism in chick tissues.

The effect of cyclic 3',5'-AMP and supplemental dietary glycine upon de novo synthesis of serine metabolic enzymes in chick livers were examined. Chicks fed crystalline amino acid diets containing 2% glycine had approximately twofold the activity in liver for 3-phosphoglycerate dehydrogenase and phosphoserine phosphatase compared to liver tissue from chicks fed diets lacking in dietary glycine. Chicks subjected to daily intraperitoneal injections of cyclic 3',5'-AMP and fed diets containing no dietary glycine contained biosynthetic enzyme activity similar to glycine-fed chicks suggesting a correlation between glycine and cyclic AMP for serine enzyme induction. The elevated enzyme activity in liver of chicks fed dietary glycine or injected with cyclic AMP was inhibited when chicks were also injected with actinomycin D indicating de novo synthesis of 3-phosphoglycerate dehydrogenase and phosphoserine phosphatase. Dietary glycine or cyclic AMP, however, did not change serine dehydratase and glycerate dehydrogenase activities in chick liver.

Animals↗
PubMed2000

Regulation of gamma-glutamyltransferase in cisplatin-resistant and -sensitive colon carcinoma cells after acute cisplatin and oxidative stress exposures.

Glutathione plays an important role in drug resistance of tumor cells and in their ability to resist oxidative stress. Improved salvage of glutathione can be obtained through increased activity of gamma-glutamyltransferase (GGT), which is of importance in the maintenance of cellular glutathione homeostasis. We investigated the regulation of GGT in 2 cisplatin-resistant and 1 cisplatin-sensitive colon carcinoma cell lines. Enzyme activity was induced in all 3 cell lines after acute exposure to cisplatin. The elevation was significantly higher in sensitive cells (3.3-fold) than in resistant (1.6- to 1.7-fold) cells. Exposure of cells to oxidative stress generated by menadione also resulted in enzyme induction but only in cisplatin-sensitive cells. Addition of anti-oxidants had different effects on the 2 inductions: N-acetylcysteine blocked the induction of both cisplatin and menadione, whereas catalase and glutathione-ester blocked only the menadione induction. Glutathione depletion alone was not sufficient to induce GGT in these cells. The data show that GGT is regulated by multiple mechanisms during anti-tumor drug treatment and oxidative stress and that reactive oxygen species were involved in the menadione, but not cisplatin, induction of the enzyme.

Antineoplastic Agents↗
PubMed2001

Induction of antioxidative enzyme by the ayurvedic herb Desmotrichum fimbriatum Bl. in mice.

The herb Desmotrichum fimbriatum Bl. (family: Orchidaceae), sold as Jibanti in West Bengal, is used in 'Rasayana therapy' in Ayurveda. Its effect on the modulation of the two antioxidant enzymes peroxidase and catalase has been studied in mice liver during 'cold water swim' (CWS) stress using appropriate controls. The drug, i.e. the aqueous ethanolic extract of the herb (whole plant) was found to increase peroxidase titre in the hepatic cells of normal mice. But in the stressed group, the drug displayed no effect on the peroxidase content, while it elicited an elevation of the catalase content. infinity-Tocoferol was used as the standard drug. These data suggested that the drug can ameliorate the peroxidative damage caused in mice by CWS stress.

Animals↗
PubMed1978

Induction of bacteriolytic enzyme from pyocinogenic Pseudomonas aeruginosa and its enzymatic properties.

Mitomycin C induced a pyocinogenic Pseudomonas aeruginosa P15 to produce a bacteriolytic enzyme, PR1-lysozyme, together with pyocin R1. No significant accumulation of the enzyme was observed inside the induced cells. The enzyme was partially purified by acrinol treatment and Amberlie CG-50 column chromatography. The mode of action of the enzyme on the host bacterial cells as well as on Micrococcus lysodeikticus cells or peptidoglycan isolated from Salmonella typhimurium, was compared with that of hen egg-white lysozyme or phage lambda-lysozyme. It is suggested that PR1-lysozyme should be classified as a glycosidase, rather than an amidase or an endopeptidase.

Bacteriolysis↗
PubMed1975

[Role of estrogens in phenobarbital induction of microsomal enzymes of the liver].

The action of estradiol dipropionate (250 microgram/kg) and of phenobarbitone-sodium salt (80 microgram/kg) was studied in separate and combined (a single injection of estradiol-dipropionate after a 4-day administration of the phenobarbital-sodium salt) administration. There was an increase in the H3-phenylalanine incorporation into the cell-free protein-synthesizing system by 86% in comparison with control ovariectomized group. Under these conditions estradiol-dipropionate increased the incorporation of the labeled amino acid by 53%. A combined administration of the estrogen and of the barbiturate was not accompanied by the summation of the given effect. There was revealed a correlation between the increase in the rate of the H3-phenylalanine incorporation in vitro and an increase in the content of the cytochrome P-450 in vivo in the microsomes of hepatocytes in separate and combined administration of the preparations. The role of phenobarbitone-sodium salt as an activator of estradiol metabolism in the hepatocytes is discussed.

Animals↗
PubMed1991

[The significance of PCDD's/PCDF's (dioxins) in pediatrics].

No epidemiological data are available up to now which reveal adverse effects induced by dioxins during an exposure through breast milk. Furthermore, very few data on the concentration of PCDDs/PCDFs in the newborn and during the first year of life have been published. Of all PCDDs/PCDFs, the substance with the highest toxicity is 2,3,7,8-tetrachlorodibenzo-p-dioxin. However, in the environment this congener is often only a minor component. A sensitive biological effect triggered by TCDD is the enzyme induction of hepatic monooxygenases. Using a 14CO2-breath-test the apparent enzyme induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) of the metabolic conversion of [3-methyl14C]-caffeine was studied during the perinatal period in Wistar rats and in a non-human-primate (marmoset, Callithrix jacchus). It could be shown that the apparent induction of monooxygenase activity by TCDD in rat offspring as measured with the breath-test, is dose-dependent and mainly achieved by postnatal exposure via mothers' milk. Our data indicate that caffeine is a convenient substrate for studying monooxygenase activities (probably P450 IA-dependent) to be induced by TCDD, and very likely also by other congeners. These results, therefore, may provide the rationale for applying a [13C]-caffeine breath-test in human newborn and infants to analyse possible biological effects induced by TCDD and similar pollutants in breast-fed children. Since PCDDs/PCDFs are pollutants without any benefit, strong efforts should be continued to further reduce the output of dioxins, the human exposure, and thereby also concentrations in human milk.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Pretreatment with phenobarbitone modifies suppressant effect of cyclosporine on wound healing.

Cyclosporine has been reported to suppress the tensile strength of healing incision wound. Prednisolone, an inducer of hepatic microsomal enzymes, abolished the tensile strength suppressant effect of cyclosporine. Cyclosporine is metabolized by the hepatic cytochrome P-450 enzymes. Induction of microsomal enzymes with phenobarbitone was evaluated for its effect upon the wound healing suppressant effect of cyclosporine. Pretreatment of male rats with phenobarbitone (75 mg/kg/day, ip) for 3 days resulted in alleviating the tensile strength suppressant effect of cyclosporine (5 mg/kg/day, po for 10 days). Phenobarbitone, per se, did not affect the tensile strength. That phenobarbitone prevents cyclosporine induced nephrotoxicity without affecting the humoral immunosuppressant action of cyclosporine has recently been reported. The possibility of modulating microsomal enzymes with phenobarbitone offers another approach in preventing cyclosporine-associated toxicities during immunosuppression.

Animals↗