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Results for “Benzopyrene Hydroxylase”

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At least 19 recordsLinked to original sources
PubMed1980

[Effect of the combined and separate administration of phenobarbital and 3-methylcholanthrene on liver benzopyrene hydroxylases in "sensitive" and "resistant" inbred mice].

Combined induction of liver monooxygenases with 3-methylcholanthrene (3-MC) and phenobarbital (PB) has been studied in experiments on DBA/2 and C57B/6 mice. As is known, PB increases the number of intracellular receptor sites for polycyclic hydrocarbons. When DBA/2 mice resistant to the induction were pretreated with PB, there were no signs of induction common to those induced by 3-MC. In similar experiments with the sensitive C57BL/6 mice, PB and 3-MC produced additive effects on the induction of liver monooxygenases.

Animals↗
PubMed1987

[Determination of benzopyrene-hydroxylase (cytochrome P-450) activity in patients with lung cancer].

The study was concerned with comparison of inducibility index (ii) for benzopyrene-hydroxylase in mitogen-activated lymphocytes in patients with primary cancer of the lung, other cancers (breast, stomach, lower lip, rectum, skin and thyroid gland) and in lymphocytes of blood donors. The highest ii values were registered in bronchogenic carcinoma patients. Smokers, both lung cancer patients and healthy donors, revealed high values (80.0 and 83.3%, respectively). A modified "lymphocytic test" to assess the risk factor for primary lung cancer is suggested.

Adult↗
PubMed1982

Effects of protein-degradation inhibitors on the inactivation of tyrosine aminotransferase, tryptophan oxygenase and benzopyrene hydroxylase in isolated rat hepatocytes.

The following three potent inhibitors of hepatocytic proteolysis were investigated to see if they would inhibit the intracellular inactivation of enzymes: chymostatin and leupeptin (proteinase inhibitors) and methylamine (a lysosomotropic weak base). Chymostatin inhibited the inactivation of two of the three enzymes tested: tyrosine aminotransferase (EC 2.6.1.5) and tryptophan oxygenase (tryptophan 2,3-dioxygenase, EC 1.13.11.11). Leupeptin had no effect on any of the enzymes, whereas methylamine had only a weak inhibitory effect on tyrosine aminotransferase inactivation. Apparently proteolytic cleavage (probably by a non-lysosomal proteinase, since only chymostatin is effective) is involved in the inactivation of tyrosine aminotransferase and tryptophan oxygenase. The third enzyme, benzopyrene hydroxylase (flavoprotein-linked mono-oxygenase, EC 1.14.14.1), is probably inactivated by a non-proteolytic mechanism.

Animals↗
PubMed1984

[Correlation between cytochrome P-448 content and benzopyrene hydroxylase activity during the induction of microsomal monooxygenases using methylcholanthrene-type xenobiotics].

Using antibodies against electrophoretically homogeneous cytochrome P-448 from rat liver microsomes induced by 3-methylcholanthrene, the changes in the immunologic identity and contents by cytochrome P-448 induced by 3-methylcholanthrene, 3.4-benzpyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), were studied. No cytochrome P-448 was detected in the liver microsomes of control or phenobarbital-induced rats. This form of the cytochrome makes up to about 35% of the total content of the CO-binding hemoprotein during TCDD induction and up to 90% during 3-methylcholanthrene and 3,4-benzpyrene induction. On the other hand, 3-methylcholanthrene, 3,4-benzpyrene and TCDD significantly and equally activates the cytochrome P-448-dependent benzpyrene hydroxylase, since the antibodies against cytochrome P-448 inhibit benzpyrene metabolism in the microsomes by 85-90%. The possible reasons for the TCDD-induced increase in the catalytic activity of cytochrome P-448 as compared to the immunologically identical cytochrome P-448 induced by 3-methylcholanthrene and 3,4-benzpyrene, are discussed.

Animals↗
PubMedDate not supplied

[Age variations in ethylmorphine demethylase and benzopyrene hydroxylase activities in rat liver microsomes].

The ethylmorphine demethylase activity of the rat liver microsomes was higher in three-month animals (as compared to one-month), remained at a high level in the 12-month and decreased in old rats. The benzopyrene hydrolase activity increased in three-month animals, decreased in 12-month rats and remained the same with subsequent ageing of the organism. Asynchronicity of variations in the oxidation rate of different xenobiotics with ageing is considered as a result of changes in substrate specificity of the monooxygenase system due to metabolic peculiarities which reflect the age development of the organism and extinction of the reproduction function.

Aging↗
PubMed1990

[Benzopyrene hydroxylase induction and the functioning of the immunocompetent cells in human peripheral blood].

Xenobiotics--inducers of benzo(a)pyrene hydroxylase (BPH)--exert different effects on mitogen-stimulated and mitogen-unstimulated human peripheral blood mononuclear cells (PBC). In mitogen-stimulated culture xenobiotics highly increase BPH activity and suppress cell blast transformation. The incubation of the unstimulated PBC in the presence of xenobiotics increases insignificantly BPH activity, intensifies T-cell differentiation and concanavalin A-induced proliferation. The BPH activity is mainly associated with the PBC adhered to plastic Petri dishes. However, the control and induced levels of BPH activity depend on the interaction between adhered and nonadhered cells.

Benz(a)Anthracenes↗
PubMed1979

Metabolism of drugs and carcinogens in man: antipyrine elimination as an indicator.

The suitability of the most commonly used "prototype" drug, viz, antipyrine, in predicting drug and carcinogen metabolism was evaluated, by studying in vivo antipyrine elimination rate (Ke) and in vitro metabolism of drugs and carcinogens in liver preparations in the same individuals. Our subjects were 20 adult males undergoing abdominal surgery for gastrojejunostomy, although antipyrine Ke could be studied in only 16 subjects. Correlations of the various in vito--in vivo parameters were positive between the parameter pairs: in vivo antipyrine Ke--in vitro benzopyrene hydroxylase; benzopyrene hydroxylase--aniline hydroxylase; and benzopyrene hydroxylase--gamma-glutamyl transferase. Aminopyrine demethylase did not correlate with any of the parameters studied. The degree of correlation between antipyrine Ke and benzopyrene hydroxylase was statistically significant but was not satisfactory for predictive purposes. Our study indicates some of the problems and limitations of in vivo--in vitro comparisons and confirms earlier doubts on the usefulness of antipyrine as a "prototype" drug for predicting drug and carcinogen metabolism in man.

Adult↗
PubMed1988

Expression of cytochrome P-450 isozymes in the liver of hypophysectomized rats. Evidence for different regulation mechanisms concerning P450IIB and P450IIIA subfamilies.

1. Monooxygenase activities have been examined in rat liver to determine the effects of castration and hypophysectomy on cytochrome P-450 species. In adult males, hypophysectomy caused a decrease of total P-450 concentration, aniline hydroxylase, benzopyrene hydroxylase, benzphetamine demethylase, testosterone hydroxylase and imipramine hydroxylase and demethylase activities. The treatment of hypophysectomized animals with human growth hormone or testosterone did not restore the full activity. 2. When probed with antibodies, microsomes from hypophysectomized males and females exhibited an intense reaction with a polyclonal anti-(phenobarbital-induced P-450) which was not observed with a monoclonal antibody of anti-(phenobarbital-induced P-450). 3. These microsomal preparations also reacted with an antibody raised against a developmentally regulated P-450. No sex difference could be detected with this antibody. Furthermore, administration of human growth hormone to hypophysectomized males prevented this immunoreaction. 4. Total RNA has been prepared from the same liver; when probed with cDNAs, no changes occurred in the content in P-450 b/e, PB 24 (a constitutive member of the phenobarbital subfamily) and phenobarbital-inducible mRNA for UDP-glucuronosyltransferase. 5. In contrast, P-450 mRNA induced by pregnenolone 16 alpha-carbonitrile was modulated by hormonal manipulations: lower in females and castrated males than in intact males, increased in both sexes after hypophysectomy. Treatment of hypophysectomized males with human growth hormone abolished this rise in pregnenolone-16 alpha-carbonitrile-induced P-450 mRNA accumulation. Data collected in this study support the assumption that hypophysectomy acts differently on the regulation of various P-450 isozymes and that this regulation clearly does not involve the phenobarbital subfamily of P-450s.

Aniline Hydroxylase↗
PubMed1985

[Effect of thyroid status on microsomal enzymes during liver regeneration in the rat].

The effects of thyroid status upon cyt. P 450 concentration and ethoxycoumarin deethylase, benzopyrene hydroxylase and UDP-glucuronosyltransferase activities in the liver microsome fraction were far more important in partially hepatectomized rats than in control animals. The partial hepatectomy simultaneously lowered the MFO enzymes activities in the hepatic microsome fraction and made them more sensitive to thyroid hormones effects.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1974

Nicotine inhibition of the metabolism of 3,4-benzopyrene, a carcinogen in tobacco smoke.

A decreased rate of biliary excretion of radioactive metabolites of 3,4-benzopyrene was observed in rats given a single dose of nicotine. Prior treatment of rats with nicotine decreased benzopyrene hydroxylase activity in homogenates of liver, lung, and small intestine. The addition of nicotine to incubated tissues also decreased benzopyrene hydroxylase activity. These findings show that nicotine inhibits the metabolism of 3,4-benzopyrene in vivo and in vitro.

Animals↗
PubMed1971

Mixed-function oxidation in tumors.

Liver microsomes of the rat contain a group of hydroxylating enzymes which are coupled to a greater or lesser degree to the electron flow system. In our studies, enzymes believed to be directly associated with the electron flow chain of NADPH, ferricyanide reduction, cytochrome c, cytochrome P-450 and substrate hydroxylation have been observed in livers obtained from normal, tumor-bearing and whole body irradiated rats as well as in Morris hepatoma 7777 and dimethyl-amino-biphenyl induced breast tumors.A significant difference appeared to exist in the activity of NADPH oxidase, NADP-ferricyanide reductase and benzopyrene hydroxylase when normal liver was compared with the liver obtained from a breast-tumor-bearing animal. Both cytochrome P-450 and cytochrome b(5) were decreased in the tumor-bearing animal.Tissue distribution of benzopyrene hydroxylase in normal, lactating and tumor-bearing Wistar rats has been studied.With the exception of NADPH oxidase, the activities of NADP-cytochrome c reductase, NADPH-ferricyanide reductase, benzopyrene hydroxylase and P-450 were markedly different in liver from Morris hepatoma 7777-bearing Buffalo rat when this was compared with homologous tissue obtained from normal Buffalo rat.Whole-body irradiated animals showed increased P-450 and NADPH oxidase activity in liver as a function of irradiation and there further appeared to be a correlation with decreased ferricyanide reductase activity.

Animals↗
PubMed1985

Effect of intratracheally instilled benzo(a)pyrene on the pulmonary and hepatic drug-metabolizing enzymes in normal and vitamin A deficient rats.

The effect of intratracheal instillation of different doses of benzo(a)pyrene (0.1, 1.0 and 2.0 mg) on the drug metabolizing enzymes of lung and liver was analysed in rats fed diet with or without vitamin A for 5-6 weeks. Benzo(a)pyrene exposure at 2.0 mg dose only elevated the level of cytochrome P-450 and b5, and activity of benzopyrene hydroxylase in liver, and extent of increase was similar in normal and vitamin A deficient groups. Contrary to this, pulmonary contents of cytochrome P-450 and b5, and benzopyrene hydroxylase activity increased over control values in both the groups even at lower doses of benzo(a)pyrene. Moreover, their values were higher in vitamin A deficient-treated groups compared to normal-treated controls. Increase in these parameters was greater in lung as compared to increase in liver. NADPH cytochrome C-reductase in lung and liver was not affected either by inducing vitamin A deficiency or exposing these rats further to benzo(a)pyrene. Uridine-diphospho-glucuronosyl-transferase (UDP-GT) activity in normal and vitamin A deficient groups was enhanced following exposure to benzo(a)pyrene both in lung and liver. However, activity of this enzyme remained impaired in vitamin A deficient groups, benzo(a)pyrene exposed or not exposed when compared to respective normal controls. Glutathione S-transferase activity remained unchanged following exposure to benzo(a)pyrene both in lung and liver. The apparent increase in hepatic glutathione S-transferase and decrease in pulmonary glutathione S-transferase activity in vitamin A deficiency was only due to vitamin A deficient status of rats with no further effect of benzo(a)pyrene.

Animals↗
PubMedDate not supplied

[The enzymes of mono-oxygenase oxidation in the lymphocytes and liver of persons subjected to chlorophenoxy herbicide exposure].

The activity of benzopyrene hydroxylase (cytochrome P-450IA1) was studied in a mitogen-stimulated culture of peripheral blood lymphocytes from residents of the South Vietnam area treated with chlorophenoxy herbicides in the years of American aggression. The population residing in the untreated territory served as the control. The basal and induced benzopyrene hydroxylase activities, as well as the inducibility ratio were determined for each patient using the "lymphocytic test". The content of antipyrine metabolites and their percentage were estimated in the urine of the same patients using the antipyrine test. The computer processing of data allowed to perform primary analysis of the monooxygenase system in lymphocytes by groups in order to reveal correlations between the content of antipyrine metabolites in the urine and the cytochrome P-450IA1 in blood lymphocytes. The effect of residual amount of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) on the human monooxygenase system is discussed.

2,4,5-Trichlorophenoxyacetic Acid↗