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At least 19 recordsLinked to original sources
PubMed1976

A possible mechanism of the generation of singlet molecular oxygen in nadph-dependent microsomal lipid peroxidation.

A simplified system, consisting of NADPH, Fe3+-ADP, EDTA, liposomes, NADPH-cytochrome c reductase and Tris - HCl buffer (pH 6.8), has been employed in studies of the generation of singlet oxygen in NADPH-dependent microsomal lipid peroxidation. The light emitted by the system involves 1deltag type molecular oxygen identifiable by its characteristic emission spectrum and its behavior with beta-carotene. The generation of another excited species (a compound in the triplet state) could be demonstrated in this system by changes of light intensity and emission spectra which arise from photosensitizer (9,10-dibromoanthracene sulfonate, eosin, Rose-Bengal)-mediated energy transfers. Chemiluminescence in the visible region was markedly quenched by various radical trappers and by an inhibitor of NADPH-cytochrome c reductase, but not by superoxide dismutase. During the early stage of lipid peroxidation, the intensity of chemiluminescence was proportional to the square of the concentration of lipid peroxide. These characteristics suggest that singlet oxygen and a compound in the triplet state (probably a carbonyl compound) are generated by a self-reaction of lipid peroxy radicals.

Animals↗
PubMed1976

Interactions of some acceptors with superoxide anion radicals formed by the NADPH-specific flavoprotein in rat liver microsomal fractions.

In rat liver microsomal fractions oxidation of adrenaline was effected by superoxide anion radicals (O2-), whereas cytochrome c, 2,6-dichlorophenol-indophenol and ferricyanide accepted electrons from NADPH-specific flavoprotein only directly. Nitro Blue Tetrazolium was reduced both by O2- and by the direct acceptance of electrons. Elevation of pH and addition of menadione shift the Nitro Blue Tetrazolium reduction towards the O2--dependent pathway. From the values of the kinetic constants for interaction of adrenaline and Nitro Blue Tetrazolium with NADPH-specific flavoprotein, the rates of generation of O2- in rat liver microsomal fraction were determined.

2,6-Dichloroindophenol↗
PubMed1976

Implication of rifampicin-quinone in the irreversible binding of rifampicin to macromolecules.

1. When [3H]rifampicin is incubated with rat liver microsomes or rat liver homogenate, minor amounts are bound irreversibly to protein. This effect does not depend on the presence of NAD, NADH, NADP or NADPH. 2. Rifampicin is autoxidized at physiological pH. The product of autoxidation, rifampicin-quinone, if incubated with albumin, shows a much greater irreversible binding to the protein than the parent compound rifampicin. Hence it is concluded that rifampicin may bind irreversibly to proteins in a non-enzymic reaction after autoxidation to rifampicin-quinone. 3. Rifampicin-quinone also binds irreversibly to RNA and poly-L-lysine, if incubated with these compounds. This suggests that free amino groups of protein or RNA are involved in the binding. 4. 48 h after dosage of [3H]rifampicin (33 mg/kg) to rats, 29-2 +/- 4-1 (S.D.) pmol are bound irreversibly to 1 mg liver RNA, 15.8 +/- 8-1 pmol to 1 mg liver protein and 5-0 +/- 0-47 pmol to 1 mg protein in brain tissue. 5. Microsomal NADPH-cytochromcin-quinone to rifampicin. The KM of this reaction is 10(-4) M. Induction of the NADPH-cytochrome c reductase by pre-treatment of rats with 20 mg/kg rifampicin over 5 days results in a corresponding increase of increase of rifampicin-quinone reduction. 6. These results suggest that microsomal NADPH-cytochrome c reductase prevents accumulation of higher amounts of possibly toxic rifampicin-quinone by reduction to rifampicin.

Animals↗
PubMed1976

[Effect of 2-hydroxyestradiol-17beta on NADPH-dependent electron transfer in rat liver microsomes in vitro (author's transl)].

If rat liver microsomes are incubated with NADPH and 2-hydroxyestradiol-17beta in vitro, the following is observed: 1. Inhibition of lipid peroxidation, 2.inhibition of cytochrome P-450 reduction, and 3.inhibition of cytochrome b5 reduction. Beyond this the catechole inhibits lipid peroxidation of liposomes in vitro. These phenomena can be explained by interaction of different states of oxidation of the estrogen with the NADPH-cytochrome reductase and with 0-2 radicals, which leads to terminal "uncoupling" of microsomal electron transport.

Animals↗
PubMed1976

Higher activity of oxidative drug demethylation in the liver microsomes from dystrophic mouse.

The activities of NADPH-dependent oxidative demethylation of aminopyrine and other methyl compounds in the liver microsomes from dystrophic mice were found to be about 30% higher than those of the normal mice. Consumption of reduced pyridine nucleotides during the demethylation reactions was also significantly larger in the dystrophic mouse system than in the normal mouse system. The synergistic effect of further addition of NADH on the oxidative demethylation in the reaction system with NADPH, however, was not significant in either the normal or the dystrophic mouse system. The activities of NADPH-cytochrome c reductase and lipid peroxidation were also higher by about 30% in the dystrophic mouse than in the normal mouse, but the contents of cytochrome P-450 and phospholipids in the liver microsomes from normal and dystrophic mice were not appreciably different. The results suggest the possibility that the progressive muscular dystrophy may involve abnormal features in not only muscle but also liver and other tissues.

Aminopyrine↗
PubMed1975

The effects of the continuous administration of N,N-dimethyl-4-phenylazoaniline (DAB) on the activities and the inducibilities of some drug-metabolizing enzymes in rat liver.

(1) The effect of feeding a relatively low-protein diet containing 0.06% DAB for 29 weeks on the activity of DAB-azoreductase, nitroreductase (p-nitrobenzoic acid), N-oxidase (N,N-dimethylaniline), N-demethylase (DAB), cytochrome P-450, NADPH-cytochrome c reductase, beta-glucuronidase and arylsulphatase A were studied. Rapid decreases occurred in the activities of the first six enzymes, reaching minimal values at between 4 and 8 weeks. Activities then increased in all cases to control or nearly control levels. This rate of increase was least for cytochrome P-450. At 4 weeks azoreductase activity with the chemotherapeutic agent CB10-252 (I) as substrate was significantly higher than in control rats. Early increases occurred in the activities of beta-glucuronidase and arylsulphatase A and the activity of the latter never dropped below the control level. (2) An investigation was made of the differential effects of dye feeding on some of the enzyme activities in the two major liver lobes and differences were found. (3) The effect of phenobarbital (PB) pretreatment on the DAB-fed rats was studied at 4-week intervals. The activities of DAB-azoreductase and of nitroreductase increased throughout the whole period, while the activities of the lysosomal enzymes were decreased. (4) After feeding DAB for 4 weeks the effect of PB and 3-methylcholanthrene (MC) on the activities of DAB-azoreductase, CB10-252-azoreductase and components of the azoreductases-cytochrome P-450, NADPH-cytochrome c reductase, the CO-CB10-252-azoreductase was not induced by PB or MC, and CO did not inhibit its reduction. Its reduction depended only slightly on NADH. CO caused a greater relative decrease in the activity of DAB-azoreductase in dye-fed animals and also in animals following PB and MC pretreatment, implying a greater role of cytochrome P-450 in dye-fed animals.

Animals↗
PubMed1976

Drugs and brain mitochondrial enzymatic activities during post-natal development in rat.

The enzymatic activities of two mitochondrial enzymes, i.e. succinate dehydrogenase and NADH-cytochrome c reductase were investigated in the brain of rats at different stages of post-natal development. In addition, the effect of the pharmacological treatment with two drugs, nicergoline and bamethan, able to interact with the alpha or the beta receptors respectively, was evaluated. The results show that both the enzymatic activities rapidly increase in the first days of extra-uterine life, thus indicating an adaptation of mitochondrial oxidative processes to post-natal environmental conditions. The pharmacological treatment with the two drugs does not induce any changes in the enzymatic activities tested.

Animals↗
PubMedDate not supplied

Depression of the hepatic cytochrome P-450 mono-oxygenase system by administered tilorone (2,7-bis(2-(diethylamino)ethoxy)fluoren-9-one dihydrochloride).

The oral administration of the antiviral agent, tilorone-HCl (50 mg/day for 4 days) to rats caused losses of hepatic microsomal ethylmorphine N-demethylase, benzo(a)pyrene hydroxylase and aniline hydroxylase activities of 50, 44 and 22%, respectively. Microsomal levels of cytochrome P-450 and NADPH-cytochrome c reductase were lowered by 40 and 20% respectively, but levels of cytochrome b5 and NADH-cytochrome c reductase remained unchanged. After a single oral dose of tilorone-HCl (50 mg/kg) a loss of 38% of the microsomal cytochrome P-450 and 25% of the ethylmorphine N-demethylase activity was observed within 24 hr; recovery was complete within 8 to 10 days. Hexobarbital sleeping times and blood levels were elevated after tilorone administration (20 or 50 mg/kg/day for 4 days). In vitro, tilorone-HCl showed no inhibitory effect on microsomal drug metabolism nod did it affect the cytochrome P-450 content of the microsomes. The rate of incorporation of delta-amino(3H)levulinic acid into cytochrome P-450 was not affected by tilorone-HCl.

Aniline Hydroxylase↗
PubMedDate not supplied

Postnatal development of mixed-function oxidation as measured in microsomes from the small intestine and liver of rabbits.

The postnatal development of aminopyrine N-demethylase, aniline 4-hydroxylase, benzpyrene hydroxylase, biphenyl 4-hydroxylase, 7-ethoxycoumarin 0-deethylase activities, NADPH-cytochrome c reductase, and cytochrome P-450 was compared in microsomes from the liver and small intestine of New Zealand white rabbits. Apart from hepatic aniline hydroxylase activity, all of the xenobiotic-metabolizing enzyme activities examined had a similar pattern of development in the liver and small intestine. In both tissues the ability to metabolize xenobiotics was generally undetectable at 2 days of age and remained relatively low for the first 20 days of life. Theresfter, a rapid 2- to 5-fold increase in all the enzyme activity studied was noted, and adult values were reached or exceeded by 30 days of age. Subsequent development of xenobiotic-metabolizing enzyme activities in the small intestine, but not in the liver, exhibited a transient fall at 50 days of age before adult activities were attained after 75 days of age. The developmental pattern of cytochrome P-450 in the small intestine closely resembled that of the xenobiotic-metabolizing enzyme activities, but in the liver this correlation was less exact.

Aging↗
PubMed1975

Effect of metal ions in the culture medium on the stearoyl-coenzyme A desaturase activity of Mycobacterium phlei.

A particulate fraction prepared from Mycobacterium phlei grown in a metal-deficient medium exhibited a greatly reduced activity of stearoyl-CoA desaturase compared to that from normally grown cells. Metal deficiency, however, had no effect on the FAD-dependent NADPH-cytochrome C reductase activity, which has been suggested to participate in the desaturation process. When the cells were grown in the deficient medium supplemented with both Fe2+ and Mg2+, the desaturase activity was restored to the normal level. Supplementation with Mg2+ alone promoted growth but did not restore the desaturase activity, whereas Fe2+ alone did cause a significant restoration. Among the various metal ions tested, only Fe2+ and Fe3+ enhanced the formation of desaturase activity in the deficient medium. When added to the assay medium in vitro, Fe2+ and Fe3+ did not stimulate the desaturase activity of the particulate fraction from the deficient cells. Cultivation in the metal-deficient medium had essentially no effect on the levels of cytochromes in the particulate fraction, but dramatically decreased the non-heme iron content and the amount of a high-spin ferric species exhibiting an ESR signal at g=4.3. No labile sulfur could be detected in the normal or metal-deficient particulate fractions. It is concluded that the presence of iron ions in the culture medium is necessary for the synthesis and/or assembly of the terminal portion of the desaturase system.

Culture Media↗
PubMed1975

Subcellular structure of bovine thyroid gland. A study on bovine thyroid membranes by buoyant-density-gradient centrifugation in a B-XIV zonal rotor.

A combined mitochondrial and light mitochondrial fraction and a microsomal fraction were isolated from bovine thyroid gland and fractionated further in a B-XIV zonal rotor. A density gradient ranging from 20 to 50% (w/w) sucrose was used. The rotor was operated for 3 h at 45 000 rev./min. All manipulations were performed at 4 degrees C and at pH 7.4. 2. Membranous material was recovered in two zones: zone I, containing microsomal material derived from both smooth endoplasmic reticulum and plasma membranes and probably also from other smooth membranes; zone II, containing material from rough endoplasmic reticulum. 3. Increasing the pH of the medium up to 8.6, or the addition of Mg2+ to the medium resulted in the formation of a single zone at intermediate densities (aggregation of membranes?). An analogous effect was obtained after treatment with Pb (NO3) 2. 4. In the presence of heparin (50 i.u./ml) the bulk of the membranes was found in zone I. This was due to the release of ribosomes from the rough endoplasmic reticulum.

Acid Phosphatase↗
PubMed1976

Isolation and characterization of an unsaturated fatty acid-requiring mutant of cultured mammalian cells.

An unsaturated fatty acid-requiring mutant derived from Chinese hamster ovary (CHO) cells has been isolated and characterized. This mutant grows normally when oleate or other unsaturated fatty acids are supplemented in the growth medium. Unlike the wild-type CHO cells, growth stops when medium is deprived of unsaturated fatty acid. Whole cell pulse experiments with [14C]acetate or [14C]stearate indicate that the mutant is defective in unsaturated fatty acid synthesis. Enzyme assays in vitro show that the enzymatic defect of the mutant is localized to the microsomal stearoyl-CoA desaturase.

Acetates↗
PubMed1976

Isolation and some properties of NAD+ reductase of the green photosynthetic bacterium Prosthecochloris aestuarii.

NAD+ reductase of the green photosynthetic bacterium Prosthecochloris aestuarii was isolated and purified by ammonium sulfate fractionation, DEAE-cellulose column chromatography, and Sephadex G-200 gel filtration. This enzyme is an FAD-containing flavoprotein and has absorption maxima at 485 (shoulder0 452, 411, and 385 nm (the 411 nm band is due to cytochrome). The molecular weight of the enzyme as determined by gel filtration using Sephadex G-200 is 119,000. The enzyme catalyzes the reduction of NAD+ and NADP+ by photoreduced spinach ferredoxin or reduced benzyl viologen...

2,6-Dichloroindophenol↗
PubMed1976

Oxidation of ethane by an Acremonium species.

Ethane oxidation was studied in ethane-grown resting cells (mycelia) of an Acremonium sp. and in cell-free preparations of such mycelia. From resting cell experiments evidence was found for a pathway of ethane oxidation via ethanol, acetaldehyde, and acetic acid. In vitro studies indicated that ethane-oxidizing activity in such mycelia occurred predominantly in the microsomal fraction of crude homogenates. Microsomal preparations were inactive in the absence of added coenzyme. Marked stimulation of activity was obtained in such preparations with reduced nicotinamide adenine dinucleotide phosphate and to a much lesser degree with nicotinamide adenine dinucleotide phosphate. Ethane oxidation was inhibited by sodium azide and carbon monoxide.

Alcohol Oxidoreductases↗
PubMed1975

Thyroxine deiodination associated with NADPH-dependent lipid peroxidation in a submicrosomal system.

A lipoprotein present in trypsin-treated microsomes can be oxidized with formation of malondialdehyde in a system which contains NADPH, ferric ion-ADP complex, NADPH-cytochrome c reductase and a factor. This factor, a mixture of peptides, can be isolated from hepatic microsomes by trypsin digestion and successive gel filtration through Sephadex G-100 and G-25 columns. Lipid peroxidation in this system catalyzes the deiodination of thyroxine, as does NADPH-dependent lipid peroxidation in fresh hepatic microsomes. Thyroxine inhibits lipid peroxidation as it is deiodinated in this system.

Animals↗
PubMedDate not supplied

Studies of the metabolism of parathion with an apparently homogeneous preparation of rabbit liver cytochrome P-450.

The metabolism of parathion has been examined by use of a reconstituted mixed-function oxidase enzyme system isolated from the livers of phenobarbital-pretreated rabbits. The cytochrome P-450 used in these studies was apparently homogeneous as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by assay of the preparation for contaminating microsomal enzymes and enzyme activity. These studies revealed that the apparently homogeneous preparation of cytochrome P-450, in the presence of the appropriate cofactors, can catalyze the conversions of parathion to both paraoxon and diethyl phosphorothioic acid. The present studies have also shown that parathion is metabolized by the reconstituted mixed-function oxidase enzyme system to diethyl phosphoric acid, a product which, in previous studies with intact liver microsomes, had been thought to arise exclusively from the hydrolysis of paraoxon by a microsomal esterase(s). The available data suggest that all three of the products of the metabolism of parathion by the reconstituted mixed-function oxidase enzyme system, namely, paraoxon, diethyl phosphorothioic acid, and diethyl phosphoric acid, are formed nonenzymatically by breakdown by different pathways of a common enzymatically formed intermediate. This common intermediate is thought to be the sulfine derivative of parathion formed in the mixed-function oxidase-catalyzed addition of an oxygen atom to one of the unshared electron pairs of the thiono-sulfur atom.

Animals↗