Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.3 (diaphorase)
 5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interaction of NADPH-cytochrome c reductase with oxygen, artificial acceptors and cytochrome P-450 is investigated. It is found that generation of oxygen anion-radicals (O2-), determined from the reaction of adrenaline oxidation into adrenochrome, proceeds independently on the reactions of interaction with artificial "anaerobic" acceptors-cytochrome c, dichlorophenolindophenol. Propylgallate competitively inhibits the reaction of adrenaline oxidation by isolated DADPH-cytochrome c reductase and non-competitively suppress the reaction of cytochrome c reduction. In contrast to the process of electron transfer on cytochrome c, there is a direct correlation between the rate of cytochrome P-450 reduction and the rate of adrenaline oxidation in liver microsomes. Hexobarbital increases V of the adrenaline oxidation reaction and does not affect the Km value, while metirapon, a metabolic inhibitor, decreases the Vmax and does not change Km. On the basis of the data obtained it is suggested that the reactions of NADPH-cytochrome c reductase interaction with oxygen and artificial "anaerobic" acceptors are connected with different redox-states of flavoprotein or with different flavine coenzymes, and that the electron transport on cytochrome P-450 and directly on oxygen takes place in interrelated redox-states of flavoprotein.
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PMID:[Interrelationship between the generation of oxygen anion-radicals and the reduction of artificial acceptors and cytochrome P-450 by NADPH-cytochrome c reductase]. 19 28

1. The effects of halothane (CF3CHBrCl), a volatile anaesthetic agent, on electron transfer in isolated rat liver microsomal preparations were examined. 2. At halothane concentrations achieved in tissues during clinical anaesthesia (1-2mM), halothane shifts the redox equilibrium of microsomal cytochrome b5 in the presence of NADPH towards the oxidized form. Halothane accelerates stoicheiometric consumption of NADPH and O2, increases the rate of reoxidation of NADH-reduced microsomal ferrocytochrom b5, but does not affect NADPH- or NADH-cytochrome c reductase activity. The enhanced microsomal electron flow seen in the presence of halothane is not diminished by CO nor is it increased by pretreatment of the animals with phenobarbital. 3. The effects of halothane are maximum in microsomal preparations isolated from animals fed on a high-carbohydrate diet to induce stearate desaturase activity. Changes in microsomal electron transfer caused by halothane are in all cases abolished by low concentrations (1-2mM) of cyanide. Microsomal stearate desaturase activity is unaffected by halothane. 4. The first-order rate constant for oxidation of membrane-bound ferrocytochrome b5 in the absence of added substrate (k1 equals 1.5 times 10(-3)A-1) is similar to that for autoxidation of purified ferrocytochrome b5(k1 equals 7 times 10(-3)S-1) the rate of autoxidation of soluble ferrocytochrome b5 is unaffected by halothane. 5. It is concluded that the effects of halothane on microsomal electron transfer are not related to cytochrome P-450 linked metabolism but rather arise from the interaction of halothane with the cyanide-sensitive factor of the stearate desaturase pathway.
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PMID:The effects of halothane on hepatic microsomal electron transfer. 23 6

Different functional and structural properties of rat liver microsomes were studied during hepatocarcinogenesis induced by 0.25% DL-ethionine. During the first to fourth months of ethionine feeding, great decreases of cytochrome P-450 content, reduced nicotinamide adenine dinucleotide phosphate-dependent lipid peroxidation, and animopyrine demethylase activity occurred. No changes in the reduced nicotinamide adenine dinucleotide phosphate-cytochrome c reductase activity were observed. These functional alterations were paralleled by an increase in membrane-free ribosomes and by changes in the relative proportions of phospholipid fatty acids in microsomes. After the end of ethionine feeding, when hyperplastic nodules and/or hepatomas were present, the above functional and structural parameters were studied in the latter tissues, as well as in surrounding nonodular liver. Decreases in cytochrome P-450 content, lipid peroxidation, and animopyrine demethylase activity were documented in hyperplastic nodules and hepatomas. In hepatomas, the alterations were more marked and decrease of reduced nicotinamide adenine dinucleotide phosphate-cytochrome c reductase activity was also found. All these functional parameters were quite normal in surrounding nonnodular liver. Similarly, alterations in phospholipid fatty acid composition disappeared in surrounding nonnodular liver, but they partially persisted in both hyperplastic nodules and hepatomas. In contrast, the increase in membrane-free ribosomes also occurred in surrounding nonnodular liver, although to a lower extent than in hyperplastic nodules and hepatomas. These data are discussed in relation to the problem of the cellular precursors of hepatomas.
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PMID:Functional and structural alterations of liver ergastoplasmic membranes during DL-ethionine hepatocarcinogenesis. 24 83

We have obtained and studied a 105,000-g pellet from T-3-Cl-2 cells, a cloned line of Friend virus-induced erythroleukemia cells. By difference spectrophotometry, the pellet was shown to contain cytochrome b5 and cytochrome P-450, hemeproteins that have been shown to participate in electron-transport reactions of endoplasmic reticulum and other membranous fractions of various tissues. The pellet also possesses NADH-cytochrome c reductase activity which is inhibited by anti-cytochrome b5 gamma-globulin, indicating the presence of cytochrome b5 reductase. This is the first demonstration of membrane-bound forms of these redox proteins in erythroid cells. Dimethyl sulfoxide-treated T-3-Cl-2 cells were also shown to possess membrane-bound cytochrome b5 and NADH-cytochrome c reductase activity. We failed to detect soluble cytochrome b5 in the 105,000-g supernatant fraction from homogenates of untreated or dimethyl sulfoxide-treated T-3-Cl-2 cells. In contrast, erythrocytes obtained from mouse blood were shown to possess soluble cytochrome b5 but no membrane-bound form of this protein. These findings are supportive of our hypothesis that soluble cytochrome b5 of erythrocytes is derived from endoplasmic reticulum or some other membrane structure of immature erythroid cells during cell maturation.
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PMID:Membrane-bound redox proteins of the murine Friend virus-induced erythroleukemia cell. 29 45

Sprague-Dawley rats were fed a synthetic diet deficient in or containing thiamin (20 mcg/gm food), riboflavin (50 mcg/gm), or pyridoxine (50 mcg/gm) while receiving either norethindrone (1.0 or 10.0 mg/rat/day) or methocel solution to determine the influence of this oral contraceptive on drug-metabolizing enzymes of female rat liver. Ingestion of high levels of thiamin significantly decreased the activity of cytochrome P-450, NADPH cytochrome c reductase, and the metabolism of aniline and ethylmorphine. Diets containing riboflavin significantly depressed V max for aniline hydroxylation and ethylmorphine demethylation while NADPH cytochrome c reductase was elevated. V max for aniline hydroxylase was the only drug-metabolizing enzyme which was affected by high levels of dietary pyridoxine. Norethindrone slightly depressed or left unaffected the activity of cytochrome P-450 regardless of diet. Norethindrone increased activity of c reductase and ethylmorphine N-demethylase or left it unchanged. Norethindrone induces aniline hydroxylase in all diets except those deficient in thiamin and riboflavin. The effects of norethindrone on the kinetics of aniline metabolism were unexplained by substrate enzyme-binding kinetics. However, it is apparent that dietary status affects the parameters studied and the effects of norethindrone.
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PMID:Influence of norethindrone on drug-metabolizing enzymes of female rat liver in various B-vitamin deficiency states. 40 27

The effect of thiamin deficiency on the metabolism of the oral contraceptive mestranol by female rat liver enzymes was determined. Rats were fed a diet for 3 weeks containing 0, .3, .7, 2.0, or 20 mcg thiamin/gm food before decapitation and extraction of liver microsomes. Mestranol was incubated with 1 ml microsomes from 250 mg liver and the metabolic reaction started by addition of cofactors and NADPH. Liver microsomes from rats fed a thiamin-deficient diet had 3 times the capacity to metabolize mestranol as microsomes from rats fed a thiamin-rich diet. The incremental addition of thiamin to the diet depressed mestranol 0-demethylation, NADPH cytochrome c reductase, and cytochrome P-450 content. Pair-feeding experiments indicate that the carbohydrate portion of the food is responsible for decrease in cytochrome c, while thiamin levels are responsible for changes in the other 2.
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PMID:The influence of thiamin deficiency on the metabolism of the oral contraceptive mestranol [3-methoxy-17-ethynyl-1,3,5(10)-estratrien-17 beta-o1] by female rat liver enzymes. 41 82

SVA was used to separate liver cells from rats pretreated for 3 days with PB (40 mg/kg intraperitoneally, twice daily) or 3-MC (50 MG/KG AS A SINGLE INJECTIOn). Twelve fractions of cells were collected with s's ranging from 97 mm/hr (fraction1) to 25 mm/hr (fraction 12). Cells in each fraction were sized and counted electronically. PB caused the average volume of the largest cells recovered (fraction 1) to increase to 16, 725 micrometer3 from 10,500 micrometer3 previously reported in untreated animals. The number of cells recovered in the fast-sedimenting fractions (1 to 6) also increased, but there was only a small rise in the average model volume of hepatocytes determined prior to SVA. In cell suspensions analyzed after PB treatment no evidence was found for a discontinuity in the distribution of density-volume characteristics as previously described in hepatocytes from untreated rats. As expected, prior to sedimentation analysis, hepatocyte suspensions from rats treated with PB contained increased cytochrome P-450. The average ratio (n = 4) of P-450 in separated to unseparated cells ranged from 2.75 (fractions 1 + 2) to 0.38 (fractions 11 + 12), giving a 6.8-fold range in quantity of cytochrome per cell. Over this range, cell volume increased 4.2-fold, indicating a gradient in P-450 concentration similar to that previously reported to exist in cells from untreated rat liver. The gradient for AHH activity was 6.7-fold, suggesting that activity of MFO's paralleled the increase in cytochrome concentration. 3-MC pretreatment caused no significant increase in either size or number of cells in the fast-sedimenting fractions, but the discontinuity in density-volume characteristics which distinguished fast and slow sedimenting cells of untreated rats became marked. Furthermore, both the size and number of cells recovered in fractions 7 to 11 (which include the modal peal volume of unseparated hepatocytes) were increased. The gradient of P-450 (OR P1-450) was less steep in 3-MC-treated cells with pooled fractions 1 and 2 containing an average of 4.62 times as much cytochrome as fractions 11 and 12. The gradient for AHH was 4.29 times. The range of cell volume was 3.3-fold over this range. Additional experimental work was performed to determine whether P-450, AHH, or NADPH cytochrome c reductase exhibited differences in activity or concentration per unit of cell volume between cells on either side of fraction 7 where discontinuity had been noted. Each variable was expressed per unit of cell volume in fractions 5 and 9; ratios were compared but were indistinguishable from unity. It was concluded that induction of MFO activity had occurred equally in both populations of cells. Densities were calculated from s and cell volume. Noticeable loss of density followed PB treatment in cells of all sizes. 3-MC had less of an effect on density but enhanced the increment in density observed at fraction 7, which corresponds to the division between cells with distinct sedimentation characteristics...
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PMID:Effects of phenobarbital and 3-methylcholanthrene pretreatment on size, sedimentation velocity, and mixed function oxygenase activity of rat hepatocytes. 41

Elaidic and linoleic acids were administered at doses of 40 and 200 mg/kg i.p. every second day for 4 weeks to rats fed a fat-free diet. The fatty acids had only a slight effect on the weight gain of the animals. The amount of microsomal protein was slightly decreased with the higher dose of linoleic acid. The higher dose level of both fatty acids decreased the microsomal phospholipid content. The relative amounts of microsomal phospholipid fatty acids were also altered due to fatty acid administration. The activity of microsomal NADPH cytochrome c reductase and microsomal cytochrome P-450 contents were decreased by the higher dose of linoleic acid. The hepatic aryl hydrocarbon hydroxylase and p-nitroanisole O-demethylase activities decreased in fatty acid-treated rats. The UDP-glucuronosyltransferase activity was also lowered after the fatty acid administration. The results suggest that fatty acid-induced changes in the activities of drug-metabolizing enzymes may be due to the microenvironmental changes of membrane-bound enzymes.
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PMID:Regulation of hepatic drug metabolism by elaidic and linoleic acids in rats. 41 54

Cadmium is a potent inhibitor of hepatic microsomal drug biotransformation in the rat. Male rats receiving a single intraperitoneal dose of cadmium exhibit significant decreases in hepatic microsomal metabolism of a variety of substrates. The threshold cadmium dose is 0.84 mg Cd/kg, and the effect lasts at least 28 days. Mechanistically, the inhibitory effect results from decreased cytochrome P-450 content since cadmium does not alter NADPH cytochrome c reductase activity. This effect is also observed following acute oral administration of cadmium in doses greater than 80 mg Cd/kg but is not observed following chronic administration of the metal via drinking water in concentrations of 5-200 ppm for periods ranging from 2 to 50 weeks. A tolerance to the inhibitory cadmium effect is observed if male rats are pretreated with subthreshold doses of the metal prior to the challenge cadmium dose. The degree of tolerance can be overcome by increasing the challenge dose of cadmium. Characterization of the tolerance phenomenon in terms of onset, duration, and intensity reveals a good correlation with the kinetics of metallothionein production, suggesting that the underlying basis for the tolerance phenomenon is likely the induction of metallothionein. A sex-related difference in the inhibitory effect of cadmium was observed. Cadmium did not inhibit the metabolism of hexobarbital or ethylmorphine in female rats but did inhibit that of aniline or zoxazolamine. Cadmium did not lower cytochrome P-450 content in female rats.
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PMID:Studies on cadmium-induced inhibition of hepatic microsomal drug biotransformation in the rat. 48 42

The electrophilic properties of the quinone-hydroquinone configuration of anthracycline antibiotics suggests a possible influence on cytochrome P-450-mediated mono-oxygenase reactions. Both doxorubicin and triferric-doxorubicin (a derivative in which the quinone groups are blocked with iron) showed a similar dose-dependent inhibition of liver microsomal drug metabolism. A doxorubicin concentration-related stimulation of NADPH oxidase activity was found to be linear but that for triferric-doxorubicin was asymptotic. Neither inhibitor affected the activity of cytochrome c reductase, cytochrome b5 reductase or cytochrome P-450 reductase. However, doxorubicin did potentiate the inhibitory effect of aniline on cytochrome P-450 reductase and on ethylmorphine metabolism. It is concluded that these anthracyclines inhibit drug metabolism in vitro not by their electron-withdrawing potential but in a manner more similar to that described for type II compounds.
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PMID:Inhibition of drug oxidation and stimulation of NADPH oxidase in vitro by doxorubicin and triferric-doxorubicin. 51 68


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