Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Cytochrome P-450 monooxygenase isozymes and NADPH-cytochrome P-450 reductase were detected in the microsomal fraction of rabbit aorta by immunoblotting and by enzymatic activity. The monomeric molecular weights of aortal proteins that cross-reacted with antibodies to cytochrome P-450 forms 2 or 6 and reductase were identical to those of the proteins purified from the liver. The induction of form 6 immunoreactive protein and O-deethylation of 7-ethoxyresorufin (a reaction catalyzed by form 6) was observed in aorta following treatment of rabbits with 2,3,7,8-tetrachlorodibenzo-p-dioxin or beta-naphthoflavone. The amount of reductase protein (equivalent to 22.4 +/- 3.2 activity units/mg of protein) correlated with the cytochrome c reductase activity (18.3 +/- 1.8 units/mg) and was the same for both treated and untreated rabbits. Consistent with immunoblot data, the amount of form 2 was insufficient for detection of activity (N-demethylation of benzphetamine). Significantly, removal of the endothelium, which was confirmed by light microscopy and by scanning electron microscopy, reduced by only 8 to 32% the specific enzymatic activity or content of immunoreactive proteins; only traces of protein or activity were recovered in the endothelial fraction. In studies of the vasculature, the potential of this metabolic pathway for the activation or detoxication of mutagens, carcinogens, toxins, or drugs and metabolism of endogenous substrates warrants consideration, especially in regard to the mutational events reported to be involved in the formation of atherosclerotic plaques.
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PMID:Cytochrome P-450 monooxygenase system. Localization in smooth muscle of rabbit aorta. 392 49

The activity of various xenobiotic-metabolizing enzymes was examined throughout the growth cycle (16d) of the well-differentiated rat hepatoma cell line C2Rev7. Cytochrome P-450-dependent aldrin epoxidase activity showed a peak on day 3 after plating of cells and decreased by more than 90% during the following six days. Glutathione S-transferase and UDP-glucuronosyl transferase with 4-hydroxybiphenyl as substrate also showed decreases in their activities towards the later phase of the growth cycle, although to lesser extents than the mono-oxygenase. The activity of cytochrome c reductase and of the UDP-glucuronosyl transferase with 3-hydroxybenzo[a]pyrene as substrate remained constant throughout the growth cycle. Aldrin epoxidase activities varied markedly with the number of cells plated. The results suggest that the balance of activating and inactivating pathways may vary considerably during the growth cycle of differentiated hepatoma cells. This should be taken into account when standardizing these cells as test systems for the assessment of cytotoxic and genotoxic chemicals.
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PMID:Variability in the expression of xenobiotic-metabolizing enzymes during the growth cycle of rat hepatoma cells. 393 54

Cytochrome P-450 content (nmol/g of liver) differed within regions of rat liver according to proximity to intrahepatically implanted Morris hepatoma 7795 or 5123D. Liver adjacent to tumor had higher microsomal cytochrome P-450 content, decreased DNA content (mg/g of liver), and unaltered cytochrome c reductase activity compared to histologically indistinguishable liver far-removed from the tumor. Liver either adjacent to or far-removed from tumor contained markedly more cytochrome P-450 and higher cytochrome c reductase activity but less DNA than transplanted Morris hepatomas 7795 and 5123D that were grown intrahepatically. Compared to intramuscular implants of these same tumors, intrahepatically implanted Morris hepatomas 7795 and 5123D had increased cytochrome P-450 content. Tumor-containing liver from two human subjects revealed regional changes in cytochrome P-450-mediated monooxygenases similar to those observed in rats. These results suggest that histomorphically nontumorous mammalian liver directly adjacent to intrahepatic tumors exhibits previously unsuspected biochemical alterations.
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PMID:Enhanced drug-metabolizing capacity within liver adjacent to human and rat liver tumors. 624 68

Male and female Sprague-Dawley rats were fed synthetic diets deficient in or supplemented with thiamin for 2 or 3 weeks. One group of rats receiving the thiamin-supplemented diet was pair-fed the amount consumed by rats fed the thiamin-deficient diet. One-half of each group was administered phenobarbital sodium for four consecutive days prior to decapitation. Rats fed the thiamin-deficient diet had higher NADPH cytochrome c reductase, aniline hydroxylase, and ethylmorphine N-demethylase activities than those fed high levels of thiamin. In addition, these animals generally responded more vigorously to induction by phenobarbital in their synthesis of microsomal protein, and increased activities of NADPH cytochrome c reductase, aniline hydroxylase, and ethylmorphine N-demethylase. Cytochrome P-450 concentration was higher in the microsomes from thiamin-deficient rats and was induced to a greater degree by phenobarbital than in microsomes from rats fed thiamin-supplemented diets ad libitum. Phenobarbital-enhanced metabolism of N-nitrosodimethylamine (DMN) by liver 9,000 g supernatant as evidenced by approximately two-fold increases in formaldehyde formed per gram liver. This increase in DMN metabolism in male rats is due at least in part to the increased concentration of microsomal protein, since metabolism per milligram microsomal protein was not increased. The fact that DMN metabolism per unit of microsomal cytochrome P-450 in phenobarbital-treated animals is decreased to about one-half of that in controls indicates that DMN is either metabolized by a non-cytochrome P-450-dependent system or that it is metabolized by a form of P-450 not induced by phenobarbital. A sex difference was evident in these experiments, females generally being more sensitive to the influence of varying levels of dietary thiamin. Also female rats but not males fed high-thiamin diets responded to phenobarbital with increased DMN metabolism per milligram microsomal protein.
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PMID:Influence of dietary thiamin on phenobarbital induction of rat hepatic enzymes responsible for metabolizing drugs and carcinogens. 643 11

Hydroquinone (HQ) is used widely in industry and in commerce and is considered to have a low degree of toxicity. Although the metabolism of HQ has been studied elsewhere, a complete materials balance has not been reported. We investigated the metabolism of HQ in naive and HQ pretreated male Sprague-Dawley rats. [14C]HQ was administered by gavage in single doses of 5, 30, or 200 mg/kg to naive rats. HQ was given repeatedly by gavage to male rats at 200 mg/kg for 4 consecutive days followed by a single dose with 200 mg/kg of [14C]HQ. In separate studies rats were fed 5.6% unlabeled HQ in the diet for 2 days or were dosed by gavage with 311 mg/kg [14C]HQ. The excretion patterns of [14C]HQ and its metabolites were similar for rats dosed singly or repeatedly. Rats given a single dose of 200 mg/kg of [14C]HQ excreted 91.9% of the dose in the urine within 2-4 days; 3.8% was excreted in the feces, about 0.4% was excreted in expired air, and 1.2% remained in the carcass. Radioactivity was widely distributed throughout the tissues with higher concentrations in the liver and kidneys. A decrease in 14C tissue concentrations occurred from 48 to 96 h. The only radiolabeled compounds in the urine were HQ (1.1-8.6% of the dose), hydroquinone monosulfate (25-42%), and hydroquinone monoglucuronide (56-66%). Similar findings were observed for rats given HQ in the feed. There were no significant increases from controls for absolute or relative liver weights, liver microsomal protein concentrations, cytochrome b-5, cytochrome P-450 or cytochrome c reductase activity in rats dosed repeatedly with 200 mg/kg HQ. Cytochrome P-450 values were slightly but significantly decreased in rats dosed repeatedly with HQ compared with controls.
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PMID:Metabolic fate and disposition of [14C]hydroquinone given orally to Sprague-Dawley rats. 649 48

Administration of anesthetic doses of halothane to hyperthyroid male rats results in the development of hepatic necrosis. The severity of the hepatic lesion was dependent on the dose of triiodothyronine (T3) and the length of time it was administered. Pretreatment of rats with iodinated metabolites of thyroxin which do not induce hyperthyroidism did not result in any signs of hepatotoxicity after halothane exposure. The administration of halothane to hyperthyroid female rats or mice of either sex did not result in the development of any overt hepatotoxicity. Likewise, hyperthyroidism did not enhance the hepatotoxicity of another hepatotoxin bromobenzene. The in vitro enzymatic activities associated with cytochrome P-450-dependent metabolism and glutathione S-transferase conjugation activity were markedly altered in hyperthyroid rats. Cytochrome P-450 levels, aminopyrine N-demethylase activity, glutathione levels and glutathione S-transferase activity were all significantly lower in hyperthyroid rats. However, other enzyme activities were stimulated by T3 pretreatment; aniline hydroxylase activity was increased by 45% and cytochrome c reductase activity was increased by 54% in hyperthyroid rats. Glutathione levels were also reduced significantly in hyperthyroid male rats. Maximal changes in both the cytochrome P-450 system and in the glutathione detoxification system were required before halothane demonstrated its hepatotoxic effects. Thus, a new balance between cytochrome P-450-dependent bioactivation and glutathione conjugation of halothane may be necessary for the exaggerated hepatotoxicity of halothane seen in hyperthyroid male rats.
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PMID:Characterization of hyperthyroidism enhancement of halothane-induced hepatotoxicity. 665 74

The hepatic microsomal cytochromes P-450 and b5, as well as the enzymes of the hepatic microsomal electron-transport system (HMETS), including NADPH oxidase and NAPDH cytochrome c reductase, were monitored in male ICR mice (25 - 30 g) over a six-day period following repeated oral administration of methadone hydrochloride 12.5, 25, or 50 mg/kg per day, or an equivalent volume of water. Cytochrome P-450 content, when expressed per milligram of microsomal protein, was elevated as early as day 1 of administration. This increase in cytochrome P-450, which lasted throughout the period of administration, appeared to correlate with the previously reported increase in the hepatic microsomal enzyme methadone N-demethylase and tolerance to methadone lethality. The activities of the enzymes NADPH cytochrome c reductase and NADPH oxidase were both elevated significantly by day 2 of administration. However, these increases returned to control levels by day 6 of treatment. The only other cytochrome in the HMETS, cytochrome b5, showed no significant change following repeated oral methadone administration. Further, methadone administration depressed the hepatic microsomal protein content following two days of treatment and no elevation above control values was noted. The significance of these findings with respect to the role of the HMETS in the development of tolerance is discussed in some detail for methadone, as well as the findings previously reported by this laboratory for its acetylated congener, l-alpha-acetylmethadol.
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PMID:The role of the hepatic microsomal electron-transport system in the development of metabolic tolerance from repeated oral methadone administration in mice. 676 37

Cytochrome P-450 substrate interactions were studied with cytochrome P-450 partially purified from livers of untreated, phenobarbital-treated, benzo[a]pyrene-treated and caffeine-treated rats. Partial inhibition of aminopyrine N-demethylase in presence of in vitro caffeine observed with intact microsomes was further investigated in a reconstituted system composed of partially purified cytochrome P-450 and cytochrome c reductase. Caffeine addition (in vitro) to partially purified cytochrome P-450 altered the hexobarbital, aniline and ethylisocyanide induced spectral change, and decreased NADPH oxidation in presence of substrates aminopyrine and acetanilide. NADPH oxidation was found to be increased in presence of aminopyrine and unaltered in presence of acetanilide in reconstituted system having partially purified cytochrome P-450 from caffeine-treated rats. Our studies suggest that caffeine acts as a true modifier of cytochrome P-450 and is possibly responsible for the formation of abortive complexes with aminopyrine.
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PMID:Partial inhibition of hepatic microsomal aminopyrine N-demethylase by caffeine in partially purified cytochrome P450. 683 Aug 52

The influence of systemic application of chemically unrelated drugs and xenobiotics (phenobarbital (PB), rifampicin (Rifa), pregnenolone-16 alpha-carbonitrile (PCN) and 3-methylcholanthrene (MC) on drug metabolizing enzymes was investigated in the skin of rats of both sexes. The results were compared with those obtained in the liver. PB, Rifa and PCN induced the aryl hydrocarbon hydroxylase (AHH) in the skin though to a lesser extent than MC. The basal enzymic activity as well as the inducibility were considerably lower in the skin than in the liver. The activity of cytochrome c reductase was similar in all rats independently from the pretreatment. Only slight sex differences were noted: generally, the activity was higher in males. Cytochrome P-450 content of the skin could not be detected as well as various dealkylation activities.
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PMID:Inducibility of drug-metabolizing enzymes in the rat skin. 738 10

The presence of cytochromes b5, P-450 and P-420 and activities of NADH- and NADPH-cytochrome c redutases were determined in plasma membranes isolated from microvilli of the chick and rat intestinal epithelium and erythrocyte membranes from chick, rat and man. The results are compared with the amounts of these components found in microsomal fractions from intestinal epithelium and in nuclear membranes from chick erythrocytes. Plasma membranes from intestinal microvilli and from erythrocytes contained significant amounts of NADH-cytochrome c reductase activity and of a pigment spectrophotometrically indistinguishable from rat liver microsomal cytochrome b5. In addition, cytochrome b5 fragments were prepared from the membranes by limited trypsin digestion and consisted of two to four components with Mr values in the range 10 000-13 500. In low-temperature difference spectra, the presence of a second cytochrome was noted which was similar to cytochrome P-420. Cytochrome P-450 and NADPH-cytochrome c reductase activities were not detected in plasma membrane fractions in significant concentrations but were present in the corresponding endomembrane fractions. These findings in highly purified, well defined plasma membrane fractions, in which contamination by endomembranes is minimal, strengthen the evidence for the existence of cytochrome-containing redox systems in plasma membranes of various cells and suggest that such redox components are general components of the cell surface. Possible functions and origins of these redox components in plasma membranes are discussed.
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PMID:Plasma membranes from intestinal microvilli and erythrocytes contain cytochromes b5 and P-420. 740 43


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