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

---

Query: EC:1.6.99.3 (diaphorase)
5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies were done to determine the mechanism(s) responsible for the thermal lability of adrenal microsomal monooxygenases. Preincubation of guinea pig adrenal microsomal suspensions at 37 degrees C caused large time-dependent declines in benzo(a)pyrene (BP) hydroxylase and benzphetamine (BZ) demethylase activities. Similar preincubations with hepatic microsomes had little effect on enzyme activities. The decreases in adrenal enzyme activities were completely prevented by co-incubation of microsomes with cytosol, but were not diminished by reduced glutathione, ascorbic acid, or bovine serum albumin. Partial protection was afforded by EDTA, suggesting that lipid peroxidation might be involved, but malonaldehyde production was not demonstrable and MnCl2, a potent inhibitor of lipid peroxidation, did not affect the decline in enzyme activities. The decreases in the rates of BP and BZ metabolism were prevented by including NADPH or NADP+ in the preincubation medium. The preincubation conditions causing losses of adrenal enzyme activities did not affect cytochrome P-450 concentrations or substrate binding to cytochromes P-450, as indicated by type I difference spectra. NADH-cytochrome c reductase activity also was not affected, but there were decreases in NADPH-cytochrome c reductase activity that were proportionately similar to the declines in drug-metabolizing activities. Direct assessment of NADPH-cytochrome P-450 reductase revealed similarly large decreases in enzyme activity resulting from preincubation of adrenal microsomes. The results demonstrate a need for extra caution when doing preincubation experiments with adrenal microsomal preparations, and suggest that the thermal lability of adrenal monooxygenases is attributable to effects at the active site of NADPH-cytochrome P-450 reductase.
...
PMID:Mechanisms responsible for the thermal sensitivity of adrenal microsomal monooxygenases. 168 Jun 36

Specimens of the seawater fish annular seabream (Diplodus annularis) were caught from a polluted harbor area and from a clean reference area. Seawater concentrates and fish-muscle extracts were not mutagenic in the Salmonella reversion test. Liver preparations of fish from the 2 sources were comparatively assayed for microsomal mixed-function oxidases and cytosolic biochemical parameters, as well as for the ability of S12 fractions to activate promutagens or to detoxify direct-acting mutagens. A shift of the cytochrome P-450 peak from 450.3 to 448.5 was accompanied by a 4.5-fold increase in arylhydrocarbon hydroxylase activity in fish living in the polluted environment. At the same time, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were doubled in the cytosol of the same animals, while reduced glutathione (GSH) peroxidase and GSH S-transferase were slightly yet significantly depressed. No significant difference was recorded for other biochemical parameters, including GSH, oxidized glutathione (GSSG) reductase, NADH- and NADPH-dependent diaphorases, and DT diaphorase. In parallel, fish exposed to polluted seawater exhibited a significant and marked enhancement of the metabolic activation of the pyrolysis product Trp-P-2 and of benzo[a]pyrene-trans-7,8-diol, and at the same time were less efficient in detoxifying the antitumor compound ICR 191. Liver S12 fractions from both sources efficiently decreased the direct mutagenicity of sodium dichromate, and failed to activate benzo[a]pyrene and aflatoxin B1 to mutagenic metabolites. These results provide evidence that both biochemical parameters and the overall capacity of fish liver to activate or detoxify certain mutagens can be assumed to be sensitive indicators of exposure to mixed organic pollutants in the marine environment.
...
PMID:Enhanced liver metabolism of mutagens and carcinogens in fish living in polluted seawater. 170 59

Hepatic drug metabolism was investigated in female Sprague-Dawley rats fed ad libitum (A) or a restricted diet (R) (implemented from age 1 month), at 1.5, 4.5 and 12 months to determine the short- and long-term effects of caloric restriction. Microsomal cytochrome P-450 content and NADPH cytochrome c reductase activity were not modified by age. While dietary restriction did not affect cytochrome P-450, it significantly increased NADPH cytochrome c reductase activity at all time periods when compared to corresponding A-fed groups. Aniline hydroxylase and aminopyrine N-demethylase activity tended to decrease with age in the A-fed groups but the differences did not prove to be statistically significant. A significant decrease of aminopyrine N-demethylase was observed with age in R rats. A significant reduction of aniline hydroxylase activity was noted in the R groups compared to age-matched A-fed controls. In contrast, aminopyrine N-demethylase activity increased significantly, but only at 1.5 months of age. Glutathione S-transferase activity was augmented between 1.5 and 4.5 months of age, and this was followed by a significant decrease at age 12 months in both A and R groups. Dietary restriction had no effect on this enzymatic activity. The microsomal cholesterol and phospholipid content as well as the cholesterol/phospholipid molar ratio changed significantly between 1.5 and 4.5 months of age but not between 4.5 and 12 months of age. These parameters were unaltered by dietary restriction. In conclusion, in the female Sprague-Dawley rat there are no statistically significant changes in hepatic microsomal components and drug metabolizing capacity between 1.5 and 12 months of age. Dietary restriction resulted in significant changes in enzymes related to drug metabolism which varied with the enzyme examined. In general, these changes were similar after short- or long-term dietary intervention.
...
PMID:Hepatic drug metabolism during development in food-restricted female Sprague-Dawley rats. 174 66

Sex-related difference was observed in the levels of total cytochrome P-450 (P-450) and the mono-oxygenase activity mediated by P-450(b,e), namely, aminopyrine N-demethylase and morphine N-demethylase activity in rat brain microsomes. Male rat brain had higher activity of the above enzymes as compared to the female rat brain. On the other hand, P-450(c,d) mediated 7-ethoxycoumarin O-deethylase and benzo(a)pyrene hydroxylase activity showed no sex-related difference in rat brain. Administration of testosterone elevated the levels of total P-450, aminopyrine N-demethylase and morphine N-demethylase in female rat brain to levels comparable with that of the male rat brain. No significant change was observed in the levels of 7-ethoxycoumarin O-deethylase and benzo(a)pyrene hydroxylase and NADPH cytochrome c reductase. All of the above enzyme levels were unaffected in the male rat brain following the treatment with testosterone. These results indicate that testosterone may regulate the forms of cerebral P-450 that are associated with the sex-related difference observed in rat brain.
...
PMID:Administration of testosterone alleviates the constitutive sex difference in rat brain cytochrome P-450. 188 2

The in vivo effect of nicardipine, a well-known calcium antagonist, on microsomal omega-oxidation of laurate in clofibrate-treated rat liver was studied. The 15.3-fold induction of the activity by 2 weeks administration of 0.25% clofibrate in the diet was markedly suppressed to about 6-fold by co-administration of nicardipine at 100 mg/kg body weight. Similarly, the induction of peroxisomal beta-oxidation and carnitine acetyltransferase activities were also suppressed by this simultaneous administration by more than 50%. Although clofibrate also induced the activity of reduced nicotineamide adenine dinucleotide phosphate (NADPH)-cytochrome c reductase and increased the hepatic content of cytochrome P-450, no suppressive effect of nicardipine was observed. Contrarily, nicardipine induced the reductase activity and increased the hepatic content of cytochromes P-450 and b5. These results provide the first demonstration of a calcium antagonist, e.g. nicardipine acting as inhibitor of the induction of microsomal omega-oxidation, in association with the inhibition of peroxisome proliferation in animals. The suppression of drug-induced peroxisome proliferation and microsomal omega-oxidation by the calcium antagonist may help in elucidating the causal relationship of the induction mechanisms between peroxisomal and microsomal enzymes.
...
PMID:Co-suppression by nicardipine, a calcium antagonist, of induction of microsomal lauric acid hydroxylation with peroxisome proliferation in clofibrate-treated rat liver. 191 8

Interferon and its inducers are known to depress drug biotransformation in vivo by decreasing the levels of cytochrome P-450 (P450) monooxygenase system in the liver. However, very little is known about the effects of interferon on P450 in extrahepatic tissues. In this study we investigated the effects of a recombinant human interferon-alpha (rhIFN-alpha) on aryl hydrocarbon hydroxylase (P450IAI) in cultured human peripheral lymphocytes (HPL). Non-induced and induced (3-methylcholanthrene) mitogen activated lymphocytes were used throughout the study. rhIFN-alpha maximally depressed AHH activity to approximately 58% of control after 24 hrs of incubation in both non-induced and induced lymphocytes. However, after 48 hrs of incubation with rhIFN-alpha, AHH activity had recovered to 86% of control in induced cells and 61% in non-induced cells. rhIFN-alpha had no significant effect on either NADH cytochrome c reductase activity or on viable lymphocyte cell count. This is the first demonstration that rhIFN-alpha can have a direct depressive effect on a P450 dependent monooxygenase system in HPL.
...
PMID:Effects of recombinant human interferon alpha on aryl hydrocarbon hydroxylase activity in cultured human peripheral lymphocytes. 202 Feb 55

Using the experimental model of partial hepatectomy in the rat, we have examined the relationship between cell division and lipid peroxidation activity. In rats entrained to a regime of 12 h light/12 h dark and with a fixed 8 h feeding period in the dark phase, partial hepatectomy is followed by a rapid regeneration of liver mass with cycles of synchronized cell division at 24 h intervals. The latter phenomenon is indicated in this study by pulses of thymidine kinase activity having maxima at 24 h, 48 h and 72 h after partial hepatectomy. Microsomes prepared from regenerating livers show changes in lipid peroxidation activity (induced by NADPH/ADP/iron or by ascorbate/iron), which is significantly decreased relative to that in microsomes from sham-operated controls, again at 24 h, 48 h and 72 h after the operation. This phenomenon has been investigated with regard to possible underlying changes in the content of microsomal fatty acids, the microsomal enzymes NADPH:cytochrome c reductase and cytochrome P-450, and the physiological microsomal antioxidant alpha-tocopherol. The cycles of decreased lipid peroxidation activity are apparently due, at least in part, to changes in microsomal alpha-tocopherol content that are closely associated in time with thymidine kinase activity.
...
PMID:Studies on the hyperplasia ('regeneration') of the rat liver following partial hepatectomy. Changes in lipid peroxidation and general biochemical aspects. 210 18

The presence of redox systems in microsomes of brown adipose tissue (BAT) in cold exposed rats was investigated and compared with liver. BAT microsomes showed high activity of lipid peroxidation measured both by the formation of malondialdehyde (MDA) and by oxygen uptake. NADH and NADPH dependent cytochrome c reductase activity were present in both BAT and liver microsomes. Aminopyrine demethylase and aniline hydroxylase activities, the characteristic detoxification enzymes in liver microsomes could not be detected in BAT microsomes. BAT minces showed very poor incorporation of [1-14C]acetate and [2-14C]mevalonate in unsaponifiable lipid fraction compared to liver. Biosynthesis of cholesterol and ubiquinone, but not fatty acids, and the activity of 3-hydroxy-3-methyl glutaryl CoA reductase appear to be very low in BAT. Examination of difference spectra showed the presence of only cytochrome b5 in BAT microsomes. In addition to the inability to detect the enzyme activities dependent on cytochrome P-450, a protein with the characteristic spectrum, molecular size in SDS-PAGE and interaction with antibodies in double diffusion test, also could not be detected in BAT microsomes. The high activity of lipid peroxidation in microsomes, being associated with large oxygen uptake and oxidation of NADPH, will also contribute to the energy dissipation as heat in BAT, considered important in thermogenesis.
...
PMID:Microsomal redox systems in brown adipose tissue: high lipid peroxidation, low cholesterol biosynthesis and no detectable cytochrome P-450. 210 21

NADPH cytochrome P-450 reductase (P-450 reductase), an essential component of the cytochrome P-450 mono-oxygenase system, has been estimated in rat and mouse brain, and seven human brains obtained at autopsy. The ratio of cytochrome P-450 to P-450 reductase is lower in the rat and mouse brains (2.5-4.0) as compared to the respective livers (10.0-11.0). The rat and mouse brain P-450 reductase were immunologically similar to the rat liver P-450 reductase as examined by immunochemical inhibition, Ouchterlony double diffusion and immunoblot. The antisera to rat liver P-450 reductase inhibited rat brain aminopyrine N-demethylase activity to the same extent as NADPH cytochrome c reductase, suggesting that the level of P-450 reductase controls the rate of this cytochrome P-450 mediated activity. The human brain NADPH cytochrome c reductase exhibited regional variation, maximal activity being observed in the brain stem region. Immunochemical inhibition and immunoblot studies revealed immunological cross-reactivity between rat liver reductase and human brain medulla, while none was observed in cortex or cerebellum. Immunocytochemical studies on human brain medulla using antisera to rat liver P-450 reductase indicated localization of the P-450 reductase in neuronal cell body.
...
PMID:NADPH cytochrome P-450 reductase in rat, mouse and human brain. 210 81

Antibodies against cytochrome P-450 are found in some children with autoimmune hepatitis (antiliver/kidney microsome 1) and in patients with ticrynafen hepatitis (antiliver/kidney microsome 2). For an immune reaction against cytochrome P-450 to possibly destroy the hepatocytes, one must assume that cytochrome P-450 is present on the plasma membrane surface of hepatocytes. In a first series of experiments, plasma membranes were prepared with a technique based on the electrostatic attachment of isolated hepatocytes to polyethyleneimine-coated beads. After vortexing, beads were coated with a very pure plasma membrane fraction. Microsomal contamination, judged from the specific activities of glucose-6-phosphatase or NADH-cytochrome c reductase, was less than 1%. Nevertheless, the specific content (per milligram of protein) of CO-binding cytochrome P-450 was 20% of that in microsomes; the specific benzo(a)pyrene hydroxylase activity was 25%, and ethoxycoumarin deethylase 11%. Immunoblots showed the presence of cytochromes P-450 UT-A, UT-H, PB-B, ISF-G and PCN-E, the last three isoenzymes being inducible by, respectively, phenobarbital, 3-methylcholanthrene and dexamethasone. In a second series of experiments, nonpermeabilized isolated hepatocytes from untreated rats were incubated with anticytochrome P-450 antibodies. Immunofluorescence and immunoperoxidase staining confirmed the presence of cytochromes P-450 UT-A, PB-B and ISF-G on the membrane. In a last series of experiments, human antiliver-kidney microsomal 1 antibodies were found to react specifically with rat liver plasma membrane cytochrome P-450 UT-H (IID subfamily). We conclude that several cytochrome P-450 isoenzymes are present, active and inducible on the plasma membrane surface of hepatocytes. It is therefore conceivable that immunization against plasma membrane cytochrome P-450 might lead to the immunological destruction of hepatocytes in some patients.
...
PMID:Presence of functional cytochrome P-450 on isolated rat hepatocyte plasma membrane. 211 12


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---