Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present paper we provide a basic enzymatic characterization of biliary epithelial cells (BEC) that have been isolated from normal rat liver. When compared with liver parenchymal cells, BEC display the following major features: (a) a very high specific activity of gamma-glutamyltranspeptidase (approx. 200-times higher than the value usually found in hepatocytes); (b) a lack of enzymes that are usually associated with the endoplasmic reticulum in hepatocytes such as cytochrome P-450, aminopyrine demethylase, glucose 6-phosphatase and NADPH cytochrome-c reductase; (c) the presence of enzymes related to the glutathione redox cycle (e.g., GSH-peroxidase, GSSG-reductase and different isozymes of GSH-transferase), but accompanied by a very low content in reduced glutathione. The enzyme pattern of BEC correlates well with histochemical and immunohistochemical studies, as well as with biochemical studies on bile ductular cells isolated from rat liver during cholestasis.
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PMID:Biochemical studies on bile duct epithelial cells isolated from rat liver. 197 79

In 6 normal rabbits, the aortic arch, the descending thoracic and the abdominal aorta were tested for non proteic thiol compounds, selenium-dependent and selenium-independent glutatione peroxidase, glutatione reductase, glutatione transferase and thiobarbituric acid reactive substances. The aortic arch showed the greatest content of non proteic thiol compounds and thiobarbituric acid reactive substances, associated to the highest activities of glutathione-related enzymes. However, not significant differences were detectable between aortic arch and descending thoracic aorta, except for the glutathione transferase activity (0.395 +/- 0.031 vs 0.330 +/- 0.053 U/mg protein, p less than 0.05). Furthermore, both aortic arch and descending thoracic aorta showed significantly higher values of non proteic thiol compounds (46.05 +/- 10.15% and 33 +/- 13.5%, p less than 0.05), selenium-dependent glutathione peroxidase activity (70.35 +/- 26% and 54.3 +/- 9.5%, p less than 0.05), glutathione reductase activity (25.4 +/- 7% and 18.4 +/- 4.5%, p less than 0.05) and thiobarbituric acid reactive substances (65.8 +/- 18% and 47.2 +/- 17%, p less than 0.05) with respect to the abdominal aorta. The selenium-independent glutathione peroxidase activity was not detectable. In conclusion, a biochemical gradient in glutathione-related antioxidant defences and thiobarbituric acid reactive substances proceeding from the proximal to the distal segments seems to exist in the normal rabbit aorta. These results could contribute to explain the non homogeneous distribution of experimental atherosclerosis in the rabbit aorta.
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PMID:Regional distribution of glutathione-related antioxidant defences in the normal rabbit aorta. 204 54

Deposition of inhaled particulates onto the respiratory mucosa is relatively great in that portion of the nasal cavity unprotected by ciliated, goblet, or keratinized superficial cells. The cytochrome P-450 system is an important enzyme system involved in the biotransformation of xenobiotics into metabolites that are more readily absorbed. To examine the transitional region caudal to the nasal vestibule, nasal tissues of hamster and rat were prepared for immunocytochemistry. Blocks of tissue representing four levels along the long axis of the nasal cavity were examined. Paraffin sections were processed through the avidin-biotin peroxidase procedure, with diaminobenzidine tetrahydrochloride as the chromagen. Enzyme localization was accomplished through the use of antibodies for three rabbit cytochrome P-450 isozymes; 2, 5, and 6 (subfamilies IIB, IVB, and IA, respectively); and for rabbit NADPH-cytochrome P-450 reductase. Enzyme distribution was similar in both hamster and rat nasal tissues except in cells of striated and intercalated ducts of nasal glands and in cells of the nasolacrimal duct where immunoreactivity was greater in the hamster. Immunoreactivity for reductase and isozyme 2 was intense in nonciliated cells lining the nonolfactory epithelium, in sustentacular cells of the olfactory epithelium, and in acinar cells of olfactory glands. Distribution of reaction products to isozyme 5 and 6 were similar to but not so intense as those of reductase and isozyme 2. Reaction products for reductase and isozyme 2 occurred generally in the same cellular and intracellular regions with the following exceptions: isozyme 2 was more concentrated in cells of striated ducts and of the nasolacrimal duct, and reductase was more abundant in intercalated ducts of nasal glands.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Distribution of cytochrome P-450 monoxygenase enzymes in the nasal mucosa of hamster and rat. 204 56

A protein fraction from Escherichia Coli soluble extracts contain a NAD(P)H:hydrogen peroxide oxidoreductase activity. This activity is compared to and found to be distinct from well-known E. Coli enzymes involved in the protection from peroxides: hydroperoxidase I (HPI) and its o-dianisidine peroxidase component and the alkyl hydroperoxide reductase.
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PMID:NAD(P)H oxidation by hydrogen peroxide in Escherichia coli. 206 79

Mammalian spermatozoa are highly sensitive to lipid peroxidation and the glutathione peroxidase/reductase system provides an effective defense against oxidative damage to different degree in different species. Rabbit spermatozoa rely on superoxide dismutase as the primary enzymatic defense against lipid peroxidation and contain only low detectable endogenous glutathione reductase activity while in mouse spermatozoa the glutathione system is the major protective enzyme against cell damage by autoxidation. We describe a cytochemical quantitative assay for glucose-6-phosphate dehydrogenase activity in rabbit and mouse spermatozoa undergoing spontaneous lipid peroxidation during in vitro incubation. Microdensitometric measurements were made by a Vickers M85 a scanning microdensitometer at lambda 585 nm wavelength. Our findings suggest that in mouse spermatozoa, the enhanced glutathione reductase and peroxidase activities induced by the spontaneous lipid peroxidation increases NADPH production from the pentose phosphate shunt, while in rabbit spermatozoa, NADPH production is much lower.
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PMID:Microphotometric study of glucose-6-phosphate dehydrogenase activity in epididymal spermatozoa during spontaneous lipid peroxidation. 212 49

The hepatic glutathione (GSH) system and the influences of xenobiotics have been reviewed. Key steps in the regulation of hepatic GSH are GSH biosynthesis, the GSH-peroxidase/reductase cycle, the cystathionine pathway, and the carrier-mediated export processes. Influences of xenobiotics on these different pathways are discussed. Xenobiotics may lead to liver injury after biotransformation to highly reactive electrophilic metabolites (mainly cytochrome P-450 mediated), which easily conjugate with GSH, thus producing GSH depletion. This GSH depletion and probably an additional loss of protein sulfhydryl groups cause a disturbance of the intracellular calcium homeostasis which leads to an irreversible cell injury. The different acinar distribution of cytochromes P-450 and of GSH and GSH-related detoxication pathways points to a greater susceptibility of perivenous hepatocytes to xenobiotic-induced damage. Also, the intracellular compartmentation of GSH is important for the understanding of hepatocellular injury induced by several xenobiotics.
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PMID:The hepatic glutathione system--influences of xenobiotics. 219 11

Hydroperoxide decomposition by the NADP-glutathione system in rat liver mitochondria was analyzed. Mitochondria were found to contain high concentrations of the reduced form of glutathione (GSH) (4.32 +/- 0.50 nmol/mg) and NADPH (4.74 +/- 0.64 nmol/mg), and high activities of glutathione peroxidase and reductase. In the initial phase of the reaction, the rate of hydroperoxide decomposition was proportional to both the GSH level and the activity of GSH peroxidase. However, in the later steady state, the step of NADP reduction was rate-limiting, and the overall reaction rate was independent of the initial concentration of GSH, and activities of glutathione peroxidase and reductase. Some GSH was released from mitochondria during incubation, but the rate of the decomposition could be simply expressed as kappa [GSH]/2, where kappa is the first-order rate constant of the peroxidase and [GSH] is the intramitochondrial level of GSH in the steady state. The rate of the reaction in the steady state was also dependent on the NADPH level, its reciprocal being linearly correlated with [NADPH]-1. The rate of decomposition of hydroperoxide was influenced by the respiratory state. During state 3 respiration, the rate was greatly depressed, but was still considered to exceed by far the rate of physiological generation of hydroperoxide.
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PMID:Kinetics of hydroperoxide degradation by NADP-glutathione system in mitochondria. 222 15

Generation of radicals in vivo depends on metabolic activities. The reactions are usually influenced by (i) the presence and concentration of oxygen; (ii) the availability of transition metals (effects of binding and compartimentalization); (iii) the level of reductants and antioxidants (e.g. nutritional effects). The effects of radicals are thought to be due to (i) membrane damage (affecting passive or active transport through altered fluidity/function interrelationships, intercellular messenging through modifications in the synthesis of prostaglandins and leukotrienes); (ii) protein damage (e.g. affecting membrane transporters, channel proteins, receptor or regulatory proteins, immunomodulators); (iii) damage to DNA. Defense mechanisms consist of (i) prevention of the 'spreading' of primary damage by low molecular weight antioxidants (e.g. vitamin E, GSH, vitamin C, beta-carotene, uric acid); (ii) prevention or limitation of 'secondary' damage by enzymes (e.g. GSH-peroxidase, catalase, superoxide dismutase, DT-diaphorase) and/or chelators; (iii) repair processes, e.g. lipid degradation/membrane repair enzymes (phospholipases, peroxidases, some transferases and reductases), protein disposal or repair enzymes (proteases, GSSG-reductase), DNA degradation repair enzymes (exonuclease III, endonucleases III and IV, glycosylases, polymerases). Recent hypotheses on a messenging function of the superoxide anion O2- are discussed and possible implications of cross-reactions between O2- and nitric oxide (endothelium-derived relaxing factor EDRF) are shortly mentioned.
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PMID:Radical reactions in vivo--an overview. 228 Nov 32

Though various chemotherapy protocols lead to considerable response rates in squamous cell head and neck cancer (SCHNC), the overgrowth of a tumor cell phenotype which no longer responds to clinically achievable drug concentrations regularly impairs definite tumor control. In order to investigate mechanisms of drug resistance towards one of the most active agents in SCHNC we established four Cisplatin (CDDP)-resistant sublines (DDP1-DDP4) of the recloned human SCHNC cell line HLac 79. The 50% inhibitory drug concentration (IC50) of CDDP as determined by the colorimetric MTT-assay was increased by the factors 2.7 (DDP1), 3.3 (DDP2), 5.1 (DDP3), and 6.4 (DDP4) in the respective sublines. Three subpopulations contained significantly elevated glutathione (GSH) levels by the factors 1.4 (DDP3), 1.7 (DDP2), and 2.4 (DDP4) compared to the maternal line (50.2 nM/mg protein). DDP4 showed increased activity of gamma-glutamyl-transpeptidase (1.83 vs. 1.21 mU/mg protein), and DDP2 and DDP4 showed increased activity of GSH-S-transferase (35.6 and 51.9 vs. 25.1 mU/mg protein). Concerning both GSH-peroxidase and GSH-reductase no significant differences between the HLac 79 subpopulations were observed. Intracellular CDDP accumulation determined by neutron activation analysis revealed reduced drug uptake in DDP3 and DDP4 (60% and 76% of control value).
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PMID:Establishment and characterization of cisplatin-resistant sublines of the human squamous carcinoma cell line HLac 79. 228 22

Treatment of rats with cisplatin or with cisplatin after chronic pre-exposure to lead induced a decrease in cytochrome P-450, reduced glutathione (GSH), GSH-S-transferase, reductase and peroxidase activities, and an increase in N-glucuronyl transferase, lipid peroxidation and oxidized glutathione (GSSG). On histological examination, rats treated by lead or cisplatin and by lead + cisplatin revealed significant proximal tubular lesions which varied from minimal changes to severe necrosis. Lead toxicity was characterized by irregularity and thickening of glomerular basement membranes, and by tubular mitochondrial alterations associated with the presence of intranuclear inclusions. Cisplatin injury showed more extensive lesions with cellular disorganization. Except for an increase in N-glucuronyl transferase activity, lead did not exert any significant effect on these biochemical and histological parameters and did not significantly modify the deleterious effects of further therapy by cisplatin.
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PMID:Cisplatin nephrotoxicity in lead-pretreated rats: enzymatic and morphological studies. 230 43


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