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:3.1.3.9 (glucose-6-phosphatase)
3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in the liver resulting from the low level dietary administration of 1,1-di(p-chlorophenyl)-2-chloroethylene (DDMU),p,p'-DDT, o,p'-DDT, p,p'-DDD and p,p'-DDE to Japanese Quail have been monitored. DDMU was exceptional in causing substantial increases in relative liver wt. and hepatic glucose-6-phosphatase after feeding at 100 ppm for 28 days. The time course of liver enzyme induction by DDMU has also been studied in Japanese Quail after periods of dietary administration ranging from 1--28 days with particular reference to changes in hepatic cytochrome P-450 and relative liver wt. Structural changes in the liver have been followed by reference to protein and lipid components. The hepatic response to DDMU appears to be biphasic. Initially there are substantial increases in hepatic cytochrome P-450 and relative liver wt., but the latter is largely due to accumulation of triglycerides. After approximately 20 days the level of hepatic cytochrome P-450 remain at a high 'plateau' level. This secondary phase of liver induction probably involves cell proliferation. It is concluded that DDMU causes major changes in the avian liver and either directly or through a metabolite causes pronounced microsomal enzyme induction.
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PMID:Pesticide-induced changes in hepatic microsomal enzyme systems: further studies on the effects of 1,1,-di(p-chlorophenyl)-2-chloroethylene (DDMU) in the Japanese quail. 20 4

The effects of an analog of thyroxine, 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT), on fetal rat hepatocyte ultrastructure and microsomal function were investigated by using the techniques of quantitative electron microscopy and enzyme assays. Rats were injected with DIMIT (10 microgram/100 g BW) or vehicle daily from the 15th through the 19th day of pregnancy. Fetuses were sacrificed on the 20th day of gestation. In comparison with controls, DIMIT-treated livers 1) were devoid of glycogen; 2) contained smaller hepatocytes; 3) contained a greater number of hepatocytes; 4) had an increased volume density of mitochondria; and 5) had increased NADPH-cytochrome c reductase and glucose-6-phosphatase activities. Surface areas of rough and smooth surfaced endoplasmic reticulum were unaffected by the hormone analog, and cytochrome P-450 was not induced. All of the changes that were produced by DIMIT in the 20-day-old fetal rat, as well as smooth endoplasmic reticulum and cytochrome P-450 development, are observed in normal animals within the first 3 days after birth. The data suggest that thyroid hormone may be a physiological stimulus for certain aspects of early hepatic development, but that it acts in combination or in sequence with other factor(s) to produce the full complement of structural and functional changes that occur perinatally in the rat.
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PMID:Effects of a thyroid hormone analog on fetal rat hepatocyte ultrastructure and microsomal function. 21 99

The effect of repeated (4 weeks) oral administration of 2,4-, 2,5- or 2,6-xylidine (at dose levels of 400--500 mg/kg/day) on the morphology and microsomal drug metabolising enzyme activity of the liver was studied in rats. All 3 isomers caused hepatomegaly which was considered to be due to proliferation of the smooth endoplasmic reticulum. Decreases in glycogen content and glucose-6-phosphatase activity were demonstrated histochemically. Biochemical investigations showed increases in microsomal protein and cytochrome P-450 content in rats dosed with 2,4- or 2,5-xylidine and in glucuronyltransferase activity in rats given 2,4-, 2,5- or 2,6-xylidine. Aniline hydroxylase activity was increased in all treated rats except males dosed with 2,6-xylidine. The results of the study indicate that all isomes of xylidine can be inducers of microsomal drug-metabolising enzyme activity, that they may be metabolised by oxidation and that the xylidine molecule may be eliminated as a conjugate with glucuronic acid.
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PMID:Hepatic effects of xylidine isomers in rats. 22 31

Rat liver microsomes incubated with linoleic acid hydroperoxide (LAHPO) lost cytochrome P-450 specifically among the enzymes of microsomal electron transport systems. The loss of cytochrome P-450 content and glucose-6-phosphatase activity by LAHPO was accompanied by an increase in malondialdehyde (MDA) production. Turbidity of microsomal suspensions was decreased with increasing MDA production, but not proportionately. Diethyldithiocarbamate (DTC), N,N'-diphenyl-p-phenylenediamine and alpha-tocopherol inhibited almost completely the LAHPO-induced MDA production of microsomes, however no perfect protection against the loss of cytochrome P-450 content and glucose-6-phosphatase activity was observed. The decrease of microsomal turbidity by LAHPO was little affected in the presence of DTC. Purified cytochrome P-450 was destroyed by LAHPO, with minimal protection by the compounds described above. These results suggest the possibility that the loss of microsomal enzyme activities during lipid peroxidation may be attributed largely to a direct attack on enzyme proteins by lipid peroxides rather than indirectly to a structural damage of microsomal membranes resulting from peroxidative breakdown of membrane lipids.
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PMID:Effect of linoleic acid hydroperoxide on liver microsomal enzymes in vitro. 23 98

The inducing effect of certain barbiturates (secobarbitone, thiopentone, pentobarbitone, allobarbitone, phenobarbitone and barbitone) on the levels of the hepatic microsomal drug-metabolizing enzymes has been studied in the rat both in vivo and in vitro. The extent of induction was related to the plasma half-lives of the barbiturates; compounds with low rates of metabolism and long half-lives were the most potent inducing agents. The latter (phenobarbitone, pentobarbitone and allobarbitone) were shown by spectral technique to interact with cytochrome P-450 suggesting that their mechanism of enzyme induction was 'substrate induction' in type. Barbiturates containing an allyl group (secobarbitone and allobarbitone) had a weaker inducing effect than expected, possibly due to their destruction of cytochrome P-450. Despite its short plasma half-life of 0-5 h thiopentone was a relatively potent inducer probably due to its metabolism to pentobarbitone, which has a much longer plasma half-life (1-3 h). Barbitone is an effective inducer of the drug-metabolizing enzymes, yet does not interact spectrally with cytochrome P-450; this is in accord with the observations that although there are increases in NADPH-cytochrome c reductase and cytochrome b5, following administration of barbitone there is no increase in cytochrome P-450. Barbiturate pretreatment does not affect the activities of glucose-6-phosphatase, glucose-6-phosphate dehydrogenase or 6-phosphogluconate dehydrogenase.
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PMID:Mechanism of induction of hepatic microsomal drug metabolizing enzymes by a series of barbiturates. 24 86

Primary monolayer culture of adult rat hepatocytes represents a novel and potentially useful technique to study many aspects of hepatic physiology for extended periods of time in vitro (J Cell Biol 59:722-734, 1973). In examining the hepatic drug-metabolizing system in these cells, we have discovered that the conditions of cell culture exert rapid, selective, and reproducible changes in microsomal enzymes. In the 24- to 48-hr period immediately following preparation and culture of the isolated parenchymal cells, the level of the drug-binding microsomal hemoprotein, cytochrome P-450, measured in extracts of cell homogenates, declined to less than 20% of its in vivo level, whereas NADPH-cytochrome c reductase activity was only moderately reduced and glucose-6-phosphatase activity remained unchanged. The activity of aminopyrine-N-demethylase and aniline hydroxylase also fell, paralleling the level of cytochrome P-450. By contrast, p-nitroanisole O-demethylase activity was unchanged in the cultured hepatocytes despite evidence (type I binding spectrum, NADPH requirement, inhibition by carbon monoxide or by SKF 525A) that p-nitroanisole O-demethylase is a cytochrome P-450-dependent enzyme. In culture, as in vivo, aromatic polycyclic hydrocarbons stimulated p-nitroanisole O-demethylase and aryl hydrocarbon (benzo [a] pyrene) hydroxylase activities; however, this effect was unaccompanied by a detectable increase in total carbon monoxide-binding hemoprotein. The data indicate that the profile of microsomal oxidase enzymes and their control undergo striking changes as hepatocytes adapt to cell culture.
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PMID:Drug metabolism in adult rat hepatocytes in primary monolayer culture. 40 8

Administration of thiobenzamide in a single dose (25 mg/100 g body wt by stomach tube) to male rats induced centrilobular necrosis, which became evident 10 h after the poisoning. In the meantime liver weight and water content underwent changes, glycogen was lost, triglycerides accumulated in the liver while decreasing in serum, [3H] leucine uptake in proteins was impaired and the activity of glucose-6-phosphatase and aminopyrine demethylase decreased. The activity of NADPH-cytochrome c reductase remained unchanged, whereas a reduction of the microsomal cytochrome P-450 occurred. The liver amount of reduced glutathione underwent no significant changes. Pretreatment of the animals with cobalt chloride or 20-methylcholanthrene decreased the liver damage caused by the drug. The in vitro addition of thiobenzamide to liver microsomes resulted in a spectral change. The appearance of conjugated dienes among microsomal lipids from drug-treated rats indicated for a lipoperoxidation taking place in vivo.
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PMID:Early biochemical liver changes following thiobenzamide poisoning. 51 72

The effect of chronic ethanol consumption on the ability of isolated liver fractions to metabolize the carcinogen N-nitrosopyrrolidine (NPY) was examined. Microsomal fractions of treated animals exhibited increased rates of alpha-hydroxylation of NPY. Similar increases in the specific activities of aniline hydroxylase, reduced nicotinamide adenine dinucleotide phosphate cytochrome c reductase, and the specific content of cytochrome P-450 were also observed. In contrast, no differences in the specific activities of benzo(a)pyrene hydroxylase or glucose-6-phosphatase were observed. Liver postmitochondrial supernatants from ethanol-consuming animals were able to produce 5 times more mutants than did control preparations. It is concluded that alpha-hydroxylation of NPY is probably the mechanism by which NPY is converted to a mutagen and that this pathway can be induced by ethanol.
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PMID:Enhanced metabolism and mutagenesis of nitrosopyrrolidine in liver fractions isolated from chronic ethanol-consuming hamsters. 57 Aug 82

Rat liver endoplasmic reticulum has been separated into four ribosome-containing subfractions, two from rapidly sedimentation endoplasmic reticulum and two from the microsomes, by differential centrifugation and sucrose density centrifugation. Ribosomes from one of the rapidly sedimenting subfractions were extracted by Trion X-100 as a complex with cytochrome P-450, optimally at a detergent protein ratio of 2/1 (w/w). Upon extraction approximately 50% of the cytochrome P-450 in the membrane appeared complex-bound to ribosomes, and, maximally, 6-7 subunit molecules of the cytochrome were attached per ribosome. The specific concentration of cytochrome P-450 on these ribosomes was 2.5-times higher than in the parent membrane. Cytochrome b5, glucose-6-phosphatase, NADPH-cytochrome c reductase, NADH-ferricyanide reductase, cytochrome oxidase and phospholipids were present in small or trace amounts on the ribosomes in relation to cytochrome P-450. Ribosomes extracted from other subfractions contained much less bound cytochrome P-450. Phenobarbital treatment induced an increase in the cytochrome P-450 content that was different for the various subfractions. This increase could not be correlated with changes in the amounts of cytochrome-ribosome complexes released by detergent. We propose that cytochrome P-450 is part of a specific binding site in the membrane for a fraction of the ribosomes attached to the endoplasmic reticulum. The ribosomes may be anchored to cytochrome P-450 via nascent chain proteins.
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PMID:On the involvement of cytochrome P-450 in the binding of ribosomes to a subfraction of rat-liver rapidly sedimenting endoplasmic reticulum. 83 30

Pretreatment of rats with methylmercury hydroxide (MMH) (15 mg/kg s.c. for 2 days) protected against hepatotoxicity due to the inhalation of CCl4 vapor (4800-6100 ppm for 2 h). This was evidenced by lessening of the changes due to CCl4 in liver glucose-6-phosphatase, serum glutamic oxalacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), serum isocitrate dehydrogenase and serum sorbitol dehydrogenase. Decreases in p-nitroanisole demethylation and cytochrome P-450 were also altered. Lipid peroxidation due to CCl4 was decreased by MMH. These biochemical indices of protection were supported by histopathological observations. These results lend further support to the concept that metabolism of CCl4 is necessary for its hepatoxicity.
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PMID:Protection against carbon tetrachloride-induced hepatotoxicity by pretreatment with methylmercury hydroxide. 112 9


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