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:1.4.3.11 (glutamate dehydrogenase)
4,437 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An isomeric mixture of S-[(1 and 2)-phenyl-2-hydroxyethyl]glutathione (PHEG), a glutathione conjugate of styrene, is moderately nephrotoxic. Its in vivo nephrotoxicity was characterized by significant elevations in the urinary excretion of glucose, gamma-glutamyl transpeptidase, glutamate dehydrogenase, N-acetyl-beta-D-glucosaminidase and lactic dehydrogenase 24 h after an i.v. administration of PHEG (0.5 mmol/kg) in male Fischer-344 rats. The histologic alterations consisted of moderate tubular damage with proximal tubule vacuolization and accumulation of tubular cast material, indicating an early sign of tubular necrosis. The data suggest that nephrotoxic injury induced by PHEG lies preferentially at the tubular region of the rat kidney involving several subcellular targets. The nephrotoxicity of PHEG was blocked by acivicin, a specific inhibitor of gamma-glutamyl transpeptidase, by phenylalanylglycine, an inhibitor of cysteinylglycine dipeptidase, as well as by probenecid, a competitive inhibitor of renal organic anion transport system. On the other hand, pretreatment with aminooxyacetic acid, a specific inhibitor of renal cysteine conjugate beta-lyase, failed to inhibit the nephrotoxicity of this glutathione conjugate. Similarly, prior administration of alpha-ketobutyrate, an inducer of renal cysteine conjugate beta-lyase, failed to potentiate its nephrotoxicity, suggesting an insignificant role of beta-lyase in such toxicity. A modest decline in renal cellular GSH due to PHEG but without any concomitant oxidation of GSH to GSSG and without any increase in lipid peroxidation indicates that oxidative stress may not be an important mechanism of its nephrotoxicity. Therefore, the following steps at least, are involved in the development of its nephrotoxicity: (1) renal tubular accumulation of PHEG via a probenecid-sensitive transport process; and (2) its renal metabolism via gamma-glutamyl transpeptidase and cysteinylglycine dipeptidase to the corresponding cysteine-S-conjugate.
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PMID:In vivo nephrotoxic action of an isomeric mixture of S-(1-phenyl-2-hydroxyethyl)glutathione and S-(2-phenyl-2-hydroxyethyl)glutathione in Fischer-344 rats. 167 68

The interstitial transudate was investigated in isolated perfused rat hearts. Capillary permeability and the kinetics of interstitial uptake and release were characterized using four different marker molecules (mol wt 522 to 2 X 10(6)). The half-time (t1/2) values (less than 30 to 170 s) and the interstitial concentration after 30 min (100-44% of arterial concentration) reflected the order and inverse order of their molecular weights, respectively. Creatine kinase (CK) and glutathione (GSH) were measured during control state, hypoxia, and anoxia, followed by reoxygenation. Interstitial concentrations of CK and GSH were higher by a factor of 100 and 8, respectively, compared with the venous effluent. During hypoxia (PO2 = 110 mmHg, i.e., O2 supply = 30% of demand) and reoxygenation there was a significant increase only in the interstitial (not venous) release of CK and GSH, which was further increased during anoxia. Ischemia (75 min) and reperfusion cause no interstitial release of lysosomal (acid phosphatase) and mitochondrial (glutamate dehydrogenase) enzymes despite a massive loss of cytosolic enzymes. Examination of the interstitial transudate allows characterization of capillary transfer and provides a very sensitive measure of sarcolemmal release phenomena.
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PMID:Intra- and extracellular markers in interstitial transudate of perfused rat hearts. 245 35

Rats metabolized a sublethal gastric dose (0.73 mmol/kg) of allyl alcohol (AIOH) within 10-15 min. Oxidation of AIOH to acrolein was accompanied by an equally rapid, but only transient depletion of hepatic reduced glutathione (GSH). GSH was restored to levels above normal within 5 hrs. Simultaneously, AIOH provoked marked elevation of alanine aminotransferase, gamma-glutamyl transpeptidase, and glutamate dehydrogenase activities in plasma and formation of lesions mainly in the periportal regions of the liver. Inhibition of alcohol dehydrogenase by 4-methyl pyrazole completely counteracted these effects. On the other hand, attempts to potentiate the toxicity of acrolein by the aldehyde dehydrogenase inhibitor cyanamide enhanced only the release of alanine aminotransferase. Co-administration of ethanol (3 g/kg) inhibited the rate of AIOH oxidation by more than 90%. Although with ethanol GSH remained depleted for several hours, the release of enzymes was markedly suppressed and the histologic changes completely prevented. These results indicate that the rapid rate of acrolein formation, rather than persistently lowered GSH content, is crucial in the hepatotoxicity of AIOH. They also suggest, that oxidation of acrolein via aldehyde dehydrogenase does not represent a major pathway for its detoxication in vivo.
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PMID:Allyl alcohol liver injury: suppression by ethanol and relation to transient glutathione depletion. 288 87

The translational inhibition produced by addition of oxidized glutathione (GSSG) to hemin-containing reticulocyte lysates and the accompanying phosphorylation of the alpha subunit of the polypeptide chain initiation factor eIF-2 can be prevented or reversed by NADPH generators, including glucose 6-phosphate, deoxyglucose 6-phosphate, fructose 6-phosphate, NADPH itself, and also by dithiols, e.g., dithiothreitol, but not by reduced glutathione (GSH) or other monothiols, e.g., 2-mercaptoethanol. The same is true of the inhibition caused by addition of glutamate dehydrogenase, alpha-ketoglutarate, and NH4+, which may be entirely due to NADPH depletion via the reaction.
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PMID:Studies on the activation of the heme-stabilized translational inhibitor of reticulocyte lysates by oxidized glutathione and NADPH depletion. 400 74

Reactions between ebselen and subcellular particles of rat liver were investigated by monitoring the activity of mitochondrial glutamate dehydrogenase and microsomal glucose 6-phosphate dehydrogenase. Rat small intestine lactate dehydrogenase was purified and was also used in the reaction between cytosolic protein and ebselen. Glutamate dehydrogenase in intact rat liver mitochondria was completely resistant to ebselen, but the enzyme was significantly inactivated in broken mitochondria mediated by Triton X-100, reflecting the fact that ebselen was not transported through the mitochondrial membrane into the matrix. Glucose 6-phosphate dehydrogenase in rat liver microsomes was inactivated by ebselen, accompanied by a slight decrease in the thiol groups of microsomal membrane protein. Purified cytosolic lactate dehydrogenase was inactivated concentration- and time-dependent by ebselen. The activity of rat small intestine lactate dehydrogenase abolished by ebselen was significantly restored by incubation with purified rat small intestine thioltransferase in the presence of reduced glutathione (GSH). The level of thiol groups in rat liver microsome membrane protein decreased by ebselen was partially restored by an incubation with purified rat liver thioltransferase in the presence of GSH. The results suggested that thioltransferase can cleave the Se-S conjugates between ebselen and cytosolic proteins or microsomal membrane proteins in the presence of GSH.
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PMID:Modulation of subcellular particles of the rat small intestine and liver by ebselen. 765 15

Glutathione, both reduced (GSH) and oxidized (GSSG), was effective in displacing binding of L-[3H]-glutamic acid (L-[3H]Glu) and DL-(E)-2-[3H]amino-4-propyl-5-phosphono-3- pentenoic acid ([3H]CGP-39653) in rat brain synaptic membranes, with less potent displacement of binding of DL-alpha-amino-3-hydroxy-5-[3H]-methylisoxazole-4-propionic and [3H]kainic acids. Liquid chromatographic analysis revealed that both GSH and GSSG were contaminated with L-Glu by < 1%. Both GSH and GSSG potentiated (+)-5-[3H]methyl-10,11-dihydro-5H-dibenzo[a, d]cyclohepten-5,10-imine ([3H]MK-801) binding in a manner similar to that found with L-Glu. Pretreatment with glutamate dehydrogenase (GDH) induced a marked rightward shift of the concentration-response curve for L-Glu in the presence of NAD without affecting that in its absence, whereas GDH was ineffective in affecting the potentiation by both GSH and GSSG even in the presence of NAD. In the presence of GSH at a maximally effective concentration, both glycine (Gly) and spermidine potentiated [3H]MK-801 binding to a some-what smaller extent than that found in the presence of L-Glu at a maximally effective concentration. The potentiation of [3H]MK-801 binding by GSH was invariably attenuated by addition of CGP-39653, D-2-amino-5-phosphonovaleric acid (D-AP5), and 5,7-dichlorokynurenic acid (DCKA), whereas GSH was effective in diminishing potencies of CGP-39653, D-AP5, DCKA, and 6,7-dichloroquinoxaline-2,3-dione to inhibit [3H]MK-801 binding when determined in the presence of both L-Glu and Gly.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A possible role of glutathione as an endogenous agonist at the N-methyl-D-aspartate recognition domain in rat brain. 786 Nov 38

The main pathway for the hepatic oxidation of ethanol to acetaldehyde proceeds via ADH and is associated with the reduction of NAD to NADH; the latter produces a striking redox change with various associated metabolic disorders. NADH also inhibits xanthine dehydrogenase activity, resulting in a shift of purine oxidation to xanthine oxidase, thereby promoting the generation of oxygen-free radical species. NADH also supports microsomal oxidations, including that of ethanol, in part via transhydrogenation to NADPH. In addition to the classic alcohol dehydrogenase pathway, ethanol can also be reduced by an accessory but inducible microsomal ethanoloxidizing system. This induction is associated with proliferation of the endoplasmic reticulum, both in experimental animals and in humans, and is accompanied by increased oxidation of NADPH with resulting H2O2 generation. There is also a concomitant 4- to 10-fold induction of cytochrome P4502E1 (2E1) both in rats and in humans, with hepatic perivenular preponderance. This 2E1 induction contributes to the well-known lipid peroxidation associated with alcoholic liver injury, as demonstrated by increased rates of superoxide radical production and lipid peroxidation correlating with the amount of 2E1 in liver microsomal preparations and the inhibition of lipid peroxidation in liver microsomes by antibodies against 2E1 in control and ethanol-fed rats. Indeed, 2E1 is rather "leaky" and its operation results in a significant release of free radicals. In addition, induction of this microsomal system results in enhanced acetaldehyde production, which in turn impairs defense systems against oxidative stress. For instance, it decreases GSH by various mechanisms, including binding to cysteine or by provoking its leakage out of the mitochondria and of the cell. Hepatic GSH depletion after chronic alcohol consumption was shown both in experimental animals and in humans. Alcohol-induced increased GSH turnover was demonstrated indirectly by a rise in alpha-amino-n-butyric acid in rats and baboons and in volunteers given alcohol. The ultimate precursor of cysteine (one of the three amino acids of GSH) is methionine. Methionine, however, must be first activated to S-adenosylmethionine by an enzyme which is depressed by alcoholic liver disease. This block can be bypassed by SAMe administration which restores hepatic SAMe levels and attenuates parameters of ethanol-induced liver injury significantly such as the increase in circulating transaminases, mitochondrial lesions, and leakage of mitochondrial enzymes (e.g., glutamic dehydrogenase) into the bloodstream. SAMe also contributes to the methylation of phosphatidylethanolamine to phosphatidylcholine. The methyltransferase involved is strikingly depressed by alcohol consumption, but this can be corrected, and hepatic phosphatidylcholine levels restored, by the administration of a mixture of polyunsaturated phospholipids (polyenylphosphatidylcholine). In addition, PPC provided total protection against alcohol-induced septal fibrosis and cirrhosis in the baboon and it abolished an associated twofold rise in hepatic F2-isoprostanes, a product of lipid peroxidation. A similar effect was observed in rats given CCl4. Thus, PPC prevented CCl4- and alcohol-induced lipid peroxidation in rats and baboons, respectively, while it attenuated the associated liver injury. Similar studies are ongoing in humans.
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PMID:Role of oxidative stress and antioxidant therapy in alcoholic and nonalcoholic liver diseases. 889 26

Livers of fasted rats were perfused over 120 min in a recirculating hemoglobin-free system. Hepatotoxic injury induced by the addition of 1-butanol (130.2 mmol/l), CdCl2 (0.1 mmol/l), CuCl2 (0.03 mmol/l), Na3VO4 (2 mmol/l) or t-butylhydroperoxide (t-BuOOH, 0.5 mmol/l) to the perfusate was shown by strong increases in lactate dehydrogenase (LDH) and glutamate-pyruvate transaminase (GPT) release, decreased oxygen consumption between 50 and 60%, and a nearly complete suppression of bile flow. Hepatic adenosine triphosphate (ATP) and reduced glutathione (GSH) concentrations were reduced by between 30 and 80%, and 20 and 80% respectively. Only Na3VO4 and t-BuOOH evoked increased releases of glutamate dehydrogenase (GLDH) in the perfusate. Malondialdehyde (MDA) concentrations were enhanced by all toxicants in the perfusate and by all except 1-butanol in the liver. The MDA increase, however, was much higher after Na3VO4 and t-BuOOH than after the other toxicants. When glycine (12 mmol/l) was added 30 min before the toxicants to the perfusate it prevented the enzyme releases induced by all hepatotoxic agents by about 80%. Furthermore, glycine prevented the Na3VO4 induced increase of MDA in liver and perfusate, the hepatic ATP and GSH level reductions induced by 1-butanol and attenuated the reduction of oxygen consumption induced by CuCl2 and t-BuOOH. Glycine, however, did not reverse the reductions of oxygen consumption induced by CdCl2 and Na3VO4, the suppressions of bile flow and, with the exception of 1-butanol, the decreases of hepatic ATP levels induced by all agents.
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PMID:Influence of glycine on the damage induced in isolated perfused rat liver by five hepatotoxic agents. 970 6

We investigated the acute toxic and metabolic effects of 23-aliphatic alcohols (16 saturated and 7 unsaturated) in the isolated perfused rat liver at a concentration of 65.1 mmol/l (approximately 0.3% ethanol). The capacity of the straight chain primary alcohols (methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol) to release the enzymes glutamate-pyruvate transaminase (GPT), lactate dehydrogenase (LDH) and glutamate dehydrogenase (GLDH) into the perfusate was strongly correlated with their carbon chain length. The secondary alcohols were less active in this respect whereas branching of the carbon chain did not consistently change alcohol toxicity. Unsaturation in the straight chain but not in the branched chain alcohols was accompanied by an increase in toxicity. An increased enzyme release was in general accompanied by, and correlated to, reductions in oxygen consumption, bile secretion, and perfusion flow of the isolated livers. Statistically significant correlations exist between parameters of alcohol-induced hepatotoxicity and the membrane/buffer partition coefficents of the alcohols. With the exception of methanol, all alcohols tested increased the lactate/pyruvate ratio of the perfusate, although this effect was not correlated to the degree of hepatic injury. Hepatic ATP concentrations decreased in most cases in line with hepatic injury and were particularly correlated with changes in oxygen consumption. Hepatic concentrations of reduced glutathione (GSH) were only diminished by the unsaturated alcohols, whereas an increase in hepatic oxidized glutathione (GSSG) occurred only with some of the saturated alcohols. Hepatic concentrations of malondialdehyde (MDA) increased after two saturated and three unsaturated alcohols but did not correlate with other parameters of hepatotoxicity. In conclusion, alcohol-induced hepatotoxicity is primarily due to membrane damage induced by the direct solvent properties of the alcohols. The consequences and relative contributions of alcohol metabolization to the overall hepatotoxicity of higher alcohols requires further study.
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PMID:The toxic and metabolic effects of 23 aliphatic alcohols in the isolated perfused rat liver. 1036 51

Oxidative stress elicits an adaptive antioxidant response, which varies with tissue type. Diquat, a potent redox cycler that generates reactive oxygen species, has been used to study oxidative stress; however, its effect on the antioxidant system has not been characterized in neuronal cells. Accordingly, we measured antioxidant parameters and cell growth in human neuroblastoma SH-SY5Y cells cultured for 48 h in medium containing 5, 10, or 25 microM diquat dibromide or phosphate-buffered saline. Viable cells were assayed for glutathione (GSH) and activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPX), and glucose-6-phosphate dehydrogenase (GPDH). Mitochondrial function was evaluated by glutamate dehydrogenase (GDH) activity and MTT reduction. Diquat caused a marked concentration-related decrease in viable cell count ( by 26, 51, and 87% at 5, 10, and 25 microM diquat). Cell viability was only affected at 10 and 25 microM diquat and did not fully account for the decreased viable cell count. Concentration-related increases also occurred with GSH levels and a majority of antioxidant enzymes activities; however, the mode and magnitude varied with parameter. Increases in GSH, CAT, SOD, and GR were maximal at 25 microM diquat (to 3-, 6-, 2-, and 1.5-fold control values, respectively). GPDH activity was maximal at 10 microM diquat and then decreased to 86% of control activity at 25 microM diquat. GPX activity showed a concentration-related decrease (to 35% of control). Activity of the mitochondrial enzyme GDH increased 3-fold at 25 microM diquat, along with a lesser increase in MTT reduction. We conclude that diquat reduces cell growth in neuroblastoma cells and induces an adaptive antioxidant response, which are concentration dependent and occur at sublethal concentrations. At higher concentrations, diquat alters mitochondrial function and becomes increasingly toxic.
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PMID:Effect of diquat on the antioxidant system and cell growth in human neuroblastoma cells. 1181 26


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