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)

The role of glucocorticosteroid hormones in the developmental formation of carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, glutamate dehydrogenase, tyrosine aminotransferase, glucose-6-phosphatase, hexokinase and glucokinase activities in rat liver was investigated. Steroid hormone producing glands were either inactivated by hypophysectomy (before birth) or removed by adrenalectomy and/or gonadectomy (after birth). These procedures strongly depressed corticosterone levels. Furthermore, they decreased enzyme activities when performed before birth or after the second postnatal week. However, adrenalectomy at 1 week of age was less effective: the developmental increases in carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, tyrosine aminotransferase and glucose-6-phosphatase activity persisted despite the absence of increasing levels of circulating corticosterone.
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PMID:Multihormonal control of enzyme clusters in rat liver ontogenesis. I. Effects of adrenalectomy and gonadectomy. 727 92

The effect of carrot extract on carbon tetrachloride (CCl4)-induced acute liver damage was evaluated. The increased serum enzyme levels (viz., glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, lactate dehydrogenase, alkaline phosphatase, sorbitol and glutamate dehydrogenase) by CCl4-induction were significantly lowered due to pretreatment with the extract. The extract also decreased the elevated serum bilirubin and urea content due to CCl4 administration. Increased activities of hepatic 5'-nucleotidase, acid phosphatase, acid ribonuclease and decreased levels of succinic dehydrogenase, glucose-6-phosphatase and cytochrome P-450 produced by CCl4 were reversed by the extract in a dose-responsive way. Results of this study revealed that carrot could afford a significant protective action in the alleviation of CCl4-induced hepatocellular injury.
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PMID:Hepatoprotective activity of carrot (Daucus carota L.) against carbon tetrachloride intoxication in mouse liver. 750 Jun 38

The activity and some kinetic parameters of the key enzymes of the glycolysis, the gluconeogenesis and the amino acid catabolism from the liver of male and female mink have been determined and compared to the corresponding activities from rat and cat. The activities of glucose-6-phosphatase and pyruvate kinase are dependent on sex, both being higher in females. Except for pyruvate carboxylase the glycolytic and the gluconeogenic enzyme activities of the mink are higher than those of rat and cat; especially the activities of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase are markedly higher. The activities of glutamate dehydrogenase and glutamate oxaloacetate transaminase are smaller than the corresponding activities of rat but higher than those of cat. The results suggest that mink has a high capacity for gluconeogenesis compared to rat.
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PMID:Activities of carbohydrate and amino acid metabolizing enzymes from liver of mink (Mustela vison) and preliminary observations on steady state kinetics of the enzymes. 758 47

The probable involvement of hepatic carbamyl-P in the reciprocal relationship between hepatic ureagenesis and glycogenesis from glucose was explored. Isolated perfused liver preparations from 48-h fasted rats were employed. Moderate (9.2 mM) and relatively high levels of glucose (34 mM) were perfused. Hepatic glycogenesis, glucose-6-P, carbamyl-P, and citrulline levels, hepatic urea formation, and ureagenesis based upon perfusate urea levels were measured. Experimental probes selected to modify hepatic ureagenesis and carbamyl-P production and utilization included: (a) NH4Cl, maintained at 5 mM by continuous infusion (NH4+ is a substrate for carbamyl-P synthase I and glutamate dehydrogenase); (b) norvaline, an inhibitor of ornithine transcarbamylase which catalyzes the first committed step in the urea cycle; and (c) ethoxyzolamide, an inhibitor of carbonic anhydrase which produces HCO3-, an essential substrate for carbamyl-P synthase I. NH4+ increased ureagenesis and decreased glycogenesis. The inclusion of norvaline with NH4+ decreased ureagenesis and increased glycogenesis. Ethoxyzolamide with or without NH4+ inhibited both ureagenesis and glycogenesis, and decreased the hepatic glucose-6-P level. Glycogenesis was greater at 34 mM than 9.2 mM glucose, increased in norvaline-containing preparations correlative with increased availability of carbamyl-P, and decreased when carbamyl-P formation was inhibited by ethoxyzolamide. Kinetic analysis indicated a Km, Glc of 31 mM for glucose phosphorylation preliminary to glycogenesis. Glycogen formation via the "indirect pathway" (i.e. involving extrahepatic glycolysis, transport of lactate to the liver, and glyconeogenesis therefrom) was quantitatively insufficient to account for the observed glycogenesis. Glucokinase is contraindicated by the inverse relationship between hepatic glycogenesis and ATP availability in the ethoxyzolamide-treated preparations. In contrast, carbamyl-P:glucose phosphotransferase activity of the glucose-6-phosphatase system has the characteristics to bridge hepatic ureagenesis and glycogenesis.
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PMID:Glycogenesis from glucose and ureagenesis in isolated perfused rat livers. Influence of ammonium ion, norvaline, and ethoxyzolamide. 813 5

Freeze-substituted rat liver embedded in glycol methacrylate (GMA) has been used to demonstrate the activities of several enzymes. The following enzymes could be detected in GMA-sections by the indicated histochemical procedure(s): 5'-nucleotidase (lead salt, cerium-diaminobenzidine), alkaline phosphatase (indoxyl-tetrazolium salt), catalase (diaminobenzidine), acid phosphatase (diazonium salt), lactate dehydrogenase (tetrazolium salt) and glutamate dehydrogenase (tetrazolium salt). The activities of all these enzymes were dramatically decreased compared with the activities demonstrated in unfixed cryostat sections, with the exception of catalase. The activities of the following enzymes could not be detected in GMA-sections: glucose-6-phosphate dehydrogenase (tetrazolium salt), xanthine oxidoreductase (tetrazolium salt), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide) and glucose-6-phosphatase (cerium-diaminobenzidine). The possible role of restricted penetration of reagents into the resin was studied by measuring cytophotometrically the enzyme activities in GMA-sections of 3 and 6 microns in thickness. For all the enzymes that could be detected, the 6 microns:3 microns ratio varied from 1.4 to 2.7. An eventual retarded penetration of reagents into the resin was investigated by measuring cytophotometrically the amount of final reaction product during incubation for acid phosphatase and glutamate dehydrogenase activities. In both cases linear relationships without a lag phase were found for the specific enzyme activities with incubation time. Chemical denaturation of proteins or masking of active sites in proteins due to embedding in the resin monomer may be considered to be the main cause of decreased enzyme activities.
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PMID:Quantitative aspects of enzyme histochemistry on sections of freeze-substituted glycol methacrylate-embedded rat liver. 827 44

The effect of storage of unfixed cryostat sections from rat liver for 4 h, 24 h, 3 days and 7 days at -25 degrees C was studied on the activities of lactate dehydrogenase, glucose-6-phosphate dehydrogenase, xanthine oxidoreductase, glutamate dehydrogenase, succinate dehydrogenase (all demonstrated with tetrazolium salt procedures), glucose-6-phosphatase (cerium-diaminobenzidine method), 5'-nucleotidase (lead salt method), dipeptidyl peptidase II, acid phosphatase (both simultaneous azo coupling methods), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide procedure) and catalase (diaminobenzidine method). The effect of drying of the cryostat sections at room temperature for 5 and 60 min was investigated as well. The enzyme activities were quantified by cytophotometric measurements of test and control reactions. The test minus control reaction was taken as a measure for specific enzyme activity. It was found that the activities of all the enzymes investigated, with one exception, were affected neither by storage of the cryostat sections at -25 degrees C for up to 7 days, nor by drying of the sections at room temperature for up to 60 min. The exception was xanthine oxidoreductase, whose activity was reduced by 20% after 5 min drying of sections or after 4 h storage. Therefore, only incubations for xanthine oxidoreductase activity have to be performed immediately after cutting cryostat sections, whereas for the other enzymes a considerable margin appears to exist.
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PMID:The effects of storage on the retention of enzyme activity in cryostat sections. A quantitative histochemical study on rat liver. 846 85

Anterograde or retrograde perfusion of rat liver with digitonin selectively permeabilizes the periportal or the perivenous zone of the hepatic lobule. Digitonin perfusion is used to analyze the effluents released by permeabilized hepatocytes or, combined with collagenase perfusion, to obtain cell suspensions enriched in either periportal or perivenous hepatocytes. Despite the wide use of digitonin to study lobular heterogeneity, its affects on rat hepatocytes are not well documented. We therefore analyzed the effects of digitonin perfusion on the intracellular content of rat hepatocytes by combining electron microscopy, histoenzymology, immunohistochemistry, and in situ hybridization. At the concentration currently used for the study of lobular heterogeneity, digitonin perfusion induced a marked cytosolic clarification of permeabilized hepatocytes, while most organelles except mitochondria were well preserved. In the digitonin-altered zones, there was no histochemical detection of non-membrane-bound enzymes (lactate dehydrogenase, glutamate dehydrogenase), whereas membrane-bound enzymes (succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, NADPH dehydrogenase, glucose-6-phosphatase) were still detected. Immunohistochemistry and in situ hybridization revealed significant amounts of several plasma proteins (albumin, alpha 2-macroglobulin, alpha 1-inhibitor 3, alpha 1-acid glycoprotein) and their respective mRNAs in digitonin-permeabilized hepatocytes. The demonstration that digitonin-permeabilized hepatocytes retain many intracellular constituents shows that biochemical analysis of cellular effluents released from digitonin-permeabilized hepatocytes must be interpreted with caution and that the apparent characteristics of cell suspensions obtained by the digitonin-collagenase technique might be significantly altered by contamination with permeabilized hepatocytes from the opposite zone.
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PMID:Effects of digitonin on the intracellular content of rat hepatocytes: implications for its use in the study of intralobular heterogeneity. 815 38

Little is known about the alterations of metabolic organization of the human liver tissue in chronic liver diseases. We therefore compared the distribution of the following zonal metabolic markers in 10 samples of normal liver tissue, 10 samples of fibrotic tissue, and 22 samples of cirrhotic tissue: (a) the enzymatic activities of glucose-6-phosphatase (G6P), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), nicotinamide-adenine-dinucleotide-phosphate [NAPH] dehydrogenase (ND), beta-hydroxybutyrate dehydrogenase (HBDH), and glutamate dehydrogenase (GDH); (b) the protein glutamine synthetase (GLS); and (c) albumin messenger RNA (mRNA). The normal human hepatic lobule was characterized by the periportal predominance of G6P and SDH enzymatic activities and albumin mRNAs, the perivenous predominance of ND and GDH, the restriction of GLS to a small perivenous compartment, and the predominanc of beta-HBDH at the contact of both portal tracts and centrilobular veins. In fibrosis, the overall metabolic organization of the normal liver tissue was retained. The expression of periportal markers predominated around enlarged portal tracts and that of perivenous markers around residual centrilobular veins. GLS was constantly detected at the contact of centrilobular veins. In cirrhotic nodules, no zonation was observed for most enzymatic activities or for albumin. Only G6P usually predominated at the periphery of the nodules. GLS was constantly undetectable. No difference accordingly to the etiology of the underlying disease was observed. In conclusion, the normal human hepatic lobule presents a marked metabolic zonation, preserved in fibrotic lesions, but lost in cirrhotic nodules. The alterations of the metabolic organization observed in cirrhosis might contribute to the pathogenesis of some of the metabolic disorders associated with advanced liver disease.
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PMID:The metabolic organization of the adult human liver: a comparative study of normal, fibrotic, and cirrhotic liver tissue. 870 47

A serial cultivation system of hepatocytes was established for the first time using calf liver as a cell source and, repeating passage of more than 30 cumulative population doublings (PDs), was obtained in the presence of long-acting ascorbic acid derivative (L-ascorbic acid 2-phosphate) and epidermal growth factor. The complete purification of hepatocytes was achieved by repeating ethylenediaminetetraacetic acid (EDTA) treatment, by which hepatocytes were easily detached from the culture dish, leaving most of the nonparenchymal cells on the dish. As the population cumulatively doubled, the cell density and albumin-synthesizing ability decreased gradually, and doubling time has exceeded 120 h at about 30 cumulative PDs. In serially passaged cells, the hepatocyte-specific histochemical and biochemical markers-including glucose-6-phosphatase, ornithine carbamoyltransferase, glutamate dehydrogenase, and ammonia-metabolizing activities-have been lost after 20 cumulative PDs. However, when these passaged cells were allowed to form spheroids, the morphologic and biochemical characteristics of hepatocytes have rapidly been restored to levels comparable to those in younger generations. Because no extrinsic factor was needed for this restoration, three-dimensional cell-cell interaction would be indispensable for the differentiation of the hepatocytes. The routine serial cultivation of hepatocytes and their redifferentiation by spheroid formation will be useful for studying metabolism, gene regulation, and transplantation of hepatocytes.
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PMID:The restoration of the functions of serially passaged calf hepatocytes by spheroid formation. 883 16

The coexpression of normally periportal and perivenous markers has been described in heterotopically transplanted hepatocytes. To determine whether such a coexpression might also occur in hepatocytes retaining their original intrahepatic location, we compared in bile-duct-ligated livers and intrasplenically transplanted hepatocytes, the expression and distribution of the predominantly periportal glucose-phosphatase, succinate dehydrogenase, and lactate dehydrogenase, the predominantly perivenous glutamate dehydrogenase, NADPH-dehydrogenase, and beta-hydroxybutyrate dehydrogenase, and the strictly perivenous glutamine synthetase. The coexpression of high levels of the two periportal markers glucose-6-phosphatase and lactate dehydrogenase and of the perivenous marker NADPH dehydrogenase was observed in two situations: in clusters of hepatocytes isolated within the ductular proliferation in bile-duct-ligated livers and the majority of intrasplenically transplanted hepatocytes. The expression of glutamine synthetase was different according to the site. The protein was observed in certain intrasplenically transplanted hepatocytes bordering the splenic vessels but was never detected in hepatocyte clusters found in bile-duct-ligated livers. Our study therefore suggests that the coexpression of periportal and perivenous markers in the same hepatocytes is likely to be a non-specific consequence of the loss of the normal connections of hepatocytes with the normal liver microcirculation.
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PMID:Coexpression of periportal and perivenous enzymes in rat hepatocytes after experimental bile duct ligation: comparison with intrasplenically transplanted hepatocytes. 907 88


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