Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Though some mechanisms of photoreception have been well characterized, others remain obscure. Presumably, most, if not all, of the major players in photoreceptor-specific functions are present in large amounts in the photoreceptor layer, and a catalog of these proteins will prove a useful tool for vision researchers. As a first step toward a complete catalog of photoreceptor cells, we have developed a novel method for isolating the photoreceptor cell monolayer from bovine retina. Electron microscopic studies of both the photoreceptor layer and the residual retina from which the photoreceptor layer had been removed, indicate that the preparation contains the photoreceptor outer segments and the majority of the inner segments. Proteins were extracted from the isolated photoreceptor cell layer as well as the rest of the retina with isoelectric focusing lysis buffer, and the protein components were separated by two-dimensional gel electrophoresis. The obtained protein maps reveal several classes of proteins that appear to be expressed more abundantly or specifically in the photoreceptor layer than in the rest of the retina. Four of these protein spots were excised and in-gel digested with trypsin, and the digests were extracted with solvent. The mixture of peptides digested from each protein was analyzed by high performance liquid chromatography interfaced with electrospray ionization tandem quadrupole mass spectrometry or by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Some of the peptides were isolated and their sequences were determined by gas phase Edman degradation. RNA transcripts extracted from the photoreceptor layer or the whole retina were subjected to Northern blot analysis as well as to reverse transcriptase-polymerase chain reaction amplification of probes for the successful selection of cDNA clones. These data permit both the identification of virtually any protein detectable on a two-dimensional gel, and also enable the corresponding cDNA clone to be selected. We have validated this approach by identifying aspartate aminotransferase and creatine kinase from the populations of abundant photoreceptor layer proteins. Both aspartate aminotransferase and creatine kinase are of mitochondrial origin and are thought to play crucial roles in photoreceptor functions by producing glutamate and ATP, respectively. We also identified two photoreceptor layer specific proteins: an acidic and high molecular weight protein, interphotoreceptor retinoid-binding protein, and an acidic and small molecular weight protein, recoverin.The technique presented here will allow vision researchers to discover and identify the proteins that are expressed specifically or abundantly in the photoreceptor cell as well as the proteins that undergo post-translational modification or modulation in expression under a defined biological condition. With the use of this technology, we anticipate that a researcher who knows only the 2-D gel position of a protein of interest can identify the protein, isolate a cDNA clone, and move into molecular genetic studies. Moreover, this streamlined technology will enable one to assemble a catalog of photoreceptor proteins using a minute amount of materials in a short period of time. We believe that such a catalog will serve as a valuable resource for vision investigators and will accelerate the rate of research progress.
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PMID:Initiating ocular proteomics for cataloging bovine retinal proteins: microanalytical techniques permit the identification of proteins derived from a novel photoreceptor preparation. 1043 56

Although excessive release of the neurotransmitter glutamate contributes to ischemic neuronal damage, immunocytochemical studies have not found a loss of glutamate from ischemic axon terminals. We examined the effects of two components of ischemia, hypoxia and hypoglycemia, on glutamate loss from rat hippocampal slices. In vitro hypoglycemia induced by incubation for 1 h without glucose depleted 50% of glutamate from slices when ATP levels were about 5 nmol/mg protein. Hypoxic slices aerated with N2 reached similar ATP levels without significant glutamate depletion. To induce 50% glutamate losses with chemical hypoxia, ATP had to be depleted to < 1 nmol/mg protein. Immunocytochemical staining indicated that glutamate-like immunoreactivity was reduced throughout slices by hypoglycemia. Hypoxia decreased glutamate-like immunoreactivity in neuronal perikarya and dendrites of pyramidal cells and granule cells. However, in contrast to hypoglycemia, hypoxia maintained or increased glutamate-like immunoreactivity in many terminals. Hypoxia and hypoglycemia induced similar, ATP-dependent releases of glutamate into supernatants, which could account for only part of the hypoglycemic losses. The additional hypoglycemic losses were consistent with increased catabolism of glutamate. Glutamate losses from hypoglycemic terminals were reduced by blockade of aspartate aminotransferase or the tricarboxylic acid cycle. Exogenous glutamate increased glutamate in hypoglycemic slices to hypoxic levels and returned glutamate-like immunoreactivity to terminals, suggesting that terminals maintained glutamate uptake during metabolic insults. Hypoglycemia induces a large loss of glutamate that does not occur during hypoxia. The greater loss of glutamate from terminals during hypoglycemia is consistent with increased metabolism of glutamate via aspartate aminotransferase and not increased release of glutamate. Continued uptake of glutamate by hypoxic terminals may help to maintain their levels of glutamate. Hypoglycemic metabolism of glutamate may decrease pathologic glutamate release and contribute to the prolonged neurologic abnormalities associated with recovery from hypoglycemia.
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PMID:Glutamate in synaptic terminals is reduced by lack of glucose but not hypoxia in rat hippocampal slices. 1057 5

We investigated whether the imposition of chronic alcohol in hypertension leads to greater biochemical and cellular abnormalities of the myocardium than those arising in normotension. Fifteen-week-old spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were fed ethanol-containing diets for six weeks. Particular attention was focused on the composition of contractile proteins identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), fractional rate of protein synthesis, and synthesis rates relative to RNA (RNA activity) or DNA (cellular efficiency). In addition, myocardial enzymes and adenine nucleotides were measured. In both SHR and WKY rats chronic ethanol caused a general decrease in the contents of all nine contractile proteins with myosin heavy chain predominantly affected. Fractional rates of mixed (i.e., total) and myofibrillary proteins remained unaltered in both WKY rats and SHR, as were cellular efficiencies. The RNA activity was significantly reduced in ethanol-treated SHR but not in WKY rats. In ethanol-treated SHR, cardiac creatine kinase (CK) and malate dehydrogenase (MDH) activities were increased, AMP levels were elevated, whilst ATP levels and the energy charge were reduced. In WKY rats, the only significant change related to increased aspartate aminotransferase activities in response to alcohol feeding. Although there were only subtle differences between the response of the normotensive and hypertensive rats due to ethanol dosage, the reduced ATP levels and increased CK and MDH activities in SHR may reflect a greater susceptibility to ischaemic damage. Reduced contractile protein content, particularly myosin heavy chain, may contribute to contractile defects, a common feature of subclinical and clinical alcoholic cardiomyopathy.
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PMID:A comparative investigation into the effect of chronic alcohol feeding on the myocardium of normotensive and hypertensive rats: an electrophoretic and biochemical study. 1093 59

The protective effect of N-[(3, 5-di-tertiobutyl-4-hydroxy-1-thiophenyl)]-3-propyl-N'-(2,3, 4-trimethoxybenzyl)piperazine (S-15176) on liver injury induced by warm ischemia-reperfusion was investigated using a rat model. Animals were subjected to 2 h of ischemia followed by different reperfusion times. Hepatocyte integrity was assessed by measuring plasma alanine and aspartate aminotransferase activities, and by determining reduced and oxidized glutathione in plasma and bile. Hepatocyte function was quantitated by determining bile flow and liver ATP content. Ischemia-reperfusion resulted in severe hepatic injury involving a huge increase in alanine and aspartate aminotransferase activities, a drop in ATP content, and a decrease in bile flow. Plasma and bile reduced (GSH) and oxidized (GSSG) glutathione concentrations were inversely related: plasma levels increased when biliary levels decreased. This was associated with a decrease in animal survival (-34%). S-15176 pretreatment (1.25, 2.5, 5 or 10 mg kg(-1) day(-1)) improved the survival rate and limited tissue damages in a dose-dependent manner. The pretreatment also reduced the aminotransferase leakage from hepatocytes and the increase in plasma glutathione levels. In addition, normalization of the plasma GSSG/GSH ratio, a good index of an oxidative stress, was observed in groups treated with the higher dosage, suggesting that the antioxidant properties demonstrated for the compound in vitro (IC(50)=0.3 microM towards lipid peroxidation) could play a role in its protective effect. S-15176 pretreatment also protected the organ from the drop in ATP levels. At the higher dose, ATP content was maintained at a level almost 86% of the sham-operated group after 60 min of reperfusion. This was associated with a restoration of the biliary flow. These data suggest that S-15176 may be a useful drug in liver surgery to prevent ischemia-reperfusion injury.
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PMID:S-15176 reduces the hepatic injury in rats subjected to experimental ischemia and reperfusion. 1102 Apr 92

Recently, a family of polyketide inhibitors of F(0)F(1)-ATPase, including apoptolidin, ossamycin, and oligomycin, were shown to be among the top 0.1% most cell line selective cytotoxic agents of 37, 000 molecules tested against the 60 human cancer cell lines of the National Cancer Institute. Many cancer cells maintain a high level of anaerobic carbon metabolism even in the presence of oxygen, a phenomenon that is historically known as the Warburg effect. A mechanism-based strategy to sensitize such cells to this class of potent small molecule cytotoxic agents is presented. These natural products inhibit oxidative phosphorylation by targeting the mitochondrial F(0)F(1) ATP synthase. Evaluation of gene expression profiles in a panel of leukemias revealed a strong correlation between the expression level of the gene encoding subunit 6 of the mitochondrial F(0)F(1) ATP synthase (known to be the binding site of members of this class of macrolides) and their sensitivity to these natural products. Within the same set of leukemia cell lines, comparably strong drug-gene correlations were also observed for the genes encoding two key enzymes involved in central carbon metabolism, pyruvate kinase, and aspartate aminotransferase. We propose a simple model in which the mitochondrial apoptotic pathway is activated in response to a shift in balance between aerobic and anaerobic ATP biosynthesis. Inhibitors of both lactate formation and carbon flux through the Embden-Meyerhof pathway significantly sensitized apoptolidin-resistant tumors to this drug. Nine different cell lines derived from human leukemias and melanomas, and colon, renal, central nervous system, and ovarian tumors are also sensitized to killing by apoptolidin.
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PMID:Understanding and exploiting the mechanistic basis for selectivity of polyketide inhibitors of F(0)F(1)-ATPase. 1112 Oct 76

Reactive oxygen species generated by xanthine oxidase during reperfusion of ischemic liver might in part be responsible for ischemic organ injury. In normothermic ischemia/reperfusion rat model, we investigated whether allopurinol pretreatment improved ischemia-induced mitochondrial dysfunction. Rats were subjected to 60 min of hepatic ischemia and to 1 h and 5 h of reperfusion thereafter. At 18 h and 1 h before ischemia, the animals received 0.25 mL of either saline or allopurinol (50 mg/kg) i.p. In saline-treated ischemic rats, serum aspartate aminotransferase levels increased significantly at 5 h (4685 +/- 310 IU/L) and were significantly reduced with allopurinol pretreatment. Similarly, mitochondrial lipid peroxidation was elevated in the saline-treated ischemic group, but this elevation was prevented by allopurinol. In contrast, mitochondrial glutamate dehydrogenase activity and ketone body ratio decreased in the saline-treated group, but this decrease was also inhibited by allopurinol. Hepatic ATP levels in the saline-treated rats were 42% lower 5 h after reperfusion. However, treatment with allopurinol resulted in significantly higher ATP levels. Allopurinol treatment preserved the concentration of AMP in ischemic liver but inhibited the accumulation of xanthine in reperfused liver. Our findings suggest allopurinol protects against mitochondrial injury, which prevents a mitochondrial oxidant stress and lipid peroxidation and preserves the hepatic energy metabolism.
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PMID:Protective effect of allopurinol on hepatic energy metabolism in ischemic and reperfused rat liver. 1122 Jun 38

1) The oxygen consumption increases during Bufo bufo development in accordance with the two steps which border at the "heart beat" stage. 2) Cytochrome c oxidase activity is not proportional to the oxygen consumption: it is notable and constant in the first step, and it only increases in the second. 3) In the mitochondria of preneural embryos, citrate synthase, NADP+ dependent isocitrate dehydrogenase, and succinate dehydrogenase activities are very low in respect to malate dehydrogenase and glutamate oxaloacetate transaminase activities. The Krebs cycle results lowered at the condensing reaction level with acetyl accumulation when pyruvate is available. The same behavior has been observed in the Xenopus laevis oocytes and differentiated tissues. 4) The presence of a phosphagen system which is different from creatine phosphate and arginine phosphate, supporting ATP level, has been demonstrated in B. bufo embryos. 5) Mitochondria of postneural embryos are able to accomplish a complete Krebs cycle by increasing citrate synthase, and succinate dehydrogenase activities. 6) In all B. bufo development, malate dehydrogenase and glutamate oxaloacetate transaminase constitute a multienzymatic system by which the mitochondria accomplish a decarboxylic amino acid shunt required for the transformation of deutoplasm into protoplasm. This shunt is also operative in the X. laevis oocytes. 7) Through pyruvate production, by oxidative decarboxylation of malate, the NAD(P)+ dependent malic enzyme could carry out a fundamental anaplerotic function in the mitochondria which is specialized in the production of biosynthetic blocks belonging to the embryo in which the carbohydrates metabolism rather than the glycolytic activity is designed for pentose phosphate and glycerol phosphate synthesis for protein and cytomembrane production. 8) Consistent metabolic differences have been highlighted between B. bufo embryos and X. laevis embryos.
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PMID:Physiological differentiation of the mitochondria during Bufo bufo development. 1125 8

Acute hepatic failure was induced experimentally in rats by intraperitoneal injection of 2.5 mL kg(-1) carbon tetrachloride (CCl4), and the effects on the expression and function of P-glycoprotein in the liver, kidney and brain were evaluated. The CCl4 injection significantly increased the indicators of hepatic function (glutamate oxaloacetate transaminase, glutamate pyruvate transaminase), but not of renal function (blood urea nitrogen, glomerular filtration rate). In rats with acute hepatic failure, the hepatic P-glycoprotein concentration increased 1.5-fold and the ATP concentration decreased to approximately 40% that in control rats. In contrast, P-glycoprotein concentrations in the kidney and brain and ATP concentrations in the kidney remained unchanged. The in-vivo P-glycoprotein function in these tissues was suppressed as evaluated by biliary and renal secretory clearances and brain distribution of rhodamine 123, a P-glycoprotein substrate. These findings suggest that factors other than P-glycoprotein concentration are involved in the systemic suppression of P-glycoprotein function in diseased rats. In Caco-2 cells, plasma collected from CCl4-treated rats exhibited a greater inhibitory effect on P-glycoprotein-mediated transport of rhodamine 123 than that from control rats, suggesting the accumulation of an endogenous P-glycoprotein substrate/inhibitor in the plasma of diseased rats. In fact, the plasma concentration of corticosterone, an endogenous P-glycoprotein substrate, increased 2-fold in CCl4-treated rats compared with control rats. It was demonstrated that P-glycoprotein function is systemically suppressed in rats with CCl4-induced acute hepatic failure, not only in the target organ (liver), but also in other organs (kidney and brain), although the P-glycoprotein concentration remained unchanged in the kidney and brain, and increased in the liver. In the systemic suppression of the P-glycoprotein function in the diseased state, the alteration of plasma concentrations or components of endogenous P-glycoprotein-related compounds, such as corticosterone, would likely be involved.
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PMID:Expression and function of P-glycoprotein in rats with carbon tetrachloride-induced acute hepatic failure. 1142 64

We investigated the antiischemic properties of a new compound, S-15176, in an experimental model of rat liver subjected to 120-min normothermic ischemia followed by 30-min reperfusion. Rats were divided into groups, pretreated with different doses of S-15176 (1.25, 2.5, 5 and 10 mg/kg/day by intramuscular injection) or solvent alone, and subjected to the ischemia--reperfusion process. Another group served as the sham-operated controls. Ischemia--reperfusion induced huge alterations of hepatocyte functions, namely, a decrease in ATP content and bile flow, and membrane leakage of alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT). These effects were associated with alterations in mitochondrial functions characterized by (1) a decrease in ATP synthesis, (2) a decrease in NAD(P)H levels and mitochondrial membrane potential, and (3) an increase in mitochondrial swelling reflecting the generation of permeability transition. Pretreatment of rats with S-15176 alleviated these deleterious ischemia--reperfusion effects at both the cellular and mitochondrial levels in a dose-dependent manner. The protection of mitochondrial functions was almost complete at a dosage of 10 mg/kg/day. In addition, in vitro, S-15176 totally abolished the swelling of isolated mitochondria induced by a calcium overload with an IC(50) value of 10 microM. These data demonstrate that S-15176 protects mitochondria against the deleterious effects of ischemia-reperfusion and suggest that this protective effect could be related to the inhibition of the mitochondrial permeability transition.
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PMID:Attenuation of liver normothermic ischemia--reperfusion injury by preservation of mitochondrial functions with S-15176, a potent trimetazidine derivative. 1144 61

Ecteinascidin-743 (ET-743) is a novel marine-derived anticancer drug with clinical activity in soft tissue sarcoma and ovarian cancer. Reversible transaminitis and subclinical cholangitis have frequently been described in patients who receive ET-743. To facilitate understanding of this adverse effect and help design suitable therapeutic rescue strategies, we characterized the hepatic effects of ET-743 in rats. Female rats received ET-743 (single dose, 40 microg/kg) i.v., and liver changes were assessed from 6 h up to 3 months after dosing by histopathology, immunohistochemistry, electron microscopy, hepatic and plasma biochemistry, and DNA microarray analysis. At 24 h posttreatment and beyond, livers displayed degeneration and patchy focal necrosis of bile duct epithelial cells associated with mild inflammation followed by fibrosis. Sporadic and focal zones of hepatic necrosis and hemorrhage were observed from day 2 onward, although the majority of hepatocytes appeared normal as judged by electron microscopy. Pathological alterations persisted up to 3 months after dosing. Plasma levels of total bilirubin were elevated up to 7-fold over those in untreated rats from day 2 onward and returned to control values by day 24. Activities of alkaline phosphatase and aspartate aminotransferase in plasma were elevated for 2 and 3 months, respectively. Activities of the hepatic microsomal drug-metabolizing enzymes cytochrome P-450 A1/2, CYP2E1, and CYP3A2 were decreased. DNA microarray analysis of livers from ET-743-treated animals showed a dramatic increase in the expression of ATP binding cassette transport genes Abcb1a and Abcb1b, which impart resistance to anticancer drugs, and of Cdc2a and Ccnd1, the rodent homologues of human cell cycle genes CDC2 and cyclin D1, respectively. The cell cycle gene expression changes mirrored ET-743-induced increases in liver weight and Ki-67 labeling of liver nuclei. The results suggest that the toxicity exerted by ET-743 in the rat liver is a consequence of biliary rather than hepatocellular damage and that it is accompanied by a wave of mitogenic activity, which may be driven by the transcriptional increase in Cdc2a expression.
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PMID:Hepatobiliary damage and changes in hepatic gene expression caused by the antitumor drug ecteinascidin-743 (ET-743) in the female rat. 1215 27


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