Levels Of Glutamate Dehydrogenase Research Articles

Oligo-carrageenan kappa increases C, N and S assimilation, auxin and gibberellin contents, and growth in Pinus radiata trees

Oligo-carrageenans (OCs) obtained from pure carrageenans extracted from marine red algae stimulate growth by enhancing photosynthesis and basal metabolism in tobacco plants and Eucalyptus trees. In addition, OCs stimulate secondary metabolism, increasing the level of metabolites involved in defense against pathogens. In this work, we analyzed the effect of OC kappa on the increase in height, in activities of basal metabolism enzymes involved in carbon, nitrogen and sulphur assimilation, ribulose 1,5 biphosphate carboxylase/oxygenase (rubisco), glutamate dehydrogenase (GDH) and O-acetylserine thiol-lyase (OASTL), and in the level of growth-promoting hormones, the auxin indole acetic acid (IAA) and the gibberellin GA3, in pine (Pinus radiata) trees treated with OC kappa at concentrations of 1 and 5 mg mL−1 and cultivated for 9 months without additional treatment. Pines treated with OC kappa at 1 mg mL−1 showed a similar increase in height but displayed a higher increased in total chlorophyll, activities of rubisco, GDH and OASTL and level of IAA and GA3 than those treated with OC kappa at 5 mg mL−1. Thus, OC kappa stimulates growth and basal metabolism and increases the level of growth-promoting hormones in pine trees, mainly at 1 mg mL−1.

Reduced levels of NADH-dependent glutamate dehydrogenase decrease the glutamate content of ripe tomato fruit but have no effect on green fruit or leaves.

Glutamate (Glu) is a taste enhancer that contributes to the characteristic flavour of foods. In fruit of tomato (Solanum lycopersicum L.), the Glu content increases dramatically during the ripening process, becoming the most abundant free amino acid when the fruit become red. There is also a concomitant increase in NADH-dependent glutamate dehydrogenase (GDH) activity during the ripening transition. This enzyme is located in the mitochondria and catalyses the reversible amination of 2-oxoglutarate to Glu. To investigate the potential effect of GDH on Glu metabolism, the abundance of GDH was altered by artificial microRNA technology. Efficient silencing of all the endogenous SlGDH genes was achieved, leading to a dramatic decrease in total GDH activity. This decrease in GDH activity did not lead to any clear morphological or metabolic phenotype in leaves or green fruit. However, red fruit on the transgenic plants showed markedly reduced levels of Glu and a large increase in aspartate, glucose and fructose content in comparison to wild-type fruit. These results suggest that GDH is involved in the synthesis of Glu in tomato fruit during the ripening processes. This contrasts with the biological role ascribed to GDH in many other tissues and species. Overall, these findings suggest that GDH has a major effect on the control of metabolic composition during tomato fruit ripening, but not at other stages of development.

Effects of postprandial starvation on mRNA expression of endocrine-, amino acid and peptide transporter-, and metabolic enzyme-related genes in zebrafish (Danio rerio)

The goal of this study was to systematically evaluate the molecular activities of endocrine-, amino acid and peptide transporters-, and metabolic enzyme-related genes in 35-day-old mixed-sex zebrafish (Danio rerio) after feeding . Zebrafish with initial body weights ranging from 9 to 11mg were fasted for 384h in a controlled indoor environment. Fish were sampled at 0, 3, 6, 12, 24, 48, 96, 192, and 384h after fed. Overall, the present study results show that the regulatory mechanism that insulin-like growth factor I negative feedback regulated growth hormone is conserved in zebrafish, as it is in mammals, but that regulation of growth hormone receptors is highly intricate. Leptin and cholecystokinin are time-dependent negative feedback signals, and neuropeptide Y may be an important positive neuropeptide for food intake in zebrafish. The amino acid/carnitine transporters B(0,+) (ATB(0,+)) and broad neutral (0) amino acid transporter 1(B(0)AT1) mRNA levels measured in our study suggest that protein may be utilized during 24-96h of fasting in zebrafish. Glutamine synthetase mRNA levels were downregulated, and glutamate dehydrogenase, alanine aminotransferase, aspartate transaminase, and trypsin mRNA levels were upregulated after longtime fasting in this study. The mRNA expression levels of fatty acid synthetase decreased significantly (P < 0.05), whereas those of lipoprotein lipase rapidly increased after 96h of fasting. Fasting activated the expression of glucose synthesis genes when fasting for short periods of time; when fasting is prolonged, the mRNA levels of glucose breakdown enzymes and pentose phosphate shunt genes decreased.

Glucose replaces glutamate as energy substrate to fuel glutamate uptake in glutamate dehydrogenase-deficient astrocytes.

Cultured astrocytes treated with siRNA to knock down glutamate dehydrogenase (GDH) were used to investigate whether this enzyme is important for the utilization of glutamate as an energy substrate. By incubation of these cells in media containing different concentrations of glutamate (range 100-500 µM) in the presence or in the absence of glucose, the metabolism of these substrates was studied by using tritiated glutamate or 2-deoxyglucose as tracers. In addition, the cellular contents of glutamate and ATP were determined. The astrocytes were able to maintain physiological levels of ATP regardless of the expression level of GDH and the incubation condition, indicating a high degree of flexibility with regard to regulatory mechanisms involved in maintaining an adequate energy level in the cells. Glutamate uptake was found to be increased in these cells when exposed to increasing levels of extracellular glutamate independently of the GDH expression level. Moreover, increased intracellular glutamate content was observed in the GDH-deficient cells after a 2-hr incubation in the presence of 100 µM glutamate. It is significant that GDH-deficient cells exhibited an increased utilization of glucose in the presence of 250 and 500 µM glutamate, monitored as an increase in the accumulation of tritiated 2-deoxyglucose-6-phosphate. These findings underscore the importance of the expression level of GDH for the ability to utilize glutamate as an energy source fueling its own energy-requiring uptake.

Glutamate Dehydrogenase and Alkaline Phosphatase as Very Early Predictors of Hepatocellular Carcinoma Recurrence after Liver Transplantation

Background: Although long-term survival rates for patients undergoing liver transplant (LT) for hepatocellular carcinoma (HCC) are good, the relatively high rate of tumor recurrence after LT necessitates the identification of biological parameters that supplement morphological predictors of recurrence. Method: From chart review we identified 175 patients who received liver transplantation due to HCC at our center between January 2000 and December 2013. We documented demographic and clinical data, as well as clinicopathological characteristics of the tumors, with a focus on liver values at the time of LT. Results: HCC recurred in 23% of LT patients. Most recurrences (59%) occurred within 12 months after LT; hardly any recurrence was detected later than 3 years after LT. Recurrence was positively correlated with tumor size, tumor stage and alpha-fetoprotein level (AFP), and it was most likely with certain causes of liver disease. Interestingly, tumor recurrence was independently predicted by serum levels of glutamate dehydrogenase (GLDH) and alkaline phosphatase (AP) at the time of LT. Conclusions: Because all HCC recurrence occurs within 36 months after LT, HCC detected more than 3 years after LT may be considered de novo. Liver values, with GLDH and AP being the most preponderant, serve as easy-to-assess biomarkers which contribute to predict the risk of tumor recurrence.

To Biopsy or Not to Biopsy: Evaluation of a Large German Cohort of Patients with Abnormal Liver Tests of Unknown Etiology

Background and Aims: Despite increasingly sensitive and accurate blood tests to detect liver disease, liver biopsy remains very useful in patients with atypical clinical features and abnormal liver tests of unknown etiology. The aim was to determine those elevated laboratory liver parameters that cause the clinician to order a biopsy, and whether laboratory tests are associated with pathological findings on histology. Methods: 504 patients with unclear hepatopathy, admitted to the outpatient clinic of a university hospital between 2007 and 2010, were analyzed with respect to laboratory results, clinical data, and the results of liver biopsies. Results: Aspartate aminotransferase (AST) and glutamate dehydrogenase (GLDH) levels above the normal range significantly increased the likelihood of recommending a liver biopsy by 81% [OR with 95% CI 1.81 (1.21-2.71), p = 0.004] and 159% [OR with 95% CI 2.59 (1.70-3.93), p < 0.001], respectively. AST values above normal were associated with fibrosis (63 vs. 40% for normal AST, p = 0.010). Elevated ferritin levels pointed to a higher incidence of steatosis (48 vs. 10% for normal ferritin, p < 0.001) and inflammation (87 vs. 62% for normal ferritin, p = 0.004). Conclusions: Our results indicate that elevated AST and GLDH were associated with a greater likelihood of recommending liver biopsy. Elevated AST and ferritin levels were associated with steatosis, inflammation and fibrosis on liver biopsies. Thus, AST and ferritin may be useful non-invasive predictors of liver pathology in patients with unclear hepatopathy.

Ammonium metabolism enzymes aid Helicobacter pylori acid resistance.

The gastric pathogen Helicobacter pylori possesses a highly active urease to support acid tolerance. Urea hydrolysis occurs inside the cytoplasm, resulting in the production of NH3 that is immediately protonated to form NH4 (+). This ammonium must be metabolized or effluxed because its presence within the cell is counterproductive to the goal of raising pH while maintaining a viable proton motive force (PMF). Two compatible hypotheses for mitigating intracellular ammonium toxicity include (i) the exit of protonated ammonium outward via the UreI permease, which was shown to facilitate diffusion of both urea and ammonium, and/or (ii) the assimilation of this ammonium, which is supported by evidence that H. pylori assimilates urea nitrogen into its amino acid pools. We investigated the second hypothesis by constructing strains with altered expression of the ammonium-assimilating enzymes glutamine synthetase (GS) and glutamate dehydrogenase (GDH) and the ammonium-evolving periplasmic enzymes glutaminase (Ggt) and asparaginase (AsnB). H. pylori strains expressing elevated levels of either GS or GDH are more acid tolerant than the wild type, exhibit enhanced ammonium production, and are able to alkalize the medium faster than the wild type. Strains lacking the genes for either Ggt or AsnB are acid sensitive, have 8-fold-lower urea-dependent ammonium production, and are more acid sensitive than the parent. Additionally, we found that purified H. pylori GS produces glutamine in the presence of Mg(2+) at a rate similar to that of unadenylated Escherichia coli GS. These data reveal that all four enzymes contribute to whole-cell acid resistance in H. pylori and are likely important for assimilation and/or efflux of urea-derived ammonium.

Analysis of gene expression changes, caused by exposure to nitrite, in metabolic and antioxidant enzymes in the red claw crayfish, Cherax quadricarinatus

We evaluated the effect of acute exposure to nitrite on expression of antioxidant and metabolic enzyme genes in gill tissue of advanced juvenile Cherax quadricarinatus. A 48h nitrite exposure was conducted, using four test concentrations (NO2–N=0.5, 1, 1.5 and 2mgL−1) plus a control group. The relative mRNA expression of mitochondrial manganese superoxide dismutase (mMnSOD), cytosolic MnSOD (cMnSOD), extracellular copper/zinc SOD (exCu/ZnSOD), catalase (CAT), glutathione S-transferase (GST), arginine kinase (AK), glutamate dehydrogenase (GDH), mitochondrial malate dehydrogenase (mMDH), Na+/K+-ATPase α-subunit and phosphoenolpyruvate carboxykinase (PEPCK) in gill tissue was measured. Significantly increased mRNA expression was observed for all the antioxidant enzymes after 12 and 24h. After 48h, they all decreased at high nitrite concentrations. The gene expression levels of AK, GDH, mMDH and Na+/K+-ATPase α-subunit showed similar trends as the antioxidant enzymes. Significant depression of gene expression levels of PEPCK occurred throughout the experimental time at high nitrite concentrations. The results indicated that nitrite could induce oxidative and metabolic stress in C. quadricarinatus, in a time dependent manner, which suggests they could be helpful in predicting sublethal nitrite toxicity and useful in environmental monitoring studies.

The influence of potassium and calcium ions on nitrogen metabolism of cucumber seedlings

It was found that K&lt;sup&gt;+&lt;/sup&gt; or Ca&lt;sup&gt;2+&lt;/sup&gt; deficiency in a nitrate or ammonium medium increased the amount of accumulated total and non-protein nitrogen in some organs of cucumber seedlings, as also caused changes in accumulated potassium and calcium. Lack of K&lt;sup&gt;+&lt;/sup&gt; or Ca&lt;sup&gt;2+&lt;/sup&gt; in a medium which did not contain nitrogen led to an increased level of glutamate dehydrogenase, alanine aminotransferase and aspartate aminotransferase activity in the cotyledons and roots of cucumbers. Similar changes in the activity of these enzymes were noted in certain organs of seedlings growing in nitrate or ammonium medium with decreased K&lt;sup&gt;+&lt;/sup&gt; or Ca&lt;sup&gt;2+&lt;/sup&gt; contents, although the magnitude of these changes depended upon the applied dosage of these cations, the form of mineral nitrogen, developmental phase of plants and the plant organ dealt with.

L-Carnitine Ameliorates L-Asparaginase-Induced Acute Liver Toxicity in Steatotic Rat Livers

Background: Chemotherapy with <smlcap>L</smlcap>-asparaginase is associated with hepatotoxicity resulting in organ dysfunction in patients with preexisting liver disorders. This study investigated the protective effect of <smlcap>L</smlcap>-carnitine during chemotherapy in a steatotic rat liver model. Methods: Livers from nonsteatotic and steatotic rats were tested in an isolated liver reperfusion model adding <smlcap>L</smlcap>-asparaginase and <smlcap>L</smlcap>-carnitine to the reperfusate. Portal venous pressure (PVP), hepatic oxygen consumption, aspartate aminotransferase, lactate dehydrogenase, glutamate dehydrogenase and α-glutathione S-transferase levels were assessed. Further histopathological analysis was performed and cytotoxicity was verified in vitro. Results:<smlcap>L</smlcap>-Asparaginase induced toxicity in fatty livers whereas low toxicity was observed in normal livers. <smlcap>L</smlcap>-Carnitine induced a decline in PVP and oxygen consumption, and reduced parenchymal and mitochondrial damage in fatty livers. Cytotoxicity of <smlcap>L</smlcap>-asparaginase was not impaired by the presence of <smlcap>L</smlcap>-carnitine. Conclusions: Our study emphasizes the potential of <smlcap>L</smlcap>-carnitine to reduce <smlcap>L</smlcap>-asparaginase-induced hepatotoxicity in patients with preexisting liver disorders.

SELECTED HEMATOLOGIC AND BIOCHEMICAL VALUES IN SUBADULT AND ADULT CAPTIVE FOSSAS (CRYPTOPROCTA FEROX)

Hematologic and serum biochemical values were determined for 26 (16 males and 10 females) clinically healthy captive fossas (Cryptoprocta ferox) living at Zoo Duisburg, Germany. The animals were net-restrained and anesthetized with ketamine and medetomidine for a general examination. A total of 11 animals were classified as subadult (1-3 yr of age) and 15 as adult (aged between 4 and 13 yr). The results include reference intervals and analysis of sex and age differences. Levels of inorganic phosphorus, alkaline phosphatase, glutamate dehydrogenase, creatine kinase, lactate dehydrogenase, and calcium were significantly higher in the subadult group. The white blood cell count and red blood cell count were significantly lower in the adult group than among the subadult group.

Minimally-Invasive Implantation of Left Ventricular Assist Devices Improves the Operative Outcome in Adult Patients with Severe Heart Failure

Purpose Left ventricular assist devices (LVAD) are gaining more importance in the treatment of heart failure. The constant development of novel technologies in this field is being reflected by enhanced and considerably miniaturized LVAD-systems. However from a surgical point of view, complications like bleeding or right ventricular failure with liver impairment are still major hurdles in LVAD-therapy. Therefore, we recently developed a novel minimally invasive LVAD implantation technique in order to minimize complication rates and improve operative outcome. Methods and Materials We reviewed the early outcome of 100 consecutive end-stage heart failure patients (74% male, age 51,6 ± 12,6, DCM 49%, ICM 36%) who recently underwent LVAD (HVAD, HeartWare, USA) implantation in our institution between 2011 and 2012. Patients who were operated conventionally by a median sternotomy (group A; n = 65) were compared to patients receiving a minimal invasive upper hemisternotomy combined with an anterolateral thoracotomy (group B; n = 35). Results Intra-hospital-mortality was lower in group B (12,3% vs. 8,6%). ICU stay was significantly lower (p < 0,05) in group B (20,2 ± 4,9 days vs. 9,8 ± 2,7 days). Bleeding incidence was also significantly (p < 0,05) lower in group B (18.5% vs. 5,7%). Postoperative glutamate dehydrogenase (GLDH) levels were also significantly (p < 0,05) lower in group B (76,2 ± 238,5 U/L vs. 15,5 ± 52,1 U/L). None of the patients had a pump thrombosis. Conclusions Our data show that the applied minimally invasive LVAD-implantation technique improves the early postoperative outcome by improving survival and reducing bleeding events, liver impairment and postoperative ICU stay of terminal heart failure patients.

Assessment of Emerging Biomarkers of Liver Injury in Human Subjects

Hepatotoxicity remains a major challenge in drug development. Although alanine aminotransferase (ALT) remains the gold standard biomarker of liver injury, alternative biomarker strategies to better predict the potential for severe drug-induced liver injury (DILI) are essential. In this study, we evaluated the utility of glutamate dehydrogenase (GLDH), purine nucleoside phosphorylase (PNP), malate dehydrogenase (MDH), and paraxonase 1 (PON1) as indicators of liver injury in cohorts of human subjects, including healthy subjects across age and gender, subjects with a variety of liver impairments, and several cases of acetaminophen poisoning. In the healthy subjects, levels of GLDH and MDH were not affected by age or gender. Reference ranges for GLDH and MDH in healthy subjects were 1-10 and 79-176U/L, respectively. In contrast, the levels of PON1 and PNP were not consistent across cohorts of healthy subjects. Furthermore, GLDH and MDH had a strong correlation with elevated ALT levels and possessed a high predictive power for liver injury, as determined by ROC analysis. In contrast, PON1 and PNP did not detect liver injury in our study. Finally, evaluation of patients with acetaminophen-induced liver injury provided evidence that both GLDH and MDH might have utility as biomarkers of DILI in humans. This study is the first to evaluate GLDH, MDH, PON1, and PNP in a large number of human subjects and, and it provides an impetus for prospective clinical studies to fully evaluate the diagnostic value of GLDH and MDH for detection of liver injury.

Rhinacanthus nasutus Ameliorates Cytosolic and Mitochondrial Enzyme Levels in Streptozotocin-Induced Diabetic Rats.

The present study was conducted to evaluate the therapeutic efficacy of Rhinacanthus nasutus (R. nasutus) on mitochondrial and cytosolic enzymes in streptozotocin-induced diabetic rats. The rats were divided into five groups with 6 rats in each group. The methanolic extract of R. nasutus was orally administered at a dose of 200 mg/kg/day, and glibenclamide was administered at a dose of 50 mg/kg/day. All animals were treated for 30 days and were sacrificed. The activities of both intra- and extramitochondrial enzymes including glucose-6-phosphate dehydrogenase (G6PDH), succinate dehydrogenase (SDH), glutamate dehydrogenase (GDH), and lactate dehydrogenase (LDH) were measured in the livers of the animals. The levels of G6PDH, SDH, and GDH were significantly reduced in the diabetic rats but were significantly increased after 30 days of R. nasutus treatment. The increased LDH level in diabetic rats exhibited a significant reduction after treatment with R. nasutus. These results indicate that the administration of R. nasutus altered the activities of oxidative enzymes in a positive manner, indicating that R. nasutus improves mitochondrial energy production. Our data suggest that R. nasutus should be further explored for its role in the treatment of diabetes mellitus.

Field Investigations of Glyphosate in Urine of Danish Dairy Cows

In the present study, thirty dairy cows from each of eight Danish dairy farms were investigated for excretion of glyphosate in urine. Blood serum parameters indicative of cytotoxicity as alkaline phosphatase (AP), glutamate dehydrogenase (GLDH), glutamate oxaloacetate transaminase (GOT), creatinine kinase CK), nephrotoxicity, (urea, creatine), cholesterol and the trace elements as manganese (Mn), cobalt (Co), selenium (Se), copper (Cu) and zinc (Zn) were investigated. All cows excreted glyphosate in their urine but in varying concentrations. Increased levels of GLDH, GOT and CK in cows from all farms demonstrate a possible effect of glyphosate on liver and muscle cells. High urea levels in some farms could be due to nephrotoxicity of glyphosate. Also the unexpected very low levels of Mn and Co were observed in all animals which could be explained due to a strong mineral chelating effect of glyphosate. In contrast the mean levels of Cu, Zn and Se were within the normal reference range. In conclusion, this study gives the first documentation to which extent Danish dairy cattle are exposed to Glyphosate and its impact on blood parameters.

Gamma-amino butyric acid, glutamate dehydrogenase and glutamate decarboxylase levels in phylogenetically divergent plants

Gamma-amino butyric acid (GABA) is a nonprotein amino acid found in a wide range of organisms including plants. Several studies have shown that GABA plays different roles in plant metabolism including carbon–nitrogen metabolism, energy balance, signaling and development. It has been suggested that the occurrence of GABA and the enzymes related to GABA biosynthesis in prokaryotes and eukaryotes may be important in evolution and diversification. However, studies of GABA biosynthesis and GABA levels in an evolutionary context are restricted to sequenced plant genomes. In this study we aimed to compare the activities of GDH and GAD enzymes and total nitrogen, and the contents of total soluble protein, succinate, glutamate, proline and GABA in plants from different phylogenetic levels including Ulva lactuca, Pseudevernia furfuracea, Nephrolepsis exaltata, Ginkgo biloba, Pinus pinea, Magnolia grandiflora, Nymphaea alba, Urtica dioica, Portulaca oleraceae, Malva sylvestris, Rosa canina, Lavandula stoechas, Washingtonia filifera, Avena barbata and Iris kaempferi. The activities of GAD and GDH enzymes differed according to the species and were not always parallel to GABA levels. The discrepancy in the contents of succinate and GABA between higher and primitive plants was also prominent. Glutamate levels were high with a few exceptions and proline contents were at similar low values as compared to other amino acids. Our results support the hypothesis that the GABA shunt plays a key role in carbon and nitrogen partitioning via linking amino acid metabolism and the tricarboxylic acid cycle which is essential for higher plant species.

Inhibition of glutamate dehydrogenase and insulin secretion by KHG26377 does not involve ADP-ribosylation by SIRT4 or deacetylation by SIRT3

We investigated the mechanisms involved in KHG26377 regulation of glutamate dehydrogenase (GDH) activity, focusing on the roles of SIRT4 and SIRT3. Intraperitoneal injection of mice with KHG26377 reduced GDH activity with concomitant repression of glucose-induced insulin secretion. Consistent with their known functions, SIRT4 ribosylated GDH and reduced its activity, and SIRT3 deacetylated GDH, increasing its activity. However, KHG26377 did not affect SIRT4-mediated ADP-ribosylation/ inhibition or SIRT3-mediated deacetylation/activation of GDH. KHG26377 had no effect on SIRT4 protein levels, and did not alter total GDH, acetylated GDH, or SIRT3 protein levels in pancreatic mitochondrial lysates. These results suggest that the mechanism by which KHG26377 inhibits GDH activity and insulin secretion does not involve ADP-ribosylation of GDH by SIRT4 or deacetylation of GDH by SIRT3.

Architecture of the hypothalamo-posthypophyseal complex is controlled by monoamines

The hypothalamo-neurohypophyseal system displays significant plasticity when subjected to physiological stimuli, such as dehydration, parturition, or lactation. This plasticity arises at the neurochemical and electrophysiological levels but also at a structural level. Several studies have demonstrated the role of monoaminergic afferents in controlling neurochemical and electrophysiological plasticity of the supraoptic nucleus (SON) and of the neurohypophysis (NH), but little is known about how the changes in structural plasticity are triggered. We used Tg8 mice, disrupted for the monoamine oxidase A gene, to study monamine involvement in the architecture of the SON and of the NH. SON astrocytes in Tg8 mice displayed an active status, characterized by an increase in S100β expression and a significant decrease in vimentin expression, with no modification in glial fibrillary acidic protein (GFAP) levels. Astrocytes showed a decrease in glutamate dehydrogenase (GDH) levels, whereas glutamine synthetase (GS) levels remained constant, suggesting a reduction in astrocyte glutamate catabolism. Tenascin C and polysialic acid-neural cell adhesion molecule (PSA-NCAM) expressions were also elevated in the SON of Tg8 mice, suggesting an increased capacity for structural remodelling in the SON. In the NH, similar date were obtained with a stability in GFAP expression and an increase in PSA-NCAM immunostaining. These results establish monoamine (serotonin and noradrenaline) involvement in SON and NH structural arrangement. Monoamines therefore appear to be crucial for the coordination of the neurochemical and structural aspects of neuroendocrine plasticity, allowing the hypothalamo-neurohypopyseal system to respond appropriately when stimulated.

Cellular and molecular basis of increased ammoniagenesis in potassium deprivation

Hypokalemia is associated with increased ammoniagenesis and stimulation of net acid excretion by the kidney in both humans and experimental animals. The molecular mechanisms underlying these effects remain unknown. Toward this end, rats were placed in metabolic cages and fed a control or K(+)-deficient diet (KD) for up to 6 days. Rats subjected to KD showed normal acid-base status and serum electrolytes composition. Interestingly, urinary NH(4)(+) excretion increased significantly and correlated with a parallel decrease in urine K(+) excretion in KD vs. control animals. Molecular studies showed a specific upregulation of the glutamine transporter SN1, which correlated with the upregulation of glutaminase (GA), glutamate dehydrogenase (GDH), and phosphoenolpyruvate carboxykinase. These effects occurred as early as day 2 of KD. Rats subjected to a combined KD and 280 mM NH(4)Cl loading (to induce metabolic acidosis) for 2 days showed an additive increase in NH(4)(+) excretion along with an additive increment in the expression levels of ammoniagenic enzymes GA and GDH compared with KD or NH(4)Cl loading alone. The incubation of cultured proximal tubule cells NRK 52E or LLC-PK(1) in low-K(+) medium did not affect NH(4)(+) production and did not alter the expression of SN1, GA, or GDH in NRK cells. These results demonstrate that K(+) deprivation stimulates ammoniagenesis through a coordinated upregulation of glutamine transporter SN1 and ammoniagenesis enzymes. This effect is developed before the onset of hypokalemia. The signaling pathway mediating these events is likely independent of KD-induced intracellular acidosis. Finally, the correlation between increased NH(4)(+) production and decreased K(+) excretion indicate that NH(4)(+) synthesis and transport likely play an important role in renal K(+) conservation during hypokalemia.

The Effect Of The Oral Iron Chelator Deferiprone On The Liver Damage Induced By Tamoxifen In Female Rats

Tamoxifen (TAM) is a non-steroidal antiestrogen used in the treatment and prevention of hormone-dependent breast cancer. Tamoxifen therapy may be accompanied with hepatic injury and iron accumulation in this organ. The present study investigates the influence of the effective oral iron chelator, deferiprone (L1), in TAM-induced acute liver injury. Four groups of female Wistar rats were used: I, control; II, TAM; III, TAM+L1; IV, L1. Tamoxifen (75 mg/kg) was administered orally on the first and second day; L1 (50 mg/kg) was administered orally on the first, second and third day of the experiment. On the fourth day, parameters of oxidative state: lipid peroxidation (LP), glutathione (GSH) and catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities were estimated in liver homogenates. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamate dehydrogenase (GLDH) levels and iron hepatic content were also evaluated. The TAM-induced oxidative damage was demonstrated by increased LP (52% above controls) and decreased GPx activity (to 92% of controls). The protective effect of L1 was manifested by attenuation of LP (p <0.05) and preserving of GPx activity. The TAM-induced increase of serum ALT and AST activity remained unchanged by L1 treatment. Significant increase of hepatic iron (Fe) level (41% above controls) was found in TAM-treated rats. Hepatic Fe accumulation was completely prevented by L1 treatment.