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PubMed1982

Effects of acute metabolic acidosis on renal, gut, liver, and muscle metabolism of glutamine and ammonia in the dog.

Previous studies have shown a rise in arterial glutamine in acute acidosis in the dog. In these experiments glutamine and ammonia metabolism was studied in anesthetized dogs during normal acid-base status and following acute hydrochloric acidosis to determine the mechanism for the rise in arterial glutamine in acidosis. Splanchnic, liver, renal, and hind-half extraction/production were measured by arteriovenous (A-V) sampling and simultaneous blood flow measurements using electromagnetic flow probes. In the normal dog, muscle produced glutamine, and the kidneys, gut, hepatosplanchnic bed, and liver extracted it. Whole blood arterial glutamine rose in acidosis. Renal and muscle glutamine and ammonia extraction/production were unchanged. Gut ammonia release and hepatic ammonia uptake increased by similar amounts in acidosis, but no change in gut glutamine uptake occurred. Hepatic and total hepatosplanchnic glutamine uptake was markedly reduced thereby contributing to the raised arterial glutamine. These results demonstrate that acute metabolic acidosis in the dog-influences marked changes in glutamine extraction and ammonia metabolism across the hepatosplanchnic bed without significant changes in kidney or muscle metabolism.

Acidosis↗
PubMed1992

Influence of ammonia and pH on protein and amino acid metabolism in LLC-PK1 cells.

Metabolic acidosis inhibits protein synthesis (PS) and stimulates protein degradation (PD) in muscle and cultured myocytes but causes hypertrophy of the proximal tubule. The reason for this tissue-specific difference in response to acidosis is unknown, but it might be related to stimulation of renal ammonia production since ammonia reportedly increases PS and inhibits PD in cultured kidney cells. We examined how ammonia and pH could interact to change protein turnover in confluent LLC-PK1 cells. Varying extracellular pH from 6.95 to 7.60 did not alter PS or PD even though intracellular pH changed predictably. Six millimolar NH4Cl did not change PS while 20 mM inhibited PS; there was no interaction with pH. This unexpected difference from the reported stimulation of PS by NH4Cl could be explained by our use of L-[U-14C]phenylalanine rather than radiolabelled leucine to measure PS. NH4Cl was found to inhibit leucine degradation which would increase radiolabelled leucine available for incorporation into protein. Either 6 mM or 20 mM NH4Cl inhibited PD measured as the release of L-[14C]phenylalanine from prelabelled protein. Experiments with an inhibitor of lysosomal function, chloroquine, suggest that NH4Cl inhibits lysosomal proteolysis. There was no interaction of cell pH and ammonia-induced changes in PD. Thus, the response of renal cells to acidification differs markedly from myocytes and ammonia changes protein turnover primarily by suppressing PD.

Amino Acids↗
PubMed2006

Archaea predominate among ammonia-oxidizing prokaryotes in soils.

Ammonia oxidation is the first step in nitrification, a key process in the global nitrogen cycle that results in the formation of nitrate through microbial activity. The increase in nitrate availability in soils is important for plant nutrition, but it also has considerable impact on groundwater pollution owing to leaching. Here we show that archaeal ammonia oxidizers are more abundant in soils than their well-known bacterial counterparts. We investigated the abundance of the gene encoding a subunit of the key enzyme ammonia monooxygenase (amoA) in 12 pristine and agricultural soils of three climatic zones. amoA gene copies of Crenarchaeota (Archaea) were up to 3,000-fold more abundant than bacterial amoA genes. High amounts of crenarchaeota-specific lipids, including crenarchaeol, correlated with the abundance of archaeal amoA gene copies. Furthermore, reverse transcription quantitative PCR studies and complementary DNA analysis using novel cloning-independent pyrosequencing technology demonstrated the activity of the archaea in situ and supported the numerical dominance of archaeal over bacterial ammonia oxidizers. Our results indicate that crenarchaeota may be the most abundant ammonia-oxidizing organisms in soil ecosystems on Earth.

Ammonia↗
PubMed1998

In vitro excess ammonia production in human myeloma cell lines.

It is well known that cases with multiple myeloma reveal various clinical manifestations such as pancytopenia, hyperproteinemia, renal dysfunction, bone lesions, hypercalcemia and immunodeficiency. Recently, a few more clinical features associated with myeloma, such as salivary type hyperamylasemia and elevated serum C-reactive protein (CRP) concentration, have been reported. The elevation of CRP is thought to be related to interleukin-6 (IL-6) production by myeloma cells, because of identification of IL-6 as an autocrine and/or paracrine growth factor for myeloma cells. More recently, there have been several reports of cases with myeloma associated with hyperammonemia. This hyperammonemia is not considered to be due to liver dysfunction, because in most of these cases tests revealed normal hepatic function, and some cases showed different patterns of serum amino acid distribution than that associated with hepatic failure. However, there have been no apparent observations of ammonia production by myeloma cells. In this study, we used six human myeloma cell lines including KMS-18, which was recently established from a myeloma case associated with hyperammonemia. These lines were treated with MRA (mycoplasma removal agent) to observe ammonia production in vitro. They produced and released significantly higher levels of ammonia into culture medium than non-myeloma hematological cell lines or the HepG2 human hepatic carcinoma cell line. Although attempts to analyze the relative expression levels of the enzymes related to ammonia biosynthesis using the reverse transcriptase-polymerase chain reaction assay failed to detect any differences between these myeloma lines and other cell lines, in vitro excess ammonia production by the myeloma cells was confirmed and the relevance to clinical manifestations is discussed.

Ammonia↗
PubMed1999

Field intercomparison of diffusive samplers for measuring ammonia.

Agricultural production systems are recognised as a major source of atmospheric ammonia. Deposition of ammonia and ammonium may contribute to undesired changes in oligotrophic ecosystems. The continuous measurement of atmospheric ammonia requires expensive and sophisticated techniques and is performed only in a very restrict number of ambient air stations in Europe. Therefore, the application of passive samplers, which have the advantage of being easy to handle and cost-efficient, is useful. In the past the comparability of different passive samplers must be considered as rather scarce. In a joint European project under the leadership of the GSF-Forschungszentrum für Umwelt und Gesundheit, Neuherberg, in 1997 a comparison of different passive ammonia monitoring methods was carried out in a prealpine rural site near Garmisch-Partenkirchen. It was considered valuable to include not only well established systems but also methods still being developed. For the comparative test ten working groups with different methods took part. A wet annular denuder system, which has been developed by the Netherlands Energy Research Foundation for on-line measurement of atmospheric ammonia, served as reference of passive methods. The experiment, which started in June and finished in December, showed that most of the passive samplers fulfil the requirements and can be recommended for further measurements. Additional measurements of meteorological parameters were performed to check the influences of different weather conditions on passive sampling.

Agriculture↗
PubMed1980

The mechanism of ammonia production and the effect of mechanical work load on proteolysis and amino acid catabolism in isolated perfused rat heart.

The effect of mechanical work load on net proteolysis, amino acid catabolism and ammonia production was studied in isolated perfused beating or K+-arrested hearts. Net proteolysis was about 16 mumol/g dry wt. during 1h and was not affected by the mechanical work. The combined catabolic rate of the major amino acids was 7.1 mumol/g dry wt. in the beating heart and 2.1 mumol/g dry wt. in the arrested heart during the 1 h experimental period. The main differences lay in the deamination of aspartate plus glutamate, which was inhibited by 60% during low energy consumption, and in net alanine synthesis, which was increased by 94%. The ammonia production plus its conversion into amide nitrogen was 9.2 and 3.4 mumol/g dry wt. in the beating and arrested heart respectively during 1 h. The decrease in the total adenine nucleotide pool during the 1 h perfusion was very low, 1.0 and 0.5 mumol/g dry wt. in the beating and arrested hearts respectively, and did not contribute significantly to ammonia production. Thus ammonia production is dependent on the cellular energy state, whereas net proteolysis is not. The maximal capacities of the purine nucleotide cycle and the glutamate dehydrogenase reaction towards deamination were much higher than the observed ammonia-production rates. The anaplerotic role of amino acid catabolism in the myocardium is discussed.

Adenine Nucleotides↗
PubMed1981

The excretion of isotope in urea and ammonia for estimating protein turnover in man with [15N]glycine.

1. Four normal adults were given [15N]glycine in a single dose either orally or intravenously. Rates of whole-body protein turnover were estimated from the excretion of 15N in ammonia and in urea during the following 9 h. The rate derived from urea took account of the [15N]urea retained in body water. 2. In postabsorptive subjects the rates of protein synthesis given by ammonia were equal to those from urea, when the isotope was given orally, but lower when an intravenous dose was given. 3. In subjects receiving equal portions of food every 2 h rates of synthesis calculated from ammonia were much lower than those from urea whether an oral or intravenous isotope was given. Comparison of rates obtained during the post-absorptive and absorptive periods indicated regulation by food intake primarily of synthesis when measurements were made on urea, but regulation primarily of breakdown when measurements were made on ammonia. 4. These inconsistencies suggest that changes in protein metabolism might be assessed better by correlating results given by different end-products, and it is suggested that the mean value given by urea and ammonia will be useful for this purpose.

Adult↗
PubMed1982

Glutamine production rate and its contribution to urinary ammonia in normal man.

1. Glutamine [15N]amide was infused at a steady rate of 33.34 mumol/h into seven male adult volunteers who were in the fed state and normal acid-base status. 2. Plasma glutamine amide N enrichment and urinary ammonia N enrichment rose to a constant rate within 3 h. 3. The glutamine production rate was 51.8 +/- 7.9 mmol/h. 4. The total ammonia excretion rate was 0.87 mmol/h. Of this excreted ammonia 62.6 +/- 9% was derived from the amide N atom of glutamine. 5. The excreted glutamine amide N (0.53 mmol/h) was only 1% of the glutamine production. If half the ammonia formed by the kidney is excreted in urine and half liberated into the renal vein in subjects with normal acid-base status [E. E. Owen & R. R. Robinson (1963) Journal of Clinical Investigation, 42, 263-276], then the kidney accounts for only 2% of glutamine disposal. 6. Whole body protein turnover, measured from the urinary [15N]ammonia enrichment, was 30.3 +/- 7.7 g of N/day (2.8 g of protein day-1 kg-1).

Adult↗
PubMed1985

Leg metabolism of amino acids and ammonia in patients with chronic renal failure.

Leg metabolism of amino acids and ammonia in the postabsorptive state was evaluated in 10 patients with chronic renal failure (CRF) and in 10 patients with normal renal function (controls) by measuring the arterial-femoral venous (A-FV) differences for free amino acids and ammonia. Total amino acid release from the leg and alanine and glutamine release, which accounts for the greatest amount of the total amino acid release, are similar in patients and controls. Total amino acid uptake from the arterial blood and glutamate uptake, which is the amino acid extracted at the highest rate, are comparable in both groups. Taken together these data, in addition to the similarity of A-FV differences for proteolytic markers, namely tyrosine, phenylalanine and histidine, suggest that protein breakdown in peripheral tissues is not increased in patients with CRF. In CRF selective metabolic abnormalities for some amino acids are evident. Whilst only the A-FV differences for valine, leucine and isoleucine are decreased, additional alterations are observed by relating the A-FV difference for each amino acid to that of proteolytic markers. Such a procedure demonstrates that in CRF histidine release relative to that of proteolytic markers is reduced, whereas proline and arginine release is increased. In CRF the reduced release of some amino acids, mainly branched-chain amino acids, by the leg probably affects the pattern of circulating amino acids. Finally, both in patients and in controls a significant uptake of ammonia is observed; the ammonia uptake is related to arterial levels of this metabolite, confirming the role of peripheral tissues in removing ammonia from circulation.

Adult↗
PubMed2000

Lack of effect of aerial ammonia on atrophic rhinitis and pneumonia induced by Mycoplasma hyopneumoniae and toxigenic Pasteurella multocida.

The objective of this experimental study was to determine the effects of aerial ammonia on disease development and bacterial colonization in weaned pigs inoculated with toxigenic Pasteurella multocida and Mycoplasma hyopneumoniae. Two groups of 10 pigs each were continuously exposed to 50 and 100 p.p.m. ammonia, respectively, and compared to a non-exposed control group of 20 pigs. Following aerosol inoculation with M. hyopneumoniae at day 9, all pigs were aerosol-inoculated with toxigenic P. multocida type A at days 28, 42 and 56. At day 63 they were euthanized. Clinical signs including coughing and respiratory distress were present in all groups following inoculation. No significant differences could be established in the extent or frequency of pneumonia between ammonia-exposed pigs and controls, or in the extent of conchal atrophy, the frequency of isolation of toxigenic P. multocida from conchae, tonsils, lungs and kidneys, or the average daily weight gain. The recovery of toxigenic P. multocida from nasal swabs following inoculation was significantly greater in pigs exposed to 50 p.p.m. ammonia or more as compared to the control group. In conclusion, high levels of ammonia combined with inoculations with M. hyopneumoniae and toxigenic P. multocida had no significant effect on disease development, but may have enhanced colonization by toxigenic P. multocida on the nasal turbinates.

Administration, Inhalation↗
PubMed1994

Brain ATP depletion induced by acute ammonia intoxication in rats is mediated by activation of the NMDA receptor and Na+,K(+)-ATPase.

Injection of large doses of ammonia into rats leads to depletion of brain ATP. However, the molecular mechanism leading to ATP depletion is not clear. The aim of the present work was to assess whether ammonium-induced depletion of ATP is mediated by activation of the NMDA receptor. It is shown that injection of MK-801, an antagonist of the NMDA receptor, prevented ammonia-induced ATP depletion but did not prevent changes in glutamine, glutamate, glycogen, glucose, and ketone bodies. Ammonia injection increased Na+,K(+)-ATPase activity by 76%. This increase was also prevented by previous injection of MK-801. The molecular mechanism leading to activation of the ATPase was further studied. Na+,K(+)-ATPase activity in samples from ammonia-injected rats was normalized by "in vitro" incubation with phorbol 12-myristate 13-acetate, an activator of protein kinase C. The results obtained suggest that ammonia-induced ATP depletion is mediated by activation of the NMDA receptor, which results in decreased protein kinase C-mediated phosphorylation of Na+,K(+)-ATPase and, therefore, increased activity of the ATPase and increased consumption of ATP.

Acetates↗
PubMed1990

Ammonia and lactate: differential information on monitoring training load in sprint events.

Two hypotheses were tested concerning training relevance of ammonia in capillary blood compared with lactate after extensive and intensive high-paced runs. 1. There is a load threshold at which ammonia concentration deviates statistically significantly from the pre-load level, while lactate indicates already anaerobic metabolic processes at extensive training loads. Increased ammonia concentration is understood as the activation of type IIb fibers. 2. The increase in ammonia is primarily a consequence of increasing training load intensity. The hypotheses were tested in a field experiment with male sprinters n = 13. The experimental plan followed a design of repeated measures in a 4 x 4 Latin-square. The subjects completed four high-pace runs (300 m) at 82.5%, 85%, 87.5%, and 90% of the maximum running intensity (identified in a contest). The results confirmed our first hypothesis. Significant increase in ammonia concentration was not found until after four runs at an intensity of 87.5% or after one 300-m run at maximum running speed. In contrast to this, a glycolytic reaction became evident in one run at 82.5% of the maximum intensity. Lactate concentration exceeded the anaerobic threshold at this point. Definite instructions for training practice cannot be made at the present state of research.

Adenosine Monophosphate↗
PubMed1998

Effects of prolonged exercise on brain ammonia and amino acids.

The aim of this study was to investigate if enhanced peripheral ammonia production during exhaustive exercise increases ammonia detoxication in brain mediated by glutamine synthesis, and subsequently influences glutamate and gamma-aminobutyric acid (GABA) levels. This neurotransmitter production is related to the metabolism of glutamine. A group of rats was trained for 6 weeks by treadmill running (TR). They were compared to a group of untrained rats (UN). At the end of training, half of TR and UN rats were submitted to one session of treadmill running until exhaustion (288+/-12 min and 62+/-5 min in TR and UN group, respectively). At exhaustion, running and control rats were sacrificed in order to collect blood and to take samples of the following brain structures: cortex, striatum and cerebellum. Treadmill running until exhaustion induced an increase in blood ammonia by 140% without significant differences between TR and UN groups. Brain ammonia increased in both groups. However, TR group exhibited values 50% higher than those observed in UN group. Brain glutamine was increased at exhaustion in all groups of running rats by 30-75% of basal value whereas the glutamate only decreased in TR rats which were able to run for a longer time. In this group, the GABA level decreased in striatum. These data confirm that enhanced brain ammonia level during exercise stimulates glutamine synthesis as a mechanism of detoxication. After several hours of running, a reduction in brain glutamate levels was observed in all brain structures in trained rats but only in the striatum in untrained animals. The reduced availability of this GABA precursor decreases GABA levels only in the striatum of TR group by 45% of the resting value. These results suggest a relation between cerebral changes in neurotransmitters and excitatory amino acids, such as glutamate and GABA, and central fatigue.

Ammonia↗
PubMed2003

The reported human NADsyn2 is ammonia-dependent NAD synthetase from a pseudomonad.

Nicotinamide-adenine dinucleotide (NAD+) synthetases catalyze the last step in NAD+ metabolism in the de novo, import, and salvage pathways that originate from tryptophan (or aspartic acid), nicotinic acid, and nicotinamide, respectively, and converge on nicotinic acid mononucleotide. NAD+ synthetase converts nicotinic acid adenine dinucleotide to NAD+ via an adenylylated intermediate. All of the known eukaryotic NAD+ synthetases are glutamine-dependent, hydrolyzing glutamine to glutamic acid to provide the attacking ammonia. In the prokaryotic world, some NAD+ synthetases are glutamine-dependent, whereas others can only use ammonia. Earlier, we noted a perfect correlation between presence of a domain related to nitrilase and glutamine dependence and then proved in the accompanying paper (Bieganowski, P., Pace, H. C., and Brenner, C. (2003) J. Biol. Chem. 278, 33049-33055) that the nitrilase-related domain is an essential, obligate intramolecular, thiol-dependent glutamine amidotransferase in the yeast NAD+ synthetase, Qns1. Independently, human NAD+ synthetase was cloned and shown to depend on Cys-175 for glutamine-dependent but not ammonia-dependent NAD+ synthetase activity. Additionally, it was claimed that a 275 amino acid open reading frame putatively amplified from human glioma cell line LN229 encodes a human ammonia-dependent NAD+ synthetase and this was speculated largely to mediate NAD+ synthesis in human muscle tissues. Here we establish that the so-called NADsyn2 is simply ammonia-dependent NAD+ synthetase from Pseudomonas, which is encoded on an operon with nicotinic acid phosphoribosyltransferase and, in some Pseudomonads, with nicotinamidase.

Amide Synthases↗
PubMed2003

Gain of glutaminase function in mutants of the ammonia-specific frog carbamoyl phosphate synthetase.

Depending on their physiological role, carbamoyl phosphate synthetases (CPSs) use either glutamine or free ammonia as the nitrogen donor for carbamoyl phosphate synthesis. Sequence analysis of known CPSs indicates that, regardless of whether they are ammonia- or glutamine-specific, all CPSs contain the structural equivalent of a triad-type glutamine amidotransferase (GAT) domain. In ammonia-specific CPSs, such as those of rat or human, the catalytic inactivity of the GAT domain can be rationalized by the substitution of the Triad cysteine residue by serine (1). The ammonia-specific CPS of Rana catesbeiana (fCPS) presents an interesting anomaly in that, despite its retention of the entire catalytic triad (2) and almost all other residues conserved in Triad GATs, it is unable to utilize glutamine as a nitrogen-donating substrate (3). Based on our earlier work with the glutamine-utilizing E. coli CPS (eCPS), we have targeted residues Lys258 and Glu261 in the fCPS GAT domain as critical for preventing GAT function. Previously we have shown that substitution of the corresponding residues in eCPS by their fCPS counterparts (Leu --> Lys and Gln --> Glu) resulted in complete loss of GAT function in eCPS (3). To examine the role of these residues in the fCPS GAT component, we have cloned the full-length fCPS gene from R. catesbeiana liver. Here we report the first heterologous expression of an ammonia-specific CPS and show that a single mutation of the frog enzyme, K258L, yields a gain of glutaminase function.

Amino Acid Sequence↗
PubMed2004

Fungal ammonia fermentation, a novel metabolic mechanism that couples the dissimilatory and assimilatory pathways of both nitrate and ethanol. Role of acetyl CoA synthetase in anaerobic ATP synthesis.

Fungal ammonia fermentation is a novel dissimilatory metabolic mechanism that supplies energy under anoxic conditions. The fungus Fusarium oxysporum reduces nitrate to ammonium and simultaneously oxidizes ethanol to acetate to generate ATP (Zhou, Z., Takaya, N., Nakamura, A., Yamaguchi, M., Takeo, K., and Shoun, H. (2002) J. Biol. Chem. 277, 1892-1896). We identified the Aspergillus nidulans genes involved in ammonia fermentation by analyzing fungal mutants. The results showed that assimilatory nitrate and nitrite reductases (the gene products of niaD and niiA) were essential for reducing nitrate and for anaerobic cell growth during ammonia fermentation. We also found that ethanol oxidation is coupled with nitrate reduction and catalyzed by alcohol dehydrogenase, coenzyme A (CoA)-acylating aldehyde dehydrogenase, and acetyl-CoA synthetase (Acs). This is similar to the mechanism suggested in F. oxysporum except A. nidulans uses Acs to produce ATP instead of the ADP-dependent acetate kinase of F. oxysporum. The production of Acs requires a functional facA gene that encodes Acs and that is involved in ethanol assimilation and other metabolic processes. We purified the gene product of facA (FacA) from the fungus to show that the fungus acetylates FacA on its lysine residue(s) specifically under conditions of ammonia fermentation to regulate its substrate affinity. Acetylated FacA had higher affinity for acetyl-CoA than for acetate, whereas non-acetylated FacA had more affinity for acetate. Thus, the acetylated variant of the FacA protein is responsible for ATP synthesis during fungal ammonia fermentation. These results showed that the fungus ferments ammonium via coupled dissimilatory and assimilatory mechanisms.

Acetate-CoA Ligase↗
PubMed1996

Effects of acute cardioselective and non-selective beta-adrenergic blockade on plasma ammonia levels in exercising dogs.

The aim of this study was to assess plasma ammonia levels during acute treadmill exercise in dogs after intravenous administration of a single dose of different cardioselective (atenolol) and non-selective (sotalol and propranolol) beta-adrenergic blocking drugs. The experiments were performed on 6 male mongrel dogs (20-25 kg) trained to run on a motor driven treadmill. After administration of saline or atenolol, there was no significant increase in plasma ammonia during exercise; propranolol and sotalol however, both non-selective beta-blockers, produced a significant increase in plasma ammonia. Plasma levels of alanine and glutamine were not altered during exercise compared with resting values, and were not modified by the administration of beta-blockers. It is not clear whether the different effects on exercise induced hyperammonemia are due to different effects on muscle ammonia formation or on the ammonia clearance by the liver.

Adrenergic beta-Antagonists↗
PubMed1990

The effect of lactulose, pectin, arabinogalactan and cellulose on the production of organic acids and metabolism of ammonia by intestinal bacteria in a faecal incubation system.

An in vitro faecal incubation system was used to study the metabolism of complex carbohydrates by intestinal bacteria. Homogenates of human faeces were incubated anaerobically with added lactulose, pectin, the hemicellulose arabinogalactan, and cellulose, both before and after subjects had been pre-fed each carbohydrate. Fermentation of added substrate was assessed by the production of short-chain fatty acids (SCFA) and suppression of net ammonia generation over 48 h of incubation. Control faecal homogenates to which carbohydrate was not added yielded an average increment of SCFA of 43 mmol/l, equivalent to 172 mmol/kg in the original stool. The addition of lactulose, pectin and arabinogalactan each increased the yield of SCFA by a similar amount, averaging 6.5 mmol/g carbohydrate or 1.05 mol/mol hexose equivalent; organic acid yield was not increased by pre-feeding these substances for up to 2 weeks. Acetate was the major SCFA in all samples at all times and, after pre-feeding with extra carbohydrate, butyrate concentrations exceeded propionate in all samples. Faecal homogenates incubated with cellulose showed no greater SCFA production than controls over the first 48 h, but there was a slight increase when samples from two subjects pre-fed cellulose were incubated for 14 d. Net ammonia generation was markedly suppressed by addition of lactulose to faecal incubates with an initial period of net bacterial uptake of ammonia. Pectin and arabinogalactan also decreased ammonia generation, but the reductions were not significant unless subjects were pre-fed these materials; cellulose had no effect on ammonia generation.

Adult↗