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PubMed2006

Myocardial perfusion quantification in patients suspected of cardiac syndrome X with positive and negative exercise testing: a [13N]ammonia positron emission tomography study.

BACKGROUND: The combination of angina pectoris, angiographically normal coronary arteries, and a positive exercise stress test (EST) is referred to as cardiac syndrome X. However, a large group of patients suspected of syndrome X reveals a normal exercise stress test and weakens the diagnosis of syndrome X. Previous studies demonstrated an impaired coronary flow reserve on ammonia positron emission tomography (PET) in patients with syndrome X. AIM: To evaluate the coronary flow reserve in patients suspected of syndrome X with positive and negative EST findings, using [(13)N]ammonia PET as the diagnostic aid. METHODS: Forty-two patients with chest pain and a normal coronary angiography, were analysed by exercise stress testing (EST) and the dypyridamole stress test (DST) on [(13)N]ammonia PET. Two subgroups were predefined, based on outcome of EST: an EST positive and negative group. A normal control group was used as the reference method. RESULTS: A total of 24 (57%) out of 42 patients had significant ST-T changes (EST positive). [(13)N]ammonia PET showed a significantly lower rest flow in the EST positive and EST negative group compared to controls (P<0.001 and P=0.0028, respectively). DST [(13)N]ammonia PET perfusion was significantly reduced in flow in both the EST positive and EST negative groups (P<0.001 both), as was the DST/rest [(13)N]ammonia perfusion reserve (P<0.001 for both), compared to normal controls. CONCLUSION: PET demonstrates a reduced coronary flow reserve in patients suspected of syndrome X, irrespective of the EST findings.

Adult↗
PubMed2001

An assessment of ammonia emissions from dairy facilities in Pennsylvania.

A survey of 715 Holstein dairy farms in Pennsylvania was used to construct demographics for the average Holstein dairy farm. The average Holstein dairy farm was composed of 69 lactating cows; 11 nonlactating, pregnant cows; 44 heifers; and 18 calves. Milk production averaged 27.3 kg (60.0 lb). Crop area averaged 73.6 ha. Milk production, crop area and type, average county yields, and herd animal groups were used to construct a typical feeding program for these farms. Typical rations were constructed for six feeding groups (three milk production groups, one nonlactating group, two heifer groups) to meet milk production, pregnancy, and growth requirements. Rations were constructed based on three forage qualities (excellent, average, and poor) typically observed on Pennsylvania dairy farms. Data for animal description (milk production, body weight, growth, and pregnancy status) and ration components and amounts consumed for each animal group were input into the excretion model of the Dairy Nutrient Planner computer program (DNP). Excretion of fecal N and dry matter (DM), urinary N, and total P and K were produced for each animal group and used to assess potential volatile losses of N. Work at the Marshak Dairy, New Bolton Center, indicates the majority of urinary N is rapidly lost as ammonia from dairy facilities. Based on this observation, the losses of N as ammonia were estimated to be 4.63, 4.62, and 4.28 tonne/year for the farm with excellent, average, and poor quality forages, respectively. Volatile losses of N may be reduced most by controlling levels of urea in urine. Urinary N may be reduced through dietary manipulation of protein and carbohydrate sources. Conversion of urea to ammonia may be reduced by altering the pH of barn floors and gutters. Entrapment of ammonia may be accomplished by acidification of manure slurry. Atmospheric ammonia contributes to acid rain, eutrophication of estuaries and lakes, and particulate air pollution. Reduction of ammonia emissions from dairy barns can significantly reduce atmospheric pollution and improve air and water quality.

Air Pollution↗
PubMed2005

A non-accidental poisoning with ammonia in adolescence.

Abstract Introduction Ammonia is an important chemical agent used in industry. Accidental inhalation of ammonia has resulted in upper airway and bronchoalveolar injury. If a large amount of ammonia is breathed, the agent can cause unconsciousness, shock and even death. Case In this article, we report a case of non-accidental poisoning in adolescence. The patient was a 14-year-old boy and working as an apprentice at a workshop of a jeweller. He had drunk some amount of diluted ammonia by the force of another, 18-year-old, male apprentice. This patient presented with ammonia intoxication symptoms culminating in coma. Conclusions We reported this case as an unusual ammonia poisoning seen in adolescence.

Adolescent↗
PubMed1986

Control of urea production, glutamine release and ammonia uptake in the perfused rat liver by the sympathetic innervation.

The nervous control of hepatic urea and glutamine release and of ammonia uptake was studied in the rat liver perfused in situ. Electrical stimulation of the nerve bundles around the hepatic artery and the portal vein resulted in a reduction of urea release, of glutamine output and of ammonia uptake. At the same time, as observed before [Hartmann et al. (1982) Eur. J. Biochem. 123, 521-526], nerve stimulation led to a decrease of portal flow as well as to an increase of glucose release and a shift of lactate uptake to output. Noradrenaline infusion mimicked the nerve-dependent metabolic and hemodynamic changes in a first approximation only at the highly unphysiological concentration of 0.1 microM. It was without effect at 0.01 microM, which might be reached in the sinusoids as a result of overflow from the vasculature. In the presence of sodium nitroprusside nerve stimulation no longer reduced urea output, glutamine release and ammonia uptake or portal flow, yet it still increased glucose and lactate release. Phentolamine clearly reduced the alterations after nervous stimulation of urea output, ammonia uptake and portal flow, while propranolol was essentially not effective. The nerve-stimulation-dependent reduction of glutamine release was almost abolished in the presence of phentolamine and lowered to 50% by propranolol. Glucagon stimulated urea output but had no influence on glutamine release, ammonia uptake and portal flow. Nerve stimulation antagonized the glucagon-stimulated urea release. The present results suggest that in the perfused liver alpha-sympathetic hepatic nerves regulate urea release, glutamine output and ammonia uptake predominantly by an indirect mechanism via hemodynamic alterations, but glucose release by a direct mechanism also in the absence of circulatory changes.

Ammonia↗
PubMed1988

Regional differences in the capacity for ammonia removal by brain following portocaval anastomosis.

Portocaval anastomosis (PCA) in the rat leads, within 4 weeks, to severe liver atrophy, sustained hyperammonemia, and increased brain ammonia. Because brain is not equipped with an effective urea cycle, removal of ammonia involves glutamine synthesis and PCA results in significantly increased brain glutamine. Glutamine synthetase activities, however, are decreased by 15% in cerebral cortex and are unchanged in brainstem of shunted rats. Administration of ammonium acetate to rats following PCA results in severe encephalopathy (loss of righting reflex and, ultimately, coma). Glutamine concentrations in brainstem of comatose rats are increased a further two-fold, whereas those of cerebral cortex are unchanged. Consequently, ammonia levels in cerebral cortex reach disproportionately high levels (of the order of 5 mM). These findings suggest a limitation in the capacity of cerebral cortex to remove additional blood-borne ammonia by glutamine formation following PCA. Such mechanisms may explain the hypersensitivity of rats with PCA and of patients with portal-systemic shunting to small increases of blood ammonia. Disproportionately high levels of brain ammonia in certain regions, such as cerebral cortex, may then result in alterations of inhibitory neurotransmission and, ultimately, loss of cellular (astrocytic) integrity.

Ammonia↗
PubMedDate not supplied

Nutritional influence on serum ammonia in young patients receiving sodium valproate.

Hyperammonemia is a common side effect of valproic acid (VPA) therapy. This study was designed to investigate a potential nutritional influence on serum ammonia levels during VPA therapy. In 10 VPA-treated young patients (5 receiving monotherapy, 5 receiving VPA-primidone polytherapy), venous serum ammonia, triglycerides, and cholesterol were measured on 3 consecutive days as follows: (a) after a 13-h overnight fast; (b) 2 h after an oral fat load with butter (1.2 g fat/kg body weight); and (c) 2 h after an oral protein load with fresh cheese (1 g protein/kg body weight). Ten young adults served as controls. After protein load VPA patients had significantly higher serum ammonia levels than controls (mean: 194 vs. 75 micrograms/dl in controls; p less than 0.006). Ammonia values were higher after protein load than after fat load or after fasting (p less than 0.0001). Patients receiving polytherapy had higher ammonia levels than patients receiving monotherapy (not significant). There was no correlation to the height of serum VPA levels. Clinical symptoms attributable to hyperammonemia (vomiting, apathy) were found in only one patient, and her serum ammonia was as high as 426 micrograms/dl. Triglycerides and cholesterol did not show any VPA-induced differences. We assume that VPA alters the short-term regulation of ureasynthesis. We recommend the avoidance of high protein intake in patients receiving VPA therapy, especially in young patients receiving polytherapy or comedication, or in risk situations like serious infections.

Adult↗
PubMed1999

The amo operon in marine, ammonia-oxidizing gamma-proteobacteria.

While there is an extensive database of genes encoding ammonia monooxygenase (amo) found in the ammonia-oxidizing beta-proteobacteria, few amo sequences are available representing the gamma-proteobacteria. We sequenced the complete amo operon (amoCAB) for Nitrosococcus oceani (ATCC 19707), a marine, autotrophic, ammonia-oxidizing bacterium belonging to the gamma-subdivision of the proteobacteria. An additional autotrophic, ammonia-oxidizing bacterium isolated from a marine environment (strain C-113) was identified as belonging to the Nitrosococcus genus by 16S rDNA analysis and its amo operon was sequenced. This is the first report of a full-length sequence for the amo operon from a gamma-subdivision autotrophic ammonia-oxidizing bacterium. The N. oceani and C-113 amo genes were 88-90% identical to each other, 49-53% identical to the pmo genes encoding the related particulate methane monooxygenase of Methylococcus capsulatus (Bath), and 39-42% identical to the amo genes of the beta-subdivision autotrophic ammonia-oxidizing bacteria. In both Nitrosococcus strains, the amo operon was found as a single copy and contained three genes, amoC, amoA, amoB, with intergenic spacer regions between amoC and amoA (286 bp) and between amoA and amoB (65 bp). We conclude that the amo genes will allow for a finer scale phylogenetic differentiation than 16S rDNA within the gamma-subdivision AOB.

Amino Acid Sequence↗
PubMed1999

Muscle characteristics and plasma lactate and ammonia response after racing in Standardbred trotters: relation to performance.

Blood samples from the jugular vein and muscle biopsies (gluteus medius) in 25 Standardbred trotters were obtained 5-10 min after racing. The biopsies were analysed for fibre type composition and enzymatic profile and blood samples for plasma lactate and ammonia concentrations. Muscle characteristics, plasma lactate and ammonia concentrations after racing were compared with each horse's individual performance index (IPI). The IPI is calculated annually from the individual horse's racing performance (% placing 1, 2 or 3, total annual earnings, average earning per start, and best racing record), respectively, converted to and expressed as a percentage deviation from the average record of the same sex and age group. The IPI values were 100-116. Plasma lactate concentrations were 15.0-42.7 mmol/l (mean 31.3 mmol/l) and ammonia concentrations 65-210 micromol/l (mean 141 micromol/l) after racing. Fibre type composition varied among horses (range 9-27% for Type I, 32-54% for Type IIA, and 27-46% for Type IIB). Fibre type composition, enzyme activities, plasma lactate and ammonia responses to racing were not correlated to IPI. Ten of the horses also performed a submaximal test on the track, consisting of 5 incremental 1000 m heats at approximate speeds of 9.1, 9.5, 10.0, 10.5, and 11.1 m/s. Immediately after each heat a blood sample was drawn from the jugular vein for plasma lactate analysis. Plasma lactate response to exercise differed between horses, but no correlation was seen with IPI. Muscle characteristics, plasma lactate and ammonia concentrations after racing and lactate response to a submaximal track test did not correlate with current race performance expressed as IPI in a group of horses with average or better performance capacity at the time of testing. Analysis of lactate and ammonia in blood after racing is not a valuable tool to predict an individual performance index.

Age Factors↗
PubMed2006

Response of Nitrosospira sp. strain AF-like ammonia oxidizers to changes in temperature, soil moisture content, and fertilizer concentration.

Very little is known regarding the ecology of Nitrosospira sp. strain AF-like bacteria, a unique group of ammonia oxidizers within the Betaproteobacteria. We studied the response of Nitrosospira sp. strain AF-like ammonia oxidizers to changing environmental conditions by applying molecular methods and physiological measurements to Californian grassland soil manipulated in the laboratory. This soil is naturally high in Nitrosospira sp. strain AF-like bacteria relative to the much-better-studied Nitrosospira multiformis-like ammonia-oxidizing bacteria. Increases in temperature, soil moisture, and fertilizer interacted to reduce the relative abundance of Nitrosospira sp. strain AF-like bacteria, although they remained numerically dominant. The overall abundance of ammonia-oxidizing bacteria increased with increasing soil moisture and decreased with increasing temperature. Potential nitrification activity was altered by interactions among temperature, soil moisture, and fertilizer, with activity tending to be higher when soil moisture and temperature were increased. The increase in potential nitrification activity with increased temperature was surprising, given that the overall abundance of ammonia-oxidizing bacteria decreased significantly under these conditions. This observation suggests that (i) Nitrosospira sp. strain AF-like bacteria may respond to increased temperature with an increase in activity, despite a decrease in abundance, or (ii) that potential nitrification activity in these soils may be due to organisms other than bacteria (e.g., archaeal ammonia oxidizers), at least under conditions of increased temperature.

Ammonia↗
PubMed1997

Trichloroethylene biodegradation by mesophilic and psychrophilic ammonia oxidizers and methanotrophs in groundwater microcosms.

This study investigated the efficiency of methane and ammonium for stimulating trichloroethylene (TCE) biodegradation in groundwater microcosms (flasks and batch exchange columns) at a psychrophilic temperature (12 degrees C) typical of shallow aquifers in the northern United States or a mesophilic temperature (24 degrees C) representative of most laboratory experiments. After 140 days, TCE biodegradation rates by ammonia oxidizers and methanotrophs in mesophilic flask microcosms were similar (8 to 10 nmol day-1), but [14C]TCE mineralization (biodegradation to 14CO2) by ammonia oxidizers was significantly greater than that by methanotrophs (63 versus 53%). Under psychrophilic conditions, [14C]TCE mineralization in flask systems by ammonia oxidizers and methanotrophs was reduced to 12 and 5%, respectively. In mesophilic batch exchange columns, average TCE biodegradation rates for methanotrophs (900 nmol liter-1 day-1) were not significantly different from those of ammonia oxidizers (775 nmol liter-1 day-1). Psychrophilic TCE biodegradation rates in the columns were similar with both biostimulants and averaged 145 nmol liter-1 day-1. Methanotroph biostimulation was most adversely affected by low temperatures. At 12 degrees C, the biodegradation efficiencies (TCE degradation normalized to microbial activity) of methanotrophs and ammonia oxidizers decreased by factors of 2.6 and 1.6, respectively, relative to their biodegradation efficiencies at 24 degrees C. Collectively, these experiments demonstrated that in situ bioremediation of TCE is feasible at the psychrophilic temperatures common in surficial aquifers in the northern United States and that for such applications biostimulation of ammonia oxidizers could be more effective than has been previously reported.

Ammonia↗
PubMed2000

Effects of agronomic treatments on structure and function of ammonia-oxidizing communities.

The aim of this study was to determine the effects of different agricultural treatments and plant communities on the diversity of ammonia oxidizer populations in soil. Denaturing gradient gel electrophoresis (DGGE), coupled with specific oligonucleotide probing, was used to analyze 16S rRNA genes of ammonia oxidizers belonging to the beta subgroup of the division Proteobacteria by use of DNA extracted from cultivated, successional, and native deciduous forest soils. Community profiles of the different soil types were compared with nitrification rates and most-probable-number (MPN) counts. Despite significant variation in measured nitrification rates among communities, there were no differences in the DGGE banding profiles of DNAs extracted from these soils. DGGE profiles of DNA extracted from samples of MPN incubations, cultivated at a range of ammonia concentrations, showed the presence of bands not amplified from directly extracted DNA. Nitrosomonas-like bands were seen in the MPN DNA but were not detected in the DNA extracted directly from soils. These bands were detected in some samples taken from MPN incubations carried out with medium containing 1,000 microg of NH(4)(+)-N ml(-1), to the exclusion of bands detected in the native DNA. Cell concentrations of ammonia oxidizers determined by MPN counts were between 10- and 100-fold lower than those determined by competitive PCR (cPCR). Although no differences were seen in ammonia oxidizer MPN counts from the different soil treatments, cPCR revealed higher numbers in fertilized soils. The use of a combination of traditional and molecular methods to investigate the activities and compositions of ammonia oxidizers in soil demonstrates differences in fine-scale compositions among treatments that may be associated with changes in population size and function.

Agriculture↗
PubMed2000

Diversity and distribution of DNA sequences with affinity to ammonia-oxidizing bacteria of the beta subdivision of the class Proteobacteria in the Arctic Ocean.

The spatial distribution and diversity of ammonia-oxidizing bacteria of the beta subdivision of the class Proteobacteria (hereinafter referred to as ammonia oxidizers) in the Arctic Ocean were determined. The presence of ammonia oxidizers was detected by PCR amplification of 16S rRNA genes using a primer set specific for this group of organisms (nitA and nitB, which amplifies a 1.1-kb fragment between positions 137 and 1234, corresponding to Escherichia coli 16S rDNA numbering). We analyzed 246 samples collected from the upper water column (5 to 235 m) during March and April 1995, September and October 1996, and September 1997. Ammonia oxidizers were detected in 25% of the samples from 5 m, 80% of the samples from 55 m, 88% of the samples from 133 m, and 50% of the samples from 235 m. Analysis of nitA-nitB PCR product by nested PCR-denaturing gradient gel electrophoresis (DGGE) showed that all positive samples contained the same major band (band A), indicating the presence of a dominant, ubiquitous ammonia oxidizer in the Arctic Ocean basin. Twenty-two percent of the samples contained additional major bands. These samples were restricted to the Chukchi Sea shelf break, the Chukchi cap, and the Canada basin; areas likely influenced by Pacific inflow. The nucleotide sequence of the 1.1-kb nitA-nitB PCR product from a sample that contained only band A grouped with sequences designated group 1 marine Nitrosospira-like sequences. PCR-DGGE analysis of 122 clones from four libraries revealed that 67 to 71% of the inserts contained sequences with the same mobility as band A. Nucleotide sequences (1.1 kb) of another distinct group of clones, found only in 1995 samples (25%), fell into the group 5 marine Nitrosomonas-like sequences. Our results suggest that the Arctic Ocean beta-proteobacterial ammonia oxidizers have low diversity and are dominated by marine Nitrosospira-like organisms. Diversity appears to be higher in Western Arctic Ocean regions influenced by inflow from the Pacific Ocean through the Bering and Chukchi seas.

Ammonia↗
PubMed2001

Ammonia as an accelerator of tumor necrosis factor alpha-induced apoptosis of gastric epithelial cells in Helicobacter pylori infection.

The mechanism by which Helicobacter pylori induces apoptosis remains unclear. In a previous study using biopsy samples, we found a significant correlation between the urease activity of an H. pylori strain and the apoptosis level induced by this strain. Therefore, in this study, we investigated whether urease and/or the ammonia generated by urease can induce apoptosis. Human gastric epithelial cell lines were cocultured with H. pylori, and the levels of apoptosis and ammonia production were measured. The medium was supplemented (or not supplemented) with urea and cytokines. While a large amount of ammonia (>30 mM) accumulated in the coculture containing urease-positive H. pylori and urea, no significant degree of apoptosis occurred. In the presence of tumor necrosis factor alpha (TNF-alpha), however, a marked acceleration of apoptosis was found in this coculture. Such enhancement of apoptosis was also induced by the addition of 4 to 8 mM ammonia to the cell culture without either H. pylori or urea but containing TNF-alpha. These results suggested that ammonia accelerates cytokine-induced apoptosis in gastric epithelial cells, while ammonia or urease molecules alone are unable to induce a significant degree of apoptosis.

Ammonia↗
PubMed1972

Faecal ammonia and pH during lactulose administration in man: comparison with other cathartics.

The effect of lactulose on faecal pH and ammonia has been studied in three normal subjects with the aid of dialysis of faeces in vivo. Observations were also made with sodium sulphate and the two hexahydric alcohols, mannitol and sorbitol, given in doses sufficient to cause a similar increase in stool weight. All four cathartics rendered the stool more acid, but there was no increase in the concentration of faecal ammonia. Lactulose, despite increasing faecal volume, did not cause an increase in the absolute amount of ammonia lost in the faeces, but the other purgatives did show a modest rise. The results are inconsistent with the theory that lactulose benefits the clinical picture of portosystemic encephalopathy by trapping ammonia in an acid stool. An alternative suggestion is advanced, namely, that any cathartic (including lactulose) reduces ammonia absorption from the colon by decreasing colonic transit time, and so reducing the amount of ammonia generated by autolysis of colonic bacteria.

Adult↗
PubMed2005

Clinical and pathological responses of weaned pigs to atmospheric ammonia and dust.

Nine hundred and sixty weaned pigs were exposed for five weeks to controlled concentrations of atmospheric ammonia and dust in a single, multifactorial experiment. The treatments were a mean dust concentration of either 1.2, 2.7, 5.1 or 9.9 mg/m3 (inhalable fraction) and a mean ammonia concentration of either 0.6, 10.0, 18.8 or 37.0 ppm, concentrations representative of commercial conditions. The experiment was carried out over two years and the pigs were used in eight batches, each consisting of five lots of 24 pigs. Each treatment combination was replicated once, and an additional control lot (nominally 0 mg/m3 dust and 0 ppm ammonia) was included in each batch. The dust concentration was the same in the other four lots in each batch in which the four concentrations of ammonia were used; thus, the split-plot design was more sensitive to the effects of ammonia than dust. The groups of pigs were kept separately in five rooms in a purpose-built facility, and the pollutants were injected continuously into the air supply. Ammonia was supplied from a pressurised cylinder, and the endogenous dust in each room was supplemented by an artificial dust manufactured from feed, barley straw and faeces, mixed by weight in the proportions 5:1:4; its ingredients were oven-dried, milled and mixed, and then resuspended in the air supply. The health of the pigs was assessed in terms of general pathology, respiratory tract pathology, and the microbiology of the nasal cavity, trachea and lung. In each batch, postmortem examinations were carried out on 40 pigs after five weeks' exposure to the pollutants and on 30 pigs two weeks later to test for carryover and recovery--a total of 560 pigs. These examinations revealed minimal gross pathology and widespread minor pathological changes of little significance. The pigs' turbinate and lung scores were low and unaffected by exposure to pollutants. All the putative bacterial pathogens, with the exception of toxigenic Pasteurella multocida type D, were isolated from the respiratory tract of the pigs of both ages, but there were no differences between the effects of the different concentrations of pollutants.

Air Pollutants↗
PubMed1982

Cytochrome c554 as a possible electron donor in the hydroxylation of ammonia and carbon monoxide in Nitrosomonas europaea.

Mechanism of ammonia oxidation was studied in the reconstituted system of Nitrosomonas membrane fraction plus the Nitrosomonas cytochrome c554. The cytochrome c554 was reduced by hydroxylamine, hydrazine, and ammonia and the reduced cytochrome was oxidized upon the addition of ammonia or carbon monoxide. The oxidation of carbon monoxide in the presence of hydroxylamine or hydrazine was studied as a possible assay method for ammonia hydroxylase where hydroxylamine or hydrazine was supplying the reducing power required for the hydroxylation of carbon monoxide. The stoichiometry of the reaction, Km values for substrates, and effects of pH and inhibitors were investigated. It is concluded that carbon monoxide, a competitive inhibitor for ammonia oxidation, is an alternate substrate for ammonia hydroxylase using the reduced cytochrome c554 as the reducing power.

Ammonia↗
PubMed1992

Flow-dependent antiarrhythmic properties of ammonia during catecholamine-driven ventricular tachycardia.

Fifteen mongrel dogs weighing 22-34 kg were instrumented to investigate the antiarrhythmic effects of ammonia (0.1-0.2 mmol/min ammonium hydroxide), adenosine (1.87 mumol/min), and saline (0.9% NaCl) during norepinephrine-driven ventricular tachycardia, under conditions of controlled and natural coronary blood flow. Under natural flow conditions, the severe ectopy caused by norepinephrine (100-800 ng.kg-1.min-1) was reduced by 42 +/- 4% after 30 s of ammonia infusion. Adenosine infusion reduced percent ectopy by 97 +/- 2% at 30 s. Ammonia also significantly increased coronary blood flow by 26 +/- 4%, while adenosine increased blood flow by 72 +/- 14%. Saline infusion had no significant effect on either the severity of ventricular tachycardia or coronary blood flow. Norepinephrine consistently caused coronary functional hyperemia as previously reported. When coronary blood flow was controlled by a peristaltic pump to match natural coronary blood flow and to prevent norepinephrine-induced coronary functional hyperemia, the antiarrhythmic effects of ammonia were lost while those of adenosine were unaffected. Additionally, increasing coronary blood flow manually during norepinephrine-induced ventricular tachycardia, to a level seen with combined norepinephrine and ammonia under natural flow conditions, appeared to worsen the ventricular arrhythmias. We conclude that the antiarrhythmic properties of ammonia against norepinephrine-driven ventricular tachycardia might be dependent on coronary blood flow, while those of adenosine are independent of coronary blood flow.

Adenosine↗
PubMed1992

Ammonia and amino acid metabolism in human skeletal muscle during exercise.

This review focuses on the ammonia and amino acid metabolic responses of active human skeletal muscle, with a particular emphasis on steady-state exercise. Ammonia production in skeletal muscle involves the purine nucleotide cycle and the amino acids glutamate, glutamine, and alanine and probably also includes the branched chain amino acids as well as aspartate. Ammonia production is greatest during prolonged, steady state exercise that requires 60-80% VO2max and is associated with glutamine and alanine metabolism. Under these circumstances it is unresolved whether the purine nucleotide cycle (AMP deamination) is active; if so, it must be cycling with no IMP accumulation. It is proposed that under these circumstances the ammonia is produced from slow twitch fibers by the deamination of the branched chain amino acids. The ammonia response can be suppressed by increasing the carbohydrate availability and this may be mediated by altering the availability of the branched chain amino acids. The fate of the ammonia released into the circulation is unresolved, but there is indirect evidence that a considerable portion may be excreted by the lung in expired air.

Alanine↗