Tissue Ammonia Levels Research Articles

Ammonia‐‑nitrogen stress affects immune regulation via TNFα in yellow catfish (Pelteobagrus fulvidraco)

Ammonia‑nitrogen has become a global issue with feed-dependent intensive culture modes, which may cause toxicity in aquatic animals by affecting immune regulation. Although numerous studies have investigated the acute and short-term toxic effect of ammonia‑nitrogen in fish, there is a lack of research on the long-term effects of exposure to low concentration of ammonia‑nitrogen. In this study, yellow catfish (Pelteobagrus fulvidraco) were exposed to water supplemented with ammonia (NH4Cl was used as the ammonia source) at concentrations of 0 (control), 8, 10, 12, 14, 16 and 18 mg/L for eight-weeks, and the effects on growth performance, histopathology, antioxidant and immune capacities of yellow catfish were investigated. The results showed that long-term ammonia exposure resulted in decreased weight gain rate (WGR) and serum antioxidant capacity, increased feed coefficient (FC), serum and tissue ammonia levels. They caused extensive histopathological changes and significantly impaired inflammatory and immune responses. On the other hand, ammonia exposure significantly affected the respiratory burst and the content of reactive oxygen species (ROS) of head kidney macrophages. Still, the above phenomenon can be reversed by inhibiting tumor necrosis factor-α (TNFα), indicating that TNFα may play a key role in this process. In conclusion, our findings indicate that extended exposure to ammonia nitrogen, even at low concentrations, has a detrimental effect on the well-being of aquatic organisms. This finding underscores the necessity of long-term environmental toxicological investigations of ammonia‑nitrogen.

Is NMDA-Receptor-Mediated Oxidative Stress in Mitochondria of Peripheral Tissues the Essential Factor in the Pathogenesis of Hepatic Encephalopathy?

Background: Hepatic encephalopathy (HE) is a neuropsychiatric syndrome of increased ammonia-mediated brain dysfunction caused by impaired hepatic detoxification or when the blood bypasses the liver. Ammonia-activated signal transduction pathways of hyperactivated NMDA receptors (NMDAR) are shown to trigger a cascade of pathological reactions in the brain, leading to oxidative stress. NMDARs outside the brain are widely distributed in peripheral tissues, including the liver, heart, pancreas, and erythrocytes. To determine the contribution of these receptors to ammonia-induced oxidative stress in peripheral tissues, it is relevant to investigate if there are any ammonia-related changes in antioxidant enzymes and free radical formation and whether blockade of NMDARs prevents these changes. Methods: Hyperammonemia was induced in rats by ammonium acetate injection. Oxidative stress was measured as changes in antioxidant enzyme activities and O2•− and H2O2 production by mitochondria isolated from the tissues and cells mentioned above. The effects of the NMDAR antagonist MK-801 on oxidative stress markers and on tissue ammonia levels were evaluated. Results: Increased ammonia levels in erythrocytes and mitochondria isolated from the liver, pancreas, and heart of hyperammonemic rats are shown to cause tissue-specific oxidative stress, which is prevented completely (or partially in erythrocyte) by MK-801. Conclusions: These results support the view that the pathogenesis of HE is multifactorial and that ammonia-induced multiorgan oxidative stress-mediated by activation of NMDAR is an integral part of the disease and, therefore, the toxic effects of ammonia in HE may be more global than initially expected.

The effects of Deepwater Horizon crude oil on ammonia and urea handling in mahi-mahi (Coryphaena hippurus) early life stages

Many ecologically important fishes, including mahi-mahi (Coryphaena hippurus), and their offspring were directly exposed to crude oil following the Deepwater Horizon (DWH) oil spill. Early life stage fish are especially vulnerable to the toxicity of crude oil-derived polycyclic aromatic hydrocarbons (PAHs). In teleosts, yolk sac proteins are the main energy source during development and are usually catabolized into ammonia or urea among other byproducts. Although excretion of these waste products is sensitive to oil exposure, we know little about the underlying mechanisms of this process. In this study, we examined the effects of crude oil on ammonia and urea handling in the early life stages of mahi. Mahi embryos exposed to 30–32 μg L−1 ∑PAH exhibited increased urea excretion rates and greater accumulation of urea in the tissues before hatch suggesting that ammonia, which is highly toxic, was converted into less-toxic urea. Oil-exposed embryos (6.3–32 μg L−1 ∑PAH) displayed significantly increased tissue ammonia levels at 42 hpf and upregulated mRNA levels of ammonia transporters (Rhag, Rhbg and Rhcg1) from 30 to 54 hpf. However, despite increased accumulation and higher expression of ammonia transporters, the larvae exposed to higher ∑PAH (30 μg L−1 ∑PAH) showed reduced ammonia excretion rates after hatch. Together, the increased production of nitrogenous waste reinforces previous work that increased energy demand in oil-exposed embryos is fueled, at least in part, by protein metabolism and that urea synthesis plays a role in ammonia detoxification in oil-exposed mahi embryos. To our knowledge, this study is the first to combine physiological and molecular approaches to assess the impact of crude-oil on both nitrogenous waste excretion and accumulation in the early life stages of any teleosts.

Hypothesis: role for ammonia neutralization in the prevention and reversal of heart failure.

Ammonia plays a central role in the life and death of all living organisms and has been studied for over 100 yr. Ammonia is necessary for growth and development, but it is toxic in excess, and, as a result, differing methods of ammonia neutralization have evolved. After physiological and pathological stress to the heart, tissue ammonia levels rise. Local ammonia neutralization may be inadequate, and excess ammonia may exert its toxic effects. Phenylbutyrate (PBA), which is Federal Drug Administration approved for the treatment of elevated blood ammonia in urea cycle disorders, provides an accessory pathway for ammonia excretion. Recently, PBA has also been found to prevent specific cardiomyopathies. The central theme presents the hypothesis that stress to the myocardium from a variety of environmental sources causes injury, cell death, necrosis, and ammonia production. Ammonia, if not neutralized, exerts downstream toxic effects. Here, data are presented showing that neutralization with PBA alone and PBA combined with angiotensin-converting enzyme inhibition prevent and reverse pathophysiology associated with specific cardiomyopathies. NEW & NOTEWORTHY Ammonia produced after myocardial injury is hypothesized to be an upstream stress contributing to the pathophysiology of heart failure, effects that may be attenuated by a documented ammonia-reducing treatment. Reversal of heart failure can be achieved using an angiotensin-converting enzyme inhibitor combined with an ammonia-reducing treatment.

Effect of Environmental acidic pH on Oxygen Consumption in Different stages of Fish, Cyprinus carpio(L)

The data in table 1 and 2 showed changes in the total respiration and unit oxygen consumption of the developmental stages of fresh water fish during short-term exposure and acclimation to sub lethal acidic (pH 5.5) media. The oxygen consumption of fry significantly depleted in all the days of exposure to sub lethal acidic pH 5.5 starting from first day to fourteen days of exposure. The rate of total oxygen consumption depletion was higher in second day followed by fourth and sixth day with a gradual decreased trend was observed in the depletion up to fourteenth day of exposure. Similarly it is also observed significant decrease of total oxygen consumption and also rate of oxygen consumption of fingerling on exposure to sub lethal acidic pH in all the days of exposure, i.e., first day to fourteenth day when compared to control. The unit oxygen consumption of fry and fingerling on exposure to sub lethal pH media exhibited significant depletion when compared to control. The rate of depletion was more in the initial days of exposure and it was reduced gradually in 12 th and 14 th days of exposure. Further, the animal excretion was highly depleted in acclimated fry to sub lethal acidic media when compared to control. Similarly, excretory pattern of the fingerling also showed significant reduction on acclimation to sub lethal acidic medium over control. The tissue ammonia levels were also significantly depleted in both fry and fingerlings on acclimation to sub lethal acidic medium when compared to control (table 3). But the rate of depletion was more in fingerlings than to fry stage. It is concluded that the acclimation processes to sub lethal acidic medium induced compensatory changes in nitrogenous end products metabolism of fry and fingerlings while providing positive survival capacity under acidic stress conditions.

Fasting goldfish, Carassius auratus, and common carp, Cyprinus carpio, use different metabolic strategies when swimming

Fish need to balance their energy use between digestion and other activities, and different metabolic compromises can be pursued. We examined the effects of fasting (7days) on metabolic strategies in goldfish and common carp at different swimming levels. Fasting had no significant effect on swimming performance (Ucrit) of either species. Feeding and swimming profoundly elevated total ammonia (Tamm) excretion in both species. In fed goldfish, this resulted in increased ammonia quotients (AQ), and additionally plasma and tissue ammonia levels increased with swimming reflecting the importance of protein contribution for aerobic metabolism. In carp, AQ did not change since oxygen consumption (MO2) and Tamm excretion followed the same trend. Plasma ammonia did not increase with swimming suggesting a balance between production and excretion rate except for fasted carp at Ucrit. While both species relied on anaerobic metabolism during exhaustive swimming, carp also showed increased lactate levels during routine swimming. Fasting almost completely depleted glycogen stores in carp, but not in goldfish. Both species used liver protein for basal metabolism during fasting and muscle lipid during swimming. In goldfish, feeding metabolism was sacrificed to support swimming metabolism with similar MO2 and Ucrit between fasted and fed fish, whereas in common carp feeding increased MO2 at Ucrit to sustain feeding and swimming independently.

Air Breathing and Ammonia Excretion in the Giant Mudskipper,Periophthalmodon schlosseri

The giant mudskipper, Periophthalmodon schlosseri, is an amphibious, obligate, air-breathing teleost fish. It uses its buccal cavity for air breathing and for taking and holding large gulps of air. These fish live in mud burrows at the top of the intertidal zone of mangrove mudflats; the burrow water may be hypoxic and hypercapnic and have high ammonia levels. The buccal epithelium is highly vascularized, with small diffusion distances between air and blood. The gill epithelium is densely packed with mitochondria-rich cells. Periophthalmodon schlosseri can maintain tissue ammonia levels in the face of high ammonia concentrations in the water. This is probably achieved by active ammonium ion transport across the mitochondria-rich cells via an apical Na/H+(NH4+) exchanger and a basolateral Na/K+(NH4+) ATPase. When exposed to air, the animal reduces ammonia production, but there is some increase in tissue ammonia levels after 24 h. There is no detoxification by increased production of glutamine or urea, but there is partial amino acid catabolism, leading to the accumulation of alanine. CO2 production and proton excretion cause acidification of the burrow water to reduce ammonia toxicity. The skin has high levels of cholesterol and saturated fatty acids decreasing membrane fluidity and gas, and therefore ammonia, permeability. Exposure to elevated environmental ammonia further decreases membrane permeability. Acidification of the environment and having a skin with a low NH3 permeability reduces ammonia influx, so that the fish can maintain tissue ammonia levels by active ammonium ion excretion, even in water containing high levels of ammonia.

Accumulation of ammonia in the body and NH(3) volatilization from alkaline regions of the body surface during ammonia loading and exposure to air in the weather loach Misgurnus anguillicaudatus.

The weather loach Misgurnus anguillicaudatus inhabits rice fields that experience drought in summer and ammonia loading during agricultural fertilisation. Exposure of specimens to ammonia led to the accumulation of ammonia in muscle, liver and blood. The level of ammonia reached in the plasma was the highest reported among fishes. Ammonia was not detoxified to urea, and urea excretion rate was unaffected by ammonia exposure. Fish acidified the water to reduce ammonia loading. Ammonia loading, unlike aerial exposure, did not induce glutamine synthesis, and there was no accumulation of glutamine. This is a unique observation different from those reported for other fishes in the literature. An initial switch to partial amino acid catabolism led to the accumulation of alanine and was probably associated with a decreased rate of ammonia production. Aerial exposure led to decreases in rates of ammonia and urea excretion, as well as the accumulation of tissue ammonia. As the internal ammonia levels increased, M. anguillicaudatus was able to excrete some ammonia in the gaseous form (NH(3)). The percentage of ammonia excreted as NH(3) increased with time of exposure and with increasing temperature. It appears that air-breathing through the gut is involved, with the anterior portion of the digestive tract playing a central role: it became significantly more alkaline in fish exposed to air or to environmental ammonia. The skin, which also became more alkaline during air exposure, may also be involved in ammonia volatilization in air-exposed fish. This represents the first report of a fish using volatilization of NH(3) as part of a defence against ammonia toxicity. It can be concluded that the main strategy adopted by M. anguillicaudatus confronted with ammonia loading or air exposure is to tolerate high ammonia levels in the tissues. During periods of elevated tissue ammonia levels, some ammonia is lost by volatilization via air-breathing using the gut. In addition, some ammonia may be lost across the skin during air exposure.

Nitrogen metabolism and excretion in the mangrove killifish Rivulus marmoratus I. The influence of environmental salinity and external ammonia.

At a field site in Belize, mangrove killifish Rivulus marmoratus inhabit hypersaline waters (up to 48 per thousand containing approximately 1 mmol l(-1) ammonia. We tested the hypotheses that R. marmoratus modify their nitrogen metabolism and excretion (i) by accumulating free amino acids (FAAs) and urea in the tissues during hyperosmotic stress and (ii) by shifting to ureotelism and accumulating FAAs during hyperammonia stress. Urea excretion (J(Urea)) (but not ammonia excretion, J(Amm)) displayed a diurnal pattern, with significantly less (75 %) urea excreted at night than during the day in both laboratory-reared clones and wild-caught killifish. When fish were exposed to hypersaline conditions (45 per thousand sea water), J(Urea) was significantly reduced and tissue urea and FAA levels were elevated compared with those of control fish (15 per thousand sea water). When R. marmoratus were exposed to 0, 1, 2, 5 and 10 mmol l(-1) NH(4)Cl (pH 8) for 48 h, no differences were found in J(Urea). Remarkably, prolonged exposure (10 days) to 5 mmol l(-1) NH(4)Cl (pH 8) did not result in an elevation of tissue ammonia levels. In addition, tissue urea and total FAA levels did not differ between control and ammonia-exposed fish after > or =4 days. We propose that the euryhaline R. marmoratus retain urea and FAAs within their tissues in response to extreme osmotic stress. In contrast to many ammonia-tolerant fishes, R. marmoratus do not shift to ureotelism during prolonged hyperammonia stress, nor do they convert nitrogenous wastes into FAAs. The data suggest that killifish continue to eliminate ammonia despite an unfavourable blood-to-water gradient, thereby avoiding accumulation of ammonia.

The mudskipper,Periophthalmodon schlosseri, actively transports NH 4 + against a concentration gradient

Periophthalmodon schlosseri can maintain ammonia excretion rates and low levels of ammonia in its tissues when exposed to 8 and 30 mM NH4Cl, but tissue ammonia levels rise when the fish is exposed to 100 mM NH4Cl in 50% seawater. Because the transepithelial potential is not high enough to maintain the NH4+ concentration gradient between blood and water, ammonia excretion under such a condition would appear to be active. Branchial Na+-K+-ATPase activity is very high and can be activated by physiological levels of NH4+ instead of K+. Ammonia excretion by the fish against a concentration gradient is inhibited by the addition of ouabain and amiloride to the external medium. It is concluded that Na+-K+-ATPase and an Na+/H+ exchanger may be involved in the active excretion of ammonia across the gills. This unique ability of P. schlosseri to actively excrete ammonia is related to the special structure of its gills and allows the fish to continue to excrete ammonia while air exposed or in its burrow.

Nitrogen metabolism in goldfish, Carassius auratus (L.) activities of amidases and amide synthetases in goldfish tissues

1. 1. Activities of asparagine synthetase, asparaginase, glutamine synthetase and glutaminase have been determined in red muscle, white muscle, brain, kidney, liver and gills of goldfish. 2. 2. Muscle and brain show a capacity for net amide synthesis, while liver and gills are capable of both amide synthesis and degradation. 3. 3. These results are consistent with the hypothesis that amide synthesis and degradation functions as a mechanism controlling tissue ammonia levels and ammonia levels and ammonia excretion rates.

Effects of ammonia on liver lysosomal functionality in Salmo gairdneri Rich.

Salmo gairdneri specimens were exposed for 4-48 hours to three different concentrations of un-ionized ammonia (UIA). An increase in lysosomal sensitivity to osmotic shock and in total proteolytic activity occurs in the liver. The amount of this increase depends upon the exposure time or upon environmental and tissue ammonia levels. On the other hand ammonia does not affect lysosome hydrolases activity in vitro.

A survey of blood and tissue nitrogen compounds in terrestrial decapods of Palau

AbstractTerrestrial decapods have significant levels of ammonia, uric acid and free amino acids in their blood, but blood is hypo‐osmotic to local seawater by as much as 300 mOsm/kg. Blood water content is approximately 90%, with protein making up virtually all the difference, whereas tissue water is between 70% and 80%. The tissue free amino acid pool is composed primarily of glycine, serine, proline, alanine and arginine, which are typical of all crustaceans. The size of the muscle pool is reduced in comparison to aquatic species, while that of gill is comparable. Tissue ammonia levels are very low in comparison to FAA, but these levels are significantly higher in gill than in muscle.

Regulation of ammonia (NH3-N) metabolism in the marine pulmonate, onchidium verruculatum. I. effects of a neuroendocrine centre on tissue ammonia levels

Effect of ganglionic extirpations and replacement on the ammonia levels in the blood and various tissues of the marine pulmonate, O. verruculatum was studied. Three hrs after extirpation of the pleurovisceral (PV) complex only and not any other ganglia, revealed a significant (P < 0.001) decline in the blood and foot ammonia levels and significant (P < 0.001) increment in the hepatopancreatic ammonia level. However, no change was observed in the mantle and nephridial ammonia levels. Replacement of the PV complex, either via implantation of intact ganglia or boiled and unboiled homogenate administration (1 gn/animal) into the ganglionectomised group, restored ammonia levels in the blood and foot and showed significant (P < 0.005) decrease in hepatopancreatic ammonia levels. The results are discussed in the light of hormonal regulation of the nitrogen metabolism.

Ammonia-Forming Enzymes and Calcium-Carbonate Deposition in Terrestrial Pulmonates

The ammonia hypothesis of calcium-carbonate deposition was tested to determine its general applicability to all land snails of the subclass Pulmonata. Ten shelled (snails) and four shell-less (slugs) species were evaluated. The ammonia-forming enzyme adenosine deaminase, or urease, or both were demonstrated in the mantle tissue of all 14 species. Adenosine deaminase predominated in 10 species and urease in only one. A hypothesis is proposed whereby ammonia is generated catalytically by a modified version of the purine nucleotide cycle. In all cases, the activity level of the enzyme was theoretically able to account for known rates of calcium-carbonate deposition. The pH optimum of either urease or adenosine deaminase from the mantle tissue of shelled species was between 8.6 and 10.0. The mantle enzyme of slugs displayed either an acidic optimum or no optimum. Tissue ammonia levels in shelled, but not shell-less, species were at least two and a half times as high in the mantle as in the foot. The results of this study support the hypothesis that ammonia gas is generated enzymatically to enhance the rate of calcium-carbonate deposition in pulmonate land snails.

The influence of ammonia on the transition to ureotelism in Xenopus laevis

AbstractToads of the species Xenopus laevis were immersed in 5 mM NH4Cl or 5 mM NaCl for periods of up to 28 days. In stronger solutions of NH4Cl, toads died within one hour. The rate of excretion of ammonia and urea and the activities of carbamyl phosphate synthetase, ornithine transcarbamylase, arginase and glutamate dehydrogenase in liver and kidney were measured. In toads in 5 mM NH4Cl, the excretion of urea was increased about ten‐fold, and there were increases in the activities of carbamyl phosphate synthetase and glutamate dehydrogenase in the liver. The activities of ornithine transcarbamylase and arginase in the liver, and of glutamate dehydrogenase in the kidney, were unaffected. In toads in 5 mM NaCl, there was no change in the rate of urea excretion or in the activities of any of the enzymes assayed. It was concluded that a rise in tissue ammonia levels is followed by alterations in the metabolic pathways of the toads which result in a decrease in those levels. Thus, the transition to ureotelism in X. laevis is triggered by an increase in tissue ammonia levels. Because there was no response to immersion in 5 mM NaCl, it is concluded that a slight increase in the osmotic pressure of the external medium has no effect, and that urea is of little significance in osmotic regulation in this toad.