Exposure to low concentrations of dissolved ammonia promotes growth rate in walleye Sander vitreus

α-lipoic acid ameliorates hepatotoxicity induced by chronic ammonia toxicity in crucian carp (Carassius auratus gibelio) by alleviating oxidative stress, inflammation and inhibiting ERS pathway

High environment ammonia (HEA) poses a deadly threat to aquatic animals and indirectly impacts human healthy life, while nutritional regulation can alleviate chronic ammonia toxicity. α-lipoic acid exhibits antioxidative effects in both aqueous and lipid environments, mitigating cellular and tissue damage caused by oxidative stress by aiding in the neutralization of free radicals (reactive oxygen species). Hence, investigating its potential as an effective antioxidant and its protective mechanisms against chronic ammonia stress in crucian carp is highly valuable. Experimental fish (initial weight 20.47 ± 1.68 g) were fed diets supplemented with or without 0.1% α-lipoic acid followed by a chronic ammonia exposure (10 mg/L) for 42 days. The results revealed that chronic ammonia stress affected growth (weight gain rate, specific growth rate, and feed conversion rate), leading to oxidative stress (decreased the activities of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase; decreased total antioxidant capacity), increased lipid peroxidation (accumulation of malondialdehyde), immune suppression (decreased contents of nonspecific immune enzymes AKP and ACP, 50% hemolytic complement, and decrease of immunoglobulin M), impaired ammonia metabolism (reduced contents of Glu, GS, GSH, and Gln), imbalance of expression of induced antioxidant-related genes (downregulation of Cu/Zu SOD, CAT, Nrf2, and HO-1; upregulation of GST and Keap1), induction of pro-apoptotic molecules (transcription of BAX, Caspase3, and Caspase9), downregulation of anti-apoptotic gene Bcl-2 expression, and induction of endoplasmic reticulum stress (upregulation of IRE1, PERK, and ATF6 expression). The results suggested that the supplementation of α-lipoic acid could effectively induce humoral immunity, alleviate oxidative stress injury and endoplasmic reticulum stress, and ultimately alleviate liver injury induced by ammonia poisoning (50-60% reduction). This provides theoretical basis for revealing the toxicity of long-term ammonia stress and provides new insights into the anti-ammonia toxicity mechanism of α-lipoic acid.

Characterization of the continuous skin fibroblastoid cell line, WE-skin11f, from walleye (Sander vitreus)

A walleye dermal fibroblastoid cell line, WE-skin11f, was established and characterized. WE-skin11f was immunocytochemically positive for two known dermal fibroblast protein markers: vimentin and collagen I. At passage 26, WE-skin11f cultures contained both diploid and aneuploid populations. Ascorbic acid was required to produce extracellular collagen I fibres. Both of the skin fibroblastoid cell lines, WE-skin11f and rainbow trout-derived RTHDF, were not as good as the walleye caudal fin fibroblastoid cell line, WE-cfin11f, at forming abundant dense extracellular collagen matrices. The thermobiology of WE-skin11f was similar to that of other walleye cell lines with 26°C showing best temperature for growth and 4°C showing no growth but 100% viability. The transcript levels of b2m and mhIa genes of the major histocompatibility class I receptor in WE-skin11f were largely similar at all temperatures examined (4, 14, 20 and 26°C). Cortisol had a variety of effects on WE-skin11f cells: growth inhibition, morphological change from fibroblastoid to epithelioid, and enhancement of barrier function. Treatment of WE-skin11f cells with the physiologically relevant concentration of 100 ng/ml cortisol inhibited collagen I synthesis and matrix formation. Thus, WE-skin11f cell line could be useful in fish dermatology, endocrinology, and immunology research.

Physiological insights into largemouth bass (Micropterus salmoides) survival during long-term exposure to high environmental ammonia

Waterborne ammonia is an environmental pollutant that is toxic to all aquatic animals. However, ammonia induced toxicity as well as compensatory mechanisms to defend against high environmental ammonia (HEA) are not well documented at present for largemouth bass (Micropterus salmoides), a high value fish for culture and sport fisheries in the United States. To provide primary information on the sensitivity of this species to ammonia toxicity, a 96 h-LC₅₀ test was conducted. Thereafter, responses at physiological, ion-regulatory and transcript levels were determined to get insights into the underlying adaptive strategies to ammonia toxicity. For this purpose, fish were progressively exposed to HEA (8.31 mg/L representing 25% of 96 h-LC₅₀) for 3, 7, 14, 21 and 28 days. Temporal effects of HEA on oxygen consumption rate (MO₂), ammonia and urea dynamics, plasma ions (Na⁺, Cl^- and K⁺), branchial Na⁺/K⁺-ATPase (NKA) and H⁺-ATPase activity, muscle water content (MWC), energy store (glycogen, lipid and protein) as well as branchial mRNA expression of Rhesus (Rh) glycoproteins were assessed. Probit analysis showed that 96 h-LC₅₀ of (total) ammonia (as NH₄HCO₃) at 25 °C and pH 7.8 was 33.24 mg/L. Results from sub-lethal end-points shows that ammonia excretion rate (J_amm) was strongly inhibited after 7 days of HEA, but was unaffected at 3, 14 and 21 days. At 28 days fish were able to increase J_amm efficiently and concurrently, plasma ammonia re-established to the basal level. Urea production was increased as evidenced by a considerable elevation of plasma urea, but urea excretion rate remained unaltered. Expression of Rhcg isoform (Rhcg2) mRNA was up-regulated in parallel with restored or increased J_amm, suggesting its ammonia excreting role in largemouth bass. Exposure to HEA also displayed pronounced augmentations in NKA activity, exemplified by a rise in plasma [Na⁺]. Furthermore, [K⁺], [Cl^-] and MWC homeostasis were disrupted followed by recovery to the control levels. H⁺-ATPase activity was elevated but NKA did not appear to function preferentially as a Na⁺/NH₄⁺-ATPase. From 14 days onwards MO₂ was depressed, potentially an attempt towards minimizing catabolism. Glycogen content in liver and muscle were temporarily depleted, whereas a remarkable increment in protein was evident at the last exposure period. Overall, these data suggest that ammonia induced toxicity can disturb several biological processes in largemouth bass, however, it can adapt to the long-term sub-lethal ammonia concentrations by activating various components of ammonia excretory, ion-regulatory and metabolic pathways.

The effects of high environmental ammonia on the structure of rainbow trout hierarchies and the physiology of the individuals therein

Our goals were: (i) to determine whether sublethal concentrations of water-borne ammonia would prevent the formation of a dominance hierarchy, or alter its structure, in groups of 4 juvenile trout; (ii) to investigate the behavioral and physiological responses of individuals of different social rank exposed to a concentration of ammonia that still allowed hierarchy formation. Social hierarchies were created by using a technique in which a food delivery system that created competition also served to isolate individual fish for respirometry. Groups of 4 fish were exposed to elevated ammonia (NH₄HCO₃) 12 h before first feeding; aggression was recorded by video camera during morning feedings. Experimental ammonia concentrations were 700, 1200 and 1500 μmol L^-1 at pH 7.3, 12 °C (9.8, 16.8, and 21.0 mg L^-1 as total ammonia-N, or 0.0515, 0.0884, and 0.1105 mg L^-1 as NH₃-N). Aggression was severely reduced by 1200 and abolished by 1500 μmol L^-1 total ammonia, such that hierarchies did not form. However, groups exposed to 700 μmol L^-1 total ammonia still formed stable hierarchies but displayed lower levels of aggression in comparison to control hierarchies. Exposure continued for 11 days. Physiological parameters were recorded on day 5 (end of period 1) and day 10 (end of period 2), while feeding and plasma cortisol were measured on day 11. In control hierarchies, dominant (rank 1) trout generally exhibited higher growth rates, greater increases in condition factor, higher food consumption, and lower cortisol levels than did fish of ranks 2, 3, and 4. In comparison to controls, the 700 μmol L^-1 total ammonia hierarchies generally displayed lower growth, lower condition factor increases, lower O₂ consumption, lower cortisol levels, but similar feeding patterns, with smaller physiological differences amongst ranks during period 1. Effects attenuated during period 2, as aggression and physiological measures returned towards control levels, indicating both behavioral and physiological acclimation to ammonia. These disturbances in social behavior and associated physiology occurred at an ammonia concentration in the range of regulatory significance and relevance to aquaculture.

High environmental ammonia exposure has developmental-stage specific and long-term consequences on the cortisol stress response in zebrafish

The capacity for early life environmental stressors to induce programming effects on the endocrine stress response in fish is largely unknown. In this study we determined the effects of high environmental ammonia (HEA) exposure on the stress response in larval zebrafish, assessed the tolerance of embryonic and larval stages to HEA, and evaluated whether early life HEA exposure has long-term consequences on the cortisol response to a novel stressor. Exposure to 500-2000μM NH₄Cl for 16h did not affect the gene expression of corticotropin-releasing factor (CRF) system components in 1day post-fertilization (dpf) embryos, but differentially increased crfa, crfb and CRF binding protein (crfbp) expression and stimulated both dose- and time-dependent increases in the whole body cortisol of 5dpf larvae. Pre-acclimation to HEA at 1dpf did not affect the cortisol response to a subsequent NH₄Cl exposure at 5dpf. In contrast, pre-acclimation to HEA at 5dpf caused a small but significant reduction in the cortisol response to a second NH₄Cl exposure at 10dpf. While continuous exposure to 500-2000μM NH₄Cl between 0 and 5dpf had a modest effect on mean survival time, exposure to 400-1000μM NH₄Cl between 10 and 14dpf decreased mean survival time in a dose-dependent manner. Moreover, pre-acclimation to HEA at 5dpf significantly decreased the risk of mortality to continuous NH₄Cl exposure between 10 and 14dpf. Finally, while HEA at 1dpf did not affect the cortisol stress response to a novel vortex stressor at 5dpf, the same HEA treatment at 5dpf abolished vortex stressor-induced increases in whole body cortisol at 10 and 60dpf. Together these results show that the impact of HEA on the cortisol stress response during development is life-stage specific and closely linked to ammonia tolerance. Further, we demonstrate that HEA exposure at the larval stage can have persistent effects on the capacity to respond to stressors in later life.

Effects of chronic ammonia exposure on ammonia metabolism and excretion in marine medaka Oryzias melastigma

Ammonia is highly toxic to aquatic organisms, but whether ammonia excretion or ammonia metabolism to less toxic compounds is the major strategy for detoxification in marine fish against chronic ammonia exposure is unclear to date. In this study, we investigated the metabolism and excretion of ammonia in marine medaka Oryzias melastigma during chronic ammonia exposure. The fish were exposed to 0, 0.1, 0.3, 0.6, and 1.1 mmol l^-1 NH₄Cl spiked seawater for 8 weeks. Exposure of 0.3-1.1 mmol l^-1 NH₄Cl had deleterious effects on the fish, including significant reductions in growth, feed intake, and total protein content. However, the fish could take strategies to detoxify ammonia. The tissue ammonia (T_Amm) in the 0.3-1.1 mmol l^-1 NH₄Cl treatments was significantly higher than those in the 0 and 0.1 mmol l^-1 NH₄Cl treatments after 2 weeks of exposure, but it recovered with prolonged exposure time, ultimately reaching the control level after 8 weeks. The amino acid catabolic rate decreased to reduce the gross ammonia production with the increasing ambient ammonia concentration. The concentrations of most metabolites remained constant in the 0-0.6 mmol l^-1 NH₄Cl treatments, whereas 5 amino acids and 3 energy metabolism-related metabolites decreased in the 1.1 mmol l^-1 NH₄Cl treatment. J_Amm steadily increased in ambient ammonia from 0 to 0.6 mmol l^-1 and slightly decreased when the ambient ammonia concentration increased to 1.1 mmol l^-1. Overall, marine medaka cope with sublethal ammonia environment by regulating the tissue T_Amm via reducing the ammonia production and increasing ammonia excretion.

Feeding through your gills and turning a toxicant into a resource: how the dogfish shark scavenges ammonia from its environment

Nitrogen (N) appears to be a limiting dietary resource for elasmobranchs, required not only for protein growth but also for urea-based osmoregulation. Building on recent evidence that the toxicant ammonia can be taken up actively at the gills of the shark and made into the valuable osmolyte urea, we demonstrate that the uptake exhibits classic Michaelis–Menten saturation kinetics with an affinity constant (Km) of 379 µmol l−1, resulting in net N retention at environmentally realistic ammonia concentrations (100–400 µmol l−1) and net N loss through stimulated urea-N excretion at higher levels. Ammonia-N uptake rate increased or decreased with alterations in seawater pH, but the changes were much less than predicted by the associated changes in seawater PNH3, and more closely paralleled changes in seawater NH4+ concentration. Ammonia-N uptake rate was insensitive to amiloride (0.1 mmol l−1) or to a 10-fold elevation in seawater K+ concentration (to 100 mmol l−1), suggesting that the mechanism does not directly involve Na+ or K+ transporters, but was inhibited by blockade of glutamine synthetase, the enzyme that traps ammonia-N to fuel the ornithine–urea cycle. High seawater ammonia inhibited uptake of the ammonia analogue [14C]methylamine. The results suggest that branchial ammonia-N uptake may significantly supplement dietary N intake, amounting to about 31% of the nitrogen acquired from the diet. They further indicate the involvement of Rh glycoproteins (ammonia channels), which are expressed in dogfish gills, in normal ammonia-N uptake and retention.

Molecular responses in digestive tract of juvenile common carp after chronic exposure to sublethal tributyltin

The effect of long-term exposure to tributyltin (TBT) on the intestine-related biochemical biomarkers in common carp was investigated in this study. Fish were exposed at sub-lethal concentrations of TBT (75 ng/L, 0.75 and 7.5 μg/L) for 60 days. Multiple biomarkers were measured, including digestive enzymes (trypsin, lipase and amylase), antioxidant responses (malondialdehyde (MDA) and total antioxidative capacity (T-AOC)), RNA/DNA ratio and the expression of digestive-related genes (try, lipc and amy). TBT exposure at 0.75 and 7.5 μg/L led to significantly inhibited activities of all digestive enzymes. At higher concentration of TBT, oxidative stress was apparent as reflected by the significant higher MDA content in the fish intestine, associated with an inhibition of T-AOC activities. After 60 days, the RNA/DNA ratio in fish intestine was significantly lower in groups exposed to TBT at higher concentrations (0.75 and 7.5 μg/L). In addition, the expression levels of try, lipc and amy in intestine of all treated fish were inhibited, even at the environmental concentration (75 ng/L). Our results suggest that long-term exposure to TBT could result in different responses of intestine-related biochemical biomarkers in fish, which could be used as new potential indicators for monitoring residual TBT present in aquatic environment.

Combined effects of ammonia and microcystin on survival, growth, antioxidant responses, and lipid peroxidation of bighead carp Hypophthalmythys nobilis larvae

Hazardous materials, such as ammonia and microcystin, are released into lakes during cyanobacterial bloom degradation and may severely impact aquatic organisms. To assess the combined effects of ammonia and microcystin on survival, growth, and oxidative stress of larval fish, 14-day-old larvae of bighead carp Hypophthalmythys nobilis were exposed to solutions with different combined concentrations of ammonia (0, 0.06, 0.264mgL(-1)) and microcystin (0, 2, 10, 30μgL(-1)) for 10 days. Microcystin significantly decreased body length, while ammonia significantly increased body weight, specific growth rate, and condition factor, but there was no significant interaction between ammonia and microcystin on them. Superoxide dismutase, catalase, and malondialdehyde significantly changed with microcystin concentration, whereas glutathione was not affected by microcystin. Ammonia significantly affected the antioxidant system. There were significant interactions between ammonia and microcystin on superoxide dismutase and malondialdehyde. Our data clearly demonstrate that ammonia and microcystin adversely affect bighead carp larvae.

Biochemical and physiological responses in liver and muscle of rainbow trout after long-term exposure to propiconazole

In this study, the chronic toxic effects of PCZ, a triazole fungicide commonly present in surface and ground water, on morphological indices, ROS generation and RNA/DNA ratio in liver and white muscle of rainbow trout were investigated. Fish were exposed at sublethal concentrations of PCZ (0.2, 50 and 500 microg L(-1)) for 7, 20 and 30d. Compared with the control, there were significant lower CF and HSI in fish exposed at the highest concentration of PCZ. ROS levels in both tissues increased significantly at higher PCZ concentrations (50 and 500 microg L(-1)) after 20 d and above, as well as in muscle of fish exposed at lowest PCZ concentration (0.2 microg L(-1)) after 30 d. The hepatic antioxidant enzymes (SOD and CAT) activities were induced significantly at higher concentrations (50, 500 microg L(-1)) of PCZ after 20 d and at 50 microg L(-1) after 30 d. Additional, hepatic SOD activity was significantly induced at 0.2 microg L(-1) after 30 d. Compared with the hepatic antioxidant enzymes activities in fish exposed to 50 microg L(-1) of PCZ, there was a decreasing trend in those exposed to 500 microg L(-1) after 30 d exposure. However, both the antioxidant enzymes activities were significantly inhibited in muscle of fish exposed to 500 microg L(-1) PCZ after 30 d. Moreover there was significant lower RNA/DNA ratio in both tissues after long-term exposure to higher concentration of PCZ. In short, environmental concentrations of PCZ could not induce obvious impacts on fish, but long-term exposure to higher concentrations of CBZ could affect seriously the health status of fish.

Effects of exposure to sublethal propiconazole on intestine-related biochemical responses in rainbow trout, Oncorhynchus mykiss

The effect of long-term (30 days) exposure to PCZ (0.2, 50, and 500 microg l(-1)) on intestine-related biochemical markers in rainbow trout was investigated. Multiple biomarkers were measured, including digestive enzymes (proteolytic enzymes and amylase), antioxidant responses (TBARS, CP, SOD, CAT, GR and GPx) and energy metabolic parameters (RNA/DNA ratio, Na(+)-K(+)-ATPase). Exposure to 500 microg l(-1) PCZ led to significantly inhibited (p<0.01) proteolytic enzyme and amylase activity. Activities of the antioxidant enzymes SOD, CAT, and GPx gradually increased at lower PCZ concentrations (0.2 and 50 microg l(-1)). At the highest concentration (500 microg l(-1)), oxidative stress was apparent as significant higher (p<0.05) lipid peroxidation and protein carbonyls, associated with an inhibition of antioxidant enzymes activity. Moreover, energy metabolic parameters (RNA/DNA ratio, Na(+)-K(+)-ATPase) were significantly inhibited (p<0.01) in the intestines of fish exposed to 500 microg l(-1) PCZ, compared with controls. We suggest that long-term exposure to PCZ could result in several responses in intestine-related biochemical markers, which potentially could be used as indicators for monitoring residual PCZ present in the aquatic environment.