Metabolism and detoxification of nitrite by trout hepatocytes

Doblander, C.

doi:10.1016/0304-4165(95)00166-2

Cited by 61 publications

(32 citation statements)

References 34 publications

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“…A substantial amount of nitrite taken up across the gills is internally metabolized and detoxified to nitrate (e.g. in RBCs and liver), raising plasma nitrate levels during nitrite exposure (Doblander and Lackner, 1996;Stormer et al, 1996). This nitrate production should be taken into account when judging the magnitude of branchial nitrite uptake.…”

Section: Discussion Nitrite Uptake and Metabolismmentioning

confidence: 99%

Metabolic fates and effects of nitrite in brown trout under normoxic and hypoxic conditions: blood and tissue nitrite metabolism and interactions with branchialNOS,Na+/K+-ATPaseandhsp70expression

Frank

Gerber

Hansen

et al. 2015

Journal of Experimental Biology

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Nitrite secures essential nitric oxide (NO) bioavailability in hypoxia at low endogenous concentrations, whereas it becomes toxic at high concentrations. We exposed brown trout to normoxic and hypoxic water in the absence and presence of added ambient nitrite to decipher the cellular metabolism and effects of nitrite at basal and elevated concentrations under different oxygen regimes. We also tested hypotheses concerning the influence of nitrite on branchial nitric oxide synthase (NOS), Na + /K + -ATPase (nka) and heat shock protein (hsp70) mRNA expression. Basal plasma and erythrocyte nitrite levels were higher in hypoxia than normoxia, suggesting increased NOS activity. Nitrite exposure strongly elevated nitrite concentrations in plasma, erythrocytes, heart tissue and white muscle, which was associated with an extensive metabolism of nitrite to nitrate and to iron-nitrosylated and S-nitrosated compounds. Nitrite uptake was slightly higher in hypoxia than normoxia, and high internal nitrite levels extensively converted blood hemoglobin to methemoglobin and nitrosylhemoglobin. Hypoxia increased inducible NOS (iNOS) mRNA levels in the gills, which was overruled by a strong inhibition of iNOS expression by nitrite in both normoxia and hypoxia, suggesting negative-feedback regulation of iNOS gene expression by nitrite. A similar inhibition was absent for neuronal NOS. Branchial NKA activity stayed unchanged, but mRNA levels of the nkaα1a subunit increased with hypoxia and nitrite, which may have countered an initial NKA inhibition. Nitrite also increased hsp70 gene expression, probably contributing to the cytoprotective effects of nitrite at low concentrations. Nitrite displays a concentrationdependent switch between positive and negative effects similar to other signaling molecules.

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Section: Discussion Nitrite Uptake and Metabolismmentioning

confidence: 99%

Metabolic fates and effects of nitrite in brown trout under normoxic and hypoxic conditions: blood and tissue nitrite metabolism and interactions with branchialNOS,Na+/K+-ATPaseandhsp70expression

Frank

Gerber

Hansen

et al. 2015

Journal of Experimental Biology

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“…Since Smith and Nunn (1984) reported that uric acid inhibited the oxidation of bovine oxyhaemoglobin by nitrite. Furthermore, Doblander and Lackner (1996) found out that oxidation (i.e., detoxification) of nitrite to nitrate by iron-containing proteins in trout hepatocytes was enhanced by the addition of uric acid. As uric acid is know to be an antioxidant protecting haem proteins from oxidation.…”

Section: Discussionmentioning

confidence: 99%

The ability of recovery in common carp after nitrite poisoning

Kroupová¹,

Máchová²,

Svobodová³

et al. 2006

Vet. Med.

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The aim of the study was to assess the ability of recovery in common carp after nitrite poisoning and to distinguish the difference in nitrite poisoning of carp at two different chloride concentrations in water. Two groups of carp (group 1 and 2) were exposed to environmental nitrite concentration of 1.45 mmol/l NO2– at different chloride concentrations (group 1: 0.31 mmol/l Cl– and group 2: 3.73 mmol/l Cl–) for 48 hours. After that, they were transferred into nitrite-free water. In the group 1 mortality of 51% occurred during nitrite exposure and further 11% mortality was observed after 24 h in nitrite free water. No mortality occurred in group 2 and control. Nitrite and methaemoglobin concentrations (MetHb) markedly increased in group 1 (plasma: 10.5 ± 1.90 mmol/l NO2–, liver: 3.5 ± 1.15 mmol/kg NO2–, muscle: 1.5 ± 0.37 mmol/kg NO2–, and MetHb: 93 ± 6.1%) compared with control (plasma: 0.05 ± 0.04 mmol/l NO2–, liver: 0.02 ± 0.01 mmol/kg NO2–, muscle: 0.04 ± 0.01 mmol/kg NO2–, and MetHb: 3 ± 2.9%). After 24 h in nitrite-free water, the values mildly decreased but not significantly (plasma: 5.1 ± 1.49 mmol/l NO2–, liver: 1.8 ± 0.65 mmol/kg NO2–, muscle: 0.8 ± 0.23 mmol/kg NO2–, and MetHb: 84 ± 11.2%). After next 120 h the values decreased significantly and were compared with those found in the control group (traces of nitrite, MetHb: 3 ± 2.1%). Nitrite exposure caused also increase in plasma K+ (3.8 ± 0.29 mmol/l), ammonia (230 ± 92 µmol/l), urea (1.7 ± 0.28 mmol/l) and uric acid concentration (66 ± 54 µmol/l) in group 1. On the other hand, values of haematocrit, erythrocyte count and haemoglobin concentration were markedly lower than control values. Most changes were corrected by the end of the recovery period, only plasma potassium concentration dropped bellow the control values. Nearly no changes were found in the group 2 compared with the control during the whole experiment duration. This shows the positive effect of chlorides on the fish resistance against nitrites.

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“…Fish are also capable of detoxifying nitrite by oxidising it to low-toxic nitrate (Doblander and Lackner, 1996). Several systems are known to produce nitrate from nitrite in animals, the most commonly known being haemoglobin, catalase and cytochrome oxidase.…”

Section: Mechanism Of Detoxificationmentioning

confidence: 99%

“…Several systems are known to produce nitrate from nitrite in animals, the most commonly known being haemoglobin, catalase and cytochrome oxidase. A part of detoxification takes place in the liver, as revealed by the ability of trout hepatocytes to oxidise nitrite to nitrate (Doblander and Lackner, 1996). Attention was also paid to the capacity of erythrocytes to convert nitrite to nitrate (Doblander and Lackner, 1997).…”

Section: Mechanism Of Detoxificationmentioning

confidence: 99%

Nitrite influence on fish: a review

Kroupová¹,

Máchová²,

Svobodová³

2005

Vet. Med.

194

117

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ABSTRACT:Nitrite is an intermediate in the oxidation of ammonium to nitrate. An elevated ambient nitrite concentration is a potential problem for freshwater fish since nitrite is actively taken up across the gills in competition with chloride. Nitrite is a well-known toxicant for fish as well as a disrupter of multiple physiological functions including ion regulatory, respiratory, cardiovascular, endocrine and excretory processes. One critical consequence of nitrite accumulation is the oxidation of haemoglobin to methaemoglobin, compromising blood oxygen transport. Nitrite toxicity to fish varies considerably and depends on a large number of external and internal factors. Among the most important ones are water quality (e.g. pH, temperature, cation, anion and oxygen concentration), length of exposure, fish species, fish size and age, and individual fish susceptibility. Chloride concentration in water is considered one of the most important factors influencing nitrite toxicity to fish. The importance of individual factors is assessed and re-evaluated continuously.

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Metabolism and detoxification of nitrite by trout hepatocytes

Cited by 61 publications

References 34 publications

Metabolic fates and effects of nitrite in brown trout under normoxic and hypoxic conditions: blood and tissue nitrite metabolism and interactions with branchialNOS,Na+/K+-ATPaseandhsp70expression

Metabolic fates and effects of nitrite in brown trout under normoxic and hypoxic conditions: blood and tissue nitrite metabolism and interactions with branchialNOS,Na+/K+-ATPaseandhsp70expression

The ability of recovery in common carp after nitrite poisoning

Nitrite influence on fish: a review

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