Effects of environmental salinity on branchial permeability of rainbow trout, Salmo gairdneri.

Isaia, J.

doi:10.1113/jphysiol.1982.sp014193

Cited by 16 publications

(4 citation statements)

References 21 publications

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“…Isaia (1982) demonstrated that gill permeability to small nonelectrolytes, such as urea, was higher in freshwateradapted vs. seawater-adapted rainbow trout. Similar findings were reported by Masoni and Payan (1974) in the eel, Anguilla anguilla.…”

Section: Discussionmentioning

confidence: 97%

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Ammonia and urea excretion in the tidepool sculpin (Oligocottus maculosus): sites of excretion, effects of reduced salinity and mechanisms of urea transport

Wright

Pärt

Wood

1995

Fish Physiol Biochem

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Tidepool sculpins live in a variable environment where water temperature, salinity, gas tensions, and pH can change considerably with the daily tide cycle. Tidepool sculpins are primarily ammoniotelic, with 8-17% of nitrogen wastes excreted as urea. The majority of net ammonia (J(net) amm; 85%) and urea (J(net) urea; 74%) excretion occurred across the gill, with the remainder excreted across the skin, the kidney, and/or gut. Acute (2h) exposure to 50% seawater significantly increased J(net) urea (2.8-fold), but reduced J(net) amm (3.5-fold). In fish exposed to 50% seawater for 1 week, J(net) urea returned to control values, but J(net) amm remained slightly depressed. Unidirectional urea influx (J(in) urea) and efflux (J(out) urea) were measured using(14)C-urea to determine if urea was excreted across the gills by simple diffusion or by a carrier-mediated mechanism. J(in) urea increased in a linear manner with increasing urea water levels (0-11 mmol N l(-1)), while J(out) urea was independent of external urea concentrations. As well, J(net) urea and J(out inurea) were not significantly different from one another, indicating the absence of "back transport". Urea analogs and transport inhibitors added to the water did not have any consistent effect on unidirectional urea flux. These results demonstrate that ammonia and urea excretion rates and sites of excretion in tidepool sculpins are very similar to those found in other marine and freshwater teleosts. Urea and ammonia may play a role in osmoregulation as excretion rates and tissue levels were influenced by changes in water salinity. Finally, we found no evidence for a specific urea carrier; branchial urea excretion is likely dependent on simple diffusion.

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Section: Discussionmentioning

confidence: 97%

“…Isaia (1982) reported that small nonelectrolytes, such as water and urea, were transported across the gill epithelium by a transcellular pathway. He suggested that these molecules were transported by passive diffusion because there was a linear correlation between their permeability and their oil/water partition coefficients.…”

Section: Urea Transport Mechanismsmentioning

confidence: 99%

Ammonia and urea excretion in the tidepool sculpin (Oligocottus maculosus): sites of excretion, effects of reduced salinity and mechanisms of urea transport

Wright

Pärt

Wood

1995

Fish Physiol Biochem

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“…As one significant difference is expected in 22 tests at the 5% level (statistical type I error), it may be concluded that supplementation of 20 g kg −1 dietary urea during the sea water grow‐out period had little or no effect on the sensory quality of market‐size Atlantic salmon. Isaia (1982) demonstrated that small molecules such as water and urea are almost entirely transported transcellularly through the respiratory cells by passive diffusion. This may explain why a short period of feed deprivation significantly reduced the urea concentration in the muscle to the level of the control group and why no effects on the sensory quality were observed.…”

Section: Discussionmentioning

confidence: 99%

Urea in feeds for sea water farmed Atlantic salmon: effect on growth, carcass quality and outbreaks of winter ulcer

Rørvik

Steien

Nordrum

et al. 2001

Aquaculture Nutrition

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The main objective of the present study was to evaluate whether dietary supplementation of urea might reduce the incidence of winter ulcer in sea water-farmed Atlantic salmon. Salmon destined to be S0 smolt were fed with a urea-supplemented diet (0 or 20 g kg )1 urea) over an 8-week period prior to sea water transfer and were then fed supplemented diet (0, 5, 10 or 20 g kg )1 urea) during the ®rst and second winters in the sea. During the ®rst winter positive relationships between dietary urea and plasma urea and between plasma urea and plasma osmolality were observed. Further, plasma osmolality displayed a negative relationship to mortality. Of the salmon that died during the ®rst winter in the sea 90% had one or more skin ulcers. Both during the ®rst and second winter there were fewer salmon with ulcer among ®sh fed with the diets supplemented with urea. Salmon fed with 20 g kg )1 urea tended to have higher percentage water in the muscle. Mortality and incidence of salmon with ulcer seemed to relate to plasma osmolality amongst ®sh fed on diets that diered in levels of urea supplementation, suggesting that an osmotic imbalance may contribute to the development of winter ulcer in farmed salmon. Salmon fed with 20 g kg )1 urea showed signi®cantly greater body weight during the second winter in sea. Fish killed without prior starvation had signi®cantly higher level of muscle urea in the 20 g kg )1 urea group compared with ®sh fed with the unsupplemented diet. However, a 13-day starvation period reduced urea content in the muscle to the level of the control. No eects of dietary urea supplementation on the sensory quality of market size Atlantic salmon were observed. KEY WORDS

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“…A similar muscle urea concentration in trout fed control diet and in those fed diets with and without supplementation, may suggest that excess urea is rapidly excreted. A possible reason for elimination of excess plasma urea may be that small molecules such as water and urea are almost entirely transported transcellularly, by passive diffusion, through the respiratory cells of the secondary lamellae in the gills ( Isaia 1982).…”

Section: Discussionmentioning

confidence: 99%

Urea and trimethylamine oxide in diets for seawater farmed rainbow trout: effect on fat belching, skin vesicle, winter ulcer and quality grading

Rørvik

Steien

Saltkjelsvik

et al. 2000

Aquaculture Nutrition

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Three experiments were conducted in order to evaluate the effects of urea and trimethylamine oxide (TMAO) supplementation in diets for seawater‐farmed rainbow trout Oncorhynchus mykiss. In all experiments, commercial extruded feed was used as basal control diet, whereas experimental diets were the basal diet supplemented with either 10 g kg–1 TMAO, 10 g kg–1 urea or 10 g kg–1 TMAO and 10 g kg–1 urea. The experiments were conducted both in research units and in a commercial fish farm. Quality was evaluated in three different commercial slaughterhouses, sorting the rainbow trout into superior, ordinary or processing grade. Significantly more TMAO was observed in muscle of rainbow trout given dietary supplementation of TMAO. However, the levels were low compared with levels in marine fish in general. Trimethylamine (TMA) was not found. No increase in muscle urea content was observed in trout fed urea in the diet. Significantly reduced fat belching, seen as reduced number of fat droplets surfacing in the net pen, was observed in groups given TMAO‐supplemented feeds. At least twice as many rainbow trout with skin vesicles were observed in the control group as in the group fed urea‐supplemented diet. In addition, skin vesicles developed into open sores in the winter only in rainbow trout fed control diet. In a large‐scale trial, quality grading of almost 200 000 market‐sized rainbow trout showed significantly more (88 vs. 83%) trout of superior grade in the group fed dietary urea compared with fish fed control diet. The main reason for downgrading from superior to ordinary and processing grade was skin lesions, supporting the observations made in the experimental units.

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Effects of environmental salinity on branchial permeability of rainbow trout, Salmo gairdneri.

Cited by 16 publications

References 21 publications

Ammonia and urea excretion in the tidepool sculpin (Oligocottus maculosus): sites of excretion, effects of reduced salinity and mechanisms of urea transport

Ammonia and urea excretion in the tidepool sculpin (Oligocottus maculosus): sites of excretion, effects of reduced salinity and mechanisms of urea transport

Urea in feeds for sea water farmed Atlantic salmon: effect on growth, carcass quality and outbreaks of winter ulcer

Urea and trimethylamine oxide in diets for seawater farmed rainbow trout: effect on fat belching, skin vesicle, winter ulcer and quality grading

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