Osmotic regulation and urea metabolism in the lemon shark Negaprion brevirostris

Goldstein, Léon; Oppelt, W. W.; Th, Maren

doi:10.1152/ajplegacy.1968.215.6.1493

Cited by 63 publications

(24 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Interestingly, because euryhaline elasmobranchs can penetrate into very low-salinity environments, they experience larger external:internal osmotic gradients than marginally euryhaline elasmobranchs but have smaller increases in body weight and smaller decreases in hematocrit on dilution, and/or a more rapid return of hematocrit to predilution values (7,10,13,17,21,22). These latter findings indicate that the volume-regulatory mechanisms of euryhaline elasmobranchs can effectively counterbalance water influx.…”

mentioning

confidence: 97%

“…In response to this challenge, two strategies are employed: "osmoconformity"; i.e., plasma osmolality is varied in the same direction as the change in external salinity by altering the plasma concentrations of urea and/or Na ϩ and Cl Ϫ (13,21,22,45,47,53,54,57); and, renal excretory function is altered inversely with changes in environmental salinity (21,40,47,57; for review, see Ref. 10).…”

mentioning

confidence: 99%

“…When marginally euryhaline elasmobranchs are exposed to a dilute environment, branchial water uptake is counterbalanced by increased glomerular filtration rate, urinary flow rate, free water clearance (C H 2 O ), and urea and electrolyte excretion (21,22,40,47,57). Interestingly, because euryhaline elasmobranchs can penetrate into very low-salinity environments, they experience larger external:internal osmotic gradients than marginally euryhaline elasmobranchs but have smaller increases in body weight and smaller decreases in hematocrit on dilution, and/or a more rapid return of hematocrit to predilution values (7,10,13,17,21,22).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Effect of low environmental salinity on plasma composition and renal function of the Atlantic stingray, a euryhaline elasmobranch

Janech¹,

Fitzgibbon²,

Ploth³

et al. 2006

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

. Effect of low environmental salinity on plasma composition and renal function of the Atlantic stingray, a euryhaline elasmobranch. Am J Physiol Renal Physiol 291: F770 -F780, 2006. First published April 11, 2006 doi:10.1152/ajprenal.00026.2006.-Marine elasmobranchs maintain internal osmolality higher than their external environment, resulting in an osmotic gradient for branchial water uptake. This gradient is markedly increased in low-salinity habitats. The subsequent increase in water uptake presents a challenge to volume homeostasis. The Atlantic stingray is a marine elasmobranch that inhabits a remarkable range of environmental salinities. We hypothesized that the ability of these stingrays to regulate fluid volume in low-salinity environments is due primarily to a renal glomerular and tubular functional reserve. We tested this hypothesis by measuring renal excretory function after a rapid and sustained 50% reduction in the osmolality of the external medium. Atlantic stingrays were maintained in harbor water [control salinity (CS) ϳ850 mosmol/kgH 2O] for 1 wk. Rays were then either transferred to diluted harbor water [low salinity (LS) ϳ440 mosmol/kgH 2O] or maintained in CS for a further 24 h. Renal excretory function was markedly higher in the rays subjected to low salinity. Glomerular filtration rate was threefold higher and urine flow rate ninefold higher in the LS group. The clearance of solute-free water was greater, and solute-free water comprised a significantly larger proportion of the urine output for the stingrays transferred to dilute harbor water. We conclude that 1) the kidneys of Atlantic stingrays have a remarkable glomerular and tubular functional reserve, and 2) the marked increase in renal function attenuates the increase in fluid volume when these fish move into low-salinity habitats. free water clearance; glomerular filtration rate; tubular urea reabsorption IN GENERAL, MARINE ELASMOBRANCH fishes (sharks, skates, and rays) maintain body fluids hyperosmotic to the ambient environment as part of their osmo-and volume-regulatory strategies. In the ocean, for example, plasma osmolality is 2-10% higher than the osmolality of the surrounding seawater (for review, see Ref. 28), this being due to their ability to maintain high Na ϩ , Cl Ϫ , and urea concentrations in the extracellular fluid (for review, see Refs. 28 and 51).Most species of marine elasmobranchs are confined to marine habitats (9) and only encounter relatively small variations in environmental salinity. However, some species are found in estuaries, as well as marine environments, and therefore can be considered marginally euryhaline (9). Furthermore, a small number of species are euryhaline; i.e., they are able to reside in marine, estuarine, riverine, and even freshwater habitats for extended periods of time. Although, these euryhaline elasmobranchs appear to migrate between habitats on a seasonal basis (48, 54), at least one species, the Atlantic stingray, Dasyatis sabina, can reproduce and complete its life cycle in freshwat...

show abstract

mentioning

confidence: 97%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Effect of low environmental salinity on plasma composition and renal function of the Atlantic stingray, a euryhaline elasmobranch

Janech¹,

Fitzgibbon²,

Ploth³

et al. 2006

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

show abstract

“…Marine elasmobranchs downregulate tissue and/or blood levels of urea and/or TMAO when acclimated to dilute (50%) seawater (Price and Creaser, 1967;Goldstein et al, 1968;Goldstein and Forster, 1971;Cooper and Morris, 1998). Lower tissue osmolytes can be achieved by a short term increase in total (Goldstein et al, 1968) or renal (Goldstein and Forster, 1971;Payan et al, 1973) urea excretion and/or a sustained reduction in the rate of urea synthesis.…”

mentioning

confidence: 99%

“…Lower tissue osmolytes can be achieved by a short term increase in total (Goldstein et al, 1968) or renal (Goldstein and Forster, 1971;Payan et al, 1973) urea excretion and/or a sustained reduction in the rate of urea synthesis. Changes in urea production or OUC enzyme activities, however, have not been investigated in marine elasmobranchs exposed to dilute seawater.…”

mentioning

confidence: 99%

Dogmas and controversies in the handling of nitrogenous wastes:Osmoregulation during early embryonic development in the marine little skate Raja erinacea; response to changes in external salinity

Steele

Yancey

Wright

2004

Journal of Experimental Biology

View full text Add to dashboard Cite

Marine elasmobranchs retain relatively high levels of urea to counterbalance the osmotic strength of seawater. Oviparous species, such as the little skate Raja erinacea, release encapsulated embryos that hatch after about 9 months on the seafloor. To study the ureosmotic capability of skate embryos, we measured a variety of possible osmolytes and ornithine-urea cycle (OUC) enzyme activities in little skate embryos, and determined their physiological response to dilute seawater (75% SW) exposure relative to controls (100% SW). The urea:trimethylamine oxide (TMAO) + other osmolytes ratio was 2.3-2.7:1. At the earliest stage of development investigated (4 months), there were significant levels of the key OUC enzyme, carbamoyl phosphate synthetase III, as well as ornithine transcarbamoylase, arginase and glutamine synthetase, providing evidence for a functional OUC. Embryos (4 and 8 months) survived and recovered from exposure to 5 days of 75% SW. There was a significant increase in the rate of urea excretion (five-to tenfold), no change in OUC enzyme activities, and significant decreases in the tissue content of urea, TMAO and other osmolytes in embryos exposed to 75% SW compared to 100% SW. Taken together, the data indicate that little skate embryos synthesize and retain urea, as well as a suite of other osmolytes, in order to regulate osmotic balance with the external environment. Interestingly, these ureosmotic mechanisms are in place as early as 4 months, around the time at which the egg capsule opens and the embryo is in more direct contact with the external environment.

show abstract

Variations in Salinity, Osmolarity, and Water Availability: Vertebrates and Invertebrates

Gllles

Delpire

1997

Comprehensive Physiology

View full text Add to dashboard Cite

Osmotic regulation and urea metabolism in the lemon shark Negaprion brevirostris

Cited by 63 publications

References 0 publications

Effect of low environmental salinity on plasma composition and renal function of the Atlantic stingray, a euryhaline elasmobranch

Effect of low environmental salinity on plasma composition and renal function of the Atlantic stingray, a euryhaline elasmobranch

Dogmas and controversies in the handling of nitrogenous wastes:Osmoregulation during early embryonic development in the marine little skate Raja erinacea; response to changes in external salinity

Variations in Salinity, Osmolarity, and Water Availability: Vertebrates and Invertebrates

Contact Info

Product

Resources

About