Sodium-linked urea transport by the renal tubule of the spiny dogfish Squalus acanthias

Schmidt‐Nielsen, Bodil; Truniger, B; Rabinowitz, L.

doi:10.1016/0300-9629(72)90360-x

Cited by 97 publications

(61 citation statements)

References 9 publications

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“…16 and 27). These fish have a high fractional renal water excretion (3,17,21,47), and urine is usually hyposmotic to both plasma and seawater (3, 47, 57; for review, see Ref. 28).…”

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confidence: 99%

“…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).…”

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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).…”

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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

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. 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...

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“…16 and 27). These fish have a high fractional renal water excretion (3,17,21,47), and urine is usually hyposmotic to both plasma and seawater (3, 47, 57; for review, see Ref. 28).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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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

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“…The use of this strategy for body fluid volume regulation necessitates the efficient reabsorption of most of the filtered load of urea by the kidneys. For marine elasmobranchs maintained at ocean salinities, fractional urea reabsorption is 90 -98% (9,14,34).…”

mentioning

confidence: 99%

“…The elasmobranch nephron is anatomically far more complex than the mammalian nephron (21)(22)(23). Because urea concentration in urine is markedly less than that in plasma, it has been proposed that urea is actively reabsorbed against a concentration gradient (33,34,37). However, on the bais of the anatomical relationships between segments of the nephron (6,43) and putative low interstitial urea concentration near the terminal segment, Boylan (3) suggested that urea could also be passively reabsorbed down localized concentration gradients (3).…”

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confidence: 99%

Cloning and functional characterization of a second urea transporter from the kidney of the Atlantic stingray,Dasyatis sabina

Janech¹,

Fitzgibbon²,

Nowak³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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. Cloning and functional characterization of a second urea transporter from the kidney of the Atlantic stingray, Dasyatis sabina. Am J Physiol Regul Integr Comp Physiol 291: R844 -R853, 2006. First published April 13, 2006; doi:10.1152/ajpregu.00739.2005.-The cloning of cDNAs encoding facilitated urea transporters (UTs) from the kidneys of the elasmobranchs indicates that in these fish renal urea reabsorption occurs, at least in part, by passive processes. The previously described elasmobranch urea transporter clones from shark (shUT) and stingray (strUT-1) differ from each other primarily because of the COOHterminus of the predicted strUT-1 translation product being extended by 51-amino acid residues compared with shUT. Previously, we noted multiple UT transcripts were present in stingray kidney. We hypothesized that a COOH terminally abbreviated UT isoform, homologous to shUT, would also be present in stingray kidney. Therefore, we used 5Ј/3Ј rapid amplification of cDNA ends to identify a 3ЈUTR-variant (strUT-1a) of the cDNA that encodes (strUT-1), as well as three, 3ЈUTR-variant cDNAs (strUT-2a,b,c) that encode a second phloretinsensitive, urea transporter (strUT-2). The 5ЈUTR and the first 1,132 nucleotides of the predicted coding region of the strUT-2 cDNAs are identical to the strUT-1 cDNAs. The remainder of the coding region contains only five novel nucleotides. The strUT-2 cDNAs putatively encode a 379-amino acid protein, the first 377 amino acids identical to strUT-1 plus 2 additional amino acids. We conclude that 1) a second UT isoform is expressed in the Atlantic stingray and that this isoform is similar in size to the UT previously cloned from the kidney of the dogfish shark, and 2) at least five transcripts encoding the 2 stingray UTs are derived from a single gene product through alternative splicing and polyadenylation. elasmobranch; euryhaline; alternative splicing; osmoregulation MARINE ELASMOBRANCHS (sharks, skates, and rays) use a unique volume-and osmoregulatory strategy; in general, they maintain their body fluids hyperosmotic to the ambient environment (for a review, see Ref. 15; see also 29,42). The high body fluid osmolality is achieved, in large part, by the retention of urea. At ocean salinities, plasma urea concentrations average 350 mmol/l, and urea contributes 30 -50% of the plasma osmolality (for a review, see Ref. 15). The use of this strategy for body fluid volume regulation necessitates the efficient reabsorption of most of the filtered load of urea by the kidneys. For marine elasmobranchs maintained at ocean salinities, fractional urea reabsorption is 90 -98% (9, 14, 34).

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Osmoregulation and Excretion

Larsen

Deaton

Onken

et al. 2014

Comprehensive Physiology

185

141

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The article discusses advances in osmoregulation and excretion with emphasis on how multicellular animals in different osmotic environments regulate their milieu intérieur. Mechanisms of energy transformations in animal osmoregulation are dealt with in biophysical terms with respect to water and ion exchange across biological membranes and coupling of ion and water fluxes across epithelia. The discussion of functions is based on a comparative approach analyzing mechanisms that have evolved in different taxonomic groups at biochemical, cellular and tissue levels and their integration in maintaining whole body water and ion homeostasis. The focus is on recent studies of adaptations and newly discovered mechanisms of acclimatization during transitions of animals between different osmotic environments. Special attention is paid to hypotheses about the diversity of cellular organization of osmoregulatory and excretory organs such as glomerular kidneys, antennal glands, Malpighian tubules and insect gut, gills, integument and intestine, with accounts on experimental approaches and methods applied in the studies. It is demonstrated how knowledge in these areas of comparative physiology has expanded considerably during the last two decades, bridging seminal classical works with studies based on new approaches at all levels of anatomical and functional organization. A number of as yet partially unanswered questions are emphasized, some of which are about how water and solute exchange mechanisms at lower levels are integrated for regulating whole body extracellular water volume and ion homeostasis of animals in their natural habitats. © 2014 American Physiological Society.

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Sodium-linked urea transport by the renal tubule of the spiny dogfish Squalus acanthias

Cited by 97 publications

References 9 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

Cloning and functional characterization of a second urea transporter from the kidney of the Atlantic stingray,Dasyatis sabina

Osmoregulation and Excretion

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