Active Urea Transport in Lower Vertebrates and Mammals

Bankir, Lise

doi:10.1007/978-94-017-9343-8_13

Cited by 13 publications

(10 citation statements)

References 128 publications

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“…Ce dernier implique une réabsorption d'urée dans le rein, un passage dans la lumière intestinale (53,54) où l'urée peut être dégradée en NH 4 + CO 2 par des bactéries du microbiote exprimant l'uréase. L'azote peut alors être ré-utilisé pour former de la glutamine et retourner dans le métabolisme azoté du mammifère (28,45). Ce cycle est bien développé chez les herbivores et sans doute aussi chez les ours pendant l'hibernation (55).…”

Section: Phase 4: Concentration De L'urée Dans La Médulla Interneunclassified

Médulla rénale

Bankir

Bouby

2016

Néphrologie & Thérapeutique

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The ability to produce hyperosmotic urine allows mammals, including humans, to excrete their soluble mineral and organic waste products in the urine with a limited amount of water. The urinary concentrating capacity depends primarily on a special "loop-shaped" architecture of the nephrons and vessels, observed only in mammals. It also depends on the influence of antidiuretic hormone on the permeability to water of the collecting ducts on their entire length, and on the permeability to urea limited to the terminal portion of these ducts in the inner medulla. The ability to concentrate urine also requires (1) an "engine" able to produce an active (energy demanding) transport that generates a transepithelial concentration difference leading to increase the solute concentration in the surrounding interstitium; and (2) the expression of several membrane transporters or channels localized very specifically to limited portions of some nephron segments, collecting ducts and arterial vasa recta. These transporters and channels greatly accelerate the transport of water and some solutes across the cell membranes. Even if some nephron segments and parts of the collecting system are present in both the renal cortex and medulla (namely, the proximal tubule, the thick ascending limb and the collecting duct), their functions in the two renal zones may not be strictly similar, owing to their different peritubular environment, to the composition of the fluid running in their lumen, and to some differences in their epithelium. This paper describes some characteristics and specific functions of these structures in the renal medulla, as opposed to their corresponding structures in the cortex. These specific functions operating in the medulla may lead to various adverse consequences in some pathological situations.

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Section: Phase 4: Concentration De L'urée Dans La Médulla Interneunclassified

Médulla rénale

Bankir

Bouby

2016

Néphrologie & Thérapeutique

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“…The hydrophobic phospholipid bilayer of biological membranes has a relatively low permeability to the highly hydrophilic urea molecule (Goodman, 2002). Nevertheless, transmembrane urea movement can be augmented by urea transporters, including facilitated urea transporters (UTs) and urea active (energydependent) transporters, which are found in all living organisms (Bankir, 2014). To date, several UTs have been cloned (Sands, 2002), and a few urea active transporters that can raise the concentration of intracellular urea above that of the medium have also been identified (Bankir, 2014).…”

Section: Introductionmentioning

confidence: 99%

Light exposure enhances urea absorption in the fluted giant clam,Tridacna squamosa, and up-regulates the protein abundance of a light-dependent urea active transporter, DUR3-like, in its ctenidium

Chan

Hiong

Boo

et al. 2018

Journal of Experimental Biology

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Giant clams live in nutrient-poor reef waters of the Indo-Pacific and rely on symbiotic dinoflagellates ( spp., also known as zooxanthellae) for nutrients. As the symbionts are nitrogen deficient, the host clam has to absorb exogenous nitrogen and supply it to them. This study aimed to demonstrate light-enhanced urea absorption in the fluted giant clam, , and to clone and characterize the urea active transporter DUR3-like from its ctenidium (gill). The results indicate that absorbs exogenous urea, and the rate of urea uptake in the light was significantly higher than that in darkness. The coding sequence obtained from its ctenidium comprised 2346 bp, encoding a protein of 782 amino acids and 87.0 kDa. was expressed strongly in the ctenidium, outer mantle and kidney. Twelve hours of exposure to light had no significant effect on the transcript level of ctenidial However, between 3 and 12 h of light exposure, DUR3-like protein abundance increased progressively in the ctenidium, and became significantly greater than that in the control at 12 h. DUR3-like had an apical localization in the epithelia of the ctenidial filaments and tertiary water channels. Taken together, these results indicate that DUR3-like might participate in light-enhanced urea absorption in the ctenidium of When made available to the symbiotic zooxanthellae that are known to possess urease, the absorbed urea can be metabolized to NH and CO to support amino acid synthesis and photosynthesis, respectively, during insolation.

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“…1 Urea transporters (UT) are transmembrane urea-selective channel proteins that include two UT subfamilies, UT-A and UT-B, which are encoded by gene Slc14a2 and Slc14a1 , respectively. 2–10 UT-A subfamily includes six members, UT-A1 to UT-A6, which are derived from Slc14a2 by two distinct promoters and splicing regulation. 11–13 UT-A1, the largest form in the subfamily, is expressed on the apical plasma membrane of the inner-medullary collecting duct (IMCD).…”

Section: Introductionmentioning

confidence: 99%

Generation and phenotypic analysis of mice lacking all urea transporters

Jiang

Layton

et al. 2017

Kidney International

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Urea transporters (UT) are a family of transmembrane urea-selective channel proteins expressed in multiple tissues and play an important role in the urine concentrating mechanism of the mammalian kidney. UT inhibitors have been identified to have diuretic activity and might be developed as novel diuretics. To determine if functional deficiency of all UTs in all tissues causes physiological abnormality, we established a novel mouse model in which all UTs were knocked out by deleting an 87 kb of DNA fragment containing most parts of Slc14a1 and Slc14a2 genes. Western blot analysis and immunofluorescence confirmed that there is no expression of urea transporter in all-UT-knockout mice. Daily urine output was nearly 3.5-fold higher, with significantly lower urine osmolality, in all-UT-knockout-mice than that in wild-type mice, and urine osmolality was significantly lower. All-UT-knockout mice were not able to increase urinary urea concentration and osmolality after water deprivation, acute urea loading or high protein intake. A computational model that simulated UT knockout mouse models identified the individual contribution of each UT in urine concentrating mechanism. Knocking out all UTs also decreased the blood pressure and promoted the maturation of the male reproductive system. These results revealed that functional deficiency of all UTs caused urea selective urine concentrating defect with little physiological abnormality in extrarenal organs.

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Active Urea Transport in Lower Vertebrates and Mammals

Cited by 13 publications

References 128 publications

Médulla rénale

Médulla rénale

Light exposure enhances urea absorption in the fluted giant clam,Tridacna squamosa, and up-regulates the protein abundance of a light-dependent urea active transporter, DUR3-like, in its ctenidium

Generation and phenotypic analysis of mice lacking all urea transporters

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