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Urea transporter
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<h2 id="types">Types</h2> <p>In mammals, there are two urea transporter <a href="/facts/Gene/e1swwPY6">genes</a>: UT-A (<i><a href="/facts/SLC14A2/3UhlMm8N">SLC14A2</a></i>) and UT-B (<i><a href="/facts/SLC14A1/zqU4jNRE">SLC14A1</a></i>). Multiple <a href="/facts/Protein_isoform/oWmzfg4l">protein isoforms</a> derived from each gene are produced by <a href="/facts/Alternative_splicing/nNRwPVNK">alternative splicing</a> and alternative <a href="/facts/Promoter_(biology)/YDYBzLfg">promoters</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h3>UT-A1</h3> <p>Urea transporter A1 transports urea across the <a href="/facts/Apical_membrane/vAXSD0DT">apical membrane</a> into the <a href="/facts/Intracellular_space/UEPUhSN8">intracellular space</a> of luminal cells in the <a href="/facts/Inner_medullary_collecting_duct/MmpNcpLA">inner medullary collecting duct</a> of the <a href="/facts/Kidneys/HBspPrv9">kidneys</a>. UT-1 is activated by <a href="/facts/Vasopressin/B1EksWWY">ADH</a>, but is a passive transporter. It reabsorbs up to 70% of the original filtered load of urea.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h3>UT-A2</h3> <p>Urea Transporter 2 transports urea across the <a href="/facts/Apical_membrane/vAXSD0DT">apical membrane</a> into the luminal space of cells in the <a href="/facts/Thin_descending_loop_of_Henle/fhWzywys">thin descending loop of Henle</a> of the <a href="/facts/Kidneys/HBspPrv9">kidneys</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h3>UT-A3</h3> <p>Urea transporter 3 transports urea into the interstitium of the Inner Medullary Collecting Duct.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <h3>UT-A4</h3> <p>Urea transporter 4 has been detected in rat but not mouse kidney medulla.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h3>UT-A5</h3> <p>Urea transporter 5 is not expressed in the kidney but in the testis.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h3>UT-B</h3> <p>UT-B is widely expressed and has been studied in <a href="/facts/Erythrocyte/Kggpq8Jh">erythrocytes</a>,<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> <a href="/facts/Kidney/HBspPrv9">kidney</a>, <a href="/facts/Intestine/nK2zwqBS">intestine</a>,<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> and at the <a href="/facts/Blood%25E2%2580%2593brain_barrier/xYzvVwdu">blood–brain barrier</a>.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> The <a href="/facts/SLC14A1/zqU4jNRE">SLC14A1</a> gene codes for the UT-B protein. UT-B is expressed at the basolateral and apical regions of the descending <a href="/facts/Straight_arterioles_of_kidney/w4az9nhj">Vasa recta</a>.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Maciver B, Smith CP, Hill WG, Zeidel ML (April 2008). "Functional characterization of mouse urea transporters UT-A2 and UT-A3 expressed in purified Xenopus laevis oocyte plasma membranes". Am. J. Physiol. Renal Physiol. 294 (4): F956–64. doi:10.1152/ajprenal.00229.2007. PMID 18256317. <a href="http://ajprenal.physiology.org/cgi/reprint/294/4/F956" target="_blank">http://ajprenal.physiology.org/cgi/reprint/294/4/F956</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Sands JM, Blount MA, Klein JD (2011). "Regulation of renal urea transport by vasopressin". Trans. Am. Clin. Climatol. Assoc. 122: 82–92. PMC 3116377. PMID 21686211. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3116377" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3116377</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Levin EJ, Quick M, Zhou M (December 2009). "Crystal structure of a bacterial homologue of the kidney urea transporter". Nature. 462 (7274): 757–61. Bibcode:2009Natur.462..757L. doi:10.1038/nature08558. PMC 2871279. PMID 19865084. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871279" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871279</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Chou CL, Knepper MA (September 1989). "Inhibition of urea transport in inner medullary collecting duct by phloretin and urea analogues". Am. J. Physiol. 257 (3 Pt 2): F359–65. doi:10.1152/ajprenal.1989.257.3.F359. PMID 2506765. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Fenton RA, Knepper MA (March 2007). "Urea and renal function in the 21st century: insights from knockout mice". J. Am. Soc. Nephrol. 18 (3): 679–88. doi:10.1681/ASN.2006101108. PMID 17251384. <a href="https://doi.org/10.1681%2FASN.2006101108" target="_blank">https://doi.org/10.1681%2FASN.2006101108</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Fenton RA, Knepper MA (March 2007). "Urea and renal function in the 21st century: insights from knockout mice". J. Am. Soc. Nephrol. 18 (3): 679–88. doi:10.1681/ASN.2006101108. PMID 17251384. <a href="https://doi.org/10.1681%2FASN.2006101108" target="_blank">https://doi.org/10.1681%2FASN.2006101108</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Fenton RA, Knepper MA (March 2007). "Urea and renal function in the 21st century: insights from knockout mice". J. Am. Soc. Nephrol. 18 (3): 679–88. doi:10.1681/ASN.2006101108. PMID 17251384. <a href="https://doi.org/10.1681%2FASN.2006101108" target="_blank">https://doi.org/10.1681%2FASN.2006101108</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Fenton RA, Knepper MA (March 2007). "Urea and renal function in the 21st century: insights from knockout mice". J. Am. Soc. Nephrol. 18 (3): 679–88. doi:10.1681/ASN.2006101108. PMID 17251384. <a href="https://doi.org/10.1681%2FASN.2006101108" target="_blank">https://doi.org/10.1681%2FASN.2006101108</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Fenton RA (2005). "Urea transporter UT-A". UCSD Nature Molecule Pages. 18: 679. doi:10.1038/mp.a002589.01. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Fenton RA (2005). "Urea transporter UT-A". UCSD Nature Molecule Pages. 18: 679. doi:10.1038/mp.a002589.01. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Fenton RA (2005). "Urea transporter UT-A". UCSD Nature Molecule Pages. 18: 679. doi:10.1038/mp.a002589.01. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Yang B, Verkman AS (September 2002). "Analysis of double knockout mice lacking aquaporin-1 and urea transporter UT-B. Evidence for UT-B-facilitated water transport in erythrocytes". J. Biol. Chem. 277 (39): 36782–6. doi:10.1074/jbc.M206948200. PMID 12133842. <a href="https://doi.org/10.1074%2Fjbc.M206948200" target="_blank">https://doi.org/10.1074%2Fjbc.M206948200</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Collins D, Winter DC, Hogan AM, Schirmer L, Baird AW, Stewart GS (March 2010). "Differential protein abundance and function of UT-B urea transporters in human colon". Am. J. Physiol. Gastrointest. Liver Physiol. 298 (3): G345–51. doi:10.1152/ajpgi.00405.2009. PMC 3774180. PMID 19926813. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3774180" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3774180</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Dahlin A, Royall J, Hohmann JG, Wang J (May 2009). "Expression profiling of the solute carrier gene family in the mouse brain". J. Pharmacol. Exp. Ther. 329 (2): 558–70. doi:10.1124/jpet.108.149831. PMC 2672879. PMID 19179540. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2672879" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2672879</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Fenton RA, Knepper MA (March 2007). "Urea and renal function in the 21st century: insights from knockout mice". J. Am. Soc. Nephrol. 18 (3): 679–88. doi:10.1681/ASN.2006101108. PMID 17251384. <a href="https://doi.org/10.1681%2FASN.2006101108" target="_blank">https://doi.org/10.1681%2FASN.2006101108</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> </ol>