Inoue Hideki, Jackson Shelley D, Vikulina Tatyana, Klein Janet D, Tomita Kimio, Bagnasco Serena M
Department of Pathology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Am J Physiol Cell Physiol. 2004 Jul;287(1):C30-5. doi: 10.1152/ajpcell.00443.2003. Epub 2004 Feb 25.
We have identified a urea transporter from the mucosa of the human colon that has characteristics consistent with a Kidd antigen/UT-B urea transporter. This intestinal urea transporter encodes a 389-amino acid peptide with a sequence identical to that previously reported for the UT-B urea transporter in erythrocytes. Expression of a UT-B 2-kb mRNA transcript and of approximately 50- and approximately 98-kDa UT-B proteins is detected in human colonic mucosa by Northern and Western blot analysis. The UT-B protein is localized in the cell membrane and cytoplasm of the superficial intestinal epithelium and in the epithelial cells in the crypts. A 2-kb UT-B mRNA transcript and the UT-B protein were also identified in the intestinal cell line Caco-2. The transepithelial flux of (14)C urea was examined in Caco-2 cells growing on porous membrane support and was significantly inhibited by phloretin, 1,3-dimethylurea, and thiourea, suggesting that the transfer of urea across the Caco-2 monolayer could be mediated, at least in part, by the UT-B urea transporter. We conclude that the Kidd antigen/UT-B urea transporter is physiologically expressed in the human colon epithelium, where it could participate in the transport of urea across the colon mucosa.
我们从人结肠黏膜中鉴定出一种尿素转运体，其特性与基德抗原/UT-B尿素转运体一致。这种肠道尿素转运体编码一个389个氨基酸的肽段，其序列与先前报道的红细胞中UT-B尿素转运体的序列相同。通过Northern印迹和Western印迹分析，在人结肠黏膜中检测到UT-B 2-kb mRNA转录本以及约50 kDa和约98 kDa的UT-B蛋白的表达。UT-B蛋白定位于表层肠上皮的细胞膜和细胞质以及隐窝中的上皮细胞。在肠细胞系Caco-2中也鉴定出了2-kb的UT-B mRNA转录本和UT-B蛋白。在多孔膜支持物上生长的Caco-2细胞中检测了¹⁴C尿素的跨上皮通量，其受到根皮素、1,3-二甲基脲和硫脲的显著抑制，这表明尿素跨Caco-2单层的转运至少部分可由UT-B尿素转运体介导。我们得出结论，基德抗原/UT-B尿素转运体在人结肠上皮中生理性表达，它可能参与尿素跨结肠黏膜的转运。
