Localization of the ammonium transporters, Rh B glycoprotein and Rh C glycoprotein, in the mouse liver.
Localization of the ammonium transporters, Rh B glycoprotein and Rh C glycoprotein, in the mouse liver.
复制标题
DOI：
10.1016/s0016-5085(03)00277-4
复制
发表时间：
2003-05
期刊：
影响因子：
29.4
通讯作者：
I. Weiner;R.Tyler Miller;J. Verlander
中科院分区：
文献类型：
--
作者：
I. Weiner;R.Tyler Miller;J. Verlander
背景与目的肝氨代谢是维持正常健康的关键。最近发现了三种哺乳动物的氨离子转运蛋白家族成员：Rh A糖蛋白(RHAG)、Rh B糖蛋白(RhBG)和Rh C糖蛋白(RhCG)。这项研究检测了其中哪些在小鼠肝脏中表达，在哪些细胞中表达。方法采用正常Balb/c小鼠。用常规或实时逆转录聚合酶链式反应(RT-PCR)检测信使RNA(MRNA)的表达。免疫印迹分析、免疫组织化学或免疫荧光显微镜检测蛋白表达。结果实时定量RT-PCR证实肝组织中有RhBG基因的表达。免疫印迹分析证实了∼45kodalton蛋白的表达。免疫组织化学和免疫荧光显微镜观察发现，在中央静脉周围的1-2层肝细胞中，基底外侧的RhBG免疫反应阳性。肝门周围或中带肝细胞未见免疫反应。通过与谷氨酰胺合成酶的共定位，证实了静脉周围肝细胞特异性表达。第二个氨离子转运蛋白RhCG得到了表达，但表达水平要低得多。实时荧光定量RT-PCR法检测∼为0.4%时肝组织RhCG mRNA的表达。免疫印迹分析证实了RhCG蛋白的表达，免疫荧光显微镜证实了RhCG在胆管上皮细胞中的表达。与RhBG和RhCG不同，RT-PCR未检测到rHAG基因的表达。结论SRhBG和RhCG在小鼠肝脏中表达。基底外侧的RhBG在静脉周围肝细胞中表达，在静脉周围的肝细胞中可能介导铵的摄取；在胆管上皮细胞中存在RhCG免疫反应，在那里它可能参与氨的分泌到胆汁中。
BACKGROUND & AIMSHepatic ammonium metabolism is critical for maintenance of normal health. Three mammalian members of an ammonium transporter family have recently been identified: Rh A glycoprotein (RhAG), Rh B glycoprotein (RhBG), and Rh C glycoprotein (RhCG). This study examined which of these are expressed in the mouse liver and in which cells they are expressed.METHODSNormal Balb/c mice were used. Messenger RNA (mRNA) expression was detected using either conventional or real-time reverse-transcription polymerase chain reaction (RT-PCR). Protein expression was examined using immunoblot analysis and either immunohistochemical or immunofluorescent microscopy.RESULTSWe confirmed hepatic RhBG mRNA expression using real-time RT-PCR. Immunoblot analysis identified expression of a ∼45-kilodalton protein. Immunohistochemical and immunofluorescent microscopy identified basolateral RhBG immunoreactivity in 1–2 cell layers of hepatocytes surrounding central veins. No immunoreactivity was identified in periportal or midzonal hepatocytes. Perivenous hepatocyte-specific expression was confirmed by colocalization with glutamine synthetase. A second ammonium transporter, RhCG, was expressed but at substantially lower levels. Real-time RT-PCR quantified hepatic RhCG mRNA expression at ∼0.4% of RhBG mRNA expression. Immunoblot analysis confirmed RhCG protein expression, and immunofluorescence microscopy identified RhCG expression in bile duct epithelia. In contrast to RhBG and RhCG, RhAG mRNA was not identified by RT-PCR.CONCLUSIONSRhBG and RhCG are expressed by the mouse liver. Basolateral RhBG is expressed by perivenous hepatocytes, where it may mediate ammonium uptake, and RhCG immunoreactivity is present in bile duct epithelial cells, where it may contribute to ammonium secretion into bile fluid.