Vectorial transport of unconjugated and conjugated bile salts by monolayers of LLC-PK1 cells doubly transfected with human NTCP and BSEP or with rat Ntcp and Bsep
Vectorial transport of unconjugated and conjugated bile salts by monolayers of LLC-PK1 cells doubly transfected with human NTCP and BSEP or with rat Ntcp and Bsep
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DOI：
10.1152/ajpgi.00364.2005
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发表时间：
2006-03-01
影响因子：
4.5
通讯作者：
Sugiyama, Y
中科院分区：
文献类型：
--
作者：
Mita, S;Suzuki, H;Sugiyama, Y
用人NTCP和BSEP或大鼠Ntcp和Bsep双重转染的LLC-PK 1细胞单层对未结合和结合胆汁盐的矢量转运。Am J Physiol Gastrointest Liver Physiol 290：G550-G556，2006; doi：10.1152/ajpgi. 00364.2005.- Na+-牛磺胆酸盐共转运肽（NTCP）/SLC 10 A1和胆盐输出泵（BSEP）/ABCB 11协同作用在肝细胞转运胆盐中发挥重要作用。在这项研究中，我们将人NTCP和BSEP或大鼠NTCP和Bsep转染到LLC-PK 1细胞中，LLC-PK 1细胞是一种没有胆盐转运蛋白的细胞系。这些细胞的转运特征集中在大鼠和人之间的底物特异性。牛磺胆酸盐穿过表达NTCP和BSEP的LLC-PK 1单层的基底至顶端通量比相反方向的通量高10倍，而穿过对照和NTCP或BSEP单表达细胞单层的通量未显示任何载体转运。牛磺胆酸盐从基底到顶端的通量饱和，Km值为20 μ M。载体的跨细胞转运也观察到胆酸盐，鹅脱氧胆酸盐，熊脱氧胆酸盐，其牛磺酸和甘氨酸共轭物，牛磺脱氧胆酸盐和glycodeoxycholate，而没有运输的石胆酸盐检测。为了评估NTCP和BSEP各自的功能，并将其与大鼠Ntcp和Bsep的功能进行比较，我们计算了该系统中每个转运蛋白的清除率。在人和大鼠转运蛋白的转运之间，观察到所检查的胆汁盐（胆酸盐、鹅脱氧胆酸盐、熊脱氧胆酸盐及其牛磺酸或甘氨酸结合物）的清除率具有良好的相关性，其等级顺序为：对于NTCP，牛磺酸结合物>甘氨酸结合物>未结合胆汁盐，对于BSEP，未结合胆汁盐和甘氨酸结合物>牛磺酸结合物。总之，在生理条件下，人和大鼠NTCP和BSEP的底物特异性似乎非常相似，至少对于单价胆汁盐而言是如此。
Vectorial transport of unconjugated and conjugated bile salts by monolayers of LLC-PK1 cells doubly transfected with human NTCP and BSEP or with rat Ntcp and Bsep. Am J Physiol Gastrointest Liver Physiol 290: G550-G556, 2006; doi: 10.1152/ajpgi. 00364.2005.-Na+-taurocholate-cotransporting peptide (NTCP)/SLC10A1 and bile salt export pump (BSEP)/ABCB11 synergistically play an important role in the transport of bile salts by the hepatocyte. In this study, we transfected human NTCP and BSEP or rat Ntcp and Bsep into LLC-PK1 cells, a cell line devoid of bile salts transporters. Transport by these cells was characterized with a focus on substrate specificity between rats and humans. The basal to apical flux of taurocholate across NTCP- and BSEP-expressing LLC-PK1 monolayers was 10 times higher than that in the opposite direction, whereas the flux across the monolayer of control and NTCP or BSEP single- expressing cells did not show any vectorial transport. The basal to apical flux of taurocholate was saturated with a Km value of 20 mu M. Vectorial transcellular transport was also observed for cholate, chenodeoxycholate, ursodeoxycholate, their taurine and glycine conjugates, and taurodeoxycholate and glycodeoxycholate, whereas no transport of lithocholate was detected. To evaluate the respective functions of NTCP and BSEP and to compare them with those of rat Ntcp and Bsep, we calculated the clearance by each transporter in this system. A good correlation in the clearance of the examined bile salts (cholate, chenodeoxycholate, ursodeoxycholate, and their taurine or glycine conjugates) was observed between transport by human and that of rat transporters in terms of their rank order: for NTCP, taurine conjugates > glycine conjugates > unconjugated bile salts, and for BSEP, unconjugated bile salts and glycine conjugates > taurine conjugates. In conclusion, the substrate specificity of human and rat NTCP and BSEP appear to be very similar at least for monovalent bile salts under physiological conditions.