Hata Soichiro, Wang Pijun, Eftychiou Nicole, Ananthanarayanan Meenakshisundaram, Batta Ashok, Salen Gerald, Pang K Sandy, Wolkoff Allan W
Marion Bessin Liver Research Center, 625 Ullmann Bldg., Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
Am J Physiol Gastrointest Liver Physiol. 2003 Nov;285(5):G829-39. doi: 10.1152/ajpgi.00352.2002. Epub 2003 Jul 3.
Transport of a series of 3H-radiolabeled C23, C24, and C27 bile acid derivatives was compared and contrasted in HeLa cell lines stably transfected with rat Na+/taurocholate cotransporting polypeptide (ntcp) or organic anion transporting polypeptide 1 (oatp1) in which expression was under regulation of a zinc-inducible promoter. Similar uptake patterns were observed for both ntcp and oatp1, except that unconjugated hyodeoxycholate was a substrate of oatp1 but not ntcp. Conjugated bile acids were transported better than nonconjugated bile acids, and the configuration of the hydroxyl groups (alpha or beta) had little influence on uptake. Although cholic and 23 norcholic acids were transported by ntcp and oatp1, other unconjugated bile acids (chenodeoxycholic, ursodeoxycholic) were not. In contrast to ntcp, oatp1-mediated uptake of the trihydroxy bile acids taurocholate and glycocholate was four- to eightfold below that of the corresponding dihydroxy conjugates. Ntcp mediated high affinity, sodium-dependent transport of [35S]sulfobromophthalein with a Km similar to that of oatp1-mediated transport of [35S]sulfobromophthalein (Km = 3.7 vs. 3.3 muM, respectively). In addition, for both transporters, uptake of sulfobromophthalein and taurocholic acid showed mutual competitive inhibition. These results indicate that the substrate specificity of ntcp is considerably broader than previously suspected and caution the extrapolation of transport data obtained in vitro to physiological function in vivo.
在稳定转染了大鼠Na+/牛磺胆酸盐共转运多肽（ntcp）或有机阴离子转运多肽1（oatp1）的HeLa细胞系中，对一系列3H放射性标记的C23、C24和C27胆汁酸衍生物的转运进行了比较和对比，其中oatp1的表达受锌诱导启动子调控。ntcp和oatp1观察到相似的摄取模式，不同的是未结合的猪去氧胆酸是oatp1的底物而不是ntcp的底物。结合型胆汁酸的转运优于未结合型胆汁酸，羟基的构型（α或β）对摄取影响不大。虽然胆酸和23-降胆酸可被ntcp和oatp1转运，但其他未结合型胆汁酸（鹅去氧胆酸、熊去氧胆酸）则不能。与ntcp不同，oatp1介导的三羟基胆汁酸牛磺胆酸盐和甘氨胆酸盐的摄取比相应的二羟基结合物低4至8倍。ntcp介导[35S]磺溴酞钠的高亲和力、钠依赖性转运，其Km与oatp1介导的[35S]磺溴酞钠转运的Km相似（分别为3.7和3.3μM）。此外，对于这两种转运体，磺溴酞钠和牛磺胆酸的摄取表现出相互竞争性抑制。这些结果表明，ntcp的底物特异性比以前怀疑的要宽得多，并提醒人们注意将体外获得的转运数据外推到体内生理功能时需谨慎。
