Sugiyama D, Kusuhara H, Shitara Y, Abe T, Meier P J, Sekine T, Endou H, Suzuki H, Sugiyama Y
Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.
J Pharmacol Exp Ther. 2001 Jul;298(1):316-22.
The contribution of organic anion transporters to the total efflux of 17beta-estradiol-D-17beta-glucuronide (E(2)17betaG) through the blood-brain barrier (BBB) was investigated using the Brain Efflux Index method by examining the inhibitory effects of probenecid, taurocholate (TCA), p-aminohippurate (PAH), and digoxin. E(2)17betaG was eliminated through the BBB with a rate constant of 0.037 min(-1) after the microinjection into the brain. Probenecid and TCA inhibited this elimination with an IC50 value of 34 and 1.8 nmol/0.5 microl of injectate, respectively, whereas PAH and digoxin reduced the total efflux to about 80 and 60% of the control value, respectively. The selectivity of these inhibitors was confirmed by examining their inhibitory effects on the transport via organic anion transporting polypeptide 1 (Oatp1), Oatp2, organic anion transporter 1 (Oat1), and Oat3 transfectants using LLC-PK1 cells as hosts. Digoxin specifically inhibited the transport via Oatp2 (K(i) = 0.037 microM). The K(i) values of TCA for Oatp1 and Oatp2 (11 and 39 microM, respectively) were about 20 times lower than those for Oat1 and Oat3 (2.8 and 0.8 mM, respectively). PAH did not affect the transport via the Oatp family, but had a similar affinity for Oat1 and Oat3 (85 and 300 microM, respectively). Probenecid had a similar affinity for these transporters (Oatp1, Oatp2, Oat1, and Oat3) examined in this study. Taking the selectivity of these inhibitors into consideration, the maximum contribution made by the Oatp2 and Oat family to the total efflux of E(2)17betaG from the brain appears to be about 40 and 20%, respectively.
采用脑外排指数法，通过检测丙磺舒、牛磺胆酸盐（TCA）、对氨基马尿酸（PAH）和地高辛的抑制作用，研究了有机阴离子转运体对17β-雌二醇-D-17β-葡萄糖醛酸苷（E(2)17βG）通过血脑屏障（BBB）的总外排的贡献。向脑内微量注射E(2)17βG后，其通过BBB消除的速率常数为0.037 min(-1)。丙磺舒和TCA抑制这种消除，IC50值分别为34和1.8 nmol/0.5 μl注射液，而PAH和地高辛分别将总外排降低至对照值的约80%和60%。通过检测它们对以LLC-PK1细胞为宿主的有机阴离子转运多肽1（Oatp1）、Oatp2、有机阴离子转运体1（Oat1）和Oat3转染体转运的抑制作用，证实了这些抑制剂的选择性。地高辛特异性抑制通过Oatp2的转运（K(i)=0.037 μM）。TCA对Oatp1和Oatp2的K(i)值（分别为11和39 μM）比对Oat1和Oat3的K(i)值（分别为2.8和0.8 mM）低约20倍。PAH不影响通过Oatp家族的转运，但对Oat1和Oat3具有相似的亲和力（分别为85和300 μM）。丙磺舒对本研究中检测的这些转运体（Oatp1、Oatp2、Oat1和Oat3）具有相似的亲和力。考虑到这些抑制剂的选择性，Oatp2和Oat家族对E(2)17βG从脑内的总外排的最大贡献似乎分别约为40%和
