Sugiyama Daisuke, Kusuhara Hiroyuki, Lee Yong-Joo, Sugiyama Yuichi
Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Pharm Res. 2003 Sep;20(9):1394-400. doi: 10.1023/a:1025749925541.
The purpose of present study is to investigate the involve ment of multidrug resistance-associated protein 1 (Mrp1), Mrp2, an P-glycoprotein (Mdr1a) in the efflux transport of 17beta-estradiol-D-17beta-glucuronide (E217betaG) across the blood-brain barrier (BBB).
The expression of Mrp1 and Mrp2 at the BBB was investigated by RT-PCR and Western blot analyses. The time profiles of the remaining radioactivity of [3H]E217pG in the brain were compared in wild-type, Mdr1a/Mdr1b and Mrp1 knockout mice and normal and Mrp2-deficient mutant rats [Sprague-Dawley and Eisai hyperbilirubinemic rats (EHBR), respectively] after intracerebral microinjection.
RT-PCR and Western blot analyses revealed the expression of Mrp1 in isolated rat brain capillary; however, RT-PCR was unable to detect any expression of Mrp2. Significant elimination of E217betaG was observed in wild-type mice at a rate constant of 0.007 min(-1) which was significantly decreased (0.004 min(-1)) in Mrp1 knockout mice. In contrast, there was no difference in the efflux of E217betaG from the brain in wild-type and Mdr1a/Mdr1b knockout mice and in normal and EHBR. No significant difference was observed in the accumulation of E217betaG by brain slices prepared from wild-type and Mrp1 knockout mice.
Mrp1, but not Mrp2, is involved in the excretion of E217betaG at the BBB and provides a barrier function by extruding conjugated metabolites into the blood.
本研究旨在探讨多药耐药相关蛋白1（Mrp1）、Mrp2和P-糖蛋白（Mdr1a）在17β-雌二醇-D-17β-葡萄糖醛酸苷（E217βG）跨血脑屏障（BBB）外排转运中的作用。
通过逆转录聚合酶链反应（RT-PCR）和蛋白质免疫印迹分析研究BBB处Mrp1和Mrp2的表达。在脑室内微量注射后，比较野生型、Mdr1a/Mdr1b和Mrp1基因敲除小鼠以及正常和Mrp2缺陷型突变大鼠[分别为Sprague-Dawley大鼠和Eisai高胆红素血症大鼠（EHBR）]脑中[3H]E217βG剩余放射性的时间曲线。
RT-PCR和蛋白质免疫印迹分析显示，Mrp1在分离的大鼠脑微血管中有表达；然而，RT-PCR未能检测到Mrp2的任何表达。在野生型小鼠中观察到E217βG以0.007 min-1的速率常数显著消除，在Mrp1基因敲除小鼠中该速率常数显著降低（0.004 min-1）。相比之下，野生型和Mdr1a/Mdr1b基因敲除小鼠以及正常和EHBR大鼠脑内E217βG的外排没有差异。野生型和Mrp1基因敲除小鼠制备的脑片对E217βG的摄取没有显著差异。
Mrp1而非Mrp2参与BBB处E217βG的排泄，并通过将结合代谢物排入血液发挥屏障功能。
