Involvement of multidrug resistance associated protein 1 (Mrp1) in the efflux transport of 17beta estradiol-D-17beta-glucuronide (E217betaG) across the blood-brain barrier.
Involvement of multidrug resistance associated protein 1 (Mrp1) in the efflux transport of 17beta estradiol-D-17beta-glucuronide (E217betaG) across the blood-brain barrier.
复制标题
多药耐药相关蛋白 1 (Mrp1) 参与 17β 雌二醇-D-17β-葡萄糖苷酸 (E217betaG) 穿过血脑屏障的外流转运。
作者：
D. Sugiyama;H. Kusuhara;Yong;Y. Sugiyama
目的
本研究旨在探讨多药耐药相关蛋白1（Mrp 1）、Mrp 2（一种P-糖蛋白Mdr 1a）在17 β-雌二醇-D-17 β-葡萄糖醛酸苷（E217 betaG）跨血脑屏障（BBB）外排转运中的作用。
方法
采用RT-PCR和Western blot检测Mrp 1和Mrp 2在血脑屏障的表达。在脑内显微注射后，在野生型、Mdr 1a/Mdr 1b和Mrp 1基因敲除小鼠以及正常和Mrp 2基因敲除突变大鼠[分别为Sprague-Dawley和EHBR高血红蛋白血症大鼠]中比较脑中[3 H] E217 pG剩余放射性的时间曲线。
结果
RT-PCR和Western blot分析显示Mrp 1在离体大鼠脑毛细血管中表达;然而，RT-PCR无法检测到任何Mrp 2的表达。在野生型小鼠中观察到E217 β G的显著消除，其速率常数为0.007 min（-1），而在Mrp 1敲除小鼠中显著降低（0.004 min（-1））。相比之下，野生型和Mdr 1a/Mdr 1b基因敲除小鼠以及正常和EHBR小鼠的E217 β G从脑中的流出量没有差异。野生型和Mrp 1基因敲除小鼠脑切片中E217 β G的积累无显著差异。
结论
Mrp 1而不是Mrp 2参与E217 β G在BBB的排泄，并通过将结合代谢物挤出到血液中提供屏障功能。
PURPOSE
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).
METHOD
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.
RESULTS
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.
CONCLUSION
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.