FUNCTIONAL ANALYSIS OF DOG MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN 2 (MRP2) IN COMPARISON WITH RAT MRP2
FUNCTIONAL ANALYSIS OF DOG MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN 2 (MRP2) IN COMPARISON WITH RAT MRP2
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DOI：
10.1124/dmd.104.002196
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发表时间：
2005-02
影响因子：
3.9
通讯作者：
M. Ninomiya;Kousei Ito;T. Horie
中科院分区：
文献类型：
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作者：
M. Ninomiya;Kousei Ito;T. Horie
我们研究了某些Mrp 2底物的胆汁排泄活性的种属差异是否归因于Mrp 2的内在转运潜力或表达水平，特别是在大鼠和犬中。从比格犬肝脏中分离犬Mrp 2 cDNA，并使用在昆虫Sf 9细胞中表达的重组大鼠和犬Mrp 2进行囊泡转运研究。17β-雌二醇17-（β-d-葡糖苷酸）（[3 H]E217βG）和白三烯C4（[3 H] LTC 4）的ATP依赖性转运（通过绝对蛋白表达水平标准化）在两种Mrp 2中相似。犬肝脏中的Mrp 2蛋白表达量仅为大鼠肝脏中的10%，与替莫卡普拉作为Mrp 2底物的胆汁排泄清除率的报告差异相当。与LTC 4相反，E217βG在犬Mrp 2中的独特转运动力学明显。除了Km值为3.25 ± 0.10 μM的高亲和力位点（与大鼠Mrp 2的Km值（4.81 ± 1.21 μM）相似）外，犬Mrp 2还具有一个额外的低亲和力位点（约75 μM），该位点对E217βG的转运做出了主要贡献（在示踪剂浓度下占总转运能力的65%）。总之，大鼠和犬之间Mrp 2底物的胆汁排泄活性差异取决于Mrp 2蛋白表达水平，而不是转运蛋白分子的内在转运活性。犬Mrp 2对葡糖苷酸结合物的独特转运特性可能导致涉及药物相互作用或药物诱导的高胆固醇血症的种属差异。
We investigated whether the species difference in the biliary excretion activity of some Mrp2 substrates was attributable to the intrinsic transport potential or the expression level of Mrp2, especially in rat and dog. Dog Mrp2 cDNA was isolated from beagle dog liver, and a vesicle transport study was performed using recombinant rat and dog Mrp2 expressed in insect Sf9 cells. The ATP-dependent transport of 17β-estradiol 17-(β-d-glucuronide) ([3H]E217βG) and leukotriene C4 ([3H]LTC4), normalized by the absolute protein expression level, was similar in both Mrp2s. The Mrp2 protein expression in dog liver was only 10% of that in rat liver and was comparable with the reported difference in the biliary excretion clearance of temocaprilat as Mrp2 substrate. In contrast to LTC4, unique transport kinetics for E217βG were evident in dog Mrp2. In addition to the high-affinity site with a Km value of 3.25 ± 0.10 μM, which is similar to that in rat Mrp2 (4.81 ± 1.21 μM), dog Mrp2 has an additional low-affinity site (≫75 μM), which makes a major contribution to the transport of E217βG (65% of the total transport capacity at tracer concentration). In summary, the difference in the biliary excretion activity of Mrp2 substrates between rat and dog depends on the Mrp2 protein expression level rather than the intrinsic transport activity of the transporter molecules. The unique transport properties of glucuronide conjugates by dog Mrp2 may lead to the species difference involving the drug-drug interaction or drug-induced hyperbilirubinemia on the bile canalicular membrane.