Accelerated urinary excretion of methylmercury following administration of its antidote N-acetylcysteine requires Mrp2/Abcc2, the apical multidrug resistance-associated protein
Accelerated urinary excretion of methylmercury following administration of its antidote N-acetylcysteine requires Mrp2/Abcc2, the apical multidrug resistance-associated protein
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DOI：
10.1124/jpet.107.122812
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发表时间：
2007-07-01
影响因子：
3.5
通讯作者：
Ballatori, Nazzareno
中科院分区：
文献类型：
--
作者：
Madejczyk, Michael S.;Aremu, David A.;Ballatori, Nazzareno
N-乙酰半胱氨酸（NAC）是一种含巯基的化合物，其在中毒小鼠中产生尿甲基汞（MeHg）排泄的显著加速，但这种作用的分子机制尚不清楚。甲基汞很容易与NAC结合形成MeHg-NAC复合物，最近的研究表明，该复合物是基底外侧有机阴离子转运蛋白（Oat）-1，Oat 1/Slc 22 a6的良好底物，从而可能解释了从血液中摄取到肾小管细胞中的原因。本研究验证了这样的假设，即细胞内的甲基汞随后被转运通过细胞的顶膜进入小管液作为甲基汞- NAC复合物使用多药耐药相关蛋白2（Mrp 2/Abcc 2）。NAC明显刺激野生型Wistar大鼠尿[ C-14]甲基汞排泄，第二次剂量的NAC在刺激甲基汞排泄方面与第一次剂量一样有效。与正常Wistar大鼠相比，NAC刺激尿中甲基汞排泄的Mrp 2缺陷（TR-）Wistar大鼠的有效性要低得多。TR-大鼠的甲基汞排泄量仅为野生型动物的30%.为了直接测试MeHg-NAC是否是Mrp 2的底物，在从TR-和对照Wistar大鼠的肝脏分离的质膜囊泡中进行了研究。在TR-大鼠制备的囊泡中，甲基汞- NAC的转运较低，而甲基汞-半胱氨酸的转运在对照组和TR-大鼠中相似。这些结果表明，Mrp 2参与了NAC给药后尿中甲基汞的排泄，并表明转运的分子最有可能是MeHg-NAC复合物。
N- Acetylcysteine ( NAC) is a sulfhydryl- containing compound that produces a dramatic acceleration of urinary methylmercury ( MeHg) excretion in poisoned mice, but the molecular mechanism for this effect is poorly defined. MeHg readily binds to NAC to form the MeHg- NAC complex, and recent studies indicate that this complex is an excellent substrate for the basolateral organic anion transporter ( Oat)-1, Oat1/ Slc22a6, thus potentially explaining the uptake from blood into the renal tubular cells. The present study tested the hypothesis that intracellular MeHg is subsequently transported across the apical membrane of the cells into the tubular fluid as a MeHg- NAC complex using the multidrug resistance- associated protein-2 ( Mrp2/ Abcc2). NAC markedly stimulated urinary [ C-14] MeHg excretion in wild- type Wistar rats, and a second dose of NAC was as effective as the first dose in stimulating MeHg excretion. In contrast with the normal Wistar rats, NAC was much less effective at stimulating urinary MeHg excretion in the Mrp2-deficient ( TR-) Wistar rats. The TR- rats excreted only similar to 30% of the MeHg excreted by the wild- type animals. To directly test whether MeHg- NAC is a substrate for Mrp2, studies were carried out in plasma membrane vesicles isolated from livers of TR- and control Wistar rats. Transport of MeHg- NAC was lower in vesicles prepared from TR- rats, whereas transport of MeHg- cysteine was similar in control and TR- rats. These results indicate that Mrp2 is involved in urinary MeHg excretion after NAC administration and suggest that the transported molecule is most likely the MeHg- NAC complex.