Ruiz María L, Villanueva Silvina S M, Luquita Marcelo G, Vore Mary, Mottino Aldo D, Catania Viviana A
Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Argentina.
Drug Metab Dispos. 2006 Jun;34(6):1030-4. doi: 10.1124/dmd.106.009316. Epub 2006 Mar 22.
We evaluated the effect of ethynylestradiol (EE) administration (5 mg/kg b.wt. s.c., for 5 consecutive days) on the expression and activity of multidrug resistance-associated protein 3 (Mrp3) in rats. Western blotting analysis revealed decreased Mrp2 (-41%) and increased Mrp3 (+200%) expression by EE. To determine the functional impact of up-regulation of Mrp3 versus Mrp2, we measured the excretion of acetaminophen glucuronide (APAP-glu), a common substrate for both transporters, into bile and perfusate in the recirculating isolated perfused liver (IPL) model. APAP-glu was generated endogenously from acetaminophen (APAP), which was administered as a tracer dose (2 micromol/ml) into the perfusate. Biliary excretion of APAP-glu after 60 min of perfusion was reduced in EE-treated rats (-80%). In contrast, excretion into the perfusate was increased by EE (+45%). Liver content of APAP-glu at the end of the experiment was reduced by 36% in the EE group. The total amount of glucuronide remained the same in both groups. Taken together, these results indicate that up-regulation of Mrp3 led to an exacerbated basolateral versus canalicular excretion of conjugated APAP in IPL. We conclude that induced expression of basolateral Mrp3 by EE may represent a compensatory mechanism to prevent intracellular accumulation of common Mrp substrates, either endogenous or exogenous, due to reduced expression and activity of apical Mrp2.
我们评估了乙炔雌二醇（EE）给药（5毫克/千克体重，皮下注射，连续5天）对大鼠多药耐药相关蛋白3（Mrp3）表达和活性的影响。蛋白质免疫印迹分析显示，EE使Mrp2表达降低（-41%），Mrp3表达增加（+200%）。为了确定Mrp3上调相对于Mrp2上调的功能影响，我们在循环离体灌注肝（IPL）模型中测量了对乙酰氨基酚葡糖醛酸苷（APAP-葡糖醛酸苷）（这两种转运蛋白的常见底物）向胆汁和灌注液中的排泄。APAP-葡糖醛酸苷由对乙酰氨基酚（APAP）内源性生成，APAP作为示踪剂量（2微摩尔/毫升）注入灌注液中。灌注60分钟后，EE处理的大鼠中APAP-葡糖醛酸苷的胆汁排泄减少（-80%）。相反，EE使灌注液中的排泄增加（+45%）。实验结束时，EE组中APAP-葡糖醛酸苷的肝脏含量降低了36%。两组中葡糖醛酸苷的总量保持不变。综上所述，这些结果表明，Mrp3的上调导致IPL中共轭APAP的基底外侧排泄相对于胆小管排泄加剧。我们得出结论，EE诱导基底外侧Mrp3的表达可能代表一种补偿机制，以防止由于顶端Mrp2表达和活性降低而导致内源性或外源性常见Mrp底物在细胞内积累。
