多药耐药相关蛋白2与谷胱甘肽共转运体系对肝脏砷代谢的影响

目的 用谷胱甘肽（GSH）合成酶抑制剂丁硫氨酸亚甲矾胺（BSO）抑制大鼠GSH合成,探讨多药耐药相关蛋白2（MRP2）与GSH共转运体系在肝脏砷代谢过程中的作用.方法 30只健康Wistar大鼠随机分为5组：第1组为对照组,给予生理盐水;第2～4组为染砷组,分别给予4、10和20mg/kg体重的亚砷酸钠溶液,隔天染毒1次,2周后将动物处死.第5组为BSO干预组,在实验结束的前3 d,每天大鼠预先腹腔注射2 mmol/kg体重BSO溶液,4 h后再经口给予20 mg/kg体重的亚砷酸钠溶液,其他处理同上.原子吸收分光光度法测定胆汁、肝组织和全血中的总砷含量.蛋白印记法测定肝细胞膜上MRP2的含量改变.结果 和对照组比较,各砷染毒组胆汁、肝脏和血砷含量均明显增高,差异有统计学意义（P＜0.05）;而3个染毒组间血砷差异无统计学意义（P＞0.05）.随着染砷剂量增加,MRP2表达有增加的趋势,且MRP2表达量与胆汁砷的含量呈正相关（r=0.986,P＜0.05）.大鼠经BSO预处理后再给予20 mg/kg体重的亚砷酸钠溶液,胆汁砷含量明显高于对照组,而低于高剂量组;肝脏和血砷水平明显高于对照组和高剂量组,差异有统计学意义（P＜0.05）;MPR2表达量比高剂量组减少.结论 亚砷酸钠可以诱导MRP2的表达,随染砷剂量增加,MRP2表达量增加.MRP2在砷及其代谢产物的胆汁排泄过程中发挥了重要作用.MRP2转运砷及其代谢产物的作用与细胞内GSH水平相关,BSO通过抑制GSH合成,导致MRP2-GSH共转运功能减弱,砷在肝脏内蓄积增加.

Effects of MRP2-GSH cotransport system on hepatic arsenic metabolism in rats

Objective To investigate the role of multidrug resistant protein 2(MRP2) and glutathione (GSH) cotransport system in hepatic arsenic metabolism in rats. Methods Thirty healthy Wistar rats were divided randomizedly into five groups. The first group was the control group and the rats in this group were administered with normal saline.In the second, third and fourth group the rats were administered with 4,10 and 20 mgAs+ 3/kg BW of sodium arsenite respectively every other day for two weeks. The fifth group was the benzene-soluble organics (BSO) intervention group and in this group the rats were administered with 2 mmol/kg BW BSO intraperitoneally every day three days before the end of the experiment. The other treatment was the same as in other groups. All rats were sacrificed two weeks after the treatments. Arsenic contents in bile, liver and blood were detected by atomic absorption spectroscopy(AAS) ,and the expression of MRP2 in the membrane of hepatocyte was determined by Western-blot analysis. Results The level of total arsenic (including organic arsenic and inorganic arsenic) in bile,liver and blood in all three different dose groups was higher than those in the control groups (P < 0.05). Arsenic levels of bile and liver were increased with intragastric arsenic dose. Blood arsenic levels were not significantly different in three different dose groups. Expression of hepatic MRP2 was increased with intragastric arsenic concentration. A positive correlation between biliary arsenic concentration and MRP2 levels was found in liver ( r = 0.986, P < 0.05) . For the rats pretreated with BSO, the biliary arsenic was significandy higher than that in the control group but lower than that in the high dose group; the liver and blood arsenic was higher than that in the control group and in the high dose group. Expression of MRP2 pretreated with BSO was decreased. Conclusion Sodium arsenite can induce expression of MRP2 and the up-regulation of MRP2 may play an important role in the bile secretion of arsenite and its metabolites. The function of MRP2 for transportation of arsenic and its metabolites is associated with the intracellular GSH level.BSO inhibits the synthesis of GSH, which weakens the function of the MRP2-GSH co-transport system and makes the liver arsenic increased.