RESUMO
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 mg As(+)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 significantly 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 cotransport system and makes the liver arsenic increased.
