The Effects Of MRP2 And MRP2-GSH Cotransport Systerm On Hepatic Arsenic Metabolism In Rats

Objective To determine whether expression of MRP2 increased with increasing arsenic concentration and to observe effects of BSO, an inhibitor of GSH synthesis on hepatic arsenic metabolism in rats.Methods Thirty healthy Wistar rats were divided randomly into five groups and challenged with different concentrations of sodium arsenite : 0, 4, 10 and 20 mgAs/kgBW. High dose animals were also pretreated with BSO before arsenic administration. All animals were sacrificed 2 weeks after this treatment. Arsenic in liven blood and bile were detected by atomic absorption spectroscopy (AAS), and expression of MRP2 in the membrane of hepatocyte was determined by Western-blot analysis. By light microscopy and eletric microscopy, the morphological changes of liver were observed. Five biochemical indexes: Alanine aminotransferase (ALT) , total bilirubin in serum, glutathione (GSH), glutathione peroxidase (GSH-PX),and malonicacid (MDA) were selected to show the toxic effects on rats.Results The level of total arsenic in blood, bile and liver at all three different dose groups were higher than those in control groups. Significant difference can seen between two dose group in arsenic level of bile and liver, but there is no difference between two dose group in arsenic level of blood. Expression of MRP2 increased with increasing arsenic concentration. A clear tendency for apositive correlation between biliary arsenic concentration and MRP2 levels was found in liver. The activity of ALT increased as the dose increasing and showed a dose-effect manner. Compared with controls, total bilirubin in serum was increased in high-dose group. The contents of GSH and the activity of GSH-PX in high-dose group were higher than those in controls. The level of MDA in middle and high-dose groups increased markedly. Pretreatment with BSO decreased GSH level and increased lipid peroxidation. Biliary arsenic of rats pretreated with BSO was lower than that in rats of high-dose group and pretreatment with BSO increased arsenic content in tissues of rats. Expression of MRP2 pretreated with BSO was slightly decreasing. There was a little proliferation and necrosis in hepatocytes by LM. In bile canaliculi microvilli became swelling and sparse and the shape of nuclear showed irregular and some of mitochondrial cristae missed or broken by EM compared with control groups. Conclusion Sodium arsenite can induced expression of MRP2. The up-regulation of MRP2 proteins play an important role in the bile secretion of arsenite and its metabolies. Depletion of GSH reduced the function of MRP2-GSH cotransport system.