Protective Effect Of Vitamin C Against Hepatotoxicity Induced By Cr(â…¥) And Its Probable Mechanisms In Rats

Objective:To explore the effect of pretreatment with Vitamin C on hepatic injury induced by hexavalent chromium [Cr(Ⅵ)] and its probable mechanism by in vivo test and in vitro test.Methods:In vivio test, sixty healthy SD rats were randomly divided into 6 groups(10 rats each group with half female and half male), control group, low-dose Cr(Ⅵ) group, high-dose Cr(Ⅵ) group, Vit-C group, Vit-C pretreated low-dose Cr(Ⅵ) group and Vit-C pretreated high-dose Cr(Ⅵ) group. Vitamin C was administered by gavage to animals at 500mg/kg.bw in Vit-C pretreated group, the same volume of normal saline in the other groups. Half hour after above administration, animals in low-dose and high-dose Cr(Ⅵ) groups were treated with Cr(Ⅵ) at 8.84mg/kg.bw and 17.68mg/kg.bw by gavage respectively, however the others were given with the same volume of normal saline once every day for seven days. The toxic manifestations were observed during the test, and excrement, urine, blood as well as hepatic tissues were collected at the end of the test. The levels of ALT and AST in serum were detected by AU 400 full Automatic Biochemistry Analyzer, SOD, GSH and MDA in liver homogenate were analyzed by ultraviolet-visible spectrophotometry, and clearing ability of flee radical by fluorescence spectrophotometry. Moreover, the contents of Cr(Ⅵ) in the excrement, urine, blood as well as hepatic tissues were examined by flame atomic absorption spectrometry. Slides of liver tissue were stained with hematoxylin and eosin (HE), and the morphological changes were observed by light microscopy.In vitro test, the effects of Cr(Ⅵ) or Vit-C on cell survival rate were assessed by the reductions of tetrazolium dye(MTT) in cultured L-02 hepatocytes. L-02 heptocytes in all tests were incubated with 32μmol/L Cr(Ⅵ) and 30, 90μmol/L Vit-C for 6h according to cell survival rate. The contents of extracellular and entracellular Cr(Ⅵ), GSH, MDA and activities of SOD were detected by above methods.Results:In vivio test, obvious toxic symptom of animals and pathological changes of liver tissues were observed in Cr(Ⅵ) groups. Vit-C pretreatment protected against these toxic effects induced by Cr(Ⅵ). The contents of chromium in the excrement, urine, blood as well as hepatic tissues in Cr(Ⅵ) groups were significantly higher than that in control group (P＜0.05). The contents of chromium in the excrement and urine in rats of Vit-C pretreated groups were significantly higher than that in single Cr(Ⅵ) groups (P＜0.05) . The levels of ALT and AST in blood of rats treated with high-dose Cr(Ⅵ) were higher than that in control group (P＜0.05) , and ALT in blood of Vit-C pretreated rats was significantly lower than that of only low-dose Cr(Ⅵ) group (P＜0.05).The levels of SOD and GSH and the clearing ability of ROS in liver tissue of Cr(Ⅵ) groups decreased significantly, and the content of MDA increased significantly compared to control group (P＜0.05). The levels of SOD and GSH and the clearing ability of ROS in liver tissue of Vit-C pretreated group were significantly higher than single Cr(Ⅵ) group (P＜0.05). The content of Vit-C in blood of animals in Cr(Ⅵ) group was higher than that in control group, but without significance (P＞0.05). The content of Vit-C in blood of Vit-C pretreated group was higher than that in single Cr(Ⅵ) group (P＜0.05)In vitro test, the levels of SOD and GSH in L-02 hepatocytes treated with 32μmol/L Cr(VⅥ) were significantly lower than that in control (P＜0.05), and the content of MDA was significantly higher than that in control (P＜0.05). The levels of SOD and GSH in 30μmol/L and 90μmol/L Vit-C pretreated groups increased significantly, and the content of MDA decreased significantly compared to single Cr(Ⅵ) group (P＜0.05) . The levels of SOD and GSH in L-02 hepatocyte pretreated with 30μmol/L Vit-C for 30mins and then eluting Vit-C were significantly lower than that single Cr(VⅥgroup (P＜0.05). The levels of SOD and GSH in L-02 hepatocyte pretreated with 90μmol/L Vit-C and and then eluting Vit-C were significantly higher than that single Cr(Ⅵ) group (P＜0.05). The contents of MDA of 30μmol/L and 90μmol/L Vit-C pretreated groups were significantly lower than that single Cr(Ⅵ) group (P＜0.05) The extracellular content of chromium in 90~μmol/L Vit-C pretreated Cr(Ⅵ) group was higher than that in single Cr(Ⅵ) group, and the entracellular content of chromium was lower than that in single Cr(Ⅵ) group, the contents of chromium within and outsides of cells pretreated with 90μmol/L Vit-C for 30mins and then eluting Vit-C were similar to that in single Cr(Ⅵ) group.Conclusion:(1)Cr(Ⅵ) at 8.84 mg/kg.bw and 17.68mg/kg.bw can induce obvious hepatic damage in SD rats, and liver is the toxic target organ for chromium.(2)Vit-C at 500mg/kg.bw can alleviate hepatic injury induced by Cr(Ⅵ) in rats.(3)Vit-C can reduce Cr(Ⅵ) to Cr(Ⅲ) outside cells, so as to block Cr(Ⅵ) into cells. Vit-C in cells can strengthen oxidative damage induced by Cr(Ⅵ).(4)The mechanism of Vit-C against hepatotoxicity induced by Cr(Ⅵ) is that Vit-C reduces Cr(Ⅵ) to Cr(Ⅲ) outside cells.